draft-ietf-taps-interface-12.txt   draft-ietf-taps-interface-13.txt 
TAPS Working Group B. Trammell, Ed. TAPS Working Group B. Trammell, Ed.
Internet-Draft Google Switzerland GmbH Internet-Draft Google Switzerland GmbH
Intended status: Standards Track M. Welzl, Ed. Intended status: Standards Track M. Welzl, Ed.
Expires: 11 October 2021 University of Oslo Expires: 13 January 2022 University of Oslo
T. Enghardt T. Enghardt
Netflix Netflix
G. Fairhurst G. Fairhurst
University of Aberdeen University of Aberdeen
M. Kuehlewind M. Kuehlewind
Ericsson Ericsson
C. Perkins C. Perkins
University of Glasgow University of Glasgow
P. Tiesel P. Tiesel
SAP SE SAP SE
C.A. Wood C.A. Wood
Cloudflare Cloudflare
T. Pauly T. Pauly
Apple Inc. Apple Inc.
K. Rose K. Rose
Akamai Technologies, Inc. Akamai Technologies, Inc.
9 April 2021 12 July 2021
An Abstract Application Layer Interface to Transport Services An Abstract Application Layer Interface to Transport Services
draft-ietf-taps-interface-12 draft-ietf-taps-interface-13
Abstract Abstract
This document describes an abstract application programming This document describes an abstract application programming
interface, API, to the transport layer, following the Transport interface, API, to the transport layer that enables the selection of
Services Architecture. It supports the asynchronous, atomic transport protocols and network paths dynamically at runtime. This
transmission of messages over transport protocols and network paths API enables faster deployment of new protocols and protocol features
dynamically selected at runtime. It is intended to replace the without requiring changes to the applications. The specified API
traditional BSD sockets API as the common interface to the transport follows the Transport Services Architecture by providing
layer, in an environment where endpoints could select from multiple asynchronous, atomic transmission of messages. It is intended to
interfaces and potential transport protocols. replace the traditional BSD sockets API as the common interface to
the transport layer, in an environment where endpoints could select
from multiple interfaces and potential transport protocols.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on 11 October 2021. This Internet-Draft will expire on 13 January 2022.
Copyright Notice Copyright Notice
Copyright (c) 2021 IETF Trust and the persons identified as the Copyright (c) 2021 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/ Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document. license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights Please review these documents carefully, as they describe your rights
and restrictions with respect to this document. Code Components and restrictions with respect to this document. Code Components
extracted from this document must include Simplified BSD License text extracted from this document must include Simplified BSD License text
as described in Section 4.e of the Trust Legal Provisions and are as described in Section 4.e of the Trust Legal Provisions and are
provided without warranty as described in the Simplified BSD License. provided without warranty as described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Terminology and Notation . . . . . . . . . . . . . . . . 5 1.1. Terminology and Notation . . . . . . . . . . . . . . . . 5
1.2. Specification of Requirements . . . . . . . . . . . . . . 6 1.2. Specification of Requirements . . . . . . . . . . . . . . 7
2. Overview of Interface Design . . . . . . . . . . . . . . . . 7 2. Overview of Interface Design . . . . . . . . . . . . . . . . 7
3. API Summary . . . . . . . . . . . . . . . . . . . . . . . . . 7 3. API Summary . . . . . . . . . . . . . . . . . . . . . . . . . 8
3.1. Usage Examples . . . . . . . . . . . . . . . . . . . . . 8 3.1. Usage Examples . . . . . . . . . . . . . . . . . . . . . 9
3.1.1. Server Example . . . . . . . . . . . . . . . . . . . 9 3.1.1. Server Example . . . . . . . . . . . . . . . . . . . 10
3.1.2. Client Example . . . . . . . . . . . . . . . . . . . 10 3.1.2. Client Example . . . . . . . . . . . . . . . . . . . 10
3.1.3. Peer Example . . . . . . . . . . . . . . . . . . . . 11 3.1.3. Peer Example . . . . . . . . . . . . . . . . . . . . 12
3.2. Transport Properties . . . . . . . . . . . . . . . . . . 12 4. Transport Properties . . . . . . . . . . . . . . . . . . . . 13
3.2.1. Transport Property Names . . . . . . . . . . . . . . 12 4.1. Transport Property Names . . . . . . . . . . . . . . . . 13
3.2.2. Transport Property Types . . . . . . . . . . . . . . 13 4.2. Transport Property Types . . . . . . . . . . . . . . . . 14
3.3. Scope of the Interface Definition . . . . . . . . . . . . 14 5. Scope of the Interface Definition . . . . . . . . . . . . . . 15
4. Pre-Establishment Phase . . . . . . . . . . . . . . . . . . . 15 6. Pre-Establishment Phase . . . . . . . . . . . . . . . . . . . 16
4.1. Specifying Endpoints . . . . . . . . . . . . . . . . . . 16 6.1. Specifying Endpoints . . . . . . . . . . . . . . . . . . 17
4.1.1. Using Multicast Endpoints . . . . . . . . . . . . . . 17 6.1.1. Using Multicast Endpoints . . . . . . . . . . . . . . 18
4.1.2. Endpoint Aliases . . . . . . . . . . . . . . . . . . 17 6.1.2. Endpoint Aliases . . . . . . . . . . . . . . . . . . 18
4.1.3. Endpoint Examples . . . . . . . . . . . . . . . . . . 18 6.1.3. Endpoint Examples . . . . . . . . . . . . . . . . . . 19
4.2. Specifying Transport Properties . . . . . . . . . . . . . 19 6.2. Specifying Transport Properties . . . . . . . . . . . . . 20
4.2.1. Reliable Data Transfer (Connection) . . . . . . . . . 22 6.2.1. Reliable Data Transfer (Connection) . . . . . . . . . 23
4.2.2. Preservation of Message Boundaries . . . . . . . . . 22 6.2.2. Preservation of Message Boundaries . . . . . . . . . 23
4.2.3. Configure Per-Message Reliability . . . . . . . . . . 22 6.2.3. Configure Per-Message Reliability . . . . . . . . . . 24
4.2.4. Preservation of Data Ordering . . . . . . . . . . . . 22 6.2.4. Preservation of Data Ordering . . . . . . . . . . . . 24
4.2.5. Use 0-RTT Session Establishment with a Safely 6.2.5. Use 0-RTT Session Establishment with a Safely
Replayable Message . . . . . . . . . . . . . . . . . 23 Replayable Message . . . . . . . . . . . . . . . . . 24
4.2.6. Multistream Connections in Group . . . . . . . . . . 23 6.2.6. Multistream Connections in Group . . . . . . . . . . 24
4.2.7. Full Checksum Coverage on Sending . . . . . . . . . . 23 6.2.7. Full Checksum Coverage on Sending . . . . . . . . . . 25
4.2.8. Full Checksum Coverage on Receiving . . . . . . . . . 23 6.2.8. Full Checksum Coverage on Receiving . . . . . . . . . 25
4.2.9. Congestion control . . . . . . . . . . . . . . . . . 24 6.2.9. Congestion control . . . . . . . . . . . . . . . . . 25
4.2.10. Keep alive . . . . . . . . . . . . . . . . . . . . . 24 6.2.10. Keep alive . . . . . . . . . . . . . . . . . . . . . 26
4.2.11. Interface Instance or Type . . . . . . . . . . . . . 24 6.2.11. Interface Instance or Type . . . . . . . . . . . . . 26
4.2.12. Provisioning Domain Instance or Type . . . . . . . . 25 6.2.12. Provisioning Domain Instance or Type . . . . . . . . 27
4.2.13. Use Temporary Local Address . . . . . . . . . . . . . 26 6.2.13. Use Temporary Local Address . . . . . . . . . . . . . 28
4.2.14. Multipath Transport . . . . . . . . . . . . . . . . . 27 6.2.14. Multipath Transport . . . . . . . . . . . . . . . . . 28
4.2.15. Advertisement of Alternative Addresses . . . . . . . 28 6.2.15. Advertisement of Alternative Addresses . . . . . . . 29
4.2.16. Direction of communication . . . . . . . . . . . . . 28 6.2.16. Direction of communication . . . . . . . . . . . . . 30
4.2.17. Notification of ICMP soft error message arrival . . . 29 6.2.17. Notification of ICMP soft error message arrival . . . 30
4.2.18. Initiating side is not the first to write . . . . . . 29 6.2.18. Initiating side is not the first to write . . . . . . 31
4.3. Specifying Security Parameters and Callbacks . . . . . . 29 6.3. Specifying Security Parameters and Callbacks . . . . . . 31
4.3.1. Pre-Connection Parameters . . . . . . . . . . . . . . 30 6.3.1. Specifying Security Parameters on a Pre-Connection . 31
4.3.2. Connection Establishment Callbacks . . . . . . . . . 31 6.3.2. Connection Establishment Callbacks . . . . . . . . . 33
5. Establishing Connections . . . . . . . . . . . . . . . . . . 31 7. Establishing Connections . . . . . . . . . . . . . . . . . . 33
5.1. Active Open: Initiate . . . . . . . . . . . . . . . . . . 31 7.1. Active Open: Initiate . . . . . . . . . . . . . . . . . . 34
5.2. Passive Open: Listen . . . . . . . . . . . . . . . . . . 33 7.2. Passive Open: Listen . . . . . . . . . . . . . . . . . . 35
5.3. Peer-to-Peer Establishment: Rendezvous . . . . . . . . . 34 7.3. Peer-to-Peer Establishment: Rendezvous . . . . . . . . . 36
5.4. Connection Groups . . . . . . . . . . . . . . . . . . . . 36 7.4. Connection Groups . . . . . . . . . . . . . . . . . . . . 38
6. Managing Connections . . . . . . . . . . . . . . . . . . . . 37 8. Managing Connections . . . . . . . . . . . . . . . . . . . . 39
6.1. Generic Connection Properties . . . . . . . . . . . . . . 39 8.1. Generic Connection Properties . . . . . . . . . . . . . . 41
6.1.1. Required Minimum Corruption Protection Coverage for 8.1.1. Required Minimum Corruption Protection Coverage for
Receiving . . . . . . . . . . . . . . . . . . . . . . 39 Receiving . . . . . . . . . . . . . . . . . . . . . . 41
6.1.2. Connection Priority . . . . . . . . . . . . . . . . . 39 8.1.2. Connection Priority . . . . . . . . . . . . . . . . . 42
6.1.3. Timeout for Aborting Connection . . . . . . . . . . . 40 8.1.3. Timeout for Aborting Connection . . . . . . . . . . . 42
6.1.4. Timeout for keep alive packets . . . . . . . . . . . 40 8.1.4. Timeout for keep alive packets . . . . . . . . . . . 42
6.1.5. Connection Group Transmission Scheduler . . . . . . . 40 8.1.5. Connection Group Transmission Scheduler . . . . . . . 43
6.1.6. Capacity Profile . . . . . . . . . . . . . . . . . . 41 8.1.6. Capacity Profile . . . . . . . . . . . . . . . . . . 43
6.1.7. Policy for using Multipath Transports . . . . . . . . 42 8.1.7. Policy for using Multipath Transports . . . . . . . . 45
6.1.8. Bounds on Send or Receive Rate . . . . . . . . . . . 43 8.1.8. Bounds on Send or Receive Rate . . . . . . . . . . . 46
6.1.9. Group Connection Limit . . . . . . . . . . . . . . . 43 8.1.9. Group Connection Limit . . . . . . . . . . . . . . . 46
6.1.10. Isolate Session . . . . . . . . . . . . . . . . . . . 44 8.1.10. Isolate Session . . . . . . . . . . . . . . . . . . . 46
6.1.11. Read-only Connection Properties . . . . . . . . . . . 44 8.1.11. Read-only Connection Properties . . . . . . . . . . . 47
6.2. TCP-specific Properties: User Timeout Option (UTO) . . . 45 8.2. TCP-specific Properties: User Timeout Option (UTO) . . . 48
6.2.1. Advertised User Timeout . . . . . . . . . . . . . . . 46 8.2.1. Advertised User Timeout . . . . . . . . . . . . . . . 48
6.2.2. User Timeout Enabled . . . . . . . . . . . . . . . . 46 8.2.2. User Timeout Enabled . . . . . . . . . . . . . . . . 48
6.2.3. Timeout Changeable . . . . . . . . . . . . . . . . . 46 8.2.3. Timeout Changeable . . . . . . . . . . . . . . . . . 49
6.3. Connection Lifecycle Events . . . . . . . . . . . . . . . 46 8.3. Connection Lifecycle Events . . . . . . . . . . . . . . . 49
6.3.1. Soft Errors . . . . . . . . . . . . . . . . . . . . . 47 8.3.1. Soft Errors . . . . . . . . . . . . . . . . . . . . . 49
6.3.2. Path change . . . . . . . . . . . . . . . . . . . . . 47 8.3.2. Path change . . . . . . . . . . . . . . . . . . . . . 49
7. Data Transfer . . . . . . . . . . . . . . . . . . . . . . . . 47 9. Data Transfer . . . . . . . . . . . . . . . . . . . . . . . . 49
7.1. Messages and Framers . . . . . . . . . . . . . . . . . . 47 9.1. Messages and Framers . . . . . . . . . . . . . . . . . . 50
7.1.1. Message Contexts . . . . . . . . . . . . . . . . . . 47 9.1.1. Message Contexts . . . . . . . . . . . . . . . . . . 50
7.1.2. Message Framers . . . . . . . . . . . . . . . . . . . 48 9.1.2. Message Framers . . . . . . . . . . . . . . . . . . . 50
7.1.3. Message Properties . . . . . . . . . . . . . . . . . 50 9.1.3. Message Properties . . . . . . . . . . . . . . . . . 53
7.2. Sending Data . . . . . . . . . . . . . . . . . . . . . . 56 9.2. Sending Data . . . . . . . . . . . . . . . . . . . . . . 58
7.2.1. Basic Sending . . . . . . . . . . . . . . . . . . . . 56 9.2.1. Basic Sending . . . . . . . . . . . . . . . . . . . . 59
7.2.2. Send Events . . . . . . . . . . . . . . . . . . . . . 57 9.2.2. Send Events . . . . . . . . . . . . . . . . . . . . . 59
7.2.3. Partial Sends . . . . . . . . . . . . . . . . . . . . 58 9.2.3. Partial Sends . . . . . . . . . . . . . . . . . . . . 60
7.2.4. Batching Sends . . . . . . . . . . . . . . . . . . . 58 9.2.4. Batching Sends . . . . . . . . . . . . . . . . . . . 61
7.2.5. Send on Active Open: InitiateWithSend . . . . . . . . 59 9.2.5. Send on Active Open: InitiateWithSend . . . . . . . . 61
7.2.6. Priority in TAPS . . . . . . . . . . . . . . . . . . 59 9.2.6. Priority in TAPS . . . . . . . . . . . . . . . . . . 62
7.3. Receiving Data . . . . . . . . . . . . . . . . . . . . . 60 9.3. Receiving Data . . . . . . . . . . . . . . . . . . . . . 63
7.3.1. Enqueuing Receives . . . . . . . . . . . . . . . . . 60 9.3.1. Enqueuing Receives . . . . . . . . . . . . . . . . . 63
7.3.2. Receive Events . . . . . . . . . . . . . . . . . . . 61 9.3.2. Receive Events . . . . . . . . . . . . . . . . . . . 64
7.3.3. Receive Message Properties . . . . . . . . . . . . . 63 9.3.3. Receive Message Properties . . . . . . . . . . . . . 66
8. Connection Termination . . . . . . . . . . . . . . . . . . . 64 10. Connection Termination . . . . . . . . . . . . . . . . . . . 67
9. Connection State and Ordering of Operations and Events . . . 65 11. Connection State and Ordering of Operations and Events . . . 69
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 66 12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 70
11. Privacy and Security Considerations . . . . . . . . . . . . . 66 13. Privacy and Security Considerations . . . . . . . . . . . . . 70
12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 68 14. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 72
13. References . . . . . . . . . . . . . . . . . . . . . . . . . 68 15. References . . . . . . . . . . . . . . . . . . . . . . . . . 72
13.1. Normative References . . . . . . . . . . . . . . . . . . 69 15.1. Normative References . . . . . . . . . . . . . . . . . . 72
13.2. Informative References . . . . . . . . . . . . . . . . . 69 15.2. Informative References . . . . . . . . . . . . . . . . . 73
Appendix A. Implementation Mapping . . . . . . . . . . . . . . . 73 Appendix A. Implementation Mapping . . . . . . . . . . . . . . . 76
A.1. Types . . . . . . . . . . . . . . . . . . . . . . . . . . 73 A.1. Types . . . . . . . . . . . . . . . . . . . . . . . . . . 76
A.2. Events and Errors . . . . . . . . . . . . . . . . . . . . 73 A.2. Events and Errors . . . . . . . . . . . . . . . . . . . . 77
A.3. Time Duration . . . . . . . . . . . . . . . . . . . . . . 73 A.3. Time Duration . . . . . . . . . . . . . . . . . . . . . . 77
Appendix B. Convenience Functions . . . . . . . . . . . . . . . 74 Appendix B. Convenience Functions . . . . . . . . . . . . . . . 77
B.1. Adding Preference Properties . . . . . . . . . . . . . . 74 B.1. Adding Preference Properties . . . . . . . . . . . . . . 77
B.2. Transport Property Profiles . . . . . . . . . . . . . . . 74 B.2. Transport Property Profiles . . . . . . . . . . . . . . . 78
B.2.1. reliable-inorder-stream . . . . . . . . . . . . . . . 74 B.2.1. reliable-inorder-stream . . . . . . . . . . . . . . . 78
B.2.2. reliable-message . . . . . . . . . . . . . . . . . . 75 B.2.2. reliable-message . . . . . . . . . . . . . . . . . . 78
B.2.3. unreliable-datagram . . . . . . . . . . . . . . . . . 75 B.2.3. unreliable-datagram . . . . . . . . . . . . . . . . . 79
Appendix C. Relationship to the Minimal Set of Transport Services Appendix C. Relationship to the Minimal Set of Transport Services
for End Systems . . . . . . . . . . . . . . . . . . . . . 76 for End Systems . . . . . . . . . . . . . . . . . . . . . 80
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 79 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 83
1. Introduction 1. Introduction
This document specifies a modern abstract application programming This document specifies a modern abstract application programming
interface (API) atop the high-level architecture for transport interface (API) atop the high-level architecture for transport
services defined in [I-D.ietf-taps-arch]. It supports the services defined in [I-D.ietf-taps-arch]. The Transport Services
asynchronous, atomic transmission of messages over transport Architecture supports asynchronous, atomic transmission of messages
protocols and network paths dynamically selected at runtime. It is over transport protocols and network paths dynamically selected at
intended to replace the traditional BSD sockets API as the common runtime, in environments where an endpoint selects from multiple
interface to the transport layer, in environments where an endpoint interfaces and potential transport protocols.
selects from multiple interfaces and potential transport protocols.
As applications adopt this interface, they will benefit from a wide Applications that adopt this interface will benefit from a wide set
set of transport features that can evolve over time, and ensure that of transport features that can evolve over time. This protocol-
the system providing the interface can optimize its behavior based on independent API ensures that the system providing the interface can
the application requirements and network conditions, without optimize its behavior based on the application requirements and
requiring changes to the applications. This flexibility enables network conditions, without requiring changes to the applications.
faster deployment of new features and protocols. It can also support This flexibility enables faster deployment of new features and
applications by offering racing and fallback mechanisms, which protocols, and can support applications by offering racing and
otherwise need to be separately implemented in each application. fallback mechanisms, which otherwise need to be separately
implemented in each application.
It derives specific path and protocol selection properties and This API derives specific path and protocol selection properties and
supported transport features from the analysis provided in [RFC8095], supported transport features from the analysis provided in [RFC8095],
[RFC8923], and [RFC8922]. The design encourages implementations [RFC8923], and [RFC8922]. The design encourages implementations
underneath the interface to dynamically choose a transport protocol underneath the interface to dynamically choose a transport protocol
depending on an application's choices rather than statically binding depending on an application's choices rather than statically binding
applications to a protocol at compile time. The Transport Services applications to a protocol at compile time. Nevertheless, the
system implementations should provide applications with a way to Transport Services API also provides applications with a way to
override transport selection and instantiate a specific stack, e.g., override transport selection and instantiate a specific stack, e.g.,
to support servers wishing to listen to a specific protocol. This to support servers wishing to listen to a specific protocol.
specific transport stack choice is discouraged for general use, However, forcing a specific transport stack choice is discouraged for
because it can reduce the portability. general use, because it can reduce portability.
1.1. Terminology and Notation 1.1. Terminology and Notation
This API is described in terms of Objects with which an application This API is described in terms of
can interact; Actions the application can perform on these Objects;
Events, which an Object can send to an application asynchronously; * Objects with which an application can interact;
and Parameters associated with these Actions and Events.
* Actions the application can perform on these Objects;
* Events, which an Object can send to an application to be processed
aynchronously; and
* Parameters associated with these Actions and Events.
The following notations, which can be combined, are used in this The following notations, which can be combined, are used in this
document: document:
* An Action creates an Object: * An Action that creates an Object:
Object := Action() Object := Action()
* An Action creates an array of Objects: * An Action that creates an array of Objects:
[]Object := Action() []Object := Action()
* An Action is performed on an Object: * An Action that is performed on an Object:
Object.Action() Object.Action()
* An Object sends an Event: * An Object sends an Event:
Object -> Event<> Object -> Event<>
* An Action takes a set of Parameters; an Event contains a set of * An Action takes a set of Parameters; an Event contains a set of
Parameters. Action and Event parameters whose names are suffixed Parameters. Action and Event parameters whose names are suffixed
with a question mark are optional. with a question mark are optional.
Action(param0, param1?, ...) / Event<param0, param1, ...> Action(param0, param1?, ...) / Event<param0, param1, ...>
Actions associated with no Object are Actions on the abstract Actions associated with no Object are Actions on the abstract
interface itself; they are equivalent to Actions on a per-application interface itself; they are equivalent to Actions on a per-application
global context. global context.
Events are sent to the application or application-supplied code (e.g.
framers, see Section 9.1.2) for processing; the details of event
processing are platform- and implementation-specific.
We also make use of the following basic types: We also make use of the following basic types:
* Boolean: Instances take the value "true" or "false". * Boolean: Instances take the value "true" or "false".
* Integer: Instances take positive or negative numeric integer * Integer: Instances take positive or negative numeric integer
values, or sometimes special non-numeric (symbolic) values. values, or sometimes special non-numeric (symbolic) values.
* Numeric: Instances take positive or negative numeric values, or * Numeric: Instances take positive or negative numeric values, or
sometimes special non-numeric (symbolic) values. sometimes special non-numeric (symbolic) values.
* Enumeration: A family of types in which each instance takes one of * Enumeration: A family of types in which each instance takes one of
a fixed, predefined set of values specific to a given enumerated a fixed, predefined set of values specific to a given enumerated
type. type.
* Tuple: An ordered grouping of multiple value types, represented as * Tuple: An ordered grouping of multiple value types, represented as
a comma-separated list in parentheses, e.g., "(Enumeration, a comma-separated list in parentheses, e.g., "(Enumeration,
Preference)". Instances take a sequence of values each valid for Preference)". Instances take a sequence of values each valid for
the corresponding value type. The composition of types and their the corresponding value type.
order depends on the property and is fixed for the property.
* Array: Denoted []Type, an instance takes a value for each of zero * Array: Denoted []Type, an instance takes a value for each of zero
or more elements in a sequence of the given Type. An array may be or more elements in a sequence of the given Type. An array may be
of fixed or variable length. of fixed or variable length.
* Collection: An unordered grouping of one or more values of the * Collection: An unordered grouping of one or more values of the
same type. same type.
For guidance on how these abstract concepts may be implemented in For guidance on how these abstract concepts may be implemented in
languages in accordance with native design patterns and language and languages in accordance with native design patterns and language and
skipping to change at page 7, line 12 skipping to change at page 7, line 20
14 [RFC2119] [RFC8174] when, and only when, they appear in all 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
2. Overview of Interface Design 2. Overview of Interface Design
The design of the interface specified in this document is based on a The design of the interface specified in this document is based on a
set of principles, themselves an elaboration on the architectural set of principles, themselves an elaboration on the architectural
design principles defined in [I-D.ietf-taps-arch]. The interface design principles defined in [I-D.ietf-taps-arch]. The interface
defined in this document provides: defined in this document provides:
* Access to a variety of transport protocols, independent of the the * Access to a variety of transport protocols, independent of the
Protocol Stacks that will be used at runtime, such that all common Protocol Stacks that will be used at runtime. All common features
features of these protocol stacks are made available to the of these protocol stacks are made available to the application in
application in a transport-independent way to the degree possible, a transport-independent way to the degree possible. This enables
enabling applications written to a single API to make use of applications written to a single API to make use of transport
transport protocols in terms of the features they provide; protocols in terms of the features they provide.
* A unified interface to datagram and stream-oriented transports,
allowing use of a common API for connection establishment and
closing.
* Message-orientation, as opposed to stream-orientation, using * Message-orientation, as opposed to stream-orientation, using
application-assisted framing and deframing where the underlying application-assisted framing and deframing where the underlying
transport does not provide these; transport does not provide these.
* Asynchronous Connection establishment, transmission, and * Asynchronous Connection establishment, transmission, and
reception, allowing concurrent operations during establishment and reception. This allows concurrent operations during establishment
supporting event-driven application interactions with the and event-driven application interactions with the transport
transport layer, in line with developments in modern platforms and layer, in line with developments in modern platforms and
programming languages; programming languages;
* Explicit support for transport-specific features to be applied * Selection between alternate network paths, using additional
information about the networks over which a connection can operate
(e.g. Provisioning Domain (PvD) information [RFC7556]) where
available.
* Explicit support for transport-specific features to be applied,
should that particular transport be part of a chosen Protocol should that particular transport be part of a chosen Protocol
Stack. Stack.
* Explicit support for security properties as first-order transport * Explicit support for security properties as first-order transport
features, and for configuration of cryptographic identities and features.
* Explicit support for configuration of cryptographic identities and
transport security parameters persistent across multiple transport security parameters persistent across multiple
Connections; and Connections.
* Explicit support for multistreaming and multipath transport * Explicit support for multistreaming and multipath transport
protocols, and the grouping of related Connections into Connection protocols, and the grouping of related Connections into Connection
Groups through cloning of Connections, to allow applications to Groups through cloning of Connections. This allows applications
take full advantage of new transport protocols supporting these to take full advantage of new transport protocols supporting these
features. features.
3. API Summary 3. API Summary
The Transport Services API is the basic common abstract application The Transport Services API is the basic common abstract application
programming interface to the Transport Services Architecture defined programming interface to the Transport Services Architecture defined
in the TAPS Architecture [I-D.ietf-taps-arch]. in the TAPS Architecture [I-D.ietf-taps-arch].
An application primarily interacts with this API through two Objects: An application primarily interacts with this API through two Objects:
Preconnections and Connections. A Preconnection represents a set of Preconnections and Connections. A Preconnection object (Section 6)
properties and constraints on the selection and configuration of represents a set of properties and constraints on the selection and
paths and protocols to establish a Connection with a Remote Endpoint. configuration of paths and protocols to establish a Connection with
A Connection represents a transport Protocol Stack on which data can an Endpoint. A Connection object represents an instance of a
be sent to and/or received from a Remote Endpoint (i.e., depending on transport Protocol Stack on which data can be sent to and/or received
the kind of transport, connections can be bi-directional or from a Remote Endpoint (i.e., a logical connection that, depending on
unidirectional). Connections can be created from Preconnections in the kind of transport, can be bi-directional or unidirectional, and
three ways: by initiating the Preconnection (i.e., actively opening, that can use a stream protocol or a datagram protocol). Connections
as in a client), through listening on the Preconnection (i.e., are presented consistently to the application, irrespective of
passively opening, as in a server), or rendezvousing on the whether the underlying transport is connection-less or connection-
Preconnection (i.e. peer to peer establishment). oriented. Connections can be created from Preconnections in three
ways:
* by initiating the Preconnection (i.e., actively opening, as in a
client; Section 7.1),
* through listening on the Preconnection (i.e., passively opening,
as in a server Section 7.2),
* or rendezvousing on the Preconnection (i.e., peer to peer
establishment; Section 7.3).
