draft-ietf-taps-interface-01.txt   draft-ietf-taps-interface-02.txt 
TAPS Working Group B. Trammell, Ed. TAPS Working Group B. Trammell, Ed.
Internet-Draft ETH Zurich Internet-Draft ETH Zurich
Intended status: Informational M. Welzl, Ed. Intended status: Standards Track M. Welzl, Ed.
Expires: January 3, 2019 University of Oslo Expires: April 25, 2019 University of Oslo
T. Enghardt T. Enghardt
TU Berlin TU Berlin
G. Fairhurst G. Fairhurst
University of Aberdeen University of Aberdeen
M. Kuehlewind M. Kuehlewind
ETH Zurich ETH Zurich
C. Perkins C. Perkins
University of Glasgow University of Glasgow
P. Tiesel P. Tiesel
TU Berlin TU Berlin
C. Wood C. Wood
Apple Inc. Apple Inc.
July 02, 2018 October 22, 2018
An Abstract Application Layer Interface to Transport Services An Abstract Application Layer Interface to Transport Services
draft-ietf-taps-interface-01 draft-ietf-taps-interface-02
Abstract Abstract
This document describes an abstract programming interface to the This document describes an abstract programming interface to the
transport layer, following the Transport Services Architecture. It transport layer, following the Transport Services Architecture. It
supports the asynchronous, atomic transmission of messages over supports the asynchronous, atomic transmission of messages over
transport protocols and network paths dynamically selected at transport protocols and network paths dynamically selected at
runtime. It is intended to replace the traditional BSD sockets API runtime. It is intended to replace the traditional BSD sockets API
as the lowest common denominator interface to the transport layer, in as the lowest common denominator interface to the transport layer, in
an environment where endpoints have multiple interfaces and potential an environment where endpoints have multiple interfaces and potential
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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 January 3, 2019. This Internet-Draft will expire on April 25, 2019.
Copyright Notice Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the Copyright (c) 2018 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 Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of (https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Terminology and Notation . . . . . . . . . . . . . . . . . . 5 2. Terminology and Notation . . . . . . . . . . . . . . . . . . 5
3. Interface Design Principles . . . . . . . . . . . . . . . . . 6 3. Interface Design Principles . . . . . . . . . . . . . . . . . 6
4. API Summary . . . . . . . . . . . . . . . . . . . . . . . . . 7 4. API Summary . . . . . . . . . . . . . . . . . . . . . . . . . 7
5. Pre-Establishment Phase . . . . . . . . . . . . . . . . . . . 7 4.1. Transport Properties . . . . . . . . . . . . . . . . . . 7
5.1. Specifying Endpoints . . . . . . . . . . . . . . . . . . 8 4.2. Scope of the Interface Definition . . . . . . . . . . . . 8
5.2. Specifying Transport Properties . . . . . . . . . . . . . 9 5. Pre-Establishment Phase . . . . . . . . . . . . . . . . . . . 9
5.3. Specifying Security Parameters and Callbacks . . . . . . 10 5.1. Specifying Endpoints . . . . . . . . . . . . . . . . . . 9
5.3.1. Pre-Connection Parameters . . . . . . . . . . . . . . 11 5.2. Specifying Transport Properties . . . . . . . . . . . . . 11
5.3.2. Connection Establishment Callbacks . . . . . . . . . 12 5.2.1. Reliable Data Transfer (Connection) . . . . . . . . . 13
6. Establishing Connections . . . . . . . . . . . . . . . . . . 12 5.2.2. Configure per-Message reliability . . . . . . . . . . 13
6.1. Active Open: Initiate . . . . . . . . . . . . . . . . . . 12 5.2.3. Preservation of data ordering . . . . . . . . . . . . 13
6.2. Passive Open: Listen . . . . . . . . . . . . . . . . . . 13 5.2.4. Use 0-RTT session establishment with an idempotent
6.3. Peer-to-Peer Establishment: Rendezvous . . . . . . . . . 14 Message . . . . . . . . . . . . . . . . . . . . . . . 13
6.4. Connection Groups . . . . . . . . . . . . . . . . . . . . 16 5.2.5. Multistream Connections in Group . . . . . . . . . . 13
7. Sending Data . . . . . . . . . . . . . . . . . . . . . . . . 16 5.2.6. Control checksum coverage on sending or receiving . . 13
7.1. Basic Sending . . . . . . . . . . . . . . . . . . . . . . 17 5.2.7. Congestion control . . . . . . . . . . . . . . . . . 14
7.2. Send Events . . . . . . . . . . . . . . . . . . . . . . . 17 5.2.8. Interface Instance or Type . . . . . . . . . . . . . 14
7.2.1. Sent . . . . . . . . . . . . . . . . . . . . . . . . 18 5.2.9. Provisioning Domain Instance or Type . . . . . . . . 15
7.2.2. Expired . . . . . . . . . . . . . . . . . . . . . . . 18 5.3. Specifying Security Parameters and Callbacks . . . . . . 15
7.2.3. SendError . . . . . . . . . . . . . . . . . . . . . . 18 5.3.1. Pre-Connection Parameters . . . . . . . . . . . . . . 16
7.3. Message Context Parameters . . . . . . . . . . . . . . . 18 5.3.2. Connection Establishment Callbacks . . . . . . . . . 17
7.3.1. Lifetime . . . . . . . . . . . . . . . . . . . . . . 19 6. Establishing Connections . . . . . . . . . . . . . . . . . . 17
7.3.2. Niceness . . . . . . . . . . . . . . . . . . . . . . 20 6.1. Active Open: Initiate . . . . . . . . . . . . . . . . . . 17
7.3.3. Ordered . . . . . . . . . . . . . . . . . . . . . . . 20 6.2. Passive Open: Listen . . . . . . . . . . . . . . . . . . 18
7.3.4. Idempotent . . . . . . . . . . . . . . . . . . . . . 20 6.3. Peer-to-Peer Establishment: Rendezvous . . . . . . . . . 19
7.3.5. Final . . . . . . . . . . . . . . . . . . . . . . . . 20 6.4. Connection Groups . . . . . . . . . . . . . . . . . . . . 21
7.3.6. Corruption Protection Length . . . . . . . . . . . . 21 7. Sending Data . . . . . . . . . . . . . . . . . . . . . . . . 22
7.3.7. Transmission Profile . . . . . . . . . . . . . . . . 21 7.1. Basic Sending . . . . . . . . . . . . . . . . . . . . . . 22
7.2. Send Events . . . . . . . . . . . . . . . . . . . . . . . 22
7.4. Partial Sends . . . . . . . . . . . . . . . . . . . . . . 22 7.2.1. Sent . . . . . . . . . . . . . . . . . . . . . . . . 23
7.5. Batching Sends . . . . . . . . . . . . . . . . . . . . . 22 7.2.2. Expired . . . . . . . . . . . . . . . . . . . . . . . 23
7.6. Sender-side Framing . . . . . . . . . . . . . . . . . . . 23 7.2.3. SendError . . . . . . . . . . . . . . . . . . . . . . 23
8. Receiving Data . . . . . . . . . . . . . . . . . . . . . . . 23 7.3. Message Properties . . . . . . . . . . . . . . . . . . . 24
8.1. Enqueuing Receives . . . . . . . . . . . . . . . . . . . 23 7.3.1. Lifetime . . . . . . . . . . . . . . . . . . . . . . 24
8.2. Receive Events . . . . . . . . . . . . . . . . . . . . . 24 7.3.2. Niceness . . . . . . . . . . . . . . . . . . . . . . 25