Once a Connection is established, data can be sent and received on it Once a Connection is established, data can be sent and received on it
in the form of Messages. The interface supports the preservation of in the form of Messages. The interface supports the preservation of
message boundaries both via explicit Protocol Stack support, and via message boundaries both via explicit Protocol Stack support, and via
application support through a Message Framer which finds message application support through a Message Framer that finds message
boundaries in a stream. Messages are received asynchronously through boundaries in a stream. Messages are received asynchronously through
event handlers registered by the application. Errors and other event handlers registered by the application. Errors and other
notifications also happen asynchronously on the Connection. It is notifications also happen asynchronously on the Connection. It is
not necessary for an application to handle all Events; some Events not necessary for an application to handle all Events; some Events
may have implementation-specific default handlers. The application may have implementation-specific default handlers. The application
should not assume that ignoring Events (e.g., Errors) is always safe. should not assume that ignoring Events (e.g., Errors) is always safe.
Section 4, Section 5, Section 7.2, Section 7.3, and Section 8 Section 6, Section 7, Section 9.2, Section 9.3, and Section 10
describe the details of application interaction with Objects through describe the details of application interaction with Objects through
Actions and Events in each phase of a Connection, following the Actions and Events in each phase of a Connection, following the
phases (Pre-Establishment, Establishment, Data Transfer, and phases (Pre-Establishment, Establishment, Data Transfer, and
Termination) described in Section 4.1 of [I-D.ietf-taps-arch]. Termination) described in Section 4.1 of [I-D.ietf-taps-arch].
3.1. Usage Examples 3.1. Usage Examples
The following usage examples illustrate how an application might use The following usage examples illustrate how an application might use
a Transport Services Interface to: the Transport Services Interface to:
* Act as a server, by listening for incoming connections, receiving * Act as a server, by listening for incoming connections, receiving
requests, and sending responses, see Section 3.1.1. requests, and sending responses, see Section 3.1.1.
* Act as a client, by connecting to a Remote Endpoint using * Act as a client, by connecting to a Remote Endpoint using
Initiate, sending requests, and receiving responses, see Initiate, sending requests, and receiving responses, see
Section 3.1.2. Section 3.1.2.
* Act as a peer, by connecting to a Remote Endpoint using Rendezvous * Act as a peer, by connecting to a Remote Endpoint using Rendezvous
while simultaneously waiting for incoming Connections, sending while simultaneously waiting for incoming Connections, sending
skipping to change at page 9, line 11 skipping to change at page 9, line 50
Reliable Data Transfer, Preservation of data ordering, and Reliable Data Transfer, Preservation of data ordering, and
Preservation of Message Boundaries. In this case, the application Preservation of Message Boundaries. In this case, the application
can choose to receive only complete messages. can choose to receive only complete messages.
If none of the available transport protocols provides Preservation of If none of the available transport protocols provides Preservation of
Message Boundaries, but there is a transport protocol that provides a Message Boundaries, but there is a transport protocol that provides a
reliable ordered byte stream, an application could receive this byte reliable ordered byte stream, an application could receive this byte
stream as partial Messages and transform it into application-layer stream as partial Messages and transform it into application-layer
Messages. Alternatively, an application might provide a Message Messages. Alternatively, an application might provide a Message
Framer, which can transform a sequence of Messages into a byte stream Framer, which can transform a sequence of Messages into a byte stream
and vice versa (Section 7.1.2). and vice versa (Section 9.1.2).
3.1.1. Server Example 3.1.1. Server Example
This is an example of how an application might listen for incoming This is an example of how an application might listen for incoming
Connections using the Transport Services Interface, and receive a Connections using the Transport Services Interface, and receive a
request, and send a response. request, and send a response.
LocalSpecifier := NewLocalEndpoint() LocalSpecifier := NewLocalEndpoint()
LocalSpecifier.WithInterface("any") LocalSpecifier.WithInterface("any")
LocalSpecifier.WithService("https") LocalSpecifier.WithService("https")
TransportProperties := NewTransportProperties() TransportProperties := NewTransportProperties()
TransportProperties.Require(preserve-msg-boundaries) TransportProperties.Require(preserve-msg-boundaries)
// Reliable Data Transfer and Preserve Order are Required by default // Reliable Data Transfer and Preserve Order are Required by default
SecurityParameters := NewSecurityParameters() SecurityParameters := NewSecurityParameters()
SecurityParameters.Set(identity, myIdentity) SecurityParameters.Set(identity, myIdentity)
SecurityParameters.Set(key-pair, myPrivateKey, myPublicKey) SecurityParameters.Set(key-pair, myPrivateKey, myPublicKey)
// Specifying a remote endpoint is optional when using Listen() // Specifying a Remote Endpoint is optional when using Listen()
Preconnection := NewPreconnection(LocalSpecifier, Preconnection := NewPreconnection(LocalSpecifier,
TransportProperties, TransportProperties,
SecurityParameters) SecurityParameters)
Listener := Preconnection.Listen() Listener := Preconnection.Listen()
Listener -> ConnectionReceived<Connection> Listener -> ConnectionReceived<Connection>
// Only receive complete messages in a Conn.Received handler // Only receive complete messages in a Conn.Received handler
Connection.Receive() Connection.Receive()
skipping to change at page 10, line 21 skipping to change at page 11, line 15
RemoteSpecifier := NewRemoteEndpoint() RemoteSpecifier := NewRemoteEndpoint()
RemoteSpecifier.WithHostname("example.com") RemoteSpecifier.WithHostname("example.com")
RemoteSpecifier.WithService("https") RemoteSpecifier.WithService("https")
TransportProperties := NewTransportProperties() TransportProperties := NewTransportProperties()
TransportProperties.Require(preserve-msg-boundaries) TransportProperties.Require(preserve-msg-boundaries)
// Reliable Data Transfer and Preserve Order are Required by default // Reliable Data Transfer and Preserve Order are Required by default
SecurityParameters := NewSecurityParameters() SecurityParameters := NewSecurityParameters()
TrustCallback := NewCallback({ TrustCallback := NewCallback({
// Verify identity of the remote endpoint, return the result // Verify identity of the Remote Endpoint, return the result
}) })
SecurityParameters.SetTrustVerificationCallback(TrustCallback) SecurityParameters.SetTrustVerificationCallback(TrustCallback)
// Specifying a local endpoint is optional when using Initiate() // Specifying a local endpoint is optional when using Initiate()
Preconnection := NewPreconnection(RemoteSpecifier, Preconnection := NewPreconnection(RemoteSpecifier,
TransportProperties, TransportProperties,
SecurityParameters) SecurityParameters)
Connection := Preconnection.Initiate() Connection := Preconnection.Initiate()
Connection2 := Connection.Clone() Connection2 := Connection.Clone()
skipping to change at page 11, line 5 skipping to change at page 11, line 44
C.Receive() C.Receive()
//---- Ready event handler for any Connection C end ---- //---- Ready event handler for any Connection C end ----
Connection -> Received<messageDataResponse, messageContext> Connection -> Received<messageDataResponse, messageContext>
Connection2 -> Received<messageDataResponse, messageContext> Connection2 -> Received<messageDataResponse, messageContext>
// Close the Connection in a Receive event handler // Close the Connection in a Receive event handler
Connection.Close() Connection.Close()
Connection2.Close() Connection2.Close()
Preconnections are reusable after being used to initiate a
Connection. Hence, for example, after the Connections were closed,
the following would be correct: ~~~ //.. carry out adjustments to the
Preconnection, if desire Connection := Preconnection.Initiate() ~~~
3.1.3. Peer Example 3.1.3. Peer Example
This is an example of how an application might establish a connection This is an example of how an application might establish a connection
with a peer using Rendezvous(), send a Message, and receive a with a peer using Rendezvous(), send a Message, and receive a
Message. Message.
// Configure local candidates: a port on the local host and via a STUN server // Configure local candidates: a port on the Local Endpoint and via a STUN server
HostCandidate := NewLocalEndpoint() HostCandidate := NewLocalEndpoint()
HostCandidate.WithPort(9876) HostCandidate.WithPort(9876)
StunCandidate := NewLocalEndpoint() StunCandidate := NewLocalEndpoint()
StunCandidate.WithStunServer(address, port, credentials) StunCandidate.WithStunServer(address, port, credentials)
LocalCandidates = [HostCandidate, StunCandidate] LocalCandidates = [HostCandidate, StunCandidate]
// Configure transport and security properties // Configure transport and security properties
TransportProperties := ... TransportProperties := ...
skipping to change at page 11, line 43 skipping to change at page 12, line 43
ResolvedLocal, ResolvedRemote = Preconnection.Resolve() ResolvedLocal, ResolvedRemote = Preconnection.Resolve()
// ...Send the ResolvedLocal list to peer via signalling channel // ...Send the ResolvedLocal list to peer via signalling channel
// ...Receive a list of RemoteCandidates from peer via signalling channel // ...Receive a list of RemoteCandidates from peer via signalling channel
Preconnection.AddRemote(RemoteCandidates) Preconnection.AddRemote(RemoteCandidates)
Preconnection.Rendezvous() Preconnection.Rendezvous()
Preconnection -> RendezvousDone<Connection> Preconnection -> RendezvousDone<Connection>
//---- Ready event handler begin ---- //---- RendezvousDone event handler begin ----
Connection.Send(messageDataRequest) Connection.Send(messageDataRequest)
Connection.Receive() Connection.Receive()
//---- Ready event handler end ---- //---- RendezvousDone event handler end ----
Connection -> Received<messageDataResponse, messageContext> Connection -> Received<messageDataResponse, messageContext>
// Close the Connection in a Receive event handler // Close the Connection in a Receive event handler
Connection.Close() Connection.Close()
3.2. Transport Properties 4. Transport Properties
Each application using the Transport Services Interface declares its Each application using the Transport Services Interface declares its
preferences for how the transport service should operate using preferences for how the transport service should operate using
properties at each stage of the lifetime of a connection using properties at each stage of the lifetime of a connection using
Transport Properties, as defined in [I-D.ietf-taps-arch]. Transport Properties, as defined in [I-D.ietf-taps-arch].
Transport Properties are divided into Selection, Connection, and Transport Properties are divided into Selection, Connection, and
Message Properties. Selection Properties (see The behavior of the Message Properties. Selection Properties (see Section 6.2) can only
selected protocol stack(s) when sending Messages is controlled by be set during pre-establishment. They are only used to specify which
Message Properties (see Section 4.2) can only be set during pre- paths and protocol stacks can be used and are preferred by the
establishment. They are only used to specify which paths and application. Although Connection Properties (see Section 8.1) can be
protocol stacks can be used and are preferred by the application. set during pre-establishment, they may be changed later. They are
Although Connection Properties (see Section 6.1) can be set during used to inform decisions made during establishment and to fine-tune
pre-establishment, they may be changed later. They are used to the established connection. Calling Initiate on a Preconnection
inform decisions made during establishment and to fine-tune the creates an outbound Connection or a Listener, and the Selection
established connection.Section 7.1.3). Properties remain readable from the Connection or Listener, but
become immutable.
All Transport Properties, regardless of the phase in which they are
used, are organized within a single namespace. This enables setting
them as defaults at earlier stages and querying them in later stages:
* Connection Properties can be set on Preconnections and Connections
* Message Properties can be set on Preconnections, Connections and The behavior of the selected protocol stack(s) when sending Messages
Messages is controlled by Message Properties (see Section 9.1.3).
* The effect of Selection Properties can be queried on Connections Selection Properties can be set on Preconnections, and the effect of
and Messages Selection Properties can be queried on Connections and Messages.
Connection Properties can be set on Connections and Preconnections;
when set on Preconnections, they act as an initial default for the
resulting Connections. Message Properties can be set on Messages,
Connections, and Preconnections; when set on the latter two, they act
as an initial default for the Messages sent over those Connections,
Note that configuring Connection Properties and Message Properties on Note that configuring Connection Properties and Message Properties on
Preconnections is preferred over setting them later. Early Preconnections is preferred over setting them later. Early
specification of Connection Properties allows their use as additional specification of Connection Properties allows their use as additional
input to the selection process. Protocol Specific Properties, which input to the selection process. Protocol Specific Properties, which
enable configuration of specialized features of a specific protocol, enable configuration of specialized features of a specific protocol,
see Section 3.2 of [I-D.ietf-taps-arch], are not used as an input to see Section 3.2 of [I-D.ietf-taps-arch], are not used as an input to
the selection process but only support configuration if the the selection process, but only support configuration if the
respective protocol has been selected. respective protocol has been selected.
3.2.1. Transport Property Names 4.1. Transport Property Names
Transport Properties are referred to by property names. For the Transport Properties are referred to by property names. For the
purposes of this document, these names are alphanumeric strings in purposes of this document, these names are alphanumeric strings in
which words may be separated by hyphens. These names serve two which words may be separated by hyphens. These names serve two
purposes: purposes:
* Allowing different components of a TAPS implementation to pass * Allowing different components of a TAPS implementation to pass
Transport Properties, e.g., between a language frontend and a Transport Properties, e.g., between a language frontend and a
policy manager, or as a representation of properties retrieved policy manager, or as a representation of properties retrieved
from a file or other storage. from a file or other storage.
skipping to change at page 13, line 39 skipping to change at page 14, line 39
* Vendor or implementation specific properties MUST use a string * Vendor or implementation specific properties MUST use a string
identifying the vendor or implementation as the Namespace. identifying the vendor or implementation as the Namespace.
Namespaces for each of the keywords provided in the IANA protocol Namespaces for each of the keywords provided in the IANA protocol
numbers registry (see https://www.iana.org/assignments/protocol- numbers registry (see https://www.iana.org/assignments/protocol-
numbers/protocol-numbers.xhtml), reformatted where necessary to numbers/protocol-numbers.xhtml), reformatted where necessary to
conform to an implementation's naming conventions, are reserved for conform to an implementation's naming conventions, are reserved for
Protocol Specific Properties and MUST NOT be used for vendor or Protocol Specific Properties and MUST NOT be used for vendor or
implementation-specific properties. implementation-specific properties.
3.2.2. Transport Property Types 4.2. Transport Property Types
Transport Properties each have a type, which can be:
* One of the basic types described in Section 1.1; or Each Transport Property has a one of the basic types described in
Section 1.1.
* Preference, which is an Enumeration with five possible values: Most Selection Properties (see Section 6.2) are of the Enumeration
Prohibit, Avoid, Ignore, Prefer, or Require. Each of these type, and use the Preference Enumeration, which takes one of five
denotes a level of preference of a given property during protocol possible values (Prohibit, Avoid, Ignore, Prefer, or Require)
selection. (See Section 4.2.) The Preference type is used only denoting the level of preference for a given property during protocol
on Preconnections, and only for Selection Properties. selection.
3.3. Scope of the Interface Definition 5. Scope of the Interface Definition
This document defines a language- and platform-independent interface This document defines a language- and platform-independent interface
to a Transport Services system. Given the wide variety of languages to a Transport Services system. Given the wide variety of languages
and language conventions used to write applications that use the and language conventions used to write applications that use the
transport layer to connect to other applications over the Internet, transport layer to connect to other applications over the Internet,
this independence makes this interface necessarily abstract. this independence makes this interface necessarily abstract.
There is no interoperability benefit in tightly defining how the There is no interoperability benefit in tightly defining how the
interface is presented to application programmers across diverse interface is presented to application programmers across diverse
platforms. However, maintaining the "shape" of the abstract platforms. However, maintaining the "shape" of the abstract
skipping to change at page 15, line 5 skipping to change at page 16, line 5
delivery order for Connections over TCP. Similarly, the "msg- delivery order for Connections over TCP. Similarly, the "msg-
lifetime" Message Property can be implemented but ignored, as the lifetime" Message Property can be implemented but ignored, as the
description of this Property states that "it is not guaranteed description of this Property states that "it is not guaranteed
that a Message will not be sent when its Lifetime has expired". that a Message will not be sent when its Lifetime has expired".
* Implementations may use other representations for Transport * Implementations may use other representations for Transport
Property Names, e.g., by providing constants, but should provide a Property Names, e.g., by providing constants, but should provide a
straight-forward mapping between their representation and the straight-forward mapping between their representation and the
property names specified here. property names specified here.
4. Pre-Establishment Phase 6. Pre-Establishment Phase
The Pre-Establishment phase allows applications to specify properties The Pre-Establishment phase allows applications to specify properties
for the Connections that they are about to make, or to query the API for the Connections that they are about to make, or to query the API
about potential Connections they could make. about potential Connections they could make.
A Preconnection Object represents a potential Connection. It has A Preconnection Object represents a potential Connection. It is a
state that describes the properties of a Connection that might exist passive Object (a data structure) that merely maintains the state
in the future. This state comprises Local Endpoint and Remote that describes the properties of a Connection that might exist in the
Endpoint Objects that denote the endpoints of the potential future. This state comprises Local Endpoint and Remote Endpoint
Connection (see Section 4.1), the Selection Properties (see Objects that denote the endpoints of the potential Connection (see
Section 4.2), any preconfigured Connection Properties (Section 6.1), Section 6.1), the Selection Properties (see Section 6.2), any
and the security parameters (see Section 4.3): preconfigured Connection Properties (Section 8.1), and the security
parameters (see Section 6.3):
Preconnection := NewPreconnection([]LocalEndpoint, Preconnection := NewPreconnection([]LocalEndpoint,
[]RemoteEndpoint, []RemoteEndpoint,
TransportProperties, TransportProperties,
SecurityParameters?) SecurityParameters)
At least one Local Endpoint MUST be specified if the Preconnection is At least one Local Endpoint MUST be specified if the Preconnection is
used to Listen() for incoming Connections, but the list of Local used to Listen() for incoming Connections, but the list of Local
Endpoints MAY be empty if the Preconnection is used to Initiate() Endpoints MAY be empty if the Preconnection is used to Initiate()
connections. If no Local Endpoint is specified, the Transport connections. If no Local Endpoint is specified, the Transport
Services system will assign an ephemeral local port to the Connection Services system will assign an ephemeral local port to the Connection
on the appropriate interface(s). At least one Remote Endpoint MUST on the appropriate interface(s). At least one Remote Endpoint MUST
be specified if the Preconnection is used to Initiate() Connections, be specified if the Preconnection is used to Initiate() Connections,
but the list of Remote Endpoints MAY be empty if the Preconnection is but the list of Remote Endpoints MAY be empty if the Preconnection is
used to Listen() for incoming Connections. At least one Local used to Listen() for incoming Connections. At least one Local
Endpoint and one Remote Endpoint MUST be specified if a peer-to-peer Endpoint and one Remote Endpoint MUST be specified if a peer-to-peer
Rendezvous is to occur based on the Preconnection. Rendezvous() is to occur based on the Preconnection.
If more than one Local Endpoint is specified on a Preconnection, then If more than one Local Endpoint is specified on a Preconnection, then
all the Local Endpoints on the Preconnection MUST represent the same all the Local Endpoints on the Preconnection MUST represent the same
host. For example, they might correspond to different interfaces on host. For example, they might correspond to different interfaces on
a multi-homed host, of they might correspond to local interfaces and a multi-homed host, of they might correspond to local interfaces and
a STUN server that can be resolved to a server reflexive address for a STUN server that can be resolved to a server reflexive address for
a Preconnection used to make a peer-to-peer Rendezvous(). a Preconnection used to make a peer-to-peer Rendezvous().
If more than one Remote Endpoint is specified on the Preconnection, If more than one Remote Endpoint is specified on the Preconnection,
then all the Remote Endpoints on the Preconnection SHOULD represent then all the Remote Endpoints on the Preconnection SHOULD represent
the same host. For example, the Remote Endpoints might represent the same host. For example, the Remote Endpoints might represent
various network interfaces of a host, or a server reflexive address various network interfaces of a host, or a server reflexive address
that can be used to reach a host, or a set of hosts that provide that can be used to reach a host, or a set of hosts that provide
equivalent local balanced service. equivalent local balanced service.
In most cases, it is expected that a single Remote Endpoint will be In most cases, it is expected that a single Remote Endpoint will be
specified by name, and a later call to Initiate() on the specified by name, and a later call to Initiate() on the
Preconnection (see Section 5.1) will internally resolve that name to Preconnection (see Section 7.1) will internally resolve that name to
a list of concrete endpoints. Specifying multiple Remote Endpoints a list of concrete endpoints. Specifying multiple Remote Endpoints
on a Preconnection allows applications to override this for more on a Preconnection allows applications to override this for more
detailed control. detailed control.
Transport Properties MUST always be specified while security If Message Framers are used (see Section 9.1.2), they MUST be added
parameters are OPTIONAL.
If Message Framers are used (see Section 7.1.2), they MUST be added
to the Preconnection during pre-establishment. to the Preconnection during pre-establishment.
4.1. Specifying Endpoints 6.1. Specifying Endpoints
The transport services API uses the Local Endpoint and Remote The transport services API uses the Local Endpoint and Remote
Endpoint Objects to refer to the endpoints of a transport connection. Endpoint Objects to refer to the endpoints of a transport connection.
Endpoints can be created as either Remote or Local: Endpoints can be created as either Remote or Local:
RemoteSpecifier := NewRemoteEndpoint() RemoteSpecifier := NewRemoteEndpoint()
LocalSpecifier := NewLocalEndpoint() LocalSpecifier := NewLocalEndpoint()
A single Endpoint Object represents the identity of a network host. A single Endpoint Object represents the identity of a network host.
That endpoint can be more or less specific depending on which That endpoint can be more or less specific depending on which
identifiers are set. For example, an Endpoint that only specifies a identifiers are set. For example, an Endpoint that only specifies a
hostname may in fact end up corresponding to several different IP hostname may in fact end up corresponding to several different IP
addresses on different hosts. addresses on different hosts.
An Endpoint Object can be configured with the following identifiers: An Endpoint Object can be configured with the following identifiers:
* Hostname (string) * Hostname (string):
RemoteSpecifier.WithHostname("example.com") RemoteSpecifier.WithHostname("example.com")
* Port (a 16-bit integer) or a Service (string) that maps to a port * Port (a 16-bit integer) or a Service (string) that maps to a port:
RemoteSpecifier.WithPort(443) RemoteSpecifier.WithPort(443)
RemoteSpecifier.WithService("https") RemoteSpecifier.WithService("https")
* IP address (IPv4 or IPv6 address) * IP address (IPv4 or IPv6 address):
RemoteSpecifier.WithIPv4Address(192.0.2.21) RemoteSpecifier.WithIPv4Address(192.0.2.21)
RemoteSpecifier.WithIPv6Address(2001:db8:4920:e29d:a420:7461:7073:0a) RemoteSpecifier.WithIPv6Address(2001:db8:4920:e29d:a420:7461:7073:0a)
* Interface (string name) * Interface name (string):
LocalSpecifier.WithInterface("en0") LocalSpecifier.WithInterface("en0")
An Endpoint cannot have multiple identifiers of a same type set. An Endpoint cannot have multiple identifiers of a same type set.
That is, an endpoint cannot have two IP addresses specified. Two That is, an endpoint cannot have two IP addresses specified. Two
separate IP addresses are represented as two Endpoint Objects. If a separate IP addresses are represented as two Endpoint Objects. If a
Preconnection specifies a Remote Endpoint with a specific IP address Preconnection specifies a Remote Endpoint with a specific IP address
set, it will only establish Connections to that IP address. If, on set, it will only establish Connections to that IP address. If, on
the other hand, the Remote Endpoint specifies a hostname but no the other hand, the Remote Endpoint specifies a hostname but no
addresses, the Connection can perform name resolution and attempt addresses, the Connection can perform name resolution and attempt
using any address derived from the original hostname of the Remote using any address derived from the original hostname of the Remote
Endpoint. Endpoint.
The Transport Services API resolves names internally, when the The Transport Services API resolves names internally, when the
Initiate(), Listen(), or Rendezvous() method is called to establish a Initiate(), Listen(), or Rendezvous() method is called to establish a
Connection. Privacy considerations for the timing of this resolution Connection. Privacy considerations for the timing of this resolution
are given in Section 11. are given in Section 13.
The Resolve() action on a Preconnection can be used by the The Resolve() action on a Preconnection can be used by the
application to force early binding when required, for example with application to force early binding when required, for example with
some Network Address Translator (NAT) traversal protocols (see some Network Address Translator (NAT) traversal protocols (see
Section 5.3). Section 7.3).
4.1.1. Using Multicast Endpoints 6.1.1. Using Multicast Endpoints
Specifying a multicast group address on a Local Endpoint will Specifying a multicast group address on a Local Endpoint will
indicate to the transport system that the resulting connection will indicate to the transport system that the resulting connection will
be used to receive multicast messages. The Remote Endpoint can be be used to receive multicast messages. The Remote Endpoint can be
used to filter incoming multicast from specific senders. Such a used to filter incoming multicast from specific senders. Such a
Preconnection will only support calling Listen(), not Initiate(). Preconnection will only support calling Listen(), not Initiate().
The accepted Connections are receive-only. The accepted Connections are receive-only.
Similarly, specifying a multicast group address on the Remote Similarly, specifying a multicast group address on the Remote
Endpoint will indicate that the resulting connection will be used to Endpoint will indicate that the resulting connection will be used to
send multicast messages. send multicast messages.
4.1.2. Endpoint Aliases 6.1.2. Endpoint Aliases
An Endpoint can have an alternative definition when using different An Endpoint can have an alternative definition when using different
protocols. For example, a server that supports both TLS/TCP and QUIC protocols. For example, a server that supports both TLS/TCP and QUIC
may be accessible on two different port numbers depending on which may be accessible on two different port numbers depending on which
protocol is used. protocol is used.
To support this, Endpoint Objects can specify "aliases". An Endpoint To support this, Endpoint Objects can specify "aliases". An Endpoint
can have multiple aliases set. can have multiple aliases set.
RemoteSpecifier.AddAlias(AlternateRemoteSpecifier) RemoteSpecifier.AddAlias(AlternateRemoteSpecifier)
In order to scope an alias to a specific transport protocol, an In order to scope an alias to a specific transport protocol, an
Endpoint can specify a protocol identifier. These identifiers MUST Endpoint can specify a protocol identifier.
only be set for aliases.
RemoteSpecifier.WithProtocol(QUIC) RemoteSpecifier.WithProtocol(QUIC)
The following example shows a case where "example.com" has a server The following example shows a case where "example.com" has a server
running on port 443, with an alternate port of 8443 for QUIC. running on port 443, with an alternate port of 8443 for QUIC.
RemoteSpecifier := NewRemoteEndpoint() RemoteSpecifier := NewRemoteEndpoint()
RemoteSpecifier.WithHostname("example.com") RemoteSpecifier.WithHostname("example.com")
RemoteSpecifier.WithPort(443) RemoteSpecifier.WithPort(443)
QUICRemoteSpecifier := NewRemoteEndpoint() QUICRemoteSpecifier := NewRemoteEndpoint()
QUICRemoteSpecifier.WithHostname("example.com") QUICRemoteSpecifier.WithHostname("example.com")
QUICRemoteSpecifier.WithPort(8443) QUICRemoteSpecifier.WithPort(8443)
QUICRemoteSpecifier.WithProtocol(QUIC) QUICRemoteSpecifier.WithProtocol(QUIC)
RemoteSpecifier.AddAlias(QUICRemoteSpecifier) RemoteSpecifier.AddAlias(QUICRemoteSpecifier)
4.1.3. Endpoint Examples 6.1.3. Endpoint Examples
The following examples of Endpoints show common usage patterns. The following examples of Endpoints show common usage patterns.
Specify a Remote Endpoint using a hostname and service name: Specify a Remote Endpoint using a hostname and service name:
RemoteSpecifier := NewRemoteEndpoint() RemoteSpecifier := NewRemoteEndpoint()
RemoteSpecifier.WithHostname("example.com") RemoteSpecifier.WithHostname("example.com")
RemoteSpecifier.WithService("https") RemoteSpecifier.WithService("https")
Specify a Remote Endpoint using an IPv6 address and remote port: Specify a Remote Endpoint using an IPv6 address and remote port:
skipping to change at page 18, line 52 skipping to change at page 19, line 52
Specify a Local Endpoint using a local interface name and local port: Specify a Local Endpoint using a local interface name and local port:
LocalSpecifier := NewLocalEndpoint() LocalSpecifier := NewLocalEndpoint()
LocalSpecifier.WithInterface("en0") LocalSpecifier.WithInterface("en0")
LocalSpecifier.WithPort(443) LocalSpecifier.WithPort(443)
As an alternative to specifying an interface name for the Local As an alternative to specifying an interface name for the Local
Endpoint, an application can express more fine-grained preferences Endpoint, an application can express more fine-grained preferences
using the "Interface Instance or Type" Selection Property, see using the "Interface Instance or Type" Selection Property, see
Section 4.2.11. However, if the application specifies Selection Section 6.2.11. However, if the application specifies Selection
Properties that are inconsistent with the Local Endpoint, this will Properties that are inconsistent with the Local Endpoint, this will
result in an Error once the application attempts to open a result in an Error once the application attempts to open a
Connection. Connection.
Specify a Local Endpoint using a STUN server: Specify a Local Endpoint using a STUN server:
LocalSpecifier := NewLocalEndpoint() LocalSpecifier := NewLocalEndpoint()
LocalSpecifier.WithStunServer(address, port, credentials) LocalSpecifier.WithStunServer(address, port, credentials)
Specify a Local Endpoint using a Any-Source Multicast group to join Specify a Local Endpoint using an Any-Source Multicast group to join
on a named local interface: on a named local interface:
LocalSpecifier := NewLocalEndpoint() LocalSpecifier := NewLocalEndpoint()
LocalSpecifier.WithIPv4Address(233.252.0.0) LocalSpecifier.WithIPv4Address(233.252.0.0)
LocalSpecifier.WithInterface("en0") LocalSpecifier.WithInterface("en0")
Source-Specific Multicast requires setting both a Local and Remote Source-Specific Multicast requires setting both a Local and Remote
Endpoint: Endpoint:
LocalSpecifier := NewLocalEndpoint() LocalSpecifier := NewLocalEndpoint()
LocalSpecifier.WithIPv4Address(232.1.1.1) LocalSpecifier.WithIPv4Address(232.1.1.1)
LocalSpecifier.WithInterface("en0") LocalSpecifier.WithInterface("en0")
RemoteSpecifier := NewRemoteEndpoint() RemoteSpecifier := NewRemoteEndpoint()
RemoteSpecifier.WithIPv4Address(192.0.2.22) RemoteSpecifier.WithIPv4Address(192.0.2.22)
4.2. Specifying Transport Properties 6.2. Specifying Transport Properties
A Preconnection Object holds properties reflecting the application's A Preconnection Object holds properties reflecting the application's
requirements and preferences for the transport. These include requirements and preferences for the transport. These include
Selection Properties for selecting protocol stacks and paths, as well Selection Properties for selecting protocol stacks and paths, as well
as Connection Properties for configuration of the detailed operation as Connection Properties for configuration of the detailed operation
of the selected Protocol Stacks. of the selected Protocol Stacks.
The protocol(s) and path(s) selected as candidates during The protocol(s) and path(s) selected as candidates during
establishment are determined and configured using these properties. establishment are determined and configured using these properties.
Since there could be paths over which some transport protocols are Since there could be paths over which some transport protocols are
unable to operate, or remote endpoints that support only specific unable to operate, or remote endpoints that support only specific
network addresses or transports, transport protocol selection is network addresses or transports, transport protocol selection is
necessarily tied to path selection. This may involve choosing necessarily tied to path selection. This may involve choosing
between multiple local interfaces that are connected to different between multiple local interfaces that are connected to different
access networks. access networks.
When additional information (such as Provisioning Domain (PvD)
information Path information can include network segment PMTU, set of
supported DSCPs, expected usage, cost, etc. The usage of this
information by the Transport Services System is generally independent
of the specific mechanism/protocol used to receive the information
(e.g. zero-conf, DHCP, or IPv6 RA).[RFC7556]) is available about the
networks over which an endpoint can operate, this can inform the
selection between alternate network paths.
Most Selection Properties are represented as Preferences, which can Most Selection Properties are represented as Preferences, which can
take one of five values: take one of five values:
+============+========================================+ +============+========================================+
| Preference | Effect | | Preference | Effect |
+============+========================================+ +============+========================================+
| Require | Select only protocols/paths providing | | Require | Select only protocols/paths providing |
| | the property, fail otherwise | | | the property, fail otherwise |
+------------+----------------------------------------+ +------------+----------------------------------------+
| Prefer | Prefer protocols/paths providing the | | Prefer | Prefer protocols/paths providing the |
skipping to change at page 20, line 38 skipping to change at page 22, line 9
path selection as well, outcomes can vary given the same Selection path selection as well, outcomes can vary given the same Selection
Properties, because the available protocols and paths can differ Properties, because the available protocols and paths can differ
across systems and contexts. However, implementations are across systems and contexts. However, implementations are
RECOMMENDED to seek to provide a consistent outcome to an RECOMMENDED to seek to provide a consistent outcome to an
application, given the same set of Selection Properties. application, given the same set of Selection Properties.
Note that application preferences can conflict with each other. For Note that application preferences can conflict with each other. For
example, if an application indicates a preference for a specific path example, if an application indicates a preference for a specific path
by specifying an interface, but also a preference for a protocol, a by specifying an interface, but also a preference for a protocol, a
situation might occur in which the preferred protocol is not situation might occur in which the preferred protocol is not
available on the preferred path. In such cases, implementations available on the preferred path. In such cases, applications can
SHOULD prioritize Selection Properties that select paths over those expect properties that determine path selection to be prioritized
that select protocols. Therefore, the transport system SHOULD race over properties that determine protocol selection. The transport
the path first, ignoring the protocol preference if a specific system SHOULD determine the preferred path first, regardless of
protocol does not work on the path. protocol preferences. This ordering is chosen to provide consistency
across implementations, based on the fact that it is more common for
the use of a given network path to determine cost to the user (i.e.,
an interface type preference might be based on a user's preference to
avoid being charged more for a cellular data plan).
Selection and Connection Properties, as well as defaults for Message Selection and Connection Properties, as well as defaults for Message
Properties, can be added to a Preconnection to configure the Properties, can be added to a Preconnection to configure the
selection process and to further configure the eventually selected selection process and to further configure the eventually selected
protocol stack(s). They are collected into a TransportProperties protocol stack(s). They are collected into a TransportProperties
object to be passed into a Preconnection object: object to be passed into a Preconnection object:
TransportProperties := NewTransportProperties() TransportProperties := NewTransportProperties()
Individual properties are then set on the TransportProperties Object. Individual properties are then set on the TransportProperties Object.
Setting a Transport Property to a value overrides the previous value Setting a Transport Property to a value overrides the previous value
of this Transport Property. of this Transport Property.
TransportProperties.Set(property, value) TransportProperties.Set(property, value)
To aid readability, implementations MAY provide additional To aid readability, implementations MAY provide additional
convenience functions to simplify use of Selection Properties: see convenience functions to simplify use of Selection Properties: see
Appendix B.1 for examples. In addition, implementations MAY provide Appendix B.1 for examples. In addition, implementations MAY provide
a mechanism to create TransportProperties objects that are a mechanism to create TransportProperties objects that are
skipping to change at page 21, line 17 skipping to change at page 22, line 40
TransportProperties.Set(property, value) TransportProperties.Set(property, value)
To aid readability, implementations MAY provide additional To aid readability, implementations MAY provide additional
convenience functions to simplify use of Selection Properties: see convenience functions to simplify use of Selection Properties: see
Appendix B.1 for examples. In addition, implementations MAY provide Appendix B.1 for examples. In addition, implementations MAY provide
a mechanism to create TransportProperties objects that are a mechanism to create TransportProperties objects that are
preconfigured for common use cases as outlined in Appendix B.2. preconfigured for common use cases as outlined in Appendix B.2.
Transport Properties for an established connection can be queried via Transport Properties for an established connection can be queried via
the Connection object, as outlined in Section 6. the Connection object, as outlined in Section 8.
A Connection gets its Transport Properties either by being explicitly A Connection gets its Transport Properties either by being explicitly
configured via a Preconnection, by configuration after establishment, configured via a Preconnection, by configuration after establishment,
or by inheriting them from an antecedent via cloning; see Section 5.4 or by inheriting them from an antecedent via cloning; see Section 7.4
for more. for more.
Section 6.1 provides a list of Connection Properties, while Selection Section 8.1 provides a list of Connection Properties, while Selection
Properties are listed in the subsections below. Many properties are Properties are listed in the subsections below. Many properties are
only considered during establishment, and can not be changed after a only considered during establishment, and can not be changed after a
Connection is established; however, they can still be queried. The Connection is established; however, they can still be queried. The
return type of a queried Selection Property is Boolean, where "true" return type of a queried Selection Property is Boolean, where "true"
means that the Selection Property has been applied and "false" means means that the Selection Property has been applied and "false" means
that the Selection Property has not been applied. Note that "true" that the Selection Property has not been applied. Note that "true"
does not mean that a request has been honored. For example, if does not mean that a request has been honored. For example, if
"Congestion control" was requested with preference level "Prefer", "Congestion control" was requested with preference level "Prefer",
but congestion control could not be supported, querying the but congestion control could not be supported, querying the
"congestionControl" property yields the value "false". If the "congestionControl" property yields the value "false". If the
preference level "Avoid" was used for "Congestion control", and, as preference level "Avoid" was used for "Congestion control", and, as
requested, the Connection is not congestion controlled, querying the requested, the Connection is not congestion controlled, querying the
"congestionControl" property also yields the value "false". "congestionControl" property also yields the value "false".
An implementation of this interface must provide sensible defaults An implementation of this interface must provide sensible defaults
for Selection Properties. The recommended default values for each for Selection Properties. The default values for each property below
property below represent a configuration that can be implemented over represent a configuration that can be implemented over TCP. If these
TCP. If these default values are used and TCP is not supported by a default values are used and TCP is not supported by a Transport
Transport Services implementation, then an application using the Services implementation, then an application using the default set of
default set of Properties might not succeed in establishing a Properties might not succeed in establishing a connection. Using the
connection. Using the same default values for independent Transport same default values for independent Transport Services
Services implementations can be beneficial when applications are implementations can be beneficial when applications are ported
ported between different implementations/platforms, even if this between different implementations/platforms, even if this default
default could lead to a connection failure when TCP is not available. could lead to a connection failure when TCP is not available. If
If default values other than those recommended below are used, it is default values other than those suggested below are used, it is
recommended to clearly document any differences. RECOMMENDED to clearly document any differences.
4.2.1. Reliable Data Transfer (Connection) 6.2.1. Reliable Data Transfer (Connection)
Name: reliability Name: reliability
Type: Preference Type: Preference
Default: Require Default: Require
This property specifies whether the application needs to use a This property specifies whether the application needs to use a
transport protocol that ensures that all data is received at the transport protocol that ensures that all data is received at the
Remote Endpoint without corruption. When reliable data transfer is Remote Endpoint without corruption. When reliable data transfer is
enabled, this also entails being notified when a Connection is closed enabled, this also entails being notified when a Connection is closed
or aborted. or aborted.
4.2.2. Preservation of Message Boundaries 6.2.2. Preservation of Message Boundaries
Name: preserveMsgBoundaries Name: preserveMsgBoundaries
Type: Preference Type: Preference
Default: Prefer Default: Ignore
This property specifies whether the application needs or prefers to This property specifies whether the application needs or prefers to
use a transport protocol that preserves message boundaries. use a transport protocol that preserves message boundaries.
4.2.3. Configure Per-Message Reliability 6.2.3. Configure Per-Message Reliability
Name: perMsgReliability Name: perMsgReliability
Type: Preference Type: Preference
Default: Ignore Default: Ignore
This property specifies whether an application considers it useful to This property specifies whether an application considers it useful to
indicate its reliability requirements on a per-Message basis. This specify different reliability requirements for individual Messages in
property applies to Connections and Connection Groups. a Connection.
4.2.4. Preservation of Data Ordering 6.2.4. Preservation of Data Ordering
Name: preserveOrder Name: preserveOrder
Type: Preference Type: Preference
Default: Require Default: Require
This property specifies whether the application wishes to use a This property specifies whether the application wishes to use a
transport protocol that can ensure that data is received by the transport protocol that can ensure that data is received by the
application on the other end in the same order as it was sent. application on the other end in the same order as it was sent.
4.2.5. Use 0-RTT Session Establishment with a Safely Replayable Message 6.2.5. Use 0-RTT Session Establishment with a Safely Replayable Message
Name: zeroRttMsg Name: zeroRttMsg
Type: Preference Type: Preference
Default: Ignore Default: Ignore
This property specifies whether an application would like to supply a This property specifies whether an application would like to supply a
Message to the transport protocol before Connection establishment Message to the transport protocol before Connection establishment
that will then be reliably transferred to the other side before or that will then be reliably transferred to the other side before or
during Connection establishment. This Message can potentially be during Connection establishment. This Message can potentially be
received multiple times (i.e., multiple copies of the message data received multiple times (i.e., multiple copies of the message data
may be passed to the Remote Endpoint). See also Section 7.1.3.4. may be passed to the Remote Endpoint). See also Section 9.1.3.4.
Note that disabling this property has no effect for protocols that
are not connection-oriented and do not protect against duplicated
messages, e.g., UDP.
4.2.6. Multistream Connections in Group 6.2.6. Multistream Connections in Group
Name: multistreaming Name: multistreaming
Type: Preference Type: Preference
Default: Prefer Default: Prefer
This property specifies that the application would prefer multiple This property specifies that the application would prefer multiple
Connections within a Connection Group to be provided by streams of a Connections within a Connection Group to be provided by streams of a
single underlying transport connection where possible. single underlying transport connection where possible.
4.2.7. Full Checksum Coverage on Sending 6.2.7. Full Checksum Coverage on Sending
Name: perMsgChecksumLenSend Name: FullChecksumSend
Type: Preference Type: Preference
Default: Require Default: Require
This property specifies the application's need for protection against This property specifies the application's need for protection against
corruption for all data transmitted on this Connection. Disabling corruption for all data transmitted on this Connection. Disabling
this property could enable later control of the sender checksum this property could enable later control of the sender checksum
coverage (see Section 7.1.3.6). coverage (see Section 9.1.3.6).
4.2.8. Full Checksum Coverage on Receiving 6.2.8. Full Checksum Coverage on Receiving
Name: perMsgChecksumLenRecv Name: FullChecksumRecv
Type: Preference Type: Preference
Default: Require Default: Require
This property specifies the application's need for protection against This property specifies the application's need for protection against
corruption for all data received on this Connection. Disabling this corruption for all data received on this Connection. Disabling this
property could enable later control of the required minimum receiver property could enable later control of the required minimum receiver
checksum coverage (see Section 6.1.1). checksum coverage (see Section 8.1.1).
4.2.9. Congestion control 6.2.9. Congestion control
Name: congestionControl Name: congestionControl
Type: Preference Type: Preference
Default: Require Default: Require
This property specifies whether the application would like the This property specifies whether the application would like the
Connection to be congestion controlled or not. Note that if a Connection to be congestion controlled or not. Note that if a
Connection is not congestion controlled, an application using such a Connection is not congestion controlled, an application using such a
Connection SHOULD itself perform congestion control in accordance Connection SHOULD itself perform congestion control in accordance
with [RFC2914] or use a circuit breaker in accordance with [RFC8084], with [RFC2914] or use a circuit breaker in accordance with [RFC8084],
whichever is appropriate. Also note that reliability is usually whichever is appropriate. Also note that reliability is usually
combined with congestion control in protocol implementations, combined with congestion control in protocol implementations,
rendering "reliable but not congestion controlled" a request that is rendering "reliable but not congestion controlled" a request that is
unlikely to succeed. If the Connection is congestion controlled, unlikely to succeed. If the Connection is congestion controlled,
performing additional congestion control in the application can have performing additional congestion control in the application can have
skipping to change at page 24, line 31 skipping to change at page 26, line 16
Connection is not congestion controlled, an application using such a Connection is not congestion controlled, an application using such a
Connection SHOULD itself perform congestion control in accordance Connection SHOULD itself perform congestion control in accordance
with [RFC2914] or use a circuit breaker in accordance with [RFC8084], with [RFC2914] or use a circuit breaker in accordance with [RFC8084],
whichever is appropriate. Also note that reliability is usually whichever is appropriate. Also note that reliability is usually
combined with congestion control in protocol implementations, combined with congestion control in protocol implementations,
rendering "reliable but not congestion controlled" a request that is rendering "reliable but not congestion controlled" a request that is
unlikely to succeed. If the Connection is congestion controlled, unlikely to succeed. If the Connection is congestion controlled,
performing additional congestion control in the application can have performing additional congestion control in the application can have
negative performance implications. negative performance implications.
4.2.10. Keep alive 6.2.10. Keep alive
Name: keepAlive Name: keepAlive
Type: Preference Type: Preference
Default: Ignore Default: Ignore
This property specifies whether the application would like the This property specifies whether the application would like the
Connection to send keep-alive packets or not. Note that if a Connection to send keep-alive packets or not. Note that if a
Connection determines that keep-alive packets are being sent, the Connection determines that keep-alive packets are being sent, the
applicaton should itself avoid generating additional keep alive applicaton should itself avoid generating additional keep alive
messages. Note that when supported, the system will use the default messages. Note that when supported, the system will use the default
period for generation of the keep alive-packets. (See also period for generation of the keep alive-packets. (See also
Section 6.1.4). Section 8.1.4).
4.2.11. Interface Instance or Type 6.2.11. Interface Instance or Type
Name: interface Name: interface
Type: Collection of (Preference, Enumeration) Type: Collection of (Preference, Enumeration)
Default: Empty (not setting a preference for any interface) Default: Empty (not setting a preference for any interface)
This property allows the application to select any specific network This property allows the application to select any specific network
interfaces or categories of interfaces it wants to "Require", interfaces or categories of interfaces it wants to "Require",
"Prohibit", "Prefer", or "Avoid". Note that marking a specific "Prohibit", "Prefer", or "Avoid". Note that marking a specific
interface as "Require" strictly limits path selection to that single interface as "Require" strictly limits path selection to that single
interface, and often leads to less flexible and resilient connection interface, and often leads to less flexible and resilient connection
establishment. establishment.
In contrast to other Selection Properties, this property is a tuple In contrast to other Selection Properties, this property is a tuple
skipping to change at page 25, line 24 skipping to change at page 27, line 10
of an (Enumerated) interface identifier and a preference, and can of an (Enumerated) interface identifier and a preference, and can
either be implemented directly as such, or for making one preference either be implemented directly as such, or for making one preference
available for each interface and interface type available on the available for each interface and interface type available on the
system. system.
The set of valid interface types is implementation- and system- The set of valid interface types is implementation- and system-
specific. For example, on a mobile device, there may be "Wi-Fi" and specific. For example, on a mobile device, there may be "Wi-Fi" and
"Cellular" interface types available; whereas on a desktop computer, "Cellular" interface types available; whereas on a desktop computer,
"Wi-Fi" and "Wired Ethernet" interface types might be available. An "Wi-Fi" and "Wired Ethernet" interface types might be available. An
implementation should provide all types that are supported on the implementation should provide all types that are supported on the
local system to all remote systems, to allow applications to be local system, to allow applications to be written generically. For
written generically. For example, if a single implementation is used example, if a single implementation is used on both mobile devices
on both mobile devices and desktop devices, it should define the and desktop devices, it should define the "Cellular" interface type
"Cellular" interface type for both systems, since an application for both systems, since an application might wish to always prohibit
might wish to always prohibit cellular. cellular.
The set of interface types is expected to change over time as new The set of interface types is expected to change over time as new
access technologies become available. The taxonomy of interface access technologies become available. The taxonomy of interface
types on a given Transport Services system is implementation- types on a given Transport Services system is implementation-
specific. specific.
Interface types should not be treated as a proxy for properties of Interface types should not be treated as a proxy for properties of
interfaces such as metered or unmetered network access. If an interfaces such as metered or unmetered network access. If an
application needs to prohibit metered interfaces, this should be application needs to prohibit metered interfaces, this should be
specified via Provisioning Domain attributes (see Section 4.2.12) or specified via Provisioning Domain attributes (see Section 6.2.12) or
another specific property. another specific property.
4.2.12. Provisioning Domain Instance or Type 6.2.12. Provisioning Domain Instance or Type
Name: pvd Name: pvd
Type: Collection of (Preference, Enumeration) Type: Collection of (Preference, Enumeration)
Default: Empty (not setting a preference for any PvD) Default: Empty (not setting a preference for any PvD)
Similar to interface instances and types (see Section 4.2.11), this Similar to interface instances and types (see Section 6.2.11), this
property allows the application to control path selection by property allows the application to control path selection by
selecting which specific Provisioning Domain (PvD) or categories of selecting which specific Provisioning Domain (PvD) or categories of
PVDs it wants to "Require", "Prohibit", "Prefer", or "Avoid". PVDs it wants to "Require", "Prohibit", "Prefer", or "Avoid".
Provisioning Domains define consistent sets of network properties Provisioning Domains define consistent sets of network properties
that may be more specific than network interfaces [RFC7556]. that may be more specific than network interfaces [RFC7556].
As with interface instances and types, this property is a tuple of an As with interface instances and types, this property is a tuple of an
(Enumerated) PvD identifier and a preference, and can either be (Enumerated) PvD identifier and a preference, and can either be
implemented directly as such, or for making one preference available implemented directly as such, or for making one preference available
for each interface and interface type available on the system. for each interface and interface type available on the system.
skipping to change at page 26, line 29 skipping to change at page 28, line 15
Categories or types of PvDs are also defined to be implementation- Categories or types of PvDs are also defined to be implementation-
and system-specific. These can be useful to identify a service that and system-specific. These can be useful to identify a service that
is provided by a PvD. For example, if an application wants to use a is provided by a PvD. For example, if an application wants to use a
PvD that provides a Voice-Over-IP service on a Cellular network, it PvD that provides a Voice-Over-IP service on a Cellular network, it
can use the relevant PvD type to require a PvD that provides this can use the relevant PvD type to require a PvD that provides this
service, without needing to look up a particular instance. While service, without needing to look up a particular instance. While
this does restrict path selection, it is broader than requiring this does restrict path selection, it is broader than requiring
specific PvD instances or interface instances, and should be specific PvD instances or interface instances, and should be
preferred over these options. preferred over these options.
4.2.13. Use Temporary Local Address 6.2.13. Use Temporary Local Address
Name: useTemporaryLocalAddress Name: useTemporaryLocalAddress
Type: Preference Type: Preference
Default: Avoid for Listeners and Rendezvous Connections. Prefer for Default: Avoid for Listeners and Rendezvous Connections. Prefer for
other Connections. other Connections.
This property allows the application to express a preference for the This property allows the application to express a preference for the
use of temporary local addresses, sometimes called "privacy" use of temporary local addresses, sometimes called "privacy"
skipping to change at page 27, line 5 skipping to change at page 28, line 37
prevent linking connections over time when a stable address, prevent linking connections over time when a stable address,
sometimes called "permanent" address, is not needed. There are some sometimes called "permanent" address, is not needed. There are some
caveats to note when specifying this property. First, if an caveats to note when specifying this property. First, if an
application Requires the use of temporary addresses, the resulting application Requires the use of temporary addresses, the resulting
Connection cannot use IPv4, because temporary addresses do not exist Connection cannot use IPv4, because temporary addresses do not exist
in IPv4. Second, temporary local addresses might involve trading off in IPv4. Second, temporary local addresses might involve trading off
privacy for performance. For instance, temporary addresses can privacy for performance. For instance, temporary addresses can
interfere with resumption mechanisms that some protocols rely on to interfere with resumption mechanisms that some protocols rely on to
reduce initial latency. reduce initial latency.
4.2.14. Multipath Transport 6.2.14. Multipath Transport
Name: multipath Name: multipath
Type: Enumeration Type: Enumeration
Default: Disabled for connections created through initiate and Default: Disabled for connections created through initiate and
rendezvous, Passive for listeners rendezvous, Passive for listeners
This property specifies whether and how applications want to take This property specifies whether and how applications want to take
advantage of transferring data across multiple paths between the same advantage of transferring data across multiple paths between the same
skipping to change at page 27, line 28 skipping to change at page 29, line 11
performance properties change. Possible values are: performance properties change. Possible values are:
Disabled: The connection will not use multiple paths once Disabled: The connection will not use multiple paths once
established, even if the chosen transport supports using multiple established, even if the chosen transport supports using multiple
paths. paths.
Active: The connection will negotiate the use of multiple paths if Active: The connection will negotiate the use of multiple paths if
the chosen transport supports this. the chosen transport supports this.
Passive: The connection will support the use of multiple paths if Passive: The connection will support the use of multiple paths if
the remote endpoint requests it. the Remote Endpoint requests it.
The policy for using multiple paths is specified using the separate The policy for using multiple paths is specified using the separate
"multipath-policy" property, see Section 6.1.7 below. To enable the "multipath-policy" property, see Section 8.1.7 below. To enable the
peer endpoint to initiate additional paths towards a local address peer endpoint to initiate additional paths towards a local address
other than the one initially used, it is necessary to set the other than the one initially used, it is necessary to set the
Alternative Addresses property (see Section 4.2.15 below). Alternative Addresses property (see Section 6.2.15 below).
Setting this property to "Active", can have privacy implications: It Setting this property to "Active", can have privacy implications: It
enables the transport to establish connectivity using alternate paths enables the transport to establish connectivity using alternate paths
that might result in users being linkable across the multiple paths, that might result in users being linkable across the multiple paths,
even if the Advertisement of Alternative Addresses property (see even if the Advertisement of Alternative Addresses property (see
Section 4.2.15 below) is set to false. Section 6.2.15 below) is set to false.
Enumeration values other than "Disabled" are interpreted as a Note that Multipath Transport has no corresponding Selection Property
preference for choosing protocols that can make use of multiple of type Preference. Enumeration values other than "Disabled" are
paths. The "Disabled" value implies a requirement not to use interpreted as a preference for choosing protocols that can make use
multiple paths in parallel but does not prevent choosing a protocol of multiple paths. The "Disabled" value implies a requirement not to
that is capable of using multiple paths, e.g., it does not prevent use multiple paths in parallel but does not prevent choosing a
choosing TCP, but prevents sending the "MP_CAPABLE" option in the TCP protocol that is capable of using multiple paths, e.g., it does not
handshake. prevent choosing TCP, but prevents sending the "MP_CAPABLE" option in
the TCP handshake.
4.2.15. Advertisement of Alternative Addresses 6.2.15. Advertisement of Alternative Addresses
Name: advertises-altaddr Name: advertises-altaddr
Type: Boolean Type: Boolean
Default: False Default: False
This property specifies whether alternative addresses, e.g., of other This property specifies whether alternative addresses, e.g., of other
interfaces, should be advertised to the peer endpoint by the protocol interfaces, should be advertised to the peer endpoint by the protocol
stack. Advertising these addresses enables the peer-endpoint to stack. Advertising these addresses enables the peer-endpoint to
establish additional connectivity, e.g., for connection migration or establish additional connectivity, e.g., for connection migration or
using multiple paths. using multiple paths.