8.2.1. Received . . . . . . . . . . . . . . . . . . . . . . 24 7.3.3. Ordered . . . . . . . . . . . . . . . . . . . . . . . 25
8.2.2. ReceivedPartial . . . . . . . . . . . . . . . . . . . 24 7.3.4. Idempotent . . . . . . . . . . . . . . . . . . . . . 25
8.2.3. ReceiveError . . . . . . . . . . . . . . . . . . . . 25 7.3.5. Final . . . . . . . . . . . . . . . . . . . . . . . . 25
8.3. Message Receive Context . . . . . . . . . . . . . . . . . 25 7.3.6. Corruption Protection Length . . . . . . . . . . . . 26
8.3.1. ECN . . . . . . . . . . . . . . . . . . . . . . . . . 26 7.3.7. Reliable Data Transfer (Message) . . . . . . . . . . 26
8.3.2. Early Data . . . . . . . . . . . . . . . . . . . . . 26 7.3.8. Transmission Profile . . . . . . . . . . . . . . . . 26
8.3.3. Receiving Final Messages . . . . . . . . . . . . . . 26 7.3.9. Singular Transmission . . . . . . . . . . . . . . . . 27
8.4. Receiver-side De-framing over Stream Protocols . . . . . 26 7.4. Partial Sends . . . . . . . . . . . . . . . . . . . . . . 27
9. Setting and Querying Connection Properties . . . . . . . . . 27 7.5. Batching Sends . . . . . . . . . . . . . . . . . . . . . 28
10. Connection Termination . . . . . . . . . . . . . . . . . . . 28 7.6. Send on Active Open: InitiateWithIdempotentSend . . . . . 28
11. Ordering of Operations and Events . . . . . . . . . . . . . . 29 7.7. Sender-side Framing . . . . . . . . . . . . . . . . . . . 29
12. Transport Properties . . . . . . . . . . . . . . . . . . . . 30 8. Receiving Data . . . . . . . . . . . . . . . . . . . . . . . 29
12.1. Transport Property Types . . . . . . . . . . . . . . . . 30 8.1. Enqueuing Receives . . . . . . . . . . . . . . . . . . . 30
12.1.1. Boolean . . . . . . . . . . . . . . . . . . . . . . 30 8.2. Receive Events . . . . . . . . . . . . . . . . . . . . . 30
12.1.2. Enumeration . . . . . . . . . . . . . . . . . . . . 31 8.2.1. Received . . . . . . . . . . . . . . . . . . . . . . 30
12.1.3. Integer . . . . . . . . . . . . . . . . . . . . . . 31 8.2.2. ReceivedPartial . . . . . . . . . . . . . . . . . . . 31
12.1.4. Preference . . . . . . . . . . . . . . . . . . . . . 31 8.2.3. ReceiveError . . . . . . . . . . . . . . . . . . . . 32
12.2. Transport Property Classification . . . . . . . . . . . 31 8.3. Message Receive Context . . . . . . . . . . . . . . . . . 32
12.2.1. Selection Properties . . . . . . . . . . . . . . . . 32 8.3.1. ECN . . . . . . . . . . . . . . . . . . . . . . . . . 32
12.2.2. Protocol Properties . . . . . . . . . . . . . . . . 33 8.3.2. Early Data . . . . . . . . . . . . . . . . . . . . . 32
12.2.3. Control Properties . . . . . . . . . . . . . . . . . 33 8.3.3. Receiving Final Messages . . . . . . . . . . . . . . 33
12.2.4. Intents . . . . . . . . . . . . . . . . . . . . . . 33 8.4. Receiver-side De-framing over Stream Protocols . . . . . 33
12.3. Mandatory Transport Properties . . . . . . . . . . . . . 34 9. Managing Connections . . . . . . . . . . . . . . . . . . . . 34
12.3.1. Final . . . . . . . . . . . . . . . . . . . . . . . 34 9.1. Generic Connection Properties . . . . . . . . . . . . . . 35
12.3.2. Reliable Data Transfer (Connection) . . . . . . . . 34 9.1.1. Notification of excessive retransmissions . . . . . . 35
12.3.3. Configure per-Message reliability . . . . . . . . . 34 9.1.2. Retransmission threshold before excessive
12.3.4. Reliable Data Transfer (Message) . . . . . . . . . . 35 retransmission notification . . . . . . . . . . . . . 36
12.3.5. Preservation of data ordering . . . . . . . . . . . 35 9.1.3. Notification of ICMP soft error message arrival . . . 36
12.3.6. Ordered . . . . . . . . . . . . . . . . . . . . . . 35 9.1.4. Required minimum coverage of the checksum for
12.3.7. Direction of communication . . . . . . . . . . . . . 36 receiving . . . . . . . . . . . . . . . . . . . . . . 36
12.3.8. Use 0-RTT session establishment with an idempotent 9.1.5. Niceness (Connection) . . . . . . . . . . . . . . . . 36
Message . . . . . . . . . . . . . . . . . . . . . . 36 9.1.6. Timeout for aborting Connection . . . . . . . . . . . 37
12.3.9. Idempotent . . . . . . . . . . . . . . . . . . . . . 36 9.1.7. Connection group transmission scheduler . . . . . . . 37
12.3.10. Multistream Connections in Group . . . . . . . . . . 37 9.1.8. Maximum message size concurrent with Connection
12.3.11. Notification of excessive retransmissions . . . . . 37 establishment . . . . . . . . . . . . . . . . . . . . 37
12.3.12. Retransmission threshold before excessive 9.1.9. Maximum Message size before fragmentation or
retransmission notification . . . . . . . . . . . . 37 segmentation . . . . . . . . . . . . . . . . . . . . 37
12.3.13. Notification of ICMP soft error message arrival . . 38 9.1.10. Maximum Message size on send . . . . . . . . . . . . 37
12.3.14. Control checksum coverage on sending or receiving . 38 9.1.11. Maximum Message size on receive . . . . . . . . . . . 37
12.3.15. Corruption Protection Length . . . . . . . . . . . . 38 9.1.12. Capacity Profile . . . . . . . . . . . . . . . . . . 38
12.3.16. Required minimum coverage of the checksum for 9.2. Soft Errors . . . . . . . . . . . . . . . . . . . . . . . 39
receiving . . . . . . . . . . . . . . . . . . . . . 39
12.3.17. Interface Instance or Type . . . . . . . . . . . . . 39 10. Connection Termination . . . . . . . . . . . . . . . . . . . 39
12.3.18. Provisioning Domain Instance or Type . . . . . . . . 40 11. Connection State and Ordering of Operations and Events . . . 40
12.3.19. Capacity Profile . . . . . . . . . . . . . . . . . . 41 12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 41
12.3.20. Congestion control . . . . . . . . . . . . . . . . . 41 13. Security Considerations . . . . . . . . . . . . . . . . . . . 41
12.3.21. Niceness . . . . . . . . . . . . . . . . . . . . . . 42 14. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 41
12.3.22. Timeout for aborting Connection . . . . . . . . . . 42 15. References . . . . . . . . . . . . . . . . . . . . . . . . . 42
12.3.23. Connection group transmission scheduler . . . . . . 43 15.1. Normative References . . . . . . . . . . . . . . . . . . 42
12.3.24. Maximum message size concurrent with Connection 15.2. Informative References . . . . . . . . . . . . . . . . . 43
establishment . . . . . . . . . . . . . . . . . . . 43 Appendix A. Additional Properties . . . . . . . . . . . . . . . 44
12.3.25. Maximum Message size before fragmentation or A.1. Experimental Transport Properties . . . . . . . . . . . . 45
segmentation . . . . . . . . . . . . . . . . . . . . 43 A.1.1. Direction of communication . . . . . . . . . . . . . 45
12.3.26. Maximum Message size on send . . . . . . . . . . . . 43 A.1.2. Suggest a timeout to the Remote Endpoint . . . . . . 45
12.3.27. Maximum Message size on receive . . . . . . . . . . 44 A.1.3. Abort timeout to suggest to the Remote Endpoint . . . 46
12.3.28. Lifetime . . . . . . . . . . . . . . . . . . . . . . 44 A.1.4. Traffic Category . . . . . . . . . . . . . . . . . . 46
12.4. Optional Transport Properties . . . . . . . . . . . . . 44 A.1.5. Size to be Sent or Received . . . . . . . . . . . . . 46
12.5. Experimental Transport Properties . . . . . . . . . . . 44 A.1.6. Duration . . . . . . . . . . . . . . . . . . . . . . 47
13. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 44 A.1.7. Send or Receive Bit-rate . . . . . . . . . . . . . . 47
14. Security Considerations . . . . . . . . . . . . . . . . . . . 45 A.1.8. Cost Preferences . . . . . . . . . . . . . . . . . . 47
15. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 45 Appendix B. Sample API definition in Go . . . . . . . . . . . . 48
16. References . . . . . . . . . . . . . . . . . . . . . . . . . 45 Appendix C. Relationship to the Minimal Set of Transport
16.1. Normative References . . . . . . . . . . . . . . . . . . 45 Services for End Systems . . . . . . . . . . . . . . 48
16.2. Informative References . . . . . . . . . . . . . . . . . 46
Appendix A. Additional Properties . . . . . . . . . . . . . . . 47
A.1. Experimental Transport Properties . . . . . . . . . . . . 47
A.1.1. Suggest a timeout to the Remote Endpoint . . . . . . 48
A.1.2. Abort timeout to suggest to the Remote Endpoint . . . 48
A.1.3. Request not to delay acknowledgment of Message . . . 48
A.1.4. Traffic Category . . . . . . . . . . . . . . . . . . 49
A.1.5. Size to be Sent or Received . . . . . . . . . . . . . 49
A.1.6. Duration . . . . . . . . . . . . . . . . . . . . . . 49
A.1.7. Send or Receive Bit-rate . . . . . . . . . . . . . . 50
A.1.8. Cost Preferences . . . . . . . . . . . . . . . . . . 50
A.1.9. Immediate . . . . . . . . . . . . . . . . . . . . . . 51
Appendix B. Sample API definition in Go . . . . . . . . . . . . 51
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 51 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 51
1. Introduction 1. Introduction
The BSD Unix Sockets API's SOCK_STREAM abstraction, by bringing The BSD Unix Sockets API's SOCK_STREAM abstraction, by bringing
network sockets into the UNIX programming model, allowing anyone who network sockets into the UNIX programming model, allowing anyone who
knew how to write programs that dealt with sequential-access files to knew how to write programs that dealt with sequential-access files to
also write network applications, was a revolution in simplicity. The also write network applications, was a revolution in simplicity. The
simplicity of this API is a key reason the Internet won the protocol simplicity of this API is a key reason the Internet won the protocol
wars of the 1980s. SOCK_STREAM is tied to the Transmission Control wars of the 1980s. SOCK_STREAM is tied to the Transmission Control
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Internet transport protocols, is evolving. The challenges that new Internet transport protocols, is evolving. The challenges that new
protocols and access paradigms present to the sockets API and to protocols and access paradigms present to the sockets API and to
programming models based on them inspire the design principles of a programming models based on them inspire the design principles of a
new approach, which we outline in Section 3. new approach, which we outline in Section 3.
As a first step to realizing this design, [I-D.ietf-taps-arch] As a first step to realizing this design, [I-D.ietf-taps-arch]
describes a high-level architecture for transport services. This describes a high-level architecture for transport services. This
document builds a modern abstract programming interface atop this document builds a modern abstract programming interface atop this
architecture, deriving specific path and protocol selection architecture, deriving specific path and protocol selection
properties and supported transport features from the analysis properties and supported transport features from the analysis
provided in [RFC8095] and [I-D.ietf-taps-minset]. provided in [RFC8095], [I-D.ietf-taps-minset], and
[I-D.ietf-taps-transport-security].
2. Terminology and Notation 2. Terminology and Notation
This API is described in terms of Objects, which an application can This API is described in terms of Objects, which an application can
interact with; Actions the application can perform on these Objects; interact with; Actions the application can perform on these Objects;
Events, which an Object can send to an application asynchronously; Events, which an Object can send to an application asynchronously;
and Parameters associated with these Actions and Events. 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:
o An Action creates an Object: o An Action creates an Object:
Object := Action() Object := Action()
o An Action creates an array of Objects:
[]Object := Action()
o An Action is performed on an Object: o An Action is performed on an Object:
Object.Action() Object.Action()
o An Object sends an Event: o An Object sends an Event:
Object -> Event<> Object -> Event<>
o An Action takes a set of Parameters; an Event contains a set of o An Action takes a set of Parameters; an Event contains a set of
Parameters: Parameters:
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Action(parameter, parameter, ...) / Event<parameter, parameter, ...> Action(parameter, parameter, ...) / Event<parameter, parameter, ...>
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.
How these abstract concepts map into concrete implementations of this How these abstract concepts map into concrete implementations of this
API in a given language on a given platform is largely dependent on API in a given language on a given platform is largely dependent on
the features of the language and the platform. Actions could be the features of the language and the platform. Actions could be
implemented as functions or method calls, for instance, and Events implemented as functions or method calls, for instance, and Events
could be implemented via callback passing or other asynchronous could be implemented via callbacks, communicating sequential
calling conventions. The method for registering callbacks and processes, or other asynchronous calling conventions. The method for
handlers is left as an implementation detail, with the caveat that dispatching and handling Events is left as an implementation detail,
the interface for receiving Messages must require the application to with the caveat that the interface for receiving Messages must
invoke the Connection.Receive() Action once per Message to be require the application to invoke the Connection.Receive() Action
received (see Section 8). once per Message to be received (see Section 8).