Note that this can have privacy implications because it might result Note that this can have privacy implications because it might result
in users being linkable across the multiple paths. Also, note that in users being linkable across the multiple paths. Also, note that
setting this to false does not prevent the local Transport Services setting this to false does not prevent the local Transport Services
system from _establishing_ connectivity using alternate paths (see system from _establishing_ connectivity using alternate paths (see
Section 4.2.14 above); it only prevents _proactive advertisement_ of Section 6.2.14 above); it only prevents _proactive advertisement_ of
addresses. addresses.
4.2.16. Direction of communication 6.2.16. Direction of communication
Name: direction Name: direction
Type: Enumeration Type: Enumeration
Default: Bidirectional Default: Bidirectional
This property specifies whether an application wants to use the This property specifies whether an application wants to use the
connection for sending and/or receiving data. Possible values are: connection for sending and/or receiving data. Possible values are:
skipping to change at page 29, line 5 skipping to change at page 30, line 37
the application cannot use the connection to receive any data the application cannot use the connection to receive any data
Unidirectional receive: The connection must support receiving data, Unidirectional receive: The connection must support receiving data,
and the application cannot use the connection to send any data and the application cannot use the connection to send any data
Since unidirectional communication can be supported by transports Since unidirectional communication can be supported by transports
offering bidirectional communication, specifying unidirectional offering bidirectional communication, specifying unidirectional
communication may cause a transport stack that supports bidirectional communication may cause a transport stack that supports bidirectional
communication to be selected. communication to be selected.
4.2.17. Notification of ICMP soft error message arrival 6.2.17. Notification of ICMP soft error message arrival
Name: softErrorNotify Name: softErrorNotify
Type: Preference Type: Preference
Default: Ignore Default: Ignore
This property specifies whether an application considers it useful to This property specifies whether an application considers it useful to
be informed when an ICMP error message arrives that does not force be informed when an ICMP error message arrives that does not force
termination of a connection. When set to true, received ICMP errors termination of a connection. When set to true, received ICMP errors
are available as SoftErrors, see Section 6.3.1. Note that even if a are available as SoftErrors, see Section 8.3.1. Note that even if a
protocol supporting this property is selected, not all ICMP errors protocol supporting this property is selected, not all ICMP errors
will necessarily be delivered, so applications cannot rely upon will necessarily be delivered, so applications cannot rely upon
receiving them [RFC8085]. receiving them [RFC8085].
4.2.18. Initiating side is not the first to write 6.2.18. Initiating side is not the first to write
Name: activeReadBeforeSend Name: activeReadBeforeSend
Type: Preference Type: Preference
Default: Ignore Default: Ignore
The most common client-server communication pattern involves the The most common client-server communication pattern involves the
client actively opening a connection, then sending data to the client actively opening a connection, then sending data to the
server. The server listens (passive open), reads, and then answers. server. The server listens (passive open), reads, and then answers.
skipping to change at page 29, line 43 skipping to change at page 31, line 27
this pattern - either by actively opening with Initiate(), this pattern - either by actively opening with Initiate(),
immediately followed by reading, or passively opening with Listen(), immediately followed by reading, or passively opening with Listen(),
immediately followed by writing. This property is ignored when immediately followed by writing. This property is ignored when
establishing connections using Rendezvous(). Requiring this property establishing connections using Rendezvous(). Requiring this property
limits the choice of mappings to underlying protocols, which can limits the choice of mappings to underlying protocols, which can
reduce efficiency. For example, it prevents the Transport Services reduce efficiency. For example, it prevents the Transport Services
system from mapping Connections to SCTP streams, where the first system from mapping Connections to SCTP streams, where the first
transmitted data takes the role of an active open signal transmitted data takes the role of an active open signal
[I-D.ietf-taps-impl]. [I-D.ietf-taps-impl].
4.3. Specifying Security Parameters and Callbacks 6.3. Specifying Security Parameters and Callbacks
Most security parameters, e.g., TLS ciphersuites, local identity and Most security parameters, e.g., TLS ciphersuites, local identity and
private key, etc., may be configured statically. Others are private key, etc., may be configured statically. Others are
dynamically configured during connection establishment. Security dynamically configured during connection establishment. Security
parameters and callbacks are partitioned based on their place in the parameters and callbacks are partitioned based on their place in the
lifetime of connection establishment. Similar to Transport lifetime of connection establishment. Similar to Transport
Properties, both parameters and callbacks are inherited during Properties, both parameters and callbacks are inherited during
cloning (see Section 5.4). cloning (see Section 7.4).
4.3.1. Pre-Connection Parameters 6.3.1. Specifying Security Parameters on a Pre-Connection
Common parameters such as TLS ciphersuites are known to Common security parameters such as TLS ciphersuites are known to
implementations. Clients should use common safe defaults for these implementations. Clients should use common safe defaults for these
values whenever possible. However, as discussed in [RFC8922], many values whenever possible. However, as discussed in [RFC8922], many
transport security protocols require specific security parameters and transport security protocols require specific security parameters and
constraints from the client at the time of configuration and actively constraints from the client at the time of configuration and actively
during a handshake. These configuration parameters need to be during a handshake. These configuration parameters need to be
specified in the pre-connection phase and are created as follows: specified in the pre-connection phase and are created as follows:
SecurityParameters := NewSecurityParameters() SecurityParameters := NewSecurityParameters()
Security configuration parameters and sample usage follow: Security configuration parameters and sample usage follow:
skipping to change at page 31, line 4 skipping to change at page 32, line 37
associated with some identity that typically identifies its use or associated with some identity that typically identifies its use or
has some protocol-specific meaning to the Remote Endpoint. has some protocol-specific meaning to the Remote Endpoint.
SecurityParameters.Set(pre-shared-key, key, identity) SecurityParameters.Set(pre-shared-key, key, identity)
* Session cache management: Used to tune session cache capacity, * Session cache management: Used to tune session cache capacity,
lifetime, and other policies. lifetime, and other policies.
SecurityParameters.Set(max-cached-sessions, 16) SecurityParameters.Set(max-cached-sessions, 16)
SecurityParameters.Set(cached-session-lifetime-seconds, 3600) SecurityParameters.Set(cached-session-lifetime-seconds, 3600)
Connections that use Transport Services SHOULD use security in
general. However, for compatibility with endpoints that do not
support transport security protocols (such as a TCP endpoint that
does not support TLS), applications can initialize their security
parameters to indicate that security can be disabled, or can be
opportunistic. If security is disabled, the Transport Services
system will not attempt to add transport security automatically. If
security is opportunistic, it will allow Connections without
transport security, but will still attempt to use security if
available.
SecurityParameters := NewDisabledSecurityParameters()
SecurityParameters := NewOpportunisticSecurityParameters()
Representation of Security Parameters in implementations should Representation of Security Parameters in implementations should
parallel that chosen for Transport Property names as recommended in parallel that chosen for Transport Property names as sugggested in
Section 3.3. Section 5.
4.3.2. Connection Establishment Callbacks 6.3.2. Connection Establishment Callbacks
Security decisions, especially pertaining to trust, are not static. Security decisions, especially pertaining to trust, are not static.
Once configured, parameters may also be supplied during connection Once configured, parameters may also be supplied during connection
establishment. These are best handled as client-provided callbacks. establishment. These are best handled as client-provided callbacks.
Security handshake callbacks that may be invoked during connection Callbacks block the progress of the connection establishment, which
establishment include: distinguishes them from other Events in the transport system. How
callbacks and events are implemented is specific to each
implementation. Security handshake callbacks that may be invoked
during connection establishment include:
* Trust verification callback: Invoked when a Remote Endpoint's * Trust verification callback: Invoked when a Remote Endpoint's
trust must be validated before the handshake protocol can trust must be validated before the handshake protocol can
continue. continue.
TrustCallback := NewCallback({ TrustCallback := NewCallback({
// Handle trust, return the result // Handle trust, return the result
}) })
SecurityParameters.SetTrustVerificationCallback(trustCallback) SecurityParameters.SetTrustVerificationCallback(trustCallback)
* Identity challenge callback: Invoked when a private key operation * Identity challenge callback: Invoked when a private key operation
is required, e.g., when local authentication is requested by a is required, e.g., when local authentication is requested by a
remote. Remote Endpoint.
ChallengeCallback := NewCallback({ ChallengeCallback := NewCallback({
// Handle challenge // Handle challenge
}) })
SecurityParameters.SetIdentityChallengeCallback(challengeCallback) SecurityParameters.SetIdentityChallengeCallback(challengeCallback)
5. Establishing Connections 7. Establishing Connections
Before a Connection can be used for data transfer, it needs to be Before a Connection can be used for data transfer, it needs to be
established. Establishment ends the pre-establishment phase; all established. Establishment ends the pre-establishment phase; all
transport properties and cryptographic parameter specification must transport properties and cryptographic parameter specification must
be complete before establishment, as these will be used to select be complete before establishment, as these will be used to select
candidate Paths and Protocol Stacks for the Connection. candidate Paths and Protocol Stacks for the Connection.
Establishment may be active, using the Initiate() Action; passive, Establishment may be active, using the Initiate() Action; passive,
using the Listen() Action; or simultaneous for peer-to-peer, using using the Listen() Action; or simultaneous for peer-to-peer, using
the Rendezvous() Action. These Actions are described in the the Rendezvous() Action. These Actions are described in the
subsections below. subsections below.
5.1. Active Open: Initiate 7.1. Active Open: Initiate
Active open is the Action of establishing a Connection to a Remote Active open is the Action of establishing a Connection to a Remote
Endpoint presumed to be listening for incoming Connection requests. Endpoint presumed to be listening for incoming Connection requests.
Active open is used by clients in client-server interactions. Active Active open is used by clients in client-server interactions. Active
open is supported by this interface through the Initiate Action: open is supported by this interface through the Initiate Action:
Connection := Preconnection.Initiate(timeout?) Connection := Preconnection.Initiate(timeout?)
The timeout parameter specifies how long to wait before aborting The timeout parameter specifies how long to wait before aborting
Active open. Before calling Initiate, the caller must have populated Active open. Before calling Initiate, the caller must have populated
skipping to change at page 32, line 21 skipping to change at page 34, line 28
to determine a suitable Local Endpoint), as well as all properties to determine a suitable Local Endpoint), as well as all properties
necessary for candidate selection. necessary for candidate selection.
The Initiate() Action returns a Connection object. Once Initiate() The Initiate() Action returns a Connection object. Once Initiate()
has been called, any changes to the Preconnection MUST NOT have any has been called, any changes to the Preconnection MUST NOT have any
effect on the Connection. However, the Preconnection can be reused, effect on the Connection. However, the Preconnection can be reused,
e.g., to Initiate another Connection. e.g., to Initiate another Connection.
Once Initiate is called, the candidate Protocol Stack(s) may cause Once Initiate is called, the candidate Protocol Stack(s) may cause
one or more candidate transport-layer connections to be created to one or more candidate transport-layer connections to be created to
the specified remote endpoint. The caller may immediately begin the specified Remote Endpoint. The caller may immediately begin
sending Messages on the Connection (see Section 7.2) after calling sending Messages on the Connection (see Section 9.2) after calling
Initiate(); note that any data marked "Safely Replayable" that is Initiate(); note that any data marked "Safely Replayable" that is
sent while the Connection is being established may be sent multiple sent while the Connection is being established may be sent multiple
times or on multiple candidates. times or on multiple candidates.
The following Events may be sent by the Connection after Initiate() The following Events may be sent by the Connection after Initiate()
is called: is called:
Connection -> Ready<> Connection -> Ready<>
The Ready Event occurs after Initiate has established a transport- The Ready Event occurs after Initiate has established a transport-
layer connection on at least one usable candidate Protocol Stack over layer connection on at least one usable candidate Protocol Stack over
at least one candidate Path. No Receive Events (see Section 7.3) at least one candidate Path. No Receive Events (see Section 9.3)
will occur before the Ready Event for Connections established using will occur before the Ready Event for Connections established using
Initiate. Initiate.
Connection -> EstablishmentError<reason?> Connection -> EstablishmentError<reason?>
An EstablishmentError occurs either when the set of transport An EstablishmentError occurs either when the set of transport
properties and security parameters cannot be fulfilled on a properties and security parameters cannot be fulfilled on a
Connection for initiation (e.g., the set of available Paths and/or Connection for initiation (e.g., the set of available Paths and/or
Protocol Stacks meeting the constraints is empty) or reconciled with Protocol Stacks meeting the constraints is empty) or reconciled with
the Local and/or Remote Endpoints; when the remote specifier cannot the Local and/or Remote Endpoints; when the remote specifier cannot
be resolved; or when no transport-layer connection can be established be resolved; or when no transport-layer connection can be established
to the Remote Endpoint (e.g., because the Remote Endpoint is not to the Remote Endpoint (e.g., because the Remote Endpoint is not
accepting connections, the application is prohibited from opening a accepting connections, the application is prohibited from opening a
Connection by the operating system, or the establishment attempt has Connection by the operating system, or the establishment attempt has
timed out for any other reason). timed out for any other reason).
Connection establishment and transmission of the first message can be Connection establishment and transmission of the first message can be
combined in a single action Section 7.2.5. combined in a single action Section 9.2.5.
5.2. Passive Open: Listen 7.2. Passive Open: Listen
Passive open is the Action of waiting for Connections from Remote Passive open is the Action of waiting for Connections from Remote
Endpoints, commonly used by servers in client-server interactions. Endpoints, commonly used by servers in client-server interactions.
Passive open is supported by this interface through the Listen Action Passive open is supported by this interface through the Listen Action
and returns a Listener object: and returns a Listener object:
Listener := Preconnection.Listen() Listener := Preconnection.Listen()
Before calling Listen, the caller must have initialized the Before calling Listen, the caller must have initialized the
Preconnection during the pre-establishment phase with a Local Preconnection during the pre-establishment phase with a Local
skipping to change at page 34, line 18 skipping to change at page 36, line 27
Parameters of the Preconnection cannot be fulfilled for listening or Parameters of the Preconnection cannot be fulfilled for listening or
cannot be reconciled with the Local Endpoint (and/or Remote Endpoint, cannot be reconciled with the Local Endpoint (and/or Remote Endpoint,
if specified), when the Local Endpoint (or Remote Endpoint, if if specified), when the Local Endpoint (or Remote Endpoint, if
specified) cannot be resolved, or when the application is prohibited specified) cannot be resolved, or when the application is prohibited
from listening by policy. from listening by policy.
Listener -> Stopped<> Listener -> Stopped<>
A Stopped Event occurs after the Listener has stopped listening. A Stopped Event occurs after the Listener has stopped listening.
5.3. Peer-to-Peer Establishment: Rendezvous 7.3. Peer-to-Peer Establishment: Rendezvous
Simultaneous peer-to-peer Connection establishment is supported by Simultaneous peer-to-peer Connection establishment is supported by
the Rendezvous() Action: the Rendezvous() Action:
Preconnection.Rendezvous() Preconnection.Rendezvous()
A Preconnection Object used in a Rendezvous() MUST have both the A Preconnection Object used in a Rendezvous() MUST have both the
Local Endpoint candidates and the Remote Endpoint candidates Local Endpoint candidates and the Remote Endpoint candidates
specified, along with the transport properties and security specified, along with the transport properties and security
parameters needed for Protocol Stack selection, before the parameters needed for Protocol Stack selection, before the
skipping to change at page 36, line 5 skipping to change at page 38, line 14
An EstablishmentError occurs either when the Properties and Security An EstablishmentError occurs either when the Properties and Security
Parameters of the Preconnection cannot be fulfilled for rendezvous or Parameters of the Preconnection cannot be fulfilled for rendezvous or
cannot be reconciled with the Local and/or Remote Endpoints, when the cannot be reconciled with the Local and/or Remote Endpoints, when the
Local Endpoint or Remote Endpoint cannot be resolved, when no Local Endpoint or Remote Endpoint cannot be resolved, when no
transport-layer connection can be established to the Remote Endpoint, transport-layer connection can be established to the Remote Endpoint,
or when the application is prohibited from rendezvous by policy: or when the application is prohibited from rendezvous by policy:
Preconnection -> EstablishmentError<reason?> Preconnection -> EstablishmentError<reason?>
5.4. Connection Groups 7.4. Connection Groups
Entangled Connections can be created using the Clone Action: Connection Groups can be created using the Clone Action:
Connection := Connection.Clone() Connection := Connection.Clone(framer?)
Calling Clone on a Connection yields a group of Connections: the Calling Clone on a Connection yields a Connection Group containing
parent Connection on which Clone was called, and a resulting cloned two Connections: the parent Connection on which Clone was called, and
Connection. The connections within a group are "entangled" with each a resulting cloned Connection. The new Connection is actively
other, and become part of a Connection Group. Calling Clone on any openend, and it will send a Ready Event or an EstablishmentError
of these Connections adds another Connection to the Connection Group, Event. Calling Clone on any of these Connections adds another
and so on. "Entangled" Connections share all Connection Properties Connection to the Connection Group. Connections in a Connection
except "Connection Priority" (see Section 6.1.2) . Like all other Group share all Connection Properties except "Connection Priority"
Properties, Connection Priority is copied to the new Connection when (see Section 8.1.2), and these Connection Properties are entangled:
calling Clone(), but it is not entangled: Changing Connection Changing one of the Connection Properties on one Connection in the
Priority on one Connection does not change it on the other Connection Group automatically changes the Connection Property for
Connections in the same Connection Group. all others. For example, changing "Timeout for aborting Connection"
(see Section 8.1.3) on one Connection in a Connection Group will
automatically make the same change to this Connection Property for
all other Connections in the Connection Group. Like all other
Properties, "Connection Priority" is copied to the new Connection
when calling Clone(), but in this case, a later change to the
"Connection Priority" on one Connection does not change it on the
other Connections in the same Connection Group.
The stack of Message Framers associated with a Connection are also Message Properties are also not entangled. For example, changing
copied to the cloned Connection when calling Clone. In other words, "Lifetime" (see Section 9.1.3.1) of a Message will only affect a
a cloned Connection has the same stack of Message Framers as the single Message on a single Connection.
Connection from which they are Cloned, but these Framers may
internally maintain per-Connection state. A new Connection created by Clone can have a Message Framer assigned
via the optional "framer" parameter of the Clone Action. If this
parameter is not supplied, the stack of Message Framers associated
with a Connection is copied to the cloned Connection when calling
Clone. Then, a cloned Connection has the same stack of Message
Framers as the Connection from which they are Cloned, but these
Framers may internally maintain per-Connection state.
It is also possible to check which Connections belong to the same It is also possible to check which Connections belong to the same
Connection Group. Calling GroupedConnections() on a specific Connection Group. Calling GroupedConnections() on a specific
Connection returns a set of all Connections in the same group. Connection returns a set of all Connections in the same group.
[]Connection := Connection.GroupedConnections() []Connection := Connection.GroupedConnections()
Connections will belong to the same group if the application Connections will belong to the same group if the application
previously called Clone. Passive Connections can also be added to previously called Clone. Passive Connections can also be added to
the same group - e.g., when a Listener receives a new Connection that the same group - e.g., when a Listener receives a new Connection that
is just a new stream of an already active multi-streaming protocol is just a new stream of an already active multi-streaming protocol
instance. instance.
Changing one of the Connection Properties on one Connection in the
group changes it for all others. Message Properties, however, are
not entangled. For example, changing "Timeout for aborting
Connection" (see Section 6.1.3) on one Connection in a group will
automatically change this Connection Property for all Connections in
the group in the same way. However, changing "Lifetime" (see
Section 7.1.3.1) of a Message will only affect a single Message on a
single Connection, entangled or not.
If the underlying protocol supports multi-streaming, it is natural to If the underlying protocol supports multi-streaming, it is natural to
use this functionality to implement Clone. In that case, entangled use this functionality to implement Clone. In that case, Connections
Connections are multiplexed together, giving them similar treatment in a Connection Group are multiplexed together, giving them similar
not only inside endpoints, but also across the end-to-end Internet treatment not only inside endpoints, but also across the end-to-end
path. Internet path.
Note that calling Clone() can result in on-the-wire signaling, e.g., Note that calling Clone() can result in on-the-wire signaling, e.g.,
to open a new connection, depending on the underlying Protocol Stack. to open a new transport connection, depending on the underlying
When Clone() leads to multiple connections being opened instead of Protocol Stack. When Clone() leads to the opening of multiple such
multi-streaming, the Transport Services system will ensure connections, the Transport Services system will ensure consistency of
consistency of Connection Properties by uniformly applying them to Connection Properties by uniformly applying them to all underlying
all underlying connections in a group. Even in such a case, there connections in a group. Even in such a case, there are possibilities
are possibilities for a Transport Services system to implement for a Transport Services system to implement prioritization within a
prioritization within a Connection Group [TCP-COUPLING] [RFC8699]. Connection Group [TCP-COUPLING] [RFC8699].
Attempts to clone a Connection can result in a CloneError: Attempts to clone a Connection can result in a CloneError:
Connection -> CloneError<reason?> Connection -> CloneError<reason?>
The Connection Priority Connection Property operates on entangled The "Connection Priority" Connection Property operates on Connections
Connections using the same approach as in Section 7.1.3.2: when in a Connection Group using the same approach as in Section 9.1.3.2:
allocating available network capacity among Connections in a when allocating available network capacity among Connections in a
Connection Group, sends on Connections with lower Priority values Connection Group, sends on Connections with lower Priority values
will be prioritized over sends on Connections with higher Priority will be prioritized over sends on Connections with higher Priority
values. Capacity will be shared among these Connections according to values. Capacity will be shared among these Connections according to
the Connection Group Transmission Scheduler property (Section 6.1.5). the Connection Group Transmission Scheduler property (Section 8.1.5).
See Section 7.2.6 for more. See Section 9.2.6 for more.
6. Managing Connections 8. Managing Connections
During pre-establishment and after establishment, connections can be During pre-establishment and after establishment, connections can be
configured and queried using Connection Properties, and asynchronous configured and queried using Connection Properties, and asynchronous
information may be available about the state of the connection via information may be available about the state of the connection via
Soft Errors. Soft Errors.
Connection Properties represent the configuration and state of the Connection Properties represent the configuration and state of the
selected Protocol Stack(s) backing a Connection. These Connection selected Protocol Stack(s) backing a Connection. These Connection
Properties may be Generic, applying regardless of transport protocol, Properties may be Generic, applying regardless of transport protocol,
or Specific, applicable to a single implementation of a single or Specific, applicable to a single implementation of a single
transport protocol stack. Generic Connection Properties are defined transport protocol stack. Generic Connection Properties are defined
in Section 6.1 below. Specific Protocol Properties are defined in a in Section 8.1 below.
transport- and implementation-specific way, and MUST NOT be assumed
to apply across different protocols. Attempts to set Specific Protocol Specific Properties are defined in a transport- and
Protocol Properties on a protocol stack not containing that specific implementation-specific way, and MUST NOT apply across different
protocol are simply ignored, and do not raise an error; however, too protocols. Too much reliance by an application on Protocol Specific
much reliance by an application on Specific Protocol Properties can Properties can significantly reduce the flexibility of a transport
significantly reduce the flexibility of a transport services services implementation.
implementation.
The application can set and query Connection Properties on a per- The application can set and query Connection Properties on a per-
Connection basis. Connection Properties that are not read-only can Connection basis. Connection Properties that are not read-only can
be set during pre-establishment (see Section 4.2), as well as on be set during pre-establishment (see Section 6.2), as well as on
connections directly using the SetProperty action: connections directly using the SetProperty action:
Connection.SetProperty(property, value) Connection.SetProperty(property, value)
Note that changing one of the Connection Properties on one Connection Note that changing one of the Connection Properties on one Connection
in a Connection Group will also change it for all other Connections in a Connection Group will also change it for all other Connections
of that group; see further Section 5.4. of that group; see further Section 7.4.
At any point, the application can query Connection Properties. At any point, the application can query Connection Properties.
ConnectionProperties := Connection.GetProperties() ConnectionProperties := Connection.GetProperties()
value := ConnectionProperties.Get(property) value := ConnectionProperties.Get(property)
if ConnectionProperties.Has(boolean_or_preference_property) then ... if ConnectionProperties.Has(boolean_or_preference_property) then ...
Depending on the status of the connection, the queried Connection Depending on the status of the connection, the queried Connection
Properties will include different information: Properties will include different information:
* The connection state, which can be one of the following: * The connection state, which can be one of the following:
Establishing, Established, Closing, or Closed. Establishing, Established, Closing, or Closed.
* Whether the connection can be used to send data. A connection can * Whether the connection can be used to send data. A connection can
not be used for sending if the connection was created with the not be used for sending if the connection was created with the
Selection Property "Direction of Communication" set to Selection Property "Direction of Communication" set to
"unidirectional receive" or if a Message marked as "Final" was "unidirectional receive" or if a Message marked as "Final" was
sent over this connection. See Section 7.1.3.5. sent over this connection. See also Section 9.1.3.5.
* Whether the connection can be used to receive data. A connection * Whether the connection can be used to receive data. A connection
cannot be used for reading if the connection was created with the cannot be used for reading if the connection was created with the
Selection Property "Direction of Communication" set to Selection Property "Direction of Communication" set to
"unidirectional send" or if a Message marked as "Final" was "unidirectional send" or if a Message marked as "Final" was
received. See Section 7.3.3.3. The latter is only supported by received. See Section 9.3.3.3. The latter is only supported by
certain transport protocols, e.g., by TCP as half-closed certain transport protocols, e.g., by TCP as half-closed
connection. connection.
* For Connections that are Established or Closing: Transport
Properties that the application specified on the Preconnection.
See Section 4.2. Selection properties of type "Preference" will
be exposed as boolean values indicating whether or not the
property applies to the selected transport.
* For Connections that are Established, Closing, or Closed: * For Connections that are Established, Closing, or Closed:
Selection (Section 4.2) and Connection Properties (Section 6.1) of Connection Properties (Section 8.1) of the actual protocols that
the actual protocols that were selected and instantiated. were selected and instantiated, and Selection Properties that the
Selection Properties indicate whether or not the Connection has or application specified on the Preconnection. Selection Properties
offers a certain Selection Property. The actually instantiated of type "Preference" will be exposed as boolean values indicating
protocol stack might not match all Protocol Selection Properties whether or not the property applies to the selected transport.
that the application specified on the Preconnection. For example, Note that the instantiated protocol stack might not match all
a certain Protocol Selection Property that an application Protocol Selection Properties that the application specified on
specified as Preferred might not actually be present in the chosen the Preconnection.
protocol stack because none of the currently available transport
protocols had this feature.
* For Connections that are Established, additional properties of the * For Connections that are Established, additional properties of the
path(s) in use. These properties can be derived from the local path(s) in use. These properties can be derived from the local
provisioning domain [RFC7556], measurements by the Protocol Stack, provisioning domain [RFC7556], measurements by the Protocol Stack,
or other sources. or other sources.
6.1. Generic Connection Properties 8.1. Generic Connection Properties
Generic Connection Properties are defined independent of the chosen Generic Connection Properties are defined independent of the chosen
protocol stack and therefore available on all Connections. protocol stack and therefore available on all Connections.
Many Connection Properties have a corresponding Selection Property Many Connection Properties have a corresponding Selection Property
that enables applications to express their preference for protocols that enables applications to express their preference for protocols
providing a supporting transport feature. providing a supporting transport feature.