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, it is recommended that implementations of applications. However, it is recommended that implementations of
this interface also return errors immediately, according to the error this interface also return errors immediately, according to the error
handling idioms of the implementation platform, for errors which can handling idioms of the implementation platform, for errors which can
be immediately detected, such as inconsistency in Transport be immediately detected, such as inconsistency in Transport
Properties. Properties.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
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o A single interface to a variety of transport protocols to be used o A single interface to a variety of transport protocols to be used
in a variety of application design patterns, independent of the in a variety of application design patterns, independent of the
properties of the application and the Protocol Stacks that will be properties of the application and the Protocol Stacks that will be
used at runtime, such that all common specialized features of used at runtime, such that all common specialized features of
these protocol stacks are made available to the application as these protocol stacks are made available to the application as
necessary in a transport-independent way, to enable applications necessary in a transport-independent way, to enable applications
written to a single API to make use of transport protocols in written to a single API to make use of transport protocols in
terms of the features they provide; terms of the features they provide;
o Explicit support for security properties as first-order transport o Message- as opposed to stream-orientation, using application-
features, and for long-term caching of cryptographic identities assisted framing and deframing where the underlying transport does
and parameters for associations among endpoints; not provide these;
o Asynchronous Connection establishment, transmission, and o Asynchronous Connection establishment, transmission, and
reception, allowing most application interactions with the reception, allowing concurrent operations during establishment and
transport layer to be Event-driven, in line with developments in supporting event-driven application interactions with the
modern platforms and programming languages; transport layer, in line with developments in modern platforms and
programming languages;
o Explicit support for security properties as first-order transport
features, and for long-term caching of cryptographic identities
and parameters for associations among endpoints; and
o Explicit support for multistreaming and multipath transport o 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, to allow applications to
take full advantage of new transport protocols supporting these take full advantage of new transport protocols supporting these
features; and features.
o Atomic transmission of data, using application-assisted framing
and deframing where the underlying transport does not provide
these.
4. API Summary 4. API Summary
The Transport Services Interface is the basic common abstract The Transport Services Interface is the basic common abstract
application programming interface to the Transport Services application programming interface to the Transport Services
Architecture defined in [I-D.ietf-taps-arch]. An application Architecture defined in [I-D.ietf-taps-arch].
primarily interacts with this interface through two Objects,
Preconnections and Connections. A Preconnection represents a set of An application primarily interacts with this interface through two
properties and constraints on the selection and configuration of Objects, Preconnections and Connections. A Preconnection represents
paths and protocols to establish a Connection with a remote endpoint. a set of properties and constraints on the selection and
A Connection represents a transport Protocol Stack on which data can configuration of paths and protocols to establish a Connection with a
be sent to and/or received from a remote endpoint (i.e., depending on remote endpoint. A Connection represents a transport Protocol Stack
the kind of transport, connections can be bi-directional or on which data can be sent to and/or received from a remote endpoint
unidirectional). Connections can be created from Preconnections in (i.e., depending on the kind of transport, connections can be bi-
three ways: by initiating the Preconnection (i.e., actively opening, directional or unidirectional). Connections can be created from
as in a client), through listening on the Preconnection (i.e., Preconnections in three ways: by initiating the Preconnection (i.e.,
passively opening, as in a server), or rendezvousing on the actively opening, as in a client), through listening on the
Preconnection (i.e. peer to peer establishment). Preconnection (i.e., passively opening, as in a server), or
rendezvousing on the Preconnection (i.e. peer to peer
establishment).
Once a Connection is established, data can be sent on it in the form Once a Connection is established, data can be sent on it in the form
of Messages. The interface supports the preservation of message of Messages. The interface supports the preservation of message
boundaries both via explicit Protocol Stack support, and via boundaries both via explicit Protocol Stack support, and via
application support through a deframing callback which finds message application support through a deframing callback which finds message
boundaries in a stream. Messages are received asynchronously through boundaries in a stream. Messages are received asynchronously through
a callback registered by the application. Errors and other a callback registered by the application. Errors and other
notifications also happen asynchronously on the Connection. notifications also happen asynchronously on the Connection.
In the following sections, we describe the details of application Section 5, Section 6, Section 7, Section 8, and Section 10 describe
interaction with Objects through Actions and Events in each phase of the details of application interaction with Objects through Actions
a Connection, following the phases described in [I-D.ietf-taps-arch]. and Events in each phase of a Connection, following the phases
described in [I-D.ietf-taps-arch].
4.1. Transport Properties
Each application using the Transport Services Interface declares its
preferences for how the transport service should operate using
properties at each stage of the lifetime of a connection. During
pre-establishment, Selection Properties Section 5.2 are used to
specify which paths and protocol stacks can be used and are preferred
by the application, and Connection Properties Section 9.1 can be used
to fine-tune the eventually established connection. These Connection
Properties can also be used to monitor and fine-tune established
connections. The behavior of the selected protocol stack(s) when
sending Messages is controlled by Message Properties Section 7.3.
Collectively, Selection, Connection, and Message Properties can be
referred to as Transport Properties. All Transport Properties,
regardless of the phase in which they are used, are organized within
a single namespace. This enables setting them as defaults in earlier
stages and querying them in later stages: - Connection Properties can
be set on Preconnections - Message Properties can be set on
Preconnections and Connections - The effect of Selection Properties
can be queried on Connections and Messages
Transport Properties can have one of a set of data types:
o Boolean: can take the values "true" and "false"; representation is
implementation-dependent.
o Integer: can take positive or negative numeric values; range and
representation is implementation-dependent.
o Enumeration: can take one value of a finite set of values,
dependent on the property itself. The representation is
implementation dependent; however, implementations MUST provide a
method for the application to determine the entire set of possible
values for each property.
o Preference: can take one of five values (Prohibit, Avoid, Ignore,
Prefer, Require) for the level of preference of a given property
during protocol selection; see Section 5.2.
4.2. Scope of the Interface Definition
This document defines a language- and platform-independent interface
to a Transport Services system. Given the wide variety of languages
and language conventions used to write applications that use the
transport layer to connect to other applications over the Internet,
this independence makes this interface necessarily abstract. While
there is no interoperability benefit to tightly defining how the
interface be presented to application programmers in diverse
platforms, maintaining the "shape" of the abstract interface across
these platforms reduces the effort for programmers who learn the
transport services interface to apply their knowledge in multiple
platforms. We therefore make the following recommendations:
o Actions, Events, and Errors in implementations of this interface
SHOULD carry the names given for them in the document, subject to
capitalization and punctuation conventions in the language of the
implementation, unless the implementation itself uses different
names for substantially equivalent objects for networking by
convention.
o Implementations of this interface SHOULD implement each Selection
Property, Connection Property, and Message Context Property
specified in this document, exclusive of appendices, even if said
implementation is a non-operation, e.g. because transport
protocols implementing a given Property are not available on the
platform.