6.1.1. Required Minimum Corruption Protection Coverage for Receiving 8.1.1. Required Minimum Corruption Protection Coverage for Receiving
Name: recvChecksumLen Name: recvChecksumLen
Type: Integer, with special value "Full Coverage" Type: Integer (non-negative with special value "Full Coverage")
Default: Full Coverage Default: Full Coverage
This property specifies the minimum number of bytes in a received This property specifies the minimum number of bytes in a received
message that need to be covered by a checksum. A special value of 0 message that need to be covered by a checksum. A special value of 0
means that no checksum is permitted. A receiving Endpoint will not means that a received packet does not need to have a non-zero
forward messages to the application that have less coverage. The checksum field. A receiving endpoint will not forward messages that
application is responsible for handling any corruption within the have less coverage to the application. The application is
non-protected part of the message [RFC8085]. responsible for handling any corruption within the non-protected part
of the message [RFC8085].
6.1.2. Connection Priority 8.1.2. Connection Priority
Name: connPrio Name: connPrio
Type: Integer Type: Integer
Default: 100 Default: 100
This Property is a non-negative integer representing the relative This Property is a non-negative integer representing the relative
inverse priority (i.e., a lower value reflects a higher priority) of inverse priority (i.e., a lower value reflects a higher priority) of
this Connection relative to other Connections in the same Connection this Connection relative to other Connections in the same Connection
Group. It has no effect on Connections not part of a Connection Group. It has no effect on Connections not part of a Connection
Group. As noted in Section 5.4, this property is not entangled when Group. As noted in Section 7.4, this property is not entangled when
Connections are cloned, i.e., changing the Priority on one Connection Connections are cloned, i.e., changing the Priority on one Connection
in a Connection Group does not change it on the other Connections in in a Connection Group does not change it on the other Connections in
the same Connection Group. No guarantees of a specific behavior the same Connection Group. No guarantees of a specific behavior
regarding Connection Priority are given; a Transport Services system regarding Connection Priority are given; a Transport Services system
may ignore this property. See Section 7.2.6 for more details. may ignore this property. See Section 9.2.6 for more details.
6.1.3. Timeout for Aborting Connection 8.1.3. Timeout for Aborting Connection
Name: connTimeout Name: connTimeout
Type: Numeric, with special value "Disabled" Type: Numeric, with special value "Disabled"
Default: Disabled Default: Disabled
This property specifies how long to wait before deciding that an This property specifies how long to wait before deciding that an
active Connection has failed when trying to reliably deliver data to active Connection has failed when trying to reliably deliver data to
the Remote Endpoint. Adjusting this Property will only take effect the Remote Endpoint. Adjusting this Property will only take effect
when the underlying stack supports reliability. The special value when the underlying stack supports reliability. The special value
"Disabled" means that no timeout is scheduled. "Disabled" means that no timeout is scheduled.
6.1.4. Timeout for keep alive packets 8.1.4. Timeout for keep alive packets
Name: keepAliveTimeout Name: keepAliveTimeout
Type: Numeric, with special value "Disabled" Type: Numeric, with special value "Disabled"
Default: Implementation-defined Default: Implementation-defined
A Transport Services system can request a protocol that supports A Transport Services system can request a protocol that supports
sending keep alive packets Section 4.2.10. This property specifies sending keep alive packets Section 6.2.10. This property specifies
the maximum length of time an idle connection (one for which no the maximum length of time an idle connection (one for which no
transport packets have been sent) should wait before the Local transport packets have been sent) should wait before the Local
Endpoint sends a keep-alive packet to the Remote Endpoint. Adjusting Endpoint sends a keep-alive packet to the Remote Endpoint. Adjusting
this Property will only take effect when the underlying stack this Property will only take effect when the underlying stack
supports sending keep-alive packets. Guidance on setting this value supports sending keep-alive packets. Guidance on setting this value
for datagram transports is provided in [RFC8085]. A value greater for datagram transports is provided in [RFC8085]. A value greater
than the connection timeout (Section 6.1.3), or the special value than the connection timeout (Section 8.1.3), or the special value
"Disabled", will disable the sending of keep-alive packets. "Disabled", will disable the sending of keep-alive packets.
6.1.5. Connection Group Transmission Scheduler 8.1.5. Connection Group Transmission Scheduler
Name: connScheduler Name: connScheduler
Type: Enumeration Type: Enumeration
Default: Weighted Fair Queueing (see Section 3.6 in [RFC8260]) Default: Weighted Fair Queueing (see Section 3.6 in [RFC8260])
This property specifies which scheduler should be used among This property specifies which scheduler should be used among
Connections within a Connection Group, see Section 5.4. The set of Connections within a Connection Group, see Section 7.4. The set of
schedulers can be taken from [RFC8260]. schedulers can be taken from [RFC8260].
6.1.6. Capacity Profile 8.1.6. Capacity Profile
Name: connCapacityProfile Name: connCapacityProfile
This property specifies the desired network treatment for traffic This property specifies the desired network treatment for traffic
sent by the application and the tradeoffs the application is prepared sent by the application and the tradeoffs the application is prepared
to make in path and protocol selection to receive that desired to make in path and protocol selection to receive that desired
treatment. When the capacity profile is set to a value other than treatment. When the capacity profile is set to a value other than
Default, the Transport Services system SHOULD select paths and Default, the Transport Services system SHOULD select paths and
configure protocols to optimize the tradeoff between delay, delay configure protocols to optimize the tradeoff between delay, delay
variation, and efficient use of the available capacity based on the variation, and efficient use of the available capacity based on the
skipping to change at page 42, line 22 skipping to change at page 44, line 39
the available capacity when sending on this connection. Transport the available capacity when sending on this connection. Transport
system implementations that map the requested capacity profile system implementations that map the requested capacity profile
onto per-connection DSCP signaling without multiplexing SHOULD onto per-connection DSCP signaling without multiplexing SHOULD
assign a DSCP Assured Forwarding (AF21,AF22,AF23,AF24) [RFC2597] assign a DSCP Assured Forwarding (AF21,AF22,AF23,AF24) [RFC2597]
PHB. PHB.
Constant-Rate Streaming: The application expects to send/receive Constant-Rate Streaming: The application expects to send/receive
data at a constant rate after Connection establishment. Delay and data at a constant rate after Connection establishment. Delay and
delay variation should be minimized at the expense of efficient delay variation should be minimized at the expense of efficient
use of the available capacity. This implies that the Connection use of the available capacity. This implies that the Connection
might fail if the desired rate cannot be maintained across the might fail if the Path is unable to maintain the desired rate. A
Path. A transport can interpret this capacity profile as transport can interpret this capacity profile as preferring a
preferring a circuit breaker [RFC8084] to a rate-adaptive circuit breaker [RFC8084] to a rate-adaptive congestion
congestion controller. Transport system implementations that map controller. Transport system implementations that map the
the requested capacity profile onto per-connection DSCP signaling requested capacity profile onto per-connection DSCP signaling
without multiplexing SHOULD assign a DSCP Assured Forwarding without multiplexing SHOULD assign a DSCP Assured Forwarding
(AF31,AF32,AF33,AF34) [RFC2597] PHB. (AF31,AF32,AF33,AF34) [RFC2597] PHB.
Capacity-Seeking: The application expects to send/receive data at Capacity-Seeking: The application expects to send/receive data at
the maximum rate allowed by its congestion controller over a the maximum rate allowed by its congestion controller over a
relatively long period of time. Transport Services system relatively long period of time. Transport Services system
implementations that map the requested capacity profile onto per- implementations that map the requested capacity profile onto per-
connection DSCP signaling without multiplexing SHOULD assign a connection DSCP signaling without multiplexing SHOULD assign a
DSCP Assured Forwarding (AF11,AF12,AF13,AF14) [RFC2597] PHB per DSCP Assured Forwarding (AF11,AF12,AF13,AF14) [RFC2597] PHB per
Section 4.8 of [RFC4594]. Section 4.8 of [RFC4594].
The Capacity Profile for a selected protocol stack may be modified on The Capacity Profile for a selected protocol stack may be modified on
a per-Message basis using the Transmission Profile Message Property; a per-Message basis using the Transmission Profile Message Property;
see Section 7.1.3.8. see Section 9.1.3.8.
6.1.7. Policy for using Multipath Transports 8.1.7. Policy for using Multipath Transports
Name: multipath-policy Name: multipath-policy
Type: Enumeration Type: Enumeration
Default: Handover Default: Handover
This property specifies the local policy for transferring data across This property specifies the local policy for transferring data across
multiple paths between the same end hosts if Multipath Transport is multiple paths between the same end hosts if Multipath Transport is
not set to Disabled (see Section 4.2.14). Possible values are: not set to Disabled (see Section 6.2.14). Possible values are:
Handover: The connection ought only to attempt to migrate between Handover: The connection ought only to attempt to migrate between
different paths when the original path is lost or becomes different paths when the original path is lost or becomes
unusable. The thresholds used to declare a path unusable are unusable. The thresholds used to declare a path unusable are
implementation specific. implementation specific.
Interactive: The connection ought only to attempt to minimize the Interactive: The connection ought only to attempt to minimize the
latency for interactive traffic patterns by transmitting data latency for interactive traffic patterns by transmitting data
across multiple paths when this is beneficial. The goal of across multiple paths when this is beneficial. The goal of
minimizing the latency will be balanced against the cost of each minimizing the latency will be balanced against the cost of each
skipping to change at page 43, line 31 skipping to change at page 46, line 5
scheduling algorithm is implementation-specific. scheduling algorithm is implementation-specific.
Aggregate: The connection ought to attempt to use multiple paths in Aggregate: The connection ought to attempt to use multiple paths in
parallel to maximize available capacity and possibly overcome the parallel to maximize available capacity and possibly overcome the
capacity limitations of the individual paths. The actual strategy capacity limitations of the individual paths. The actual strategy
is implementation specific. is implementation specific.
Note that this is a local choice - the Remote Endpoint can choose a Note that this is a local choice - the Remote Endpoint can choose a
different policy. different policy.
6.1.8. Bounds on Send or Receive Rate 8.1.8. Bounds on Send or Receive Rate
Name: minSendRate / minRecvRate / maxSendRate / maxRecvRate Name: minSendRate / minRecvRate / maxSendRate / maxRecvRate
Type: Numeric (with special value "Unlimited") / Numeric (with Type: Numeric (with special value "Unlimited") / Numeric (with
special value "Unlimited") / Numeric (with special value special value "Unlimited") / Numeric (with special value
"Unlimited") / Numeric (with special value "Unlimited") "Unlimited") / Numeric (with special value "Unlimited")
Default: Unlimited / Unlimited / Unlimited / Unlimited Default: Unlimited / Unlimited / Unlimited / Unlimited
This property specifies an upper-bound rate that a transfer is not This property specifies an upper-bound rate that a transfer is not
expected to exceed (even if flow control and congestion control allow expected to exceed (even if flow control and congestion control allow
higher rates), and/or a lower-bound rate below which the application higher rates), and/or a lower-bound rate below which the application
does not deem it will be useful. These are specified in bits per does not deem it will be useful. These are specified in bits per
second. The special value "Unlimited" indicates that no bound is second. The special value "Unlimited" indicates that no bound is
specified. specified.
6.1.9. Group Connection Limit 8.1.9. Group Connection Limit
Name: groupConnLimit Name: groupConnLimit
Type: Numeric (with special value "Unlimited") Type: Numeric (with special value "Unlimited")
Default: Unlimited Default: Unlimited
This property controls the number of Connections that can be accepted This property controls the number of Connections that can be accepted
from a peer as new members of the Connection's group. Similar to from a peer as new members of the Connection's group. Similar to
SetNewConnectionLimit(), this limits the number of ConnectionReceived SetNewConnectionLimit(), this limits the number of ConnectionReceived
Events that will occur, but constrained to the group of the Events that will occur, but constrained to the group of the
Connection associated with this property. For a multi-streaming Connection associated with this property. For a multi-streaming
transport, this limits the number of allowed streams. transport, this limits the number of allowed streams.
skipping to change at page 44, line 15 skipping to change at page 46, line 37
Default: Unlimited Default: Unlimited
This property controls the number of Connections that can be accepted This property controls the number of Connections that can be accepted
from a peer as new members of the Connection's group. Similar to from a peer as new members of the Connection's group. Similar to
SetNewConnectionLimit(), this limits the number of ConnectionReceived SetNewConnectionLimit(), this limits the number of ConnectionReceived
Events that will occur, but constrained to the group of the Events that will occur, but constrained to the group of the
Connection associated with this property. For a multi-streaming Connection associated with this property. For a multi-streaming
transport, this limits the number of allowed streams. transport, this limits the number of allowed streams.
6.1.10. Isolate Session 8.1.10. Isolate Session
Name: isolateSession Name: isolateSession
Type: Boolean Type: Boolean
Default: false Default: false
When set to true, this property will initiate new Connections using When set to true, this property will initiate new Connections using
as little cached information (such as session tickets or cookies) as as little cached information (such as session tickets or cookies) as
possible from previous connections that are not entangled with it. possible from previous connections that are not in the same
Any state generated by this Connection will only be shared with Connection Group. Any state generated by this Connection will only
entangled connections. Cloned Connections will use saved state from be shared with Connections in the same Connection Group. Cloned
within the Connection Group. This is used for separating Connection Connections will use saved state from within the Connection Group.
Contexts as specified in [I-D.ietf-taps-arch]. This is used for separating Connection Contexts as specified in
[I-D.ietf-taps-arch].
Note that this does not guarantee no leakage of information, as Note that this does not guarantee no leakage of information, as
implementations may not be able to fully isolate all caches (e.g. implementations may not be able to fully isolate all caches (e.g.
RTT estimates). Note that this property may degrade connection RTT estimates). Note that this property may degrade connection
performance. performance.
6.1.11. Read-only Connection Properties 8.1.11. Read-only Connection Properties
The following generic Connection Properties are read-only, i.e. they The following generic Connection Properties are read-only, i.e. they
cannot be changed by an application. cannot be changed by an application.
6.1.11.1. Maximum Message Size Concurrent with Connection Establishment 8.1.11.1. Maximum Message Size Concurrent with Connection Establishment
Name: zeroRttMsgMaxLen Name: zeroRttMsgMaxLen
Type: Integer Type: Integer
This property represents the maximum Message size that can be sent This property represents the maximum Message size that can be sent
before or during Connection establishment, see also Section 7.1.3.4. before or during Connection establishment, see also Section 9.1.3.4.
It is given in Bytes. It is given in Bytes.
6.1.11.2. Maximum Message Size Before Fragmentation or Segmentation 8.1.11.2. Maximum Message Size Before Fragmentation or Segmentation
Name: singularTransmissionMsgMaxLen Name: singularTransmissionMsgMaxLen
Type: Integer Type: Integer
This property, if applicable, represents the maximum Message size This property, if applicable, represents the maximum Message size
that can be sent without incurring network-layer fragmentation or that can be sent without incurring network-layer fragmentation at the
transport layer segmentation at the sender. It exposes the Maximum sender. It exposes a value to the application based on the Maximum
Packet Size (MPS) as described in Datagram PLPMTUD Packet Size (MPS) as described in Datagram PLPMTUD [RFC8899]. This
[I-D.ietf-tsvwg-datagram-plpmtud]. can allow a sending stack to avoid unwanted fragmentation at the
network-layer or segmentation by the transport layer.
6.1.11.3. Maximum Message Size on Send 8.1.11.3. Maximum Message Size on Send
Name: sendMsgMaxLen Name: sendMsgMaxLen
Type: Integer Type: Integer
This property represents the maximum Message size that an application This property represents the maximum Message size that an application
can send. can send.
6.1.11.4. Maximum Message Size on Receive 8.1.11.4. Maximum Message Size on Receive
Name: recvMsgMaxLen Name: recvMsgMaxLen
Type: Integer Type: Integer
This numeric property represents the maximum Message size that an This numeric property represents the maximum Message size that an
application can receive. application can receive.
6.2. TCP-specific Properties: User Timeout Option (UTO) 8.2. TCP-specific Properties: User Timeout Option (UTO)
These properties specify configurations for the User Timeout Option These properties specify configurations for the User Timeout Option
(UTO), in the case that TCP becomes the chosen transport protocol. (UTO), in the case that TCP becomes the chosen transport protocol.
Implementation is optional and useful only if TCP is implemented in Implementation is optional and useful only if TCP is implemented in
the Transport Services system. the Transport Services system.
These TCP-specific properties are included here because the feature These TCP-specific properties are included here because the feature
"Suggest timeout to the peer" is part of the minimal set of transport "Suggest timeout to the peer" is part of the minimal set of transport
services [RFC8923], where this feature was categorized as services [RFC8923], where this feature was categorized as
"functional". This means that when an implementation offers this "functional". This means that when an implementation offers this
feature, it has to expose an interface to it to the application. feature, it has to expose an interface to it to the application.
Otherwise, the implementation might violate assumptions by the Otherwise, the implementation might violate assumptions by the
application, which could cause the application to fail. application, which could cause the application to fail.
All of the below properties are optional (e.g., it is possible to All of the below properties are optional (e.g., it is possible to
specify "User Timeout Enabled" as true, but not specify an Advertised specify "User Timeout Enabled" as true, but not specify an Advertised
User Timeout value; in this case, the TCP default will be used). User Timeout value; in this case, the TCP default will be used).
These properties reflect the API extension specified in Section 3 of These properties reflect the API extension specified in Section 3 of
[RFC5482]. [RFC5482].
6.2.1. Advertised User Timeout 8.2.1. Advertised User Timeout
Name: tcp.userTimeoutValue Name: tcp.userTimeoutValue
Type: Integer Type: Integer
Default: the TCP default Default: the TCP default
This time value is advertised via the TCP User Timeout Option (UTO) This time value is advertised via the TCP User Timeout Option (UTO)
[RFC5482] at the Remote Endpoint to adapt its own "Timeout for [RFC5482] at the Remote Endpoint to adapt its own "Timeout for
aborting Connection" (see Section 6.1.3) value. aborting Connection" (see Section 8.1.3) value.
6.2.2. User Timeout Enabled 8.2.2. User Timeout Enabled
Name: tcp.userTimeout Name: tcp.userTimeout
Type: Boolean Type: Boolean
Default: false Default: false
This property controls whether the UTO option is enabled for a This property controls whether the UTO option is enabled for a
connection. This applies to both sending and receiving. connection. This applies to both sending and receiving.
6.2.3. Timeout Changeable 8.2.3. Timeout Changeable
Name: tcp.userTimeoutRecv Name: tcp.userTimeoutRecv
Type: Boolean Type: Boolean
Default: true Default: true
This property controls whether the "Timeout for aborting Connection" This property controls whether the "Timeout for aborting Connection"
(see Section 6.1.3) may be changed based on a UTO option received (see Section 8.1.3) may be changed based on a UTO option received
from the remote peer. This boolean becomes false when "Timeout for from the remote peer. This boolean becomes false when "Timeout for
aborting Connection" (see Section 6.1.3) is used. aborting Connection" (see Section 8.1.3) is used.
6.3. Connection Lifecycle Events 8.3. Connection Lifecycle Events
During the lifetime of a connection there are events that can occur During the lifetime of a connection there are events that can occur
when configured. when configured.
6.3.1. Soft Errors 8.3.1. Soft Errors
Asynchronous introspection is also possible, via the SoftError Event. Asynchronous introspection is also possible, via the SoftError Event.
This event informs the application about the receipt and contents of This event informs the application about the receipt and contents of
an ICMP error message related to the Connection. This will only an ICMP error message related to the Connection. This will only
happen if the underlying protocol stack supports access to soft happen if the underlying protocol stack supports access to soft
errors; however, even if the underlying stack supports it, there is errors; however, even if the underlying stack supports it, there is
no guarantee that a soft error will be signaled. no guarantee that a soft error will be signaled.
Connection -> SoftError<> Connection -> SoftError<>
6.3.2. Path change 8.3.2. Path change
This event notifies the application when at least one of the paths This event notifies the application when at least one of the paths
underlying a Connection has changed. Changes occur on a single path underlying a Connection has changed. Changes occur on a single path
when the PMTU changes as well as when multiple paths are used and when the PMTU changes as well as when multiple paths are used and
paths are added or removed, or a handover has been performed. paths are added or removed, or a handover has been performed.
Connection -> PathChange<> Connection -> PathChange<>
7. Data Transfer 9. Data Transfer
Data is sent and received as Messages, which allows the application Data is sent and received as Messages, which allows the application
to communicate the boundaries of the data being transferred. to communicate the boundaries of the data being transferred.
7.1. Messages and Framers 9.1. Messages and Framers
Each Message has an optional Message Context, which allows to add Each Message has an optional Message Context, which allows to add
Message Properties, identify Send Events related to a specific Message Properties, identify Send Events related to a specific
Message or to inspect meta-data related to the Message sent. Framers Message or to inspect meta-data related to the Message sent. Framers
can be used to extend or modify the message data with additional can be used to extend or modify the message data with additional
information that can be processed at the receiver to detect message information that can be processed at the receiver to detect message
boundaries. boundaries.
7.1.1. Message Contexts 9.1.1. Message Contexts
Using the MessageContext object, the application can set and retrieve Using the MessageContext object, the application can set and retrieve
meta-data of the message, including Message Properties (see meta-data of the message, including Message Properties (see
Section 7.1.3) and framing meta-data (see Section 7.1.2.2). Section 9.1.3) and framing meta-data (see Section 9.1.2.2).
Therefore, a MessageContext object can be passed to the Send action Therefore, a MessageContext object can be passed to the Send action
and is returned by each Send and Receive related event. and is returned by each Send and Receive related event.
Message Properties can be set and queried using the Message Context: Message Properties can be set and queried using the Message Context:
MessageContext.add(scope?, parameter, value) MessageContext.add(scope?, parameter, value)
PropertyValue := MessageContext.get(scope?, property) PropertyValue := MessageContext.get(scope?, property)
To get or set Message Properties, the optional scope parameter is To get or set Message Properties, the optional scope parameter is
left empty. To get or set meta-data for a Framer, the application left empty. To get or set meta-data for a Framer, the application
has to pass a reference to this Framer as the scope parameter. has to pass a reference to this Framer as the scope parameter.
For MessageContexts returned by send Events (see Section 7.2.2) and For MessageContexts returned by send Events (see Section 9.2.2) and
receive Events (see Section 7.3.2), the application can query receive Events (see Section 9.3.2), the application can query
information about the local and Remote Endpoint: information about the Local and Remote Endpoint:
RemoteEndpoint := MessageContext.GetRemoteEndpoint() RemoteEndpoint := MessageContext.GetRemoteEndpoint()
LocalEndpoint := MessageContext.GetLocalEndpoint() LocalEndpoint := MessageContext.GetLocalEndpoint()
7.1.2. Message Framers 9.1.2. Message Framers
Although most applications communicate over a network using well- Although most applications communicate over a network using well-
formed Messages, the boundaries and metadata of the Messages are formed Messages, the boundaries and metadata of the Messages are
often not directly communicated by the transport protocol itself. often not directly communicated by the transport protocol itself.
For example, HTTP applications send and receive HTTP messages over a For example, HTTP applications send and receive HTTP messages over a
byte-stream transport, requiring that the boundaries of HTTP messages byte-stream transport, requiring that the boundaries of HTTP messages
be parsed from the stream of bytes. be parsed from the stream of bytes.
Message Framers allow extending a Connection's Protocol Stack to Message Framers allow extending a Connection's Protocol Stack to
define how to encapsulate or encode outbound Messages, and how to define how to encapsulate or encode outbound Messages, and how to
skipping to change at page 49, line 41 skipping to change at page 52, line 5
a protocol that otherwise does not preserve message boundaries, they a protocol that otherwise does not preserve message boundaries, they
can also be used with datagram- or message-based protocols. In these can also be used with datagram- or message-based protocols. In these
cases, they add an additional transformation to further encode or cases, they add an additional transformation to further encode or
encapsulate, and can potentially support packing multiple encapsulate, and can potentially support packing multiple
application-layer Messages into individual transport datagrams. application-layer Messages into individual transport datagrams.
The API to implement a Message Framer can vary depending on the The API to implement a Message Framer can vary depending on the
implementation; guidance on implementing Message Framers can be found implementation; guidance on implementing Message Framers can be found
in [I-D.ietf-taps-impl]. in [I-D.ietf-taps-impl].
7.1.2.1. Adding Message Framers to Connections 9.1.2.1. Adding Message Framers to Pre-Connections
The Message Framer object can be added to one or more Preconnections The Message Framer object can be added to one or more Preconnections
to run on top of transport protocols. Multiple Framers may be added to run on top of transport protocols. Multiple Framers may be added
to a Preconnection; in this case, the Framers operate as a framing to a Preconnection; in this case, the Framers operate as a framing
stack, i.e. the last one added runs first when framing outbound stack, i.e. the last one added runs first when framing outbound
messages, and last when parsing inbound data. messages, and last when parsing inbound data.
The following example adds a basic HTTP Message Framer to a The following example adds a basic HTTP Message Framer to a
Preconnection: Preconnection:
framer := NewHTTPMessageFramer() framer := NewHTTPMessageFramer()
Preconnection.AddFramer(framer) Preconnection.AddFramer(framer)
Since Message Framers pass from Preconnection to Listener or Since Message Framers pass from Preconnection to Listener or
Connection, addition of Framers must happen before any operation that Connection, addition of Framers must happen before any operation that
may result in the creation of a Connection. may result in the creation of a Connection.
7.1.2.2. Framing Meta-Data 9.1.2.2. Framing Meta-Data
When sending Messages, applications can add Framer-specific key/value When sending Messages, applications can add Framer-specific key/value
pairs to a MessageContext (Section 7.1.1). This mechanism can be pairs to a MessageContext (Section 9.1.1). This mechanism can be
used, for example, to set the type of a Message for a TLV format. used, for example, to set the type of a Message for a TLV format.
The namespace of values is custom for each unique Message Framer. The namespace of values is custom for each unique Message Framer.
messageContext := NewMessageContext() messageContext := NewMessageContext()
messageContext.add(framer, key, value) messageContext.add(framer, key, value)
Connection.Send(messageData, messageContext) Connection.Send(messageData, messageContext)
When an application receives a MessageContext in a Receive event, it When an application receives a MessageContext in a Receive event, it
can also look to see if a value was set by a specific Message Framer. can also look to see if a value was set by a specific Message Framer.
messageContext.get(framer, key) -> value messageContext.get(framer, key) -> value
For example, if an HTTP Message Framer is used, the values could For example, if an HTTP Message Framer is used, the values could
correspond to HTTP headers: correspond to HTTP headers:
httpFramer := NewHTTPMessageFramer() httpFramer := NewHTTPMessageFramer()
... ...
messageContext := NewMessageContext() messageContext := NewMessageContext()
messageContext.add(httpFramer, "accept", "text/html") messageContext.add(httpFramer, "accept", "text/html")
7.1.3. Message Properties 9.1.3. Message Properties
Applications needing to annotate the Messages they send with extra Applications needing to annotate the Messages they send with extra
information (for example, to control how data is scheduled and information (for example, to control how data is scheduled and
processed by the transport protocols supporting the Connection) can processed by the transport protocols supporting the Connection) can
include this information in the Message Context passed to the Send include this information in the Message Context passed to the Send
Action. For other uses of the message context, see Section 7.1.1. Action. For other uses of the message context, see Section 9.1.1.
Message Properties are per-Message, not per-Send if partial Messages Message Properties are per-Message, not per-Send if partial Messages
are sent (Section 7.2.3). All data blocks associated with a single are sent (Section 9.2.3). All data blocks associated with a single
Message share properties specified in the Message Contexts. For Message share properties specified in the Message Contexts. For
example, it would not make sense to have the beginning of a Message example, it would not make sense to have the beginning of a Message
expire, but allow the end of a Message to still be sent. expire, but allow the end of a Message to still be sent.