5. Pre-Establishment Phase 5. Pre-Establishment Phase
The pre-establishment phase allows applications to specify properties The pre-establishment phase allows applications to specify properties
for the Connections they're about to make, or to query the API about for the Connections they are about to make, or to query the API about
potential connections they could make. potential connections they could make.
A Preconnection Object represents a potential Connection. It has A Preconnection Object represents a potential Connection. It has
state that describes properties of a Connection that might exist in state that describes properties of a Connection that might exist in
the future. This state comprises Local Endpoint and Remote Endpoint the future. This state comprises Local Endpoint and Remote Endpoint
Objects that denote the endpoints of the potential Connection (see Objects that denote the endpoints of the potential Connection (see
Section 5.1), the transport properties (see Section 12), and the Section 5.1), the Selection Properties (see Section 5.2), any
security parameters (see Section 5.3): preconfigured Connection Properties (Section 9.1), and the security
parameters (see Section 5.3):
Preconnection := NewPreconnection(LocalEndpoint, Preconnection := NewPreconnection(LocalEndpoint,
RemoteEndpoint, RemoteEndpoint,
TransportProperties, TransportProperties,
SecurityParams) SecurityParams)
The Local Endpoint MUST be specified if the Preconnection is used to The Local Endpoint MUST be specified if the Preconnection is used to
Listen() for incoming Connections, but is OPTIONAL if it is used to Listen() for incoming Connections, but is OPTIONAL if it is used to
Initiate() connections. The Remote Endpoint MUST be specified in the Initiate() connections. The Remote Endpoint MUST be specified if the
Preconnection is used to Initiate() Connections, but is OPTIONAL if Preconnection is used to Initiate() Connections, but is OPTIONAL if
it is used to Listen() for incoming Connections. The Local Endpoint it is used to Listen() for incoming Connections. The Local Endpoint
and the Remote Endpoint MUST both be specified if a peer-to-peer and the Remote Endpoint MUST both be specified if a peer-to-peer
Rendezvous is to occur based on the Preconnection. Rendezvous is to occur based on the Preconnection.
Framers (see Section 7.6) and deframers (see Section 8.4), if Framers (see Section 7.7) and deframers (see Section 8.4), if
necessary, should be bound to the Preconnection during pre- necessary, should be bound to the Preconnection during pre-
establishment. establishment.
5.1. Specifying Endpoints 5.1. Specifying Endpoints
The transport services API uses the Local Endpoint and Remote The transport services API uses the Local Endpoint and Remote
Endpoint types to refer to the endpoints of a transport connection. Endpoint types to refer to the endpoints of a transport connection.
Subtypes of these represent various different types of endpoint Subtypes of these represent various different types of endpoint
identifiers, such as IP addresses, DNS names, and interface names, as identifiers, such as IP addresses, DNS names, and interface names, as
well as port numbers and service names. well as port numbers and service names.
skipping to change at page 9, line 4 skipping to change at page 10, line 20
RemoteSpecifier.WithIPv6Address(2001:db8:4920:e29d:a420:7461:7073:0a) RemoteSpecifier.WithIPv6Address(2001:db8:4920:e29d:a420:7461:7073:0a)
RemoteSpecifier.WithPort(443) RemoteSpecifier.WithPort(443)
RemoteSpecifier := NewRemoteEndpoint() RemoteSpecifier := NewRemoteEndpoint()
RemoteSpecifier.WithIPv4Address(192.0.2.21) RemoteSpecifier.WithIPv4Address(192.0.2.21)
RemoteSpecifier.WithPort(443) RemoteSpecifier.WithPort(443)
LocalSpecifier := NewLocalEndpoint() LocalSpecifier := NewLocalEndpoint()
LocalSpecifier.WithInterface("en0") LocalSpecifier.WithInterface("en0")
LocalSpecifier.WithPort(443) LocalSpecifier.WithPort(443)
LocalSpecifier := NewLocalEndpoint() LocalSpecifier := NewLocalEndpoint()
LocalSpecifier.WithStunServer(address, port, credentials) LocalSpecifier.WithStunServer(address, port, credentials)
Implementations may also support additional endpoint representations Implementations may also support additional endpoint representations
and provide a single NewEndpoint() call that takes different endpoint and provide a single NewEndpoint() call that takes different endpoint
representations. representations.
Multiple endpoint identifiers can be specified for each Local Multiple endpoint identifiers can be specified for each Local
Endpoint and RemoteEndoint. For example, a Local Endpoint could be Endpoint and Remote Endpoint. For example, a Local Endpoint could be
configured with two interface names, or a Remote Endpoint could be configured with two interface names, or a Remote Endpoint could be
specified via both IPv4 and IPv6 addresses. These multiple specified via both IPv4 and IPv6 addresses. These multiple
identifiers refer to the same transport endpoint. identifiers refer to the same transport endpoint.
The transport services API will resolve names internally, when the The transport services API resolves names internally, when the
Initiate(), Listen(), or Rendezvous() method is called establish a Initiate(), Listen(), or Rendezvous() method is called establish a
Connection. The API does not need the application to resolve names, Connection. The API explicitly does not require the application to
and premature name resolution can damage performance by limiting the resolve names, though there is a tradeoff between early and late
scope for alternate path discovery during Connection establishment. binding of addresses to names. Early binding allows the API
The Resolve() method is, however, provided to resolve a Local implementation to reduce connection setup latency, at the cost of
Endpoint or a Remote Endpoint in cases where this is required, for potentially limited scope for alternate path discovery during
example with some Network Address Translator (NAT) traversal Connection establishment, as well as potential additional information
protocols (see Section 6.3). leakage about application interest when used with a resolution method
(such as DNS without TLS) which does not protect query
confidentiality.
The Resolve() action on Preconnection can be used by the application
to force early binding when required, for example with some Network
Address Translator (NAT) traversal protocols (see Section 6.3).
5.2. Specifying Transport Properties 5.2. 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 (Protocol and Path Selection Properties), as Selection Properties for selecting protocol stacks and paths, as well
well as Generic and Specific Protocol Properties for configuration of as Connection Properties for configuration of the detailed operation
the detailed operation of the selected Protocol Stacks. of the selected Protocol Stacks.
The protocol(s) and path(s) selected as candidates during Connection The protocol(s) and path(s) selected as candidates during
establishment are determined by a set of properties. Since there establishment are determined and configured using these properties.
could be paths over which some transport protocols are unable to Since there could be paths over which some transport protocols are
operate, or remote endpoints that support only specific network unable to operate, or remote endpoints that support only specific
addresses or transports, transport protocol selection is necessarily network addresses or transports, transport protocol selection is
tied to path selection. This may involve choosing between multiple necessarily tied to path selection. This may involve choosing
local interfaces that are connected to different access networks. between multiple local interfaces that are connected to different
access networks.