A MessageContext object contains metadata for the Messages to be sent A MessageContext object contains metadata for the Messages to be sent
or received. or received.
messageData := "hello" messageData := "hello"
messageContext := NewMessageContext() messageContext := NewMessageContext()
messageContext.add(parameter, value) messageContext.add(parameter, value)
skipping to change at page 51, line 38 skipping to change at page 54, line 6
Sending a Message with Message Properties inconsistent with the Sending a Message with Message Properties inconsistent with the
Selection Properties of the Connection yields an error. Selection Properties of the Connection yields an error.
Connection Properties describe the default behavior for all Messages Connection Properties describe the default behavior for all Messages
on a Connection. If a Message Property contradicts a Connection on a Connection. If a Message Property contradicts a Connection
Property, and if this per-Message behavior can be supported, it Property, and if this per-Message behavior can be supported, it
overrides the Connection Property for the specific Message. For overrides the Connection Property for the specific Message. For
example, if "Reliable Data Transfer (Connection)" is set to "Require" example, if "Reliable Data Transfer (Connection)" is set to "Require"
and a protocol with configurable per-Message reliability is used, and a protocol with configurable per-Message reliability is used,
setting "Reliable Data Transfer (Message)" to "false" for a setting "Reliable Data Transfer (Message)" to "false" for a
particular Message will allow this Message to be unreliably particular Message will allow this Message to be sent without any
delivered. Changing the Reliable Data Transfer property on Messages reliability guarantees. Changing the Reliable Data Transfer property
is only possible for Connections that were established enabling the on Messages is only possible for Connections that were established
Selection Property "Configure Per-Message Reliability". enabling the Selection Property "Configure Per-Message Reliability".
The following Message Properties are supported: The following Message Properties are supported:
7.1.3.1. Lifetime 9.1.3.1. Lifetime
Name: msgLifetime Name: msgLifetime
Type: Numeric Type: Numeric
Default: infinite Default: infinite
The Lifetime specifies how long a particular Message can wait to be The Lifetime specifies how long a particular Message can wait to be
sent to the Remote Endpoint before it is irrelevant and no longer sent to the Remote Endpoint before it is irrelevant and no longer
needs to be (re-)transmitted. This is a hint to the Transport needs to be (re-)transmitted. This is a hint to the Transport
Services system - it is not guaranteed that a Message will not be Services system - it is not guaranteed that a Message will not be
sent when its Lifetime has expired. sent when its Lifetime has expired.
Setting a Message's Lifetime to infinite indicates that the Setting a Message's Lifetime to infinite indicates that the
application does not wish to apply a time constraint on the application does not wish to apply a time constraint on the
transmission of the Message, but it does not express a need for transmission of the Message, but it does not express a need for
reliable delivery; reliability is adjustable per Message via the reliable delivery; reliability is adjustable per Message via the
skipping to change at page 52, line 14 skipping to change at page 54, line 31
The Lifetime specifies how long a particular Message can wait to be The Lifetime specifies how long a particular Message can wait to be
sent to the Remote Endpoint before it is irrelevant and no longer sent to the Remote Endpoint before it is irrelevant and no longer
needs to be (re-)transmitted. This is a hint to the Transport needs to be (re-)transmitted. This is a hint to the Transport
Services system - it is not guaranteed that a Message will not be Services system - it is not guaranteed that a Message will not be
sent when its Lifetime has expired. sent when its Lifetime has expired.
Setting a Message's Lifetime to infinite indicates that the Setting a Message's Lifetime to infinite indicates that the
application does not wish to apply a time constraint on the application does not wish to apply a time constraint on the
transmission of the Message, but it does not express a need for transmission of the Message, but it does not express a need for
reliable delivery; reliability is adjustable per Message via the reliable delivery; reliability is adjustable per Message via the
"Reliable Data Transfer (Message)" property (see Section 7.1.3.7). "Reliable Data Transfer (Message)" property (see Section 9.1.3.7).
The type and units of Lifetime are implementation-specific. The type and units of Lifetime are implementation-specific.
7.1.3.2. Priority 9.1.3.2. Priority
Name: msgPrio Name: msgPrio
Type: Integer (non-negative) Type: Integer (non-negative)
Default: 100 Default: 100
This property represents a hierarchy of priorities. It can specify This property specifies the priority of a Message, relative to other
the priority of a Message, relative to other Messages sent over the Messages sent over the same Connection.
same Connection.
A Message with Priority 0 will yield to a Message with Priority 1, A Message with Priority 0 will yield to a Message with Priority 1,
which will yield to a Message with Priority 2, and so on. Priorities which will yield to a Message with Priority 2, and so on. Priorities
may be used as a sender-side scheduling construct only, or be used to may be used as a sender-side scheduling construct only, or be used to
specify priorities on the wire for Protocol Stacks supporting specify priorities on the wire for Protocol Stacks supporting
prioritization. prioritization.
Note that this property is not a per-message override of the Note that this property is not a per-message override of the
connection Priority - see Section 6.1.2. The Priority properties may Connection Priority - see Section 8.1.2. The Priority properties may
interact, but can be used independently and be realized by different interact, but can be used independently and be realized by different
mechanisms; see Section 7.2.6. mechanisms; see Section 9.2.6.
7.1.3.3. Ordered 9.1.3.3. Ordered
Name: msgOrdered Name: msgOrdered
Type: Boolean Type: Boolean
Default: the queried Boolean value of the Selection Property Default: the queried Boolean value of the Selection Property
"reliability" (Section 4.2.1) "preserveOrder" (Section 6.2.4)
The order in which Messages were submitted for transmission via the The order in which Messages were submitted for transmission via the
Send Action will be preserved on delivery via Receive<> events for Send Action will be preserved on delivery via Receive<> events for
all Messages on a Connection that have this Message Property set to all Messages on a Connection that have this Message Property set to
true. true.
If false, the Message is delivered to the receiving application If false, the Message is delivered to the receiving application
without preserving the ordering. This property is used for protocols without preserving the ordering. This property is used for protocols
that support preservation of data ordering, see Section 4.2.4, but that support preservation of data ordering, see Section 6.2.4, but
allow out-of-order delivery for certain messages, e.g., by allow out-of-order delivery for certain messages, e.g., by
multiplexing independent messages onto different streams. multiplexing independent messages onto different streams.
7.1.3.4. Safely Replayable 9.1.3.4. Safely Replayable
Name: safelyReplayable Name: safelyReplayable
Type: Boolean Type: Boolean
Default: false Default: false
If true, Safely Replayable specifies that a Message is safe to send If true, Safely Replayable specifies that a Message is safe to send
to the Remote Endpoint more than once for a single Send Action. It to the Remote Endpoint more than once for a single Send Action. It
marks the data as safe for certain 0-RTT establishment techniques, marks the data as safe for certain 0-RTT establishment techniques,
where retransmission of the 0-RTT data may cause the remote where retransmission of the 0-RTT data may cause the remote
application to receive the Message multiple times. application to receive the Message multiple times.
For protocols that do not protect against duplicated messages, e.g., For protocols that do not protect against duplicated messages, e.g.,
UDP, all messages need to be marked as "Safely Replayable". To UDP, all messages need to be marked as "Safely Replayable". To
enable protocol selection to choose such a protocol, "Safely enable protocol selection to choose such a protocol, "Safely
Replayable" needs to be added to the TransportProperties passed to Replayable" needs to be added to the TransportProperties passed to
the Preconnection. If such a protocol was chosen, disabling "Safely the Preconnection. If such a protocol was chosen, disabling "Safely
Replayable" on individual messages MUST result in a SendError. Replayable" on individual messages MUST result in a SendError.
7.1.3.5. Final 9.1.3.5. Final
Name: final Name: final
Type: Boolean Type: Boolean
Default: false Default: false
If true, this indicates a Message is the last that the application If true, this indicates a Message is the last that the application
will send on a Connection. This allows underlying protocols to will send on a Connection. This allows underlying protocols to
indicate to the Remote Endpoint that the Connection has been indicate to the Remote Endpoint that the Connection has been
skipping to change at page 54, line 12 skipping to change at page 56, line 29
do not support signalling the end of a Connection in a given do not support signalling the end of a Connection in a given
direction will ignore this property. direction will ignore this property.
A Final Message must always be sorted to the end of a list of A Final Message must always be sorted to the end of a list of
Messages. The Final property overrides Priority and any other Messages. The Final property overrides Priority and any other
property that would re-order Messages. If another Message is sent property that would re-order Messages. If another Message is sent
after a Message marked as Final has already been sent on a after a Message marked as Final has already been sent on a
Connection, the Send Action for the new Message will cause a Connection, the Send Action for the new Message will cause a
SendError Event. SendError Event.
7.1.3.6. Sending Corruption Protection Length 9.1.3.6. Sending Corruption Protection Length
Name: msgChecksumLen Name: msgChecksumLen
Type: Integer (non-negative with special value "Full Coverage") Type: Integer (non-negative with special value "Full Coverage")
Default: Full Coverage Default: Full Coverage
This property specifies the minimum length of the section of a sent This property specifies the minimum length of the section of a sent
Message, starting from byte 0, that the application requires to be Message, starting from byte 0, that the application requires to be
delivered without corruption due to lower layer errors. It is used delivered without corruption due to lower layer errors. It is used
to specify options for simple integrity protection via checksums. A to specify options for simple integrity protection via checksums. A
value of 0 means that no checksum is required, and "Full Coverage" value of 0 means that no checksum needs to be calculated, and "Full
means that the entire Message needs to be protected by a checksum. Coverage" means that the entire Message needs to be protected by a
Only "Full Coverage" is guaranteed, any other requests are advisory, checksum. Only "Full Coverage" is guaranteed, any other requests are
which may result in "Full Coverage" being applied. advisory, which may result in "Full Coverage" being applied.
7.1.3.7. Reliable Data Transfer (Message) 9.1.3.7. Reliable Data Transfer (Message)
Name: msgReliable Name: msgReliable
Type: Boolean Type: Boolean
Default: the queried Boolean value of the Selection Property Default: the queried Boolean value of the Selection Property
"reliability" (Section 4.2.1) "reliability" (Section 6.2.1)
When true, this property specifies that a Message should be sent in When true, this property specifies that a Message should be sent in
such a way that the transport protocol ensures all data is received such a way that the transport protocol ensures all data is received
on the other side without corruption. Changing the "Reliable Data on the other side without corruption. Changing the "Reliable Data
Transfer" property on Messages is only possible for Connections that Transfer" property on Messages is only possible for Connections that
were established enabling the Selection Property "Configure Per- were established enabling the Selection Property "Configure Per-
Message Reliability". When this is not the case, changing Message Reliability". When this is not the case, changing
"msgReliable" will generate an error. "msgReliable" will generate an error.
Disabling this property indicates that the Transport Services system Disabling this property indicates that the Transport Services system
may disable retransmissions or other reliability mechanisms for this may disable retransmissions or other reliability mechanisms for this
particular Message, but such disabling is not guaranteed. particular Message, but such disabling is not guaranteed.
7.1.3.8. Message Capacity Profile Override 9.1.3.8. Message Capacity Profile Override
Name: msgCapacityProfile Name: msgCapacityProfile
Type: Enumeration Type: Enumeration
Default: inherited from the Connection Property Default: inherited from the Connection Property
"connCapacityProfile" (Section 6.1.6) "connCapacityProfile" (Section 8.1.6)
This enumerated property specifies the application's preferred This enumerated property specifies the application's preferred
tradeoffs for sending this Message; it is a per-Message override of tradeoffs for sending this Message; it is a per-Message override of
the Capacity Profile connection property (see Section 6.1.6). the Capacity Profile connection property (see Section 8.1.6).
7.1.3.9. No Network-Layer Fragmentation 9.1.3.9. No Network-Layer Fragmentation
Name: noFragmentation Name: noFragmentation
Type: Boolean Type: Boolean
Default: false Default: false
This property specifies that a message should be sent and received as This property specifies that a message should be sent and received
a single packet without network-layer fragmentation, if possible. without network-layer fragmentation, if possible. It can be used to
avoid network layer fragmentation when transport segmentation is
prefered.
This only takes effect when the transport uses a network layer that This only takes effect when the transport uses a network layer that
supports this functionality. When it does take effect, setting this supports this functionality. When it does take effect, setting this
property to true will cause the Don't Fragment bit to be set in the property to true will cause the sender to avoid network-layer source
IP header, and attempts to send a message with this property set to a frgementation. When using IPv4, this will result in the Don't
size greater than the transport's current estimate of its maximum Fragment bit being set in the IP header.
packet size ("singularTransmissionMsgMaxLen") will result in a
"SendError".
7.1.3.10. No Segmentation Attempts to send a message with this property that result in a size
greater than the transport's current estimate of its maximum packet
size ("singularTransmissionMsgMaxLen") can result in transport
segmentation when permitted, or in a "SendError".
Note: noSegmentation should be used when it is desired to only send a
message within a single network packet.
9.1.3.10. No Segmentation
Name: noSegmentation Name: noSegmentation
Type: Boolean Type: Boolean
Default: false Default: false
When set to true, this property requests the network layer at the When set to true, this property requests the transport layer to not
sending endpoint to not fragment the packets generated by the provide segmentation of messages larger than the maximum size
transport layer. When running over IPv4, setting this property to permitted by the network layer, and also to avoid network-layer
true will also cause the Don't Fragment bit to be set in the IP source fragmentation of messages. When running over IPv4, setting
header. When this property is set, an attempt to send a message size this property to true can result in a sending endpount setting the
Don't Fragment bit in the IPv4 header of packets generated by the
transport layer. An attempt to send a message that results in a size
greater than the transport's current estimate of its maximum packet greater than the transport's current estimate of its maximum packet
size (singularTransmissionMsgMaxLen) will result in a SendError. size (singularTransmissionMsgMaxLen) will result in a SendError.
This only takes effect when the transport and network layer support This only takes effect when the transport and network layer support
this functionality. this functionality.
7.2. Sending Data 9.2. Sending Data
Once a Connection has been established, it can be used for sending Once a Connection has been established, it can be used for sending
Messages. By default, Send enqueues a complete Message, and takes Messages. By default, Send enqueues a complete Message, and takes
optional per-Message properties (see Section 7.2.1). All Send optional per-Message properties (see Section 9.2.1). All Send
actions are asynchronous, and deliver Events (see Section 7.2.2). actions are asynchronous, and deliver Events (see Section 9.2.2).
Sending partial Messages for streaming large data is also supported Sending partial Messages for streaming large data is also supported
(see Section 7.2.3). (see Section 9.2.3).
Messages are sent on a Connection using the Send action: Messages are sent on a Connection using the Send action:
Connection.Send(messageData, messageContext?, endOfMessage?) Connection.Send(messageData, messageContext?, endOfMessage?)
where messageData is the data object to send, and messageContext where messageData is the data object to send, and messageContext
allows adding Message Properties, identifying Send Events related to allows adding Message Properties, identifying Send Events related to
a specific Message or inspecting meta-data related to the Message a specific Message or inspecting meta-data related to the Message
sent (see Section 7.1.1). sent (see Section 9.1.1).
The optional endOfMessage parameter supports partial sending and is The optional endOfMessage parameter supports partial sending and is
described in Section 7.2.3. described in Section 9.2.3.
7.2.1. Basic Sending 9.2.1. Basic Sending
The most basic form of sending on a connection involves enqueuing a The most basic form of sending on a connection involves enqueuing a
single Data block as a complete Message with default Message single Data block as a complete Message with default Message
Properties. Properties.
messageData := "hello" messageData := "hello"
Connection.Send(messageData) Connection.Send(messageData)
The interpretation of a Message to be sent is dependent on the The interpretation of a Message to be sent is dependent on the
implementation, and on the constraints on the Protocol Stacks implied implementation, and on the constraints on the Protocol Stacks implied
by the Connection's transport properties. For example, a Message may by the Connection's transport properties. For example, a Message may
be a single datagram for UDP Connections; or an HTTP Request for HTTP be a single datagram for UDP Connections; or an HTTP Request for HTTP
Connections. Connections.
Some transport protocols can deliver arbitrarily sized Messages, but Some transport protocols can deliver arbitrarily sized Messages, but
other protocols constrain the maximum Message size. Applications can other protocols constrain the maximum Message size. Applications can
query the Connection Property "Maximum Message size on send" query the Connection Property "Maximum Message size on send"
(Section 6.1.11.3) to determine the maximum size allowed for a single (Section 8.1.11.3) to determine the maximum size allowed for a single
Message. If a Message is too large to fit in the Maximum Message Message. If a Message is too large to fit in the Maximum Message
Size for the Connection, the Send will fail with a SendError event Size for the Connection, the Send will fail with a SendError event
(Section 7.2.2.3). For example, it is invalid to send a Message over (Section 9.2.2.3). For example, it is invalid to send a Message over
a UDP connection that is larger than the available datagram sending a UDP connection that is larger than the available datagram sending
size. size.
7.2.2. Send Events 9.2.2. Send Events
Like all Actions in this interface, the Send Action is asynchronous. Like all Actions in this interface, the Send Action is asynchronous.
There are several Events that can be delivered in response to Sending There are several Events that can be delivered in response to Sending
a Message. Exactly one Event (Sent, Expired, or SendError) will be a Message. Exactly one Event (Sent, Expired, or SendError) will be
delivered in response to each call to Send. delivered in response to each call to Send.
Note that if partial Sends are used (Section 7.2.3), there will still Note that if partial Sends are used (Section 9.2.3), there will still
be exactly one Send Event delivered for each call to Send. For be exactly one Send Event delivered for each call to Send. For
example, if a Message expired while two requests to Send data for example, if a Message expired while two requests to Send data for
that Message are outstanding, there will be two Expired events that Message are outstanding, there will be two Expired events
delivered. delivered.
The interface should allow the application to correlate which Send The interface should allow the application to correlate which Send
Action resulted in a particular Send Event. The manner in which this Action resulted in a particular Send Event. The manner in which this
correlation is indicated is implementation-specific. correlation is indicated is implementation-specific.
7.2.2.1. Sent 9.2.2.1. Sent
Connection -> Sent<messageContext> Connection -> Sent<messageContext>
The Sent Event occurs when a previous Send Action has completed, The Sent Event occurs when a previous Send Action has completed,
i.e., when the data derived from the Message has been passed down or i.e., when the data derived from the Message has been passed down or
through the underlying Protocol Stack and is no longer the through the underlying Protocol Stack and is no longer the
responsibility of this interface. The exact disposition of the responsibility of this interface. The exact disposition of the
Message (i.e., whether it has actually been transmitted, moved into a Message (i.e., whether it has actually been transmitted, moved into a
buffer on the network interface, moved into a kernel buffer, and so buffer on the network interface, moved into a kernel buffer, and so
on) when the Sent Event occurs is implementation-specific. The Sent on) when the Sent Event occurs is implementation-specific. The Sent
Event contains a reference to the Message to which it applies. Event contains a reference to the Message Context of the Message to
which it applies.
Sent Events allow an application to obtain an understanding of the Sent Events allow an application to obtain an understanding of the
amount of buffering it creates. That is, if an application calls the amount of buffering it creates. That is, if an application calls the
Send Action multiple times without waiting for a Sent Event, it has Send Action multiple times without waiting for a Sent Event, it has
created more buffer inside the Transport Services system than an created more buffer inside the Transport Services system than an
application that always waits for the Sent Event before calling the application that always waits for the Sent Event before calling the
next Send Action. next Send Action.
7.2.2.2. Expired 9.2.2.2. Expired
Connection -> Expired<messageContext> Connection -> Expired<messageContext>
The Expired Event occurs when a previous Send Action expired before The Expired Event occurs when a previous Send Action expired before
completion; i.e. when the Message was not sent before its Lifetime completion; i.e. when the Message was not sent before its Lifetime
(see Section 7.1.3.1) expired. This is separate from SendError, as (see Section 9.1.3.1) expired. This is separate from SendError, as
it is an expected behavior for partially reliable transports. The it is an expected behavior for partially reliable transports. The
Expired Event contains a reference to the Message to which it Expired Event contains a reference to the Message Context of the
applies. Message to which it applies.
7.2.2.3. SendError 9.2.2.3. SendError
Connection -> SendError<messageContext, reason?> Connection -> SendError<messageContext, reason?>
A SendError occurs when a Message was not sent due to an error A SendError occurs when a Message was not sent due to an error
condition: an attempt to send a Message which is too large for the condition: an attempt to send a Message which is too large for the
system and Protocol Stack to handle, some failure of the underlying system and Protocol Stack to handle, some failure of the underlying
Protocol Stack, or a set of Message Properties not consistent with Protocol Stack, or a set of Message Properties not consistent with
the Connection's transport properties. The SendError contains a the Connection's transport properties. The SendError contains a
reference to the Message to which it applies. reference to the Message Context of the Message to which it applies.
7.2.3. Partial Sends 9.2.3. Partial Sends
It is not always possible for an application to send all data It is not always possible for an application to send all data
associated with a Message in a single Send Action. The Message data associated with a Message in a single Send Action. The Message data
may be too large for the application to hold in memory at one time, may be too large for the application to hold in memory at one time,
or the length of the Message may be unknown or unbounded. or the length of the Message may be unknown or unbounded.
Partial Message sending is supported by passing an endOfMessage Partial Message sending is supported by passing an endOfMessage
boolean parameter to the Send Action. This value is always true by boolean parameter to the Send Action. This value is always true by
default, and the simpler forms of Send are equivalent to passing true default, and the simpler forms of Send are equivalent to passing true
for endOfMessage. for endOfMessage.
skipping to change at page 58, line 45 skipping to change at page 61, line 27
Connection.Send(messageData, messageContext, endOfMessage) Connection.Send(messageData, messageContext, endOfMessage)
messageData := "lo" messageData := "lo"
endOfMessage := true endOfMessage := true
Connection.Send(messageData, messageContext, endOfMessage) Connection.Send(messageData, messageContext, endOfMessage)
All data sent with the same MessageContext object will be treated as All data sent with the same MessageContext object will be treated as
belonging to the same Message, and will constitute an in-order series belonging to the same Message, and will constitute an in-order series
until the endOfMessage is marked. until the endOfMessage is marked.
7.2.4. Batching Sends 9.2.4. Batching Sends
To reduce the overhead of sending multiple small Messages on a To reduce the overhead of sending multiple small Messages on a
Connection, the application could batch several Send Actions Connection, the application could batch several Send Actions
together. This provides a hint to the system that the sending of together. This provides a hint to the system that the sending of
these Messages ought to be coalesced when possible, and that sending these Messages ought to be coalesced when possible, and that sending
any of the batched Messages can be delayed until the last Message in any of the batched Messages can be delayed until the last Message in
the batch is enqueued. the batch is enqueued.
The semantics for starting and ending a batch can be implementation- The semantics for starting and ending a batch can be implementation-
specific, but need to allow multiple Send Actions to be enqueued. specific, but need to allow multiple Send Actions to be enqueued.
Connection.StartBatch() Connection.StartBatch()
Connection.Send(messageData) Connection.Send(messageData)
Connection.Send(messageData) Connection.Send(messageData)
Connection.EndBatch() Connection.EndBatch()
7.2.5. Send on Active Open: InitiateWithSend 9.2.5. Send on Active Open: InitiateWithSend
For application-layer protocols where the Connection initiator also For application-layer protocols where the Connection initiator also
sends the first message, the InitiateWithSend() action combines sends the first message, the InitiateWithSend() action combines
Connection initiation with a first Message sent: Connection initiation with a first Message sent:
Connection := Preconnection.InitiateWithSend(messageData, messageContext?, timeout?) Connection := Preconnection.InitiateWithSend(messageData, messageContext?, timeout?)
Whenever possible, a messageContext should be provided to declare the Whenever possible, a messageContext should be provided to declare the
Message passed to InitiateWithSend as "Safely Replayable". This Message passed to InitiateWithSend as "Safely Replayable". This
allows the Transport Services system to make use of 0-RTT allows the Transport Services system to make use of 0-RTT
establishment in case this is supported by the available protocol establishment in case this is supported by the available protocol
stacks. When the selected stack(s) do not support transmitting data stacks. When the selected stack(s) do not support transmitting data
upon connection establishment, InitiateWithSend is identical to upon connection establishment, InitiateWithSend is identical to
Initiate() followed by Send(). Initiate() followed by Send().
Neither partial sends nor send batching are supported by Neither partial sends nor send batching are supported by
InitiateWithSend(). InitiateWithSend().
skipping to change at page 59, line 36 skipping to change at page 62, line 19
upon connection establishment, InitiateWithSend is identical to upon connection establishment, InitiateWithSend is identical to
Initiate() followed by Send(). Initiate() followed by Send().
Neither partial sends nor send batching are supported by Neither partial sends nor send batching are supported by
InitiateWithSend(). InitiateWithSend().
The Events that may be sent after InitiateWithSend() are equivalent The Events that may be sent after InitiateWithSend() are equivalent
to those that would be sent by an invocation of Initiate() followed to those that would be sent by an invocation of Initiate() followed
immediately by an invocation of Send(), with the caveat that a send immediately by an invocation of Send(), with the caveat that a send
failure that occurs because the Connection could not be established failure that occurs because the Connection could not be established
will not result in a SendError separate from the InitiateError will not result in a SendError separate from the EstablishmentError
signaling the failure of Connection establishment. signaling the failure of Connection establishment.
7.2.6. Priority in TAPS 9.2.6. Priority in TAPS
The Transport Services interface provides two properties to allow a The Transport Services interface provides two properties to allow a
sender to signal the relative priority of data transmission: the sender to signal the relative priority of data transmission: the
Priority Message Property Section 7.1.3.2, and the Connection Priority Message Property Section 9.1.3.2, and the Connection
Priority Connection Property Section 6.1.2. These properties are Priority Connection Property Section 8.1.2. These properties are
designed to allow the expression and implementation of a wide variety designed to allow the expression and implementation of a wide variety
of approaches to transmission priority in the transport and of approaches to transmission priority in the transport and
application layer, including those which do not appear on the wire application layer, including those which do not appear on the wire
(affecting only sender-side transmission scheduling) as well as those (affecting only sender-side transmission scheduling) as well as those
that do (e.g. [I-D.ietf-httpbis-priority]. that do (e.g. [I-D.ietf-httpbis-priority].
A Transport Services system gives no guarantees about how its A Transport Services system gives no guarantees about how its
expression of relative priorities will be realized; for example, if a expression of relative priorities will be realized. However, the
transport stack that only provides a single in-order reliable stream Transport Services system will seek to ensure that performance of
is selected, prioritization information can only be ignored. relatively-prioritized connections and messages is not worse with
However, the Transport Services system will seek to ensure that respect to those connections and messages than an equivalent
performance of relatively-prioritized connections and messages is not configuration in which all prioritization properties are left at
worse with respect to those connections and messages than an their defaults.
equivalent configuration in which all prioritization properties are
left at their defaults.
The Transport Services interface does order Connection Priority over The Transport Services interface does order Connection Priority over
the Priority Message Property. In the absense of other externalities the Priority Message Property. In the absense of other externalities
(e.g., transport-layer flow control), a priority 1 Message on a (e.g., transport-layer flow control), a priority 1 Message on a
priority 0 Connection will be sent before a priority 0 Message on a priority 0 Connection will be sent before a priority 0 Message on a
priority 1 Connection in the same group. priority 1 Connection in the same group.