Selection properties are represented as preferences, which can have
one of five preference levels:
+------------+------------------------------------------------------+
| Preference | Effect |
+------------+------------------------------------------------------+
| Require | Select only protocols/paths providing the property, |
| | fail otherwise |
| | |
| Prefer | Prefer protocols/paths providing the property, |
| | proceed otherwise |
| | |
| Ignore | Cancel any system default preference for this |
| | property |
| | |
| Avoid | Prefer protocols/paths not providing the property, |
| | proceed otherwise |
| | |
| Prohibit | Select only protocols/paths not providing the |
| | property, fail otherwise |
+------------+------------------------------------------------------+
Internally, the transport system will first exclude all protocols and Internally, the transport system will first exclude all protocols and
paths that match a Prohibit, then exclude all protocols and paths paths that match a Prohibit, then exclude all protocols and paths
that do not match a Require, then sort candidates according to that do not match a Require, then sort candidates according to
Preferred properties, and then use Avoided properties as a Preferred properties, and then use Avoided properties as a
tiebreaker. In case of conflicts between Protocol and Path Selection tiebreaker. Selection Properties which select paths take preference
Properties, Path Selection Properties take precedence. For example, over those which select protocols. For example, if an application
if an application indicates a preference for a specific path, but indicates a preference for a specific path by specifying an
also a preference for a protocol not available on this path, the interface, but also a preference for a protocol not available on this
transport system will try the path first, so the Protocol Selection path, the transport system will try the path first, ignoring the
Property might not have an effect. preference.
All Transport Properties used in the pre-establishment phase are Both Selection and Connection Properties can be added to a
collected in a TransportProperties Object that is passed to the Preconnection to configure the selection process, and to further
Preconnection Object. configure the eventually selected protocol stack(s). They are
collected into a TransportProperties object to be passed into a
Preconnection object:
TransportProperties := NewTransportProperties() TransportProperties := NewTransportProperties()
The Individual properties are then added to the TransportProperties Individual properties are then added to the TransportProperties
Object. Object:
TransportProperties.Add(property, value) TransportProperties.Add(property, value)
Transport Properties of Preference Type, see Section 12.1.4, can use Selection Properties can be added to a TransportProperties object
special calls to add a Property with a specific preference level, using special actions for each preference level i.e,
i.e, "TransportProperties.Add('some preference', avoid)" is "TransportProperties.Add(some_property, avoid)" is equivalent to
equivalent to "TransportProperties.Avoid('some preference')" "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)
For an existing Connection, the Transport Properties can be queried For an existing Connection, the Transport Properties can be queried
any time by using the following call on the Connection Object: any time by using the following call on the Connection Object:
TransportProperties := Connection.GetTransportProperties() TransportProperties := Connection.GetTransportProperties()
Section 12 provides a list of Transport Properties. A Connection gets its Transport Properties either by being explicitly
configured via a Preconnection, by configuration after establishment,
or by inheriting them from an antecedent via cloning; see Section 6.4
for more.
Note that most properties are only considered for Connection Section 9.1 provides a list of Connection Properties, while Selection
establishment and can not be changed after a Connection is Properties are listed in the subsections below. Note that many
established; however, they can be queried. See Section 9. properties are only considered during establishment, and can not be
changed after a Connection is established; however, they can be
queried. Querying a Selection Property after establishment yields
the value Required for properties of the selected protocol and path,
Avoid for properties avoided during selection, and Ignore for all
other properties.
A Connection gets its Transport Properties either by being explicitly An implementation of this interface must provide sensible defaults
configured via a Preconnection, or by inheriting them from an for Selection Properties. The recommended defaults given for each
antecedent via cloning; see Section 6.4 for more. property below represent a configuration that can be implemented over
TCP. An alternate set of default Protocol Selection Properties would
represent a configuration that can be implemented over UDP.
5.2.1. Reliable Data Transfer (Connection)
This property specifies whether the application needs to use a
transport protocol that ensures that all data is received on the
other side without corruption. This also entails being notified when
a Connection is closed or aborted. The recommended default is to
enable Reliable Data Transfer.
5.2.2. Configure per-Message reliability
This property specifies whether an application considers it useful to
indicate its reliability requirements on a per-Message basis. This
property applies to Connections and Connection Groups. The
recommended default is to not have this option.
5.2.3. Preservation of data ordering
This property specifies whether the application wishes to use a
transport protocol that can ensure that data is received by the
application on the other end in the same order as it was sent. The
recommended default is to preserve data ordering.
5.2.4. Use 0-RTT session establishment with an idempotent Message
This property specifies whether an application would like to supply a
Message to the transport protocol before Connection establishment,
which will then be reliably transferred to the other side before or
during Connection establishment, potentially multiple times. See
also Section 7.3.4. The recommended default is to not have this
option.
5.2.5. Multistream Connections in Group
This property specifies that the application would prefer multiple
Connections within a Connection Group to be provided by streams of a
single underlying transport connection where possible. The
recommended default is to not have this option.
5.2.6. Control checksum coverage on sending or receiving
This property specifies whether the application considers it useful
to enable, disable, or configure a checksum when sending a Message,
or configure whether to require a checksum or not when receiving.
The recommended default is full checksum coverage without the option
to configure it, and requiring a checksum when receiving.
5.2.7. Congestion control
This property specifies whether the application would like the
Connection to be congestion controlled or not. Note that if a
Connection is not congestion controlled, an application using such a
Connection should itself perform congestion control in accordance
with [RFC2914]. Also note that reliability is usually combined with
congestion control in protocol implementations, rendering "reliable
but not congestion controlled" a request that is unlikely to succeed.
The recommended default is that the Connection is congestion
controlled.
5.2.8. Interface Instance or Type
This property allows the application to select which specific network
interfaces or categories of interfaces it wants to "Require",
"Prohibit", "Prefer", or "Avoid".
In contrast to other Selection Properties, this property is tuple of
an (Enumerated) interface identifier and a preference, and can either
be implemented directly as such, or for making one preference
available for each interface and interface type available on the
system.
Note that marking a specific interface as "Required" strictly limits
path selection to a single interface, and leads to less flexible and
resilient connection establishment.
The set of valid interface types is implementation- and system-
specific. For example, on a mobile device, there may be "Wi-Fi" and
"Cellular" interface types available; whereas on a desktop computer,
there may be "Wi-Fi" and "Wired Ethernet" interface types available.
Implementations should provide all types that are supported on some
system to all systems, in order to allow applications to write
generic code. For example, if a single implementation is used on
both mobile devices and desktop devices, it should define the
"Cellular" interface type for both systems, since an application may
want to always "Prohibit Cellular". Note that marking a specific
interface type as "Required" limits path selection to a small set of
interfaces, and leads to less flexible and resilient connection
establishment.
The set of interface types is expected to change over time as new
access technologies become available.
Interface types should not be treated as a proxy for properties of
interfaces such as metered or unmetered network access. If an
application needs to prohibit metered interfaces, this should be
specified via Provisioning Domain attributes (see Section 5.2.9) or
another specific property.
5.2.9. Provisioning Domain Instance or Type
Similar to interface instances and types (see Section 5.2.8), this
property allows the application to control path selection by
selecting which specific Provisioning Domains or categories of
Provisioning Domains it wants to "Require", "Prohibit", "Prefer", or
"Avoid". Provisioning Domains define consistent sets of network
properties that may be more specific than network interfaces
[RFC7556].
As with interface instances and types, this property is tuple of an
(Enumerated) PvD identifier and a preference, and can either be
implemented directly as such, or for making one preference available
for each interface and interface type available on the system.
The identification of a specific Provisioning Domain (PvD) is defined
to be implementation- and system-specific, since there is not a
portable standard format for a PvD identitfier. For example, this
identifier may be a string name or an integer. As with requiring
specific interfaces, requiring a specific PvD strictly limits path
selection.
Categories or types of PvDs are also defined to be implementation-
and system-specific. These may be useful to identify a service that
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
can use the relevant PvD type to require some PvD that provides this
service, without needing to look up a particular instance. While
this does restrict path selection, it is broader than requiring
specific PvD instances or interface instances, and should be
preferred over these options.
5.3. Specifying Security Parameters and Callbacks 5.3. 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. Thus, we dynamically configured during connection establishment. Thus, we
partition security parameters and callbacks based on their place in partition security parameters and callbacks based on their place in
the lifetime of connection establishment. Similar to Transport the 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 6.4). cloning (see Section 6.4).
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at the time of configuration and actively during a handshake. These at the time of configuration and actively during a handshake. These
configuration parameters are created as follows: configuration parameters are created as follows:
SecurityParameters := NewSecurityParameters() SecurityParameters := NewSecurityParameters()
Security configuration parameters and sample usage follow: Security configuration parameters and sample usage follow:
o Local identity and private keys: Used to perform private key o Local identity and private keys: Used to perform private key
operations and prove one's identity to the Remote Endpoint. operations and prove one's identity to the Remote Endpoint.
(Note, if private keys are not available, e.g., since they are (Note, if private keys are not available, e.g., since they are
stored in HSMs, handshake callbacks must be used. See below for stored in hardware security modules (HSMs), handshake callbacks
details.) must be used. See below for details.)
SecurityParameters.AddIdentity(identity) SecurityParameters.AddIdentity(identity)
SecurityParameters.AddPrivateKey(privateKey, publicKey) SecurityParameters.AddPrivateKey(privateKey, publicKey)
o Supported algorithms: Used to restrict what parameters are used by o Supported algorithms: Used to restrict what parameters are used by
underlying transport security protocols. When not specified, underlying transport security protocols. When not specified,
these algorithms should default to known and safe defaults for the these algorithms should default to known and safe defaults for the
system. Parameters include: ciphersuites, supported groups, and system. Parameters include: ciphersuites, supported groups, and
signature algorithms. signature algorithms.
skipping to change at page 13, line 4 skipping to change at page 17, line 50
subsections below. subsections below.
6.1. Active Open: Initiate 6.1. 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() Connection := Preconnection.Initiate()
Before calling Initiate, the caller must have populated a Before calling Initiate, the caller must have populated a
Preconnection Object with a Remote Endpoint specifier, optionally a Preconnection Object with a Remote Endpoint specifier, optionally a
Local Endpoint specifier (if not specified, the system will attempt Local Endpoint specifier (if not specified, the system will attempt
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. After calling Initiate, no necessary for candidate selection.
further properties may be added to the Preconnection. The Initiate()
call consumes the Preconnection and creates a Connection Object. A The Initiate() Action consumes the Preconnection. Once Initiate()
Preconnection can only be initiated once. has been called, no further properties may be added to the
Preconnection, and no subsequent establishment call may be made on
the Preconnection.
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) after calling sending Messages on the Connection (see Section 7) after calling
Initate(); note that any idempotent data sent while the Connection is Initate(); note that any idempotent data sent while the Connection is
being established may be sent multiple times or on multiple being established may be sent multiple times or on multiple
candidates. candidates.
The following Events may be sent by the Connection after Initiate() The following Events may be sent by the Connection after Initiate()
skipping to change at page 13, line 35 skipping to change at page 18, line 35
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 8) will at least one candidate Path. No Receive Events (see Section 8) will
occur before the Ready Event for Connections established using occur before the Ready Event for Connections established using
Initiate. Initiate.
Connection -> InitiateError<> Connection -> InitiateError<>
An InitiateError occurs either when the set of transport properties An InitiateError occurs either when the set of transport properties
and cryptographic parameters cannot be fulfilled on a Connection for and security parameters cannot be fulfilled on a Connection for
initiation (e.g. the set of available Paths and/or Protocol Stacks initiation (e.g. the set of available Paths and/or Protocol Stacks
meeting the constraints is empty) or reconciled with the local and/or meeting the constraints is empty) or reconciled with the local and/or
remote endpoints; when the remote specifier cannot be resolved; or remote endpoints; when the remote specifier cannot be resolved; or
when no transport-layer connection can be established to the remote when no transport-layer connection can be established to the remote
endpoint (e.g. because the remote endpoint is not accepting endpoint (e.g. because the remote endpoint is not accepting
connections, or the application is prohibited from opening a connections, or the application is prohibited from opening a
Connection by the operating system). Connection by the operating system).
See also Section 7.6 to combine Connection establishment and
transmission of the first message in a single action.
6.2. Passive Open: Listen 6.2. 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 Passive open is supported by this interface through the Listen
Action: Action:
Preconnection.Listen() 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
Endpoint specifier, as well as all properties necessary for Protocol Endpoint specifier, as well as all properties necessary for Protocol
Stack selection. A Remote Endpoint may optionally be specified, to Stack selection. A Remote Endpoint may optionally be specified, to
constrain what Connections are accepted. The Listen() Action constrain what Connections are accepted. The Listen() Action
consumes the Preconnection. Once Listen() has been called, no consumes the Preconnection. Once Listen() has been called, no
further properties may be added to the Preconnection, and no further properties may be added to the Preconnection, and no
subsequent establishment call may be made on the Preconnection. subsequent establishment call may be made on the Preconnection.
Listening continues until the global context shuts down, or until the Listening continues until the global context shuts down, or until the
skipping to change at page 15, line 39 skipping to change at page 20, line 45
fulfilled for listening, when the Local Endpoint or Remote Endpoint fulfilled for listening, when the Local Endpoint or Remote Endpoint
cannot be resolved, when no transport-layer connection can be cannot be resolved, when no transport-layer connection can be
established to the Remote Endpoint, or when the application is established to the Remote Endpoint, or when the application is
prohibited from rendezvous by policy. prohibited from rendezvous by policy.
When using some NAT traversal protocols, e.g., Interactive When using some NAT traversal protocols, e.g., Interactive
Connectivity Establishment (ICE) [RFC5245], it is expected that the Connectivity Establishment (ICE) [RFC5245], it is expected that the
Local Endpoint will be configured with some method of discovering NAT Local Endpoint will be configured with some method of discovering NAT
bindings, e.g., a Session Traversal Utilities for NAT (STUN) server. bindings, e.g., a Session Traversal Utilities for NAT (STUN) server.