7.3. Receiving Data 9.3. Receiving Data
Once a Connection is established, it can be used for receiving data Once a Connection is established, it can be used for receiving data
(unless the "Direction of Communication" property is set to (unless the "Direction of Communication" property is set to
"unidirectional send"). As with sending, the data is received in "unidirectional send"). As with sending, the data is received in
Messages. Receiving is an asynchronous operation, in which each call Messages. Receiving is an asynchronous operation, in which each call
to Receive enqueues a request to receive new data from the to Receive enqueues a request to receive new data from the
connection. Once data has been received, or an error is encountered, connection. Once data has been received, or an error is encountered,
an event will be delivered to complete any pending Receive requests an event will be delivered to complete any pending Receive requests
(see Section 7.3.2). If Messages arrive at the Transport Services (see Section 9.3.2). If Messages arrive at the Transport Services
system before Receive requests are issued, ensuing Receive requests system before Receive requests are issued, ensuing Receive requests
will first operate on these Messages before awaiting any further will first operate on these Messages before awaiting any further
Messages. Messages.
7.3.1. Enqueuing Receives 9.3.1. Enqueuing Receives
Receive takes two parameters to specify the length of data that an Receive takes two parameters to specify the length of data that an
application is willing to receive, both of which are optional and application is willing to receive, both of which are optional and
have default values if not specified. have default values if not specified.
Connection.Receive(minIncompleteLength?, maxLength?) Connection.Receive(minIncompleteLength?, maxLength?)
By default, Receive will try to deliver complete Messages in a single By default, Receive will try to deliver complete Messages in a single
event (Section 7.3.2.1). event (Section 9.3.2.1).
The application can set a minIncompleteLength value to indicate the The application can set a minIncompleteLength value to indicate the
smallest partial Message data size in bytes that should be delivered smallest partial Message data size in bytes that should be delivered
in response to this Receive. By default, this value is infinite, in response to this Receive. By default, this value is infinite,
which means that only complete Messages should be delivered (see which means that only complete Messages should be delivered (see
Section 7.3.2.2 and Section 7.1.2 for more information on how this is Section 9.3.2.2 and Section 9.1.2 for more information on how this is
accomplished). If this value is set to some smaller value, the accomplished). If this value is set to some smaller value, the
associated receive event will be triggered only when at least that associated receive event will be triggered only when at least that
many bytes are available, or the Message is complete with fewer many bytes are available, or the Message is complete with fewer
bytes, or the system needs to free up memory. Applications should bytes, or the system needs to free up memory. Applications should
always check the length of the data delivered to the receive event always check the length of the data delivered to the receive event
and not assume it will be as long as minIncompleteLength in the case and not assume it will be as long as minIncompleteLength in the case
of shorter complete Messages or memory issues. of shorter complete Messages or memory issues.
The maxLength argument indicates the maximum size of a Message in The maxLength argument indicates the maximum size of a Message in
bytes that the application is currently prepared to receive. The bytes that the application is currently prepared to receive. The
default value for maxLength is infinite. If an incoming Message is default value for maxLength is infinite. If an incoming Message is
larger than the minimum of this size and the maximum Message size on larger than the minimum of this size and the maximum Message size on
receive for the Connection's Protocol Stack, it will be delivered via receive for the Connection's Protocol Stack, it will be delivered via
ReceivedPartial events (Section 7.3.2.2). ReceivedPartial events (Section 9.3.2.2).
Note that maxLength does not guarantee that the application will Note that maxLength does not guarantee that the application will
receive that many bytes if they are available; the interface could receive that many bytes if they are available; the interface could
return ReceivedPartial events with less data than maxLength according return ReceivedPartial events with less data than maxLength according
to implementation constraints. Note also that maxLength and to implementation constraints. Note also that maxLength and
minIncompleteLength are intended only to manage buffering, and are minIncompleteLength are intended only to manage buffering, and are
not interpreted as a receiver preference for message reordering. not interpreted as a receiver preference for message reordering.
7.3.2. Receive Events 9.3.2. Receive Events
Each call to Receive will be paired with a single Receive Event, Each call to Receive will be paired with a single Receive Event,
which can be a success or an error. This allows an application to which can be a success or an error. This allows an application to
provide backpressure to the transport stack when it is temporarily provide backpressure to the transport stack when it is temporarily
not ready to receive messages. not ready to receive messages.
The interface should allow the application to correlate which call to The interface should allow the application to correlate which call to
Receive resulted in a particular Receive Event. The manner in which Receive resulted in a particular Receive Event. The manner in which
this correlation is indicated is implementation-specific. this correlation is indicated is implementation-specific.
7.3.2.1. Received 9.3.2.1. Received
Connection -> Received<messageData, messageContext> Connection -> Received<messageData, messageContext>
A Received event indicates the delivery of a complete Message. It A Received event indicates the delivery of a complete Message. It
contains two objects, the received bytes as messageData, and the contains two objects, the received bytes as messageData, and the
metadata and properties of the received Message as messageContext. metadata and properties of the received Message as messageContext.
The messageData object provides access to the bytes that were The messageData object provides access to the bytes that were
received for this Message, along with the length of the byte array. received for this Message, along with the length of the byte array.
The messageContext is provided to enable retrieving metadata about The messageContext is provided to enable retrieving metadata about
the message and referring to the message, e.g., to send replies and the message and referring to the message, e.g., to send replies and
map responses to their requests. See Section 7.1.1 for details. map responses to their requests. See Section 9.1.1 for details.
See Section 7.1.2 for handling Message framing in situations where See Section 9.1.2 for handling Message framing in situations where
the Protocol Stack only provides a byte-stream transport. the Protocol Stack only provides a byte-stream transport.
7.3.2.2. ReceivedPartial 9.3.2.2. ReceivedPartial
Connection -> ReceivedPartial<messageData, messageContext, endOfMessage> Connection -> ReceivedPartial<messageData, messageContext, endOfMessage>
If a complete Message cannot be delivered in one event, one part of If a complete Message cannot be delivered in one event, one part of
the Message can be delivered with a ReceivedPartial event. To the Message can be delivered with a ReceivedPartial event. To
continue to receive more of the same Message, the application must continue to receive more of the same Message, the application must
invoke Receive again. invoke Receive again.
Multiple invocations of ReceivedPartial deliver data for the same Multiple invocations of ReceivedPartial deliver data for the same
Message by passing the same MessageContext, until the endOfMessage Message by passing the same MessageContext, until the endOfMessage
flag is delivered or a ReceiveError occurs. All partial blocks of a flag is delivered or a ReceiveError occurs. All partial blocks of a
single Message are delivered in order without gaps. This event does single Message are delivered in order without gaps. This event does
not support delivering discontiguous partial Messages. If, for not support delivering discontiguous partial Messages. If, for
example, Message A is divided into three pieces (A1, A2, A3) and example, Message A is divided into three pieces (A1, A2, A3) and
Message B is divided into three pieces (B1, B2, B3), the Message B is divided into three pieces (B1, B2, B3), and
ReceivedPartial may deliver them in a sequence like this: A1, B1, B2, preserveOrder is not Required, the ReceivedPartial may deliver them
A2, A3, B3, because the messageContext allows the application to in a sequence like this: A1, B1, B2, A2, A3, B3, because the
identify the pieces as belonging to Message A and B, respectively. messageContext allows the application to identify the pieces as
However, a sequence like: A1, A3 will never occur. belonging to Message A and B, respectively. However, a sequence
like: A1, A3 will never occur.
If the minIncompleteLength in the Receive request was set to be If the minIncompleteLength in the Receive request was set to be
infinite (indicating a request to receive only complete Messages), infinite (indicating a request to receive only complete Messages),
the ReceivedPartial event may still be delivered if one of the the ReceivedPartial event may still be delivered if one of the
following conditions is true: following conditions is true:
* the underlying Protocol Stack supports message boundary * the underlying Protocol Stack supports message boundary
preservation, and the size of the Message is larger than the preservation, and the size of the Message is larger than the
buffers available for a single message; buffers available for a single message;
* the underlying Protocol Stack does not support message boundary * the underlying Protocol Stack does not support message boundary
preservation, and the Message Framer (see Section 7.1.2) cannot preservation, and the Message Framer (see Section 9.1.2) cannot
determine the end of the message using the buffer space it has determine the end of the message using the buffer space it has
available; or available; or
* the underlying Protocol Stack does not support message boundary * the underlying Protocol Stack does not support message boundary
preservation, and no Message Framer was supplied by the preservation, and no Message Framer was supplied by the
application application
Note that in the absence of message boundary preservation or a Note that in the absence of message boundary preservation or a
Message Framer, all bytes received on the Connection will be Message Framer, all bytes received on the Connection will be
represented as one large Message of indeterminate length. represented as one large Message of indeterminate length.
7.3.2.3. ReceiveError 9.3.2.3. ReceiveError
Connection -> ReceiveError<messageContext, reason?> Connection -> ReceiveError<messageContext, reason?>
A ReceiveError occurs when data is received by the underlying A ReceiveError occurs when data is received by the underlying
Protocol Stack that cannot be fully retrieved or parsed, or when some Protocol Stack that cannot be fully retrieved or parsed, and when it
other indication is received that reception has failed. In contrast, is useful for the application to be notified of such errors. For
conditions that irrevocably lead to the termination of the Connection example, a ReceiveError can indicate that a Message (identified via
are instead signaled using ConnectionError (see Section 8). the MessageContext) that was being partially received previously, but
had not completed, encountered an error and will not be completed.
This can be useful for an application, which may want to use this
error as a hint to remove previously received Message parts from
memory. As another example, if an incoming Message does not fulfill
the Required Minimum Corruption Protection Coverage for Receiving
property (see Section 8.1.1), an application can use this error as a
hint to inform the peer application to adjust the Sending Corruption
Protection Length property (see Section 9.1.3.6).
The ReceiveError event passes an optional associated MessageContext. In contrast, internal protocol reception errors (e.g., loss causing
This can indicate that a Message that was being partially received retransmissions in TCP) are not signalled by this Event. Conditions
previously, but had not completed, encountered an error and will not that irrevocably lead to the termination of the Connection are
be completed. signaled using ConnectionError (see Section 10).
7.3.3. Receive Message Properties 9.3.3. Receive Message Properties
Each Message Context may contain metadata from protocols in the Each Message Context may contain metadata from protocols in the
Protocol Stack; which metadata is available is Protocol Stack Protocol Stack; which metadata is available is Protocol Stack
dependent. These are exposed though additional read-only Message dependent. These are exposed through additional read-only Message
Properties that can be queried from the MessageContext object (see Properties that can be queried from the MessageContext object (see
Section 7.1.1) passed by the receive event. The following metadata Section 9.1.1) passed by the receive event. The following metadata
values are supported: values are supported:
7.3.3.1. UDP(-Lite)-specific Property: ECN 9.3.3.1. UDP(-Lite)-specific Property: ECN
When available, Message metadata carries the value of the Explicit When available, Message metadata carries the value of the Explicit
Congestion Notification (ECN) field. This information can be used Congestion Notification (ECN) field. This information can be used
for logging and debugging, and for building applications that need for logging and debugging, and for building applications that need
access to information about the transport internals for their own access to information about the transport internals for their own
operation. This property is specific to UDP and UDP-Lite because operation. This property is specific to UDP and UDP-Lite because
these protocols do not implement congestion control, and hence expose these protocols do not implement congestion control, and hence expose
this functionality to the application. this functionality to the application (see [RFC8293], following the
guidance in [RFC8085])
7.3.3.2. Early Data 9.3.3.2. Early Data
In some cases it can be valuable to know whether data was read as In some cases it can be valuable to know whether data was read as
part of early data transfer (before connection establishment has part of early data transfer (before connection establishment has
finished). This is useful if applications need to treat early data finished). This is useful if applications need to treat early data
separately, e.g., if early data has different security properties separately, e.g., if early data has different security properties
than data sent after connection establishment. In the case of TLS than data sent after connection establishment. In the case of TLS
1.3, client early data can be replayed maliciously (see [RFC8446]). 1.3, client early data can be replayed maliciously (see [RFC8446]).
Thus, receivers might wish to perform additional checks for early Thus, receivers might wish to perform additional checks for early
data to ensure it is safely replayable. If TLS 1.3 is available and data to ensure it is safely replayable. If TLS 1.3 is available and
the recipient Message was sent as part of early data, the the recipient Message was sent as part of early data, the
corresponding metadata carries a flag indicating as such. If early corresponding metadata carries a flag indicating as such. If early
data is enabled, applications should check this metadata field for data is enabled, applications should check this metadata field for
Messages received during connection establishment and respond Messages received during connection establishment and respond
accordingly. accordingly.
7.3.3.3. Receiving Final Messages 9.3.3.3. Receiving Final Messages
The Message Context can indicate whether or not this Message is the The Message Context can indicate whether or not this Message is the
Final Message on a Connection. For any Message that is marked as Final Message on a Connection. For any Message that is marked as
Final, the application can assume that there will be no more Messages Final, the application can assume that there will be no more Messages
received on the Connection once the Message has been completely received on the Connection once the Message has been completely
delivered. This corresponds to the Final property that may be marked delivered. This corresponds to the Final property that may be marked
on a sent Message, see Section 7.1.3.5. on a sent Message, see Section 9.1.3.5.
Some transport protocols and peers do not support signaling of the Some transport protocols and peers do not support signaling of the
Final property. Applications therefore should not rely on receiving Final property. Applications therefore should not rely on receiving
a Message marked Final to know that the sending endpoint is done a Message marked Final to know that the sending endpoint is done
sending on a connection. sending on a connection.
Any calls to Receive once the Final Message has been delivered will Any calls to Receive once the Final Message has been delivered will
result in errors. result in errors.
8. Connection Termination 10. Connection Termination
A Connection can be terminated i) by the Local Endpoint (i.e., the
application calls the Close, CloseGroup, Abort or AbortGroup Action),
ii) by the Remote Endpoint (i.e., the remote application calls the
Close, CloseGroup, Abort or AbortGroup Action), or iii) because of an
error (e.g., a timeout). A local call of the Close Action will cause
the Connection to either send a Closed Event or a ConnectionError
Event, and a local call of the CloseGroup Action will cause all of
the Connections in the group to either send a Closed Event or a
ConnectionError Event. A local call of the Abort Action will cause
the Connection to send a ConnectionError Event, indicating local
Abort as a reason, and a local call of the AbortGroup Action will
cause all of the Connections in the group to send a ConnectionError
Event, indicating local Abort as a reason.
Remote Action calls map to Events similar to local calls (e.g., a
remote Close causes the Connection to either send a Closed Event or a
ConnectionError Event), but, different from local Action calls, it is
not guaranteed that such Events will indeed be invoked. When an
application needs to free resources associated with a Connection, it
should therefore not rely on the invocation of such Events due to
termination calls from the Remote Endpoint, but instead use the local
termination Actions.
Close terminates a Connection after satisfying all the requirements Close terminates a Connection after satisfying all the requirements
that were specified regarding the delivery of Messages that the that were specified regarding the delivery of Messages that the
application has already given to the Transport Services system. For application has already given to the Transport Services system. Upon
example, if reliable delivery was requested for a Message handed over successfully satisfying all these requirements, the Connection will
before calling Close, the Closed Event will signify that this Message send the Closed Event. For example, if reliable delivery was
has indeed been delivered. This action does not affect any other requested for a Message handed over before calling Close, the Closed
Connection that is entangled with this one in a Connection Group. Event will signify that this Message has indeed been delivered. This
Action does not affect any other Connection in the same Connection
Group.
Connection.Close() Connection.Close()
The Closed Event informs the application that the Remote Endpoint has The Closed Event informs the application that a Close Action has
closed the Connection. There is no guarantee that a remote Close successfully completed, or that the Remote Endpoint has closed the
will indeed be signaled. Connection. There is no guarantee that a remote Close will be
signaled.
Connection -> Closed<> Connection -> Closed<>
Abort terminates a Connection without delivering any remaining Abort terminates a Connection without delivering any remaining
Messages. This action does not affect any other Connection that is Messages. This action does not affect any other Connection that is
entangled with this one in a Connection Group. entangled with this one in a Connection Group. When the Abort Action
has finished, the Connection will send a ConnectionError Event,
indicating local Abort as a reason.
Connection.Abort() Connection.Abort()
CloseGroup gracefully terminates a Connection and any other CloseGroup gracefully terminates a Connection and any other
Connections that are entangled with this one in a Connection Group. Connections in the same Connection Group. For example, all of the
For example, all of the Connections in a group might be streams of a Connections in a group might be streams of a single session for a
single session for a multistreaming protocol; closing the entire multistreaming protocol; closing the entire group will close the
group will close the underlying session. See also Section 5.4. As underlying session. See also Section 7.4. All Connections in the
with Close, any Messages remaining to be processed on a Connection group will send a Closed Event when the CloseGroup Action was
will be handled prior to closing. successful. As with Close, any Messages remaining to be processed on
a Connection will be handled prior to closing.
Connection.CloseGroup() Connection.CloseGroup()
AbortGroup terminates a Connection and any other Connections that are AbortGroup terminates a Connection and any other Connections that are
entangled with this one in a Connection Group without delivering any in the same Connection Group without delivering any remaining
remaining Messages. Messages. When the AbortGroup Action has finished, all Connections
in the group will send a ConnectionError Event, indicating local
Abort as a reason.
Connection.AbortGroup() Connection.AbortGroup()
A ConnectionError informs the application that: 1) data could not be A ConnectionError informs the application that: 1) data could not be
delivered to the peer after a timeout, or 2) the Connection has been delivered to the peer after a timeout, or 2) the Connection has been
aborted (e.g., because the peer has called Abort). There is no aborted (e.g., because the peer has called Abort). There is no
guarantee that an Abort will indeed be signaled. guarantee that an Abort from the peer will be signaled.
Connection -> ConnectionError<reason?> Connection -> ConnectionError<reason?>
9. Connection State and Ordering of Operations and Events 11. Connection State and Ordering of Operations and Events
This interface is designed to be independent of an implementation's This interface is designed to be independent of an implementation's
concurrency model. The details of how exactly actions are handled, concurrency model. The details of how exactly actions are handled,
and how events are dispatched, are implementation dependent. and how events are dispatched, are implementation dependent.
Each transition of connection state is associated with one of more Each transition of connection state is associated with one of more
events: events:
* Ready<> occurs when a Connection created with Initiate() or * Ready<> occurs when a Connection created with Initiate() or
InitiateWithSend() transitions to Established state. InitiateWithSend() transitions to Established state.
* ConnectionReceived<> occurs when a Connection created with * ConnectionReceived<> occurs when a Connection created with
Listen() transitions to Established state. Listen() transitions to Established state.
* RendezvousDone<> occurs when a Connection created with * RendezvousDone<> occurs when a Connection created with
Rendezvous() transitions to Established state. Rendezvous() transitions to Established state.
* Closed<> occurs when a Connection transitions to Closed state * Closed<> occurs when a Connection transitions to Closed state
without error. without error.
* InitiateError<> occurs when a Connection created with Initiate() * EstablishmentError<> occurs when a Connection created with
transitions from Establishing state to Closed state due to an Initiate() transitions from Establishing state to Closed state due
error. to an error.
* ConnectionError<> occurs when a Connection transitions to Closed * ConnectionError<> occurs when a Connection transitions to Closed
state due to an error in all other circumstances. state due to an error in all other circumstances.
The following diagram shows the possible states of a Connection and The following diagram shows the possible states of a Connection and
the events that occur upon a transition from one state to another. the events that occur upon a transition from one state to another.
(*) (**) (*) (**)
Establishing -----> Established -----> Closing ------> Closed Establishing -----> Established -----> Closing ------> Closed
| ^ | ^
| | | |
+---------------------------------------------------+ +---------------------------------------------------+
InitiateError<> EstablishmentError<>
(*) Ready<>, ConnectionReceived<>, RendezvousDone<> (*) Ready<>, ConnectionReceived<>, RendezvousDone<>
(**) Closed<>, ConnectionError<> (**) Closed<>, ConnectionError<>
Figure 2: Connection State Diagram Figure 2: Connection State Diagram
The interface provides the following guarantees about the ordering of The interface provides the following guarantees about the ordering of
operations: operations:
* Sent<> events will occur on a Connection in the order in which the * Sent<> events will occur on a Connection in the order in which the
Messages were sent (i.e., delivered to the kernel or to the Messages were sent (i.e., delivered to the kernel or to the
network interface, depending on implementation). network interface, depending on implementation).
* Received<> will never occur on a Connection before it is * Received<> will never occur on a Connection before it is
Established; i.e. before a Ready<> event on that Connection, or a Established; i.e. before a Ready<> event on that Connection, or a
ConnectionReceived<> or RendezvousDone<> containing that ConnectionReceived<> or RendezvousDone<> containing that
Connection. Connection.
* No events will occur on a Connection after it is Closed; i.e., * No events will occur on a Connection after it is Closed; i.e.,
after a Closed<> event, an InitiateError<> or ConnectionError<> after a Closed<> event, an EstablishmentError<> or
will not occur on that connection. To ensure this ordering, ConnectionError<> will not occur on that connection. To ensure
Closed<> will not occur on a Connection while other events on the this ordering, Closed<> will not occur on a Connection while other
Connection are still locally outstanding (i.e., known to the events on the Connection are still locally outstanding (i.e.,
interface and waiting to be dealt with by the application). known to the interface and waiting to be dealt with by the
application).
10. IANA Considerations 12. IANA Considerations
RFC-EDITOR: Please remove this section before publication. RFC-EDITOR: Please remove this section before publication.
This document has no Actions for IANA. Later versions of this This document has no Actions for IANA. Later versions of this
document may create IANA registries for generic transport property document may create IANA registries for generic transport property
names and transport property namespaces (see Section 3.2.1). names and transport property namespaces (see Section 4.1).
11. Privacy and Security Considerations 13. Privacy and Security Considerations
This document describes a generic API for interacting with a This document describes a generic API for interacting with a
transport services (TAPS) system. Part of this API includes transport services (TAPS) system. Part of this API includes
configuration details for transport security protocols, as discussed configuration details for transport security protocols, as discussed
in Section 4.3. It does not recommend use (or disuse) of specific in Section 6.3. It does not recommend use (or disuse) of specific
algorithms or protocols. Any API-compatible transport security algorithms or protocols. Any API-compatible transport security
protocol ought to work in a TAPS system. Security considerations for protocol ought to work in a TAPS system. Security considerations for
these protocols are discussed in the respective specifications. these protocols are discussed in the respective specifications.
The described API is used to exchange information between an The described API is used to exchange information between an
application and the Transport Services system. While it is not application and the Transport Services system. While it is not
necessarily expected that both systems are implemented by the same necessarily expected that both systems are implemented by the same
authority, it is expected that the Transport Services system authority, it is expected that the Transport Services system
implementation is either provided as a library that is selected by implementation is either provided as a library that is selected by
the application from a trusted party, or that it is part of the the application from a trusted party, or that it is part of the
skipping to change at page 67, line 48 skipping to change at page 71, line 34
more than one connection establishment. This is the case, for more than one connection establishment. This is the case, for
example, when the Transport Services system also executes name example, when the Transport Services system also executes name
resolution, when support mechanisms such as TURN or ICE are used to resolution, when support mechanisms such as TURN or ICE are used to
establish connectivity, if protocols or paths are raised, or if a establish connectivity, if protocols or paths are raised, or if a
path fails and fallback or re-establishment is supported in the path fails and fallback or re-establishment is supported in the
Transport Services system. Transport Services system.
Applications should also take care to not assume that all data Applications should also take care to not assume that all data
received using the Transport Services API is always complete or well- received using the Transport Services API is always complete or well-
formed. Specifically, messages that are received partially formed. Specifically, messages that are received partially
Section 7.3.2.2 could be a source of truncation attacks if Section 9.3.2.2 could be a source of truncation attacks if
applications do not distinguish between partial messages and complete applications do not distinguish between partial messages and complete
messages. messages.
The interface explicitly does not require the application to resolve The interface explicitly does not require the application to resolve
names, though there is a tradeoff between early and late binding of names, though there is a tradeoff between early and late binding of
addresses to names. Early binding allows the API implementation to addresses to names. Early binding allows the API implementation to
reduce connection setup latency, at the cost of potentially limited reduce connection setup latency, at the cost of potentially limited
scope for alternate path discovery during Connection establishment, scope for alternate path discovery during Connection establishment,
as well as potential additional information leakage about application as well as potential additional information leakage about application
interest when used with a resolution method (such as DNS without TLS) interest when used with a resolution method (such as DNS without TLS)
skipping to change at page 68, line 27 skipping to change at page 72, line 12
layer. This enables applications to more dynamically benefit from layer. This enables applications to more dynamically benefit from
innovations and new protocols in the transport, although it reduces innovations and new protocols in the transport, although it reduces
transparency of the underlying communication actions to the transparency of the underlying communication actions to the
application itself. The TAPS API is designed such that protocol and application itself. The TAPS API is designed such that protocol and
path selection can be limited to a small and controlled set if path selection can be limited to a small and controlled set if
required by the application for functional or security purposes. required by the application for functional or security purposes.
Further, TAPS implementations should provide an interface to poll Further, TAPS implementations should provide an interface to poll
information about which protocol and path is currently in use as well information about which protocol and path is currently in use as well
as provide logging about the communication events of each connection. as provide logging about the communication events of each connection.
12. Acknowledgements 14. Acknowledgements
This work has received funding from the European Union's Horizon 2020 This work has received funding from the European Union's Horizon 2020
research and innovation programme under grant agreements No. 644334 research and innovation programme under grant agreements No. 644334
(NEAT) and No. 688421 (MAMI). (NEAT) and No. 688421 (MAMI).
This work has been supported by Leibniz Prize project funds of DFG - This work has been supported by Leibniz Prize project funds of DFG -
German Research Foundation: Gottfried Wilhelm Leibniz-Preis 2011 (FKZ German Research Foundation: Gottfried Wilhelm Leibniz-Preis 2011 (FKZ
FE 570/4-1). FE 570/4-1).
This work has been supported by the UK Engineering and Physical This work has been supported by the UK Engineering and Physical
skipping to change at page 68, line 51 skipping to change at page 72, line 36
its "Toppforsk" programme through the "OCARINA" project. its "Toppforsk" programme through the "OCARINA" project.
Thanks to Stuart Cheshire, Josh Graessley, David Schinazi, and Eric Thanks to Stuart Cheshire, Josh Graessley, David Schinazi, and Eric
Kinnear for their implementation and design efforts, including Happy Kinnear for their implementation and design efforts, including Happy
Eyeballs, that heavily influenced this work. Thanks to Laurent Chuat Eyeballs, that heavily influenced this work. Thanks to Laurent Chuat
and Jason Lee for initial work on the Post Sockets interface, from and Jason Lee for initial work on the Post Sockets interface, from
which this work has evolved. Thanks to Maximilian Franke for asking which this work has evolved. Thanks to Maximilian Franke for asking
good questions based on implementation experience and for good questions based on implementation experience and for
contributing text, e.g., on multicast. contributing text, e.g., on multicast.
13. References 15. References
13.1. Normative References
15.1. Normative References
[I-D.ietf-taps-arch] [I-D.ietf-taps-arch]
Pauly, T., Trammell, B., Brunstrom, A., Fairhurst, G., Pauly, T., Trammell, B., Brunstrom, A., Fairhurst, G.,
Perkins, C., Tiesel, P., and C. Wood, "An Architecture for Perkins, C., Tiesel, P. S., and C. A. Wood, "An
Transport Services", Work in Progress, Internet-Draft, Architecture for Transport Services", Work in Progress,
draft-ietf-taps-arch-09, 2 November 2020, Internet-Draft, draft-ietf-taps-arch-10, 30 April 2021,
<http://www.ietf.org/internet-drafts/draft-ietf-taps-arch- <https://www.ietf.org/archive/id/draft-ietf-taps-arch-
09.txt>. 10.txt>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC2914] Floyd, S., "Congestion Control Principles", BCP 41, [RFC2914] Floyd, S., "Congestion Control Principles", BCP 41,
RFC 2914, DOI 10.17487/RFC2914, September 2000, RFC 2914, DOI 10.17487/RFC2914, September 2000,
<https://www.rfc-editor.org/info/rfc2914>. <https://www.rfc-editor.org/info/rfc2914>.
skipping to change at page 69, line 49 skipping to change at page 73, line 35
[RFC8303] Welzl, M., Tuexen, M., and N. Khademi, "On the Usage of [RFC8303] Welzl, M., Tuexen, M., and N. Khademi, "On the Usage of
Transport Features Provided by IETF Transport Protocols", Transport Features Provided by IETF Transport Protocols",
RFC 8303, DOI 10.17487/RFC8303, February 2018, RFC 8303, DOI 10.17487/RFC8303, February 2018,
<https://www.rfc-editor.org/info/rfc8303>. <https://www.rfc-editor.org/info/rfc8303>.
[RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol [RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol
Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018, Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
<https://www.rfc-editor.org/info/rfc8446>. <https://www.rfc-editor.org/info/rfc8446>.
13.2. Informative References 15.2. Informative References
[I-D.ietf-httpbis-priority] [I-D.ietf-httpbis-priority]
Oku, K. and L. Pardue, "Extensible Prioritization Scheme Oku, K. and L. Pardue, "Extensible Prioritization Scheme
for HTTP", Work in Progress, Internet-Draft, draft-ietf- for HTTP", Work in Progress, Internet-Draft, draft-ietf-
httpbis-priority-03, 11 January 2021, httpbis-priority-03, 11 January 2021,
<http://www.ietf.org/internet-drafts/draft-ietf-httpbis- <https://www.ietf.org/archive/id/draft-ietf-httpbis-
priority-03.txt>. priority-03.txt>.
[I-D.ietf-taps-impl] [I-D.ietf-taps-impl]
Brunstrom, A., Pauly, T., Enghardt, T., Grinnemo, K., Brunstrom, A., Pauly, T., Enghardt, T., Grinnemo, K.,
Jones, T., Tiesel, P., Perkins, C., and M. Welzl, Jones, T., Tiesel, P. S., Perkins, C., and M. Welzl,
"Implementing Interfaces to Transport Services", Work in "Implementing Interfaces to Transport Services", Work in
Progress, Internet-Draft, draft-ietf-taps-impl-08, 2 Progress, Internet-Draft, draft-ietf-taps-impl-09, 30
November 2020, <http://www.ietf.org/internet-drafts/draft- April 2021, <https://www.ietf.org/archive/id/draft-ietf-
ietf-taps-impl-08.txt>. taps-impl-09.txt>.
[I-D.ietf-tsvwg-datagram-plpmtud]
Fairhurst, G., Jones, T., Tuexen, M., Ruengeler, I., and
T. Voelker, "Packetization Layer Path MTU Discovery for
Datagram Transports", Work in Progress, Internet-Draft,
draft-ietf-tsvwg-datagram-plpmtud-22, 10 June 2020,
<http://www.ietf.org/internet-drafts/draft-ietf-tsvwg-
datagram-plpmtud-22.txt>.
[RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black, [RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black,
"Definition of the Differentiated Services Field (DS "Definition of the Differentiated Services Field (DS
Field) in the IPv4 and IPv6 Headers", RFC 2474, Field) in the IPv4 and IPv6 Headers", RFC 2474,
DOI 10.17487/RFC2474, December 1998, DOI 10.17487/RFC2474, December 1998,
<https://www.rfc-editor.org/info/rfc2474>. <https://www.rfc-editor.org/info/rfc2474>.
[RFC2597] Heinanen, J., Baker, F., Weiss, W., and J. Wroclawski, [RFC2597] Heinanen, J., Baker, F., Weiss, W., and J. Wroclawski,
"Assured Forwarding PHB Group", RFC 2597, "Assured Forwarding PHB Group", RFC 2597,
DOI 10.17487/RFC2597, June 1999, DOI 10.17487/RFC2597, June 1999,
skipping to change at page 72, line 15 skipping to change at page 75, line 35
[RFC8229] Pauly, T., Touati, S., and R. Mantha, "TCP Encapsulation [RFC8229] Pauly, T., Touati, S., and R. Mantha, "TCP Encapsulation
of IKE and IPsec Packets", RFC 8229, DOI 10.17487/RFC8229, of IKE and IPsec Packets", RFC 8229, DOI 10.17487/RFC8229,
August 2017, <https://www.rfc-editor.org/info/rfc8229>. August 2017, <https://www.rfc-editor.org/info/rfc8229>.
[RFC8260] Stewart, R., Tuexen, M., Loreto, S., and R. Seggelmann, [RFC8260] Stewart, R., Tuexen, M., Loreto, S., and R. Seggelmann,
"Stream Schedulers and User Message Interleaving for the "Stream Schedulers and User Message Interleaving for the
Stream Control Transmission Protocol", RFC 8260, Stream Control Transmission Protocol", RFC 8260,
DOI 10.17487/RFC8260, November 2017, DOI 10.17487/RFC8260, November 2017,
<https://www.rfc-editor.org/info/rfc8260>. <https://www.rfc-editor.org/info/rfc8260>.
[RFC8293] Ghanwani, A., Dunbar, L., McBride, M., Bannai, V., and R.
Krishnan, "A Framework for Multicast in Network
Virtualization over Layer 3", RFC 8293,
DOI 10.17487/RFC8293, January 2018,
<https://www.rfc-editor.org/info/rfc8293>.
[RFC8489] Petit-Huguenin, M., Salgueiro, G., Rosenberg, J., Wing, [RFC8489] Petit-Huguenin, M., Salgueiro, G., Rosenberg, J., Wing,
D., Mahy, R., and P. Matthews, "Session Traversal D., Mahy, R., and P. Matthews, "Session Traversal
Utilities for NAT (STUN)", RFC 8489, DOI 10.17487/RFC8489, Utilities for NAT (STUN)", RFC 8489, DOI 10.17487/RFC8489,
February 2020, <https://www.rfc-editor.org/info/rfc8489>. February 2020, <https://www.rfc-editor.org/info/rfc8489>.
[RFC8546] Trammell, B. and M. Kuehlewind, "The Wire Image of a [RFC8546] Trammell, B. and M. Kuehlewind, "The Wire Image of a
Network Protocol", RFC 8546, DOI 10.17487/RFC8546, April Network Protocol", RFC 8546, DOI 10.17487/RFC8546, April
2019, <https://www.rfc-editor.org/info/rfc8546>. 2019, <https://www.rfc-editor.org/info/rfc8546>.
[RFC8622] Bless, R., "A Lower-Effort Per-Hop Behavior (LE PHB) for [RFC8622] Bless, R., "A Lower-Effort Per-Hop Behavior (LE PHB) for
Differentiated Services", RFC 8622, DOI 10.17487/RFC8622, Differentiated Services", RFC 8622, DOI 10.17487/RFC8622,
June 2019, <https://www.rfc-editor.org/info/rfc8622>. June 2019, <https://www.rfc-editor.org/info/rfc8622>.
[RFC8699] Islam, S., Welzl, M., and S. Gjessing, "Coupled Congestion [RFC8699] Islam, S., Welzl, M., and S. Gjessing, "Coupled Congestion
Control for RTP Media", RFC 8699, DOI 10.17487/RFC8699, Control for RTP Media", RFC 8699, DOI 10.17487/RFC8699,
January 2020, <https://www.rfc-editor.org/info/rfc8699>. January 2020, <https://www.rfc-editor.org/info/rfc8699>.
[RFC8899] Fairhurst, G., Jones, T., Tüxen, M., Rüngeler, I., and T.
Völker, "Packetization Layer Path MTU Discovery for
Datagram Transports", RFC 8899, DOI 10.17487/RFC8899,
September 2020, <https://www.rfc-editor.org/info/rfc8899>.
[RFC8922] Enghardt, T., Pauly, T., Perkins, C., Rose, K., and C. [RFC8922] Enghardt, T., Pauly, T., Perkins, C., Rose, K., and C.
Wood, "A Survey of the Interaction between Security Wood, "A Survey of the Interaction between Security
Protocols and Transport Services", RFC 8922, Protocols and Transport Services", RFC 8922,
DOI 10.17487/RFC8922, October 2020, DOI 10.17487/RFC8922, October 2020,
<https://www.rfc-editor.org/info/rfc8922>. <https://www.rfc-editor.org/info/rfc8922>.
[RFC8923] Welzl, M. and S. Gjessing, "A Minimal Set of Transport [RFC8923] Welzl, M. and S. Gjessing, "A Minimal Set of Transport
Services for End Systems", RFC 8923, DOI 10.17487/RFC8923, Services for End Systems", RFC 8923, DOI 10.17487/RFC8923,
October 2020, <https://www.rfc-editor.org/info/rfc8923>. October 2020, <https://www.rfc-editor.org/info/rfc8923>.
skipping to change at page 73, line 36 skipping to change at page 77, line 14
* In C, a Tuple may be represented as a "struct" with one member for * In C, a Tuple may be represented as a "struct" with one member for
each of the value types in the ordered grouping. In Python, by each of the value types in the ordered grouping. In Python, by
contrast, a Tuple may be represented natively as a "tuple", a contrast, a Tuple may be represented natively as a "tuple", a
sequence of dynamically-typed elements. sequence of dynamically-typed elements.
* A Collection may be represented as a "std::set" in C++ or as a * A Collection may be represented as a "std::set" in C++ or as a
"set" in Python. In C, it may be represented as an array or as a "set" in Python. In C, it may be represented as an array or as a
higher-level data structure with appropriate accessors defined. higher-level data structure with appropriate accessors defined.
The objects described in Section 1.1 can similarly be represented in
different ways depending on which programming language is used.
Objects like Preconnections, Connections, and Listeners can be long-
lived, and benefit from using object-oriented constructs. Note that
in C, these objects may need to provide a way to release or free
their underlying memory when the application is done using them. For
example, since a Preconnection can be used to initiate multiple
Connections, it is the responsibility of the application to clean up
the Preconnection memory if necessary.
A.2. Events and Errors A.2. Events and Errors
This specification treats Events and Errors similarly. Errors, just This specification treats Events and Errors similarly. Errors, just
as any other Events, may occur asynchronously in network as any other Events, may occur asynchronously in network
applications. However, implementations of this interface may report applications. However, implementations of this interface may report
Errors synchronously, according to the error handling idioms of the Errors synchronously, according to the error handling idioms of the
implementation platform, where they can be immediately detected, such implementation platform, where they can be immediately detected, such
as by throwing an exception when attempting to initiate a connection as by generating an exception when attempting to initiate a
with inconsistent Transport Properties. An error can provide an connection with inconsistent Transport Properties. An error can
optional reason to the application with further details about why the provide an optional reason to the application with further details
error occurred. about why the error occurred.
A.3. Time Duration A.3. Time Duration
Time duration types are implementation-specific. For instance, it Time duration types are implementation-specific. For instance, it
could be a number of seconds, number of milliseconds, or a "struct could be a number of seconds, number of milliseconds, or a "struct
timeval" in C or a user-defined "Duration" class in C++. timeval" in C or a user-defined "Duration" class in C++.
Appendix B. Convenience Functions Appendix B. Convenience Functions
B.1. Adding Preference Properties B.1. Adding Preference Properties
As Selection Properties of type "Preference" will be set on a As Selection Properties of type "Preference" will be set on a
TransportProperties object quite frequently, implementations should TransportProperties object quite frequently, implementations can
provide special actions for adding each preference level i.e, provide special actions for adding each preference level i.e,
"TransportProperties.Set(some_property, avoid)" is equivalent to "TransportProperties.Set(some_property, avoid)" is equivalent to
"TransportProperties.Avoid(some_property)": "TransportProperties.Avoid(some_property)":
TransportProperties.Require(property) TransportProperties.Require(property)
TransportProperties.Prefer(property) TransportProperties.Prefer(property)
TransportProperties.Ignore(property) TransportProperties.Ignore(property)
TransportProperties.Avoid(property) TransportProperties.Avoid(property)
TransportProperties.Prohibit(property) TransportProperties.Prohibit(property)
B.2. Transport Property Profiles B.2. Transport Property Profiles
To ease the use of the interface specified by this document, To ease the use of the interface specified by this document,
implementations should provide a mechanism to create Transport implementations can provide a mechanism to create Transport Property
Property objects (see Section 4.2) that are pre-configured with objects (see Section 6.2) that are pre-configured with frequently
frequently used sets of properties. Implementations should at least used sets of properties; the following are in common use in current
offer short-hands to specify the following property profiles: applications:
B.2.1. reliable-inorder-stream B.2.1. reliable-inorder-stream
This profile provides reliable, in-order transport service with This profile provides reliable, in-order transport service with
congestion control. TCP is an example of a protocol that provides congestion control. TCP is an example of a protocol that provides
this service. It should consist of the following properties: this service. It should consist of the following properties:
+=======================+=========+ +=======================+=========+
| Property | Value | | Property | Value |
+=======================+=========+ +=======================+=========+
| reliability | require | | reliability | require |
+-----------------------+---------+ +-----------------------+---------+
| preserveOrder | require | | preserveOrder | require |
+-----------------------+---------+ +-----------------------+---------+
| congestionControl | require | | congestionControl | require |
+-----------------------+---------+ +-----------------------+---------+
| preserveMsgBoundaries | ignore | | preserveMsgBoundaries | ignore |
+-----------------------+---------+ +-----------------------+---------+
Table 2 Table 2: reliable-inorder-
stream preferences
B.2.2. reliable-message B.2.2. reliable-message
This profile provides message-preserving, reliable, in-order This profile provides message-preserving, reliable, in-order
transport service with congestion control. SCTP is an example of a transport service with congestion control. SCTP is an example of a
protocol that provides this service. It should consist of the protocol that provides this service. It should consist of the
following properties: following properties:
+=======================+=========+ +=======================+=========+
| Property | Value | | Property | Value |
+=======================+=========+ +=======================+=========+
| reliability | require | | reliability | require |
+-----------------------+---------+ +-----------------------+---------+
| preserveOrder | require | | preserveOrder | require |
+-----------------------+---------+ +-----------------------+---------+
| congestionControl | require | | congestionControl | require |
+-----------------------+---------+ +-----------------------+---------+
| preserveMsgBoundaries | require | | preserveMsgBoundaries | require |
+-----------------------+---------+ +-----------------------+---------+
Table 3 Table 3: reliable-message
preferences
B.2.3. unreliable-datagram B.2.3. unreliable-datagram
This profile provides unreliable datagram transport service. An This profile provides a datagram transport service without any
example of a protocol that provides this service is UDP. It consists reliability guarantee. An example of a protocol that provides this
of the following properties: service is UDP. It consists of the following properties:
+=======================+=========+ +=======================+=========+
| Property | Value | | Property | Value |
+=======================+=========+ +=======================+=========+
| reliability | ignore | | reliability | avoid |
+-----------------------+---------+ +-----------------------+---------+
| preserveOrder | ignore | | preserveOrder | avoid |
+-----------------------+---------+ +-----------------------+---------+
| congestionControl | ignore | | congestionControl | ignore |
+-----------------------+---------+ +-----------------------+---------+
| preserveMsgBoundaries | require | | preserveMsgBoundaries | require |
+-----------------------+---------+ +-----------------------+---------+
| safely replayable | true | | safely replayable | true |
+-----------------------+---------+ +-----------------------+---------+
Table 4 Table 4: unreliable-datagram
preferences
Applications that choose this Transport Property Profile for latency Applications that choose this Transport Property Profile would avoid
reasons should also consider setting an appropriate Capacity Profile the additional latency that could be introduced by retransmission or
Property, see Section 6.1.6 and could benefit from controlling reordering in a transport protocol.
checksum coverage, see Section 4.2.7 and Section 4.2.8.
Applications that choose this Transport Property Profile to reduce
latency should also consider setting an appropriate Capacity Profile
Property, see Section 8.1.6 and might benefit from controlling
checksum coverage, see Section 6.2.7 and Section 6.2.8.
Appendix C. Relationship to the Minimal Set of Transport Services for Appendix C. Relationship to the Minimal Set of Transport Services for
End Systems End Systems
[RFC8923] identifies a minimal set of transport services that end [RFC8923] identifies a minimal set of transport services that end
systems should offer. These services make all non-security-related systems should offer. These services make all non-security-related
transport features of TCP, MPTCP, UDP, UDP-Lite, SCTP and LEDBAT transport features of TCP, MPTCP, UDP, UDP-Lite, SCTP and LEDBAT
available that 1) require interaction with the application, and 2) do available that 1) require interaction with the application, and 2) do
not get in the way of a possible implementation over TCP (or, with not get in the way of a possible implementation over TCP (or, with
limitations, UDP). The following text explains how this minimal set limitations, UDP). The following text explains how this minimal set
is reflected in the present API. For brevity, it is based on the is reflected in the present API. For brevity, it is based on the
list in Section 4.1 of [RFC8923], updated according to the discussion list in Section 4.1 of [RFC8923], updated according to the discussion
in Section 5 of [RFC8923]. The present API covers all elements of in Section 5 of [RFC8923]. The present API covers all elements of
this section except "Notification of Excessive Retransmissions (early this section except "Notification of Excessive Retransmissions (early
warning below abortion threshold)". This list is a subset of the warning below abortion threshold)". This list is a subset of the
transport features in Appendix A of [RFC8923], which refers to the transport features in Appendix A of [RFC8923], which refers to the
primitives in "pass 2" (Section 4) of [RFC8303] for further details primitives in "pass 2" (Section 4) of [RFC8303] for further details
on the implementation with TCP, MPTCP, UDP, UDP-Lite, SCTP and on the implementation with TCP, MPTCP, UDP, UDP-Lite, SCTP and
LEDBAT. LEDBAT.
* Connect: "Initiate" Action (Section 5.1). * Connect: "Initiate" Action (Section 7.1).
* Listen: "Listen" Action (Section 5.2). * Listen: "Listen" Action (Section 7.2).
* Specify number of attempts and/or timeout for the first * Specify number of attempts and/or timeout for the first
establishment message: "timeout" parameter of "Initiate" establishment message: "timeout" parameter of "Initiate"
(Section 5.1) or "InitiateWithSend" Action (Section 7.2.5). (Section 7.1) or "InitiateWithSend" Action (Section 9.2.5).
* Disable MPTCP: "Multipath Transport" Property (Section 4.2.14). * Disable MPTCP: "Multipath Transport" Property (Section 6.2.14).
* Hand over a message to reliably transfer (possibly multiple times) * Hand over a message to reliably transfer (possibly multiple times)
before connection establishment: "InitiateWithSend" Action before connection establishment: "InitiateWithSend" Action
(Section 7.2.5). (Section 9.2.5).
* Change timeout for aborting connection (using retransmit limit or * Change timeout for aborting connection (using retransmit limit or
time value): "Timeout for Aborting Connection" property, using a time value): "Timeout for Aborting Connection" property, using a
time value (Section 6.1.3). time value (Section 8.1.3).
* Timeout event when data could not be delivered for too long: * Timeout event when data could not be delivered for too long:
"ConnectionError" Event (Section 8). "ConnectionError" Event (Section 10).
* Suggest timeout to the peer: "TCP-specific Properties: User * Suggest timeout to the peer: "TCP-specific Properties: User
Timeout Option (UTO)" (Section 6.2). Timeout Option (UTO)" (Section 8.2).
* Notification of ICMP error message arrival: "Notification of ICMP * Notification of ICMP error message arrival: "Notification of ICMP
soft error message arrival" property (Section 4.2.17). soft error message arrival" property (Section 6.2.17).
* Choose a scheduler to operate between streams of an association: * Choose a scheduler to operate between streams of an association:
"Connection Group Transmission Scheduler" property "Connection Group Transmission Scheduler" property
(Section 6.1.5). (Section 8.1.5).
* Configure priority or weight for a scheduler: "Connection * Configure priority or weight for a scheduler: "Connection
Priority" property (Section 6.1.2). Priority" property (Section 8.1.2).
* "Specify checksum coverage used by the sender" and "Disable * "Specify checksum coverage used by the sender" and "Disable
checksum when sending": "Sending Corruption Protection Length" checksum when sending": "Sending Corruption Protection Length"
property (Section 7.1.3.6) and "Full Checksum Coverage on Sending" property (Section 9.1.3.6) and "Full Checksum Coverage on Sending"
property (Section 4.2.7). property (Section 6.2.7).
* "Specify minimum checksum coverage required by receiver" and * "Specify minimum checksum coverage required by receiver" and
"Disable checksum requirement when receiving": "Required Minimum "Disable checksum requirement when receiving": "Required Minimum
Corruption Protection Coverage for Receiving" property Corruption Protection Coverage for Receiving" property
(Section 6.1.1) and "Full Checksum Coverage on Receiving" property (Section 8.1.1) and "Full Checksum Coverage on Receiving" property
(Section 4.2.8). (Section 6.2.8).
* "Specify DF field": "No Network-Layer Fragmentation" property * "Specify DF field": "No Network-Layer Fragmentation" property
(Section 7.1.3.9). (Section 9.1.3.9).
* "Request not to bundle messages": "No Segmentation" property
(Section 7.1.3.10).
* Get max. transport-message size that may be sent using a non- * Get max. transport-message size that may be sent using a non-
fragmented IP packet from the configured interface: "Maximum fragmented IP packet from the configured interface: "Maximum
Message Size Before Fragmentation or Segmentation" property Message Size Before Fragmentation or Segmentation" property
(Section 6.1.11.2). (Section 8.1.11.2).
* Get max. transport-message size that may be received from the * Get max. transport-message size that may be received from the
configured interface: "Maximum Message Size on Receive" property configured interface: "Maximum Message Size on Receive" property
(Section 6.1.11.4). (Section 8.1.11.4).
* Obtain ECN field: "UDP(-Lite)-specific Property: ECN" is a read- * Obtain ECN field: "UDP(-Lite)-specific Property: ECN" is a read-
only Message Property of the MessageContext object only Message Property of the MessageContext object
(Section 7.3.3.1). (Section 9.3.3.1).
* "Specify DSCP field", "Disable Nagle algorithm", "Enable and * "Specify DSCP field", "Disable Nagle algorithm", "Enable and
configure a "Low Extra Delay Background Transfer"": as suggested configure a "Low Extra Delay Background Transfer"": as suggested
in Section 5.5 of [RFC8923], these transport features are in Section 5.5 of [RFC8923], these transport features are
collectively offered via the "Capacity Profile" property collectively offered via the "Capacity Profile" property
(Section 6.1.6). Per-Message control is offered via the "Message (Section 8.1.6). Per-Message control ("Request not to bundle
Capacity Profile Override" property (Section 7.1.3.8). messages") is offered via the "Message Capacity Profile Override"
property (Section 9.1.3.8).
* Close after reliably delivering all remaining data, causing an * Close after reliably delivering all remaining data, causing an
event informing the application on the other side: this is offered event informing the application on the other side: this is offered
by the "Close" Action with slightly changed semantics in line with by the "Close" Action with slightly changed semantics in line with
the discussion in Section 5.2 of [RFC8923] (Section 8). the discussion in Section 5.2 of [RFC8923] (Section 10).
* "Abort without delivering remaining data, causing an event * "Abort without delivering remaining data, causing an event
informing the application on the other side" and "Abort without informing the application on the other side" and "Abort without
delivering remaining data, not causing an event informing the delivering remaining data, not causing an event informing the
application on the other side": this is offered by the "Abort" application on the other side": this is offered by the "Abort"
action without promising that this is signaled to the other side. action without promising that this is signaled to the other side.
If it is, a "ConnectionError" Event will fire at the peer If it is, a "ConnectionError" Event will fire at the peer
(Section 8). (Section 10).
* "Reliably transfer data, with congestion control", "Reliably * "Reliably transfer data, with congestion control", "Reliably
transfer a message, with congestion control" and "Unreliably transfer a message, with congestion control" and "Unreliably
transfer a message": data is transferred via the "Send" action transfer a message": data is transferred via the "Send" action
(Section 7.2). Reliability is controlled via the "Reliable Data (Section 9.2). Reliability is controlled via the "Reliable Data
Transfer (Connection)" (Section 4.2.1) property and the "Reliable Transfer (Connection)" (Section 6.2.1) property and the "Reliable
Data Transfer (Message)" Message Property (Section 7.1.3.7). Data Transfer (Message)" Message Property (Section 9.1.3.7).
Transmitting data as a message or without delimiters is controlled Transmitting data as a message or without delimiters is controlled
via Message Framers (Section 7.1.2). The choice of congestion via Message Framers (Section 9.1.2). The choice of congestion
control is provided via the "Congestion control" property control is provided via the "Congestion control" property
(Section 4.2.9). (Section 6.2.9).
* Configurable Message Reliability: the "Lifetime" Message Property * Configurable Message Reliability: the "Lifetime" Message Property
implements a time-based way to configure message reliability implements a time-based way to configure message reliability
(Section 7.1.3.1). (Section 9.1.3.1).
* "Ordered message delivery (potentially slower than unordered)" and * "Ordered message delivery (potentially slower than unordered)" and
"Unordered message delivery (potentially faster than ordered)": "Unordered message delivery (potentially faster than ordered)":
these two transport features are controlled via the Message these two transport features are controlled via the Message
Property "Ordered" (Section 7.1.3.3). Property "Ordered" (Section 9.1.3.3).
* Request not to delay the acknowledgement (SACK) of a message: * Request not to delay the acknowledgement (SACK) of a message:
should the protocol support it, this is one of the transport should the protocol support it, this is one of the transport
features the Transport Services system can apply when an features the Transport Services system can apply when an
application uses the "Capacity Profile" Property (Section 6.1.6) application uses the "Capacity Profile" Property (Section 8.1.6)
or the "Message Capacity Profile Override" Message Property or the "Message Capacity Profile Override" Message Property
(Section 7.1.3.8) with value "Low Latency/Interactive". (Section 9.1.3.8) with value "Low Latency/Interactive".
* Receive data (with no message delimiting): "Received" Event * Receive data (with no message delimiting): "Receive" Action
(Section 7.3.2.1). See Section 7.1.2 for handling Message framing (Section 9.3) and "Received" Event (Section 9.3.2.1).
in situations where the Protocol Stack only provides a byte-stream
transport.
* Receive a message: "Received" Event (Section 7.3.2.1), using * Receive a message: "Receive" Action (Section 9.3) and "Received"
Message Framers (Section 7.1.2). Event (Section 9.3.2.1), using Message Framers (Section 9.1.2).
* Information about partial message arrival: "ReceivedPartial" Event * Information about partial message arrival: "Receive" Action
(Section 7.3.2.2). (Section 9.3) and "ReceivedPartial" Event (Section 9.3.2.2).
* Notification of send failures: "Expired" Event (Section 7.2.2.2) * Notification of send failures: "Expired" Event (Section 9.2.2.2)
and "SendError" Event (Section 7.2.2.3). and "SendError" Event (Section 9.2.2.3).
* Notification that the stack has no more user data to send: * Notification that the stack has no more user data to send:
applications can obtain this information via the "Sent" Event applications can obtain this information via the "Sent" Event
(Section 7.2.2.1). (Section 9.2.2.1).
* Notification to a receiver that a partial message delivery has * Notification to a receiver that a partial message delivery has
been aborted: "ReceiveError" Event (Section 7.3.2.3). been aborted: "ReceiveError" Event (Section 9.3.2.3).
Authors' Addresses Authors' Addresses
Brian Trammell (editor) Brian Trammell (editor)
Google Switzerland GmbH Google Switzerland GmbH
Gustav-Gull-Platz 1 Gustav-Gull-Platz 1
CH- 8004 Zurich CH- 8004 Zurich
Switzerland Switzerland
Email: ietf@trammell.ch Email: ietf@trammell.ch
 End of changes. 356 change blocks. 
706 lines changed or deleted 839 lines changed or added

This html diff was produced by rfcdiff 1.46. The latest version is available from http://tools.ietf.org/tools/rfcdiff/