In this case, the Local Endpoint may resolve to a mixture of local In this case, the Local Endpoint may resolve to a mixture of local
and server reflexive addresses. The Resolve() method on the and server reflexive addresses. The Resolve() action on the
Preconnection can be used to discover these bindings: Preconnection can be used to discover these bindings:
PreconnectionBindings := Preconnection.Resolve() []Preconnection := Preconnection.Resolve()
The Resolve() call returns a list of Preconnection Objects, that The Resolve() call returns a list of Preconnection Objects, that
represent the concrete addresses, local and server reflexive, on represent the concrete addresses, local and server reflexive, on
which a Rendezvous() for the Preconnection will listen for incoming which a Rendezvous() for the Preconnection will listen for incoming
Connections. This list can be passed to a peer via a signalling Connections. These resolved Preconnections will share all other
protocol, such as SIP [RFC3261] or WebRTC [RFC7478], to configure the Properties with the Preconnection from which they are derived, though
remote. some Properties may be made more-specific by the resolution process.
This list can be passed to a peer via a signalling protocol, such as
SIP [RFC3261] or WebRTC [RFC7478], to configure the remote.
6.4. Connection Groups 6.4. Connection Groups
Groups of Connections can be created using the Clone Action: Groups of Connections can be created using the Clone Action:
Connection := Connection.Clone() Connection := Connection.Clone()
Calling Clone on a Connection yields a group of two Connections: the Calling Clone on a Connection yields a group of two Connections: the
parent Connection on which Clone was called, and the resulting clone parent Connection on which Clone was called, and the resulting cloned
Connection. These connections are "entangled" with each other, and Connection. These connections are "entangled" with each other, and
become part of a Connection group. Calling Clone on any of these two become part of a Connection Group. Calling Clone on any of these two
Connections adds a third Connection to the group, and so on. Connections adds a third Connection to the Connection Group, and so
Connections in a Connection Group share all their properties, and on. Connections in a Connection Group share all Protocol Properties
changing the properties on one Connection in the group changes the that are not applicable to a Message.
property for all others.
Changing one of these Protocol Properties on one Connection in the
group changes it for all others. Per-Message Protocol Properties,
however, are not entangled. For example, changing "Timeout for
aborting Connection" (see Section 9.1.6) on one Connection in a group
will automatically change this Protocol Property for all Connections
in the group in the same way. However, changing "Lifetime" (see
Section 7.3.1) 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
use this functionality to implement Clone. In that case, entangled
Connections are multiplexed together, giving them similar treatment
not only inside endpoints but also across the end-to-end Internet
path.
If the underlying Protocol Stack does not support cloning, or cannot If the underlying Protocol Stack does not support cloning, or cannot
create a new stream on the given Connection, then attempts to clone a create a new stream on the given Connection, then attempts to clone a
connection will result in a CloneError: connection will result in a CloneError:
Connection -> CloneError<> Connection -> CloneError<>
There is only one Protocol Property that is not entangled: niceness The Protocol Property "Niceness" operates on entangled Connections as
is kept as a separate per-Connection Property for individual in Section 7.3.2: when allocating available network capacity among
Connections in the group. Niceness works as in Section 12.3.21: when Connections in a Connection Group, sends on Connections with higher
allocating available network capacity among Connections in a Niceness values will be prioritized over sends on Connections with
Connection Group, sends on Connections with higher Niceness values lower Niceness values. An ideal transport system implementation
will be prioritized over sends on Connections with lower Niceness would assign each Connection the capacity share (M-N) x C / M, where
values. An ideal transport system implementation would assign the N is the Connection's Niceness value, M is the maximum Niceness value
Connection the capacity share (M-N) x C / M, where N is the used by all Connections in the group and C is the total available
Connection's Niceness value, M is the maximum Niceness value used by capacity. However, the Niceness setting is purely advisory, and no
all Connections in the group and C is the total available capacity. guarantees are given about the way capacity is shared. Each
However, the niceness setting is purely advisory, and no guarantees implementation is free to implement a way to share capacity that it
are given about the way capacity is shared. Each implementation is sees fit.
free to implement a way it shares capacity that it sees fit.
7. Sending Data 7. 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
data. Data is sent in terms of Messages, which allow the application data. Data is sent in terms of Messages, which allow the application
to communicate the boundaries of the data being transferred. By to communicate the boundaries of the data being transferred. By
default, Send enqueues a complete Message, and takes optional per- default, Send enqueues a complete Message, and takes optional per-
Message properties (see Section 7.1). All Send actions are Message properties (see Section 7.1). All Send actions are
asynchronous, and deliver events (see Section 7.2). Sending partial asynchronous, and deliver events (see Section 7.2). Sending partial
Messages for streaming large data is also supported (see Messages for streaming large data is also supported (see
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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 protocol property Maximum Message Size on Send to determine query the protocol property Maximum Message Size on Send to determine
the maximum size allowed for a single Message. If a Message is too the maximum size allowed for a single Message. If a Message is too
large to fit in the Maximum Message Size for the Connection, the Send large to fit in the Maximum Message Size for the Connection, the Send
will fail with a SendError event (Section 7.2.3). For example, it is will fail with a SendError event (Section 7.2.3). For example, it is
invalid to send a Message over a UDP connection that is larger than invalid to send a Message over a UDP connection that is larger than
the available datagram sending size. the available datagram sending size.
If Send is called on a Connection which has not yet been established,
an Initiate Action will be implicitly performed simultaneously with
the Send. Together with the Idempotent property (see
Section 12.3.9), this can be used to send data during establishment
for 0-RTT session resumption on Protocol Stacks that support it.
7.2. Send Events 7.2. 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. a Message.
Note that if partial Sends are used (Section 7.4), there will still Note that if partial Sends are used (Section 7.4), 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
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disposition of the Message (i.e., whether it has actually been disposition of the Message (i.e., whether it has actually been
transmitted, moved into a buffer on the network interface, moved into transmitted, moved into a buffer on the network interface, moved into
a kernel buffer, and so on) when the Sent Event occurs is a kernel buffer, and so on) when the Sent Event occurs is
implementation-specific. The Sent Event contains an implementation- implementation-specific. The Sent Event contains an implementation-
specific reference to the Message to which it applies. specific reference to 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 system than an application created more buffer inside the transport system than an application
that only issues a Send after this Event fires. that always waits for the Sent Event before calling the next Send
Action.
7.2.2. Expired 7.2.2. Expired
Connection -> Expired<msgRef> Connection -> Expired<msgRef>
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 12.3.28) expired. This is separate from SendError, as (see Section 7.3.1) expired. This is separate from SendError, as it
it is an expected behavior for partially reliable transports. The is an expected behavior for partially reliable transports. The
Expired Event contains an implementation-specific reference to the Expired Event contains an implementation-specific reference to the
Message to which it applies. Message to which it applies.
7.2.3. SendError 7.2.3. SendError
Connection -> SendError<msgRef> Connection -> SendError<msgRef>
A SendError occurs when a Message could not be sent due to an error A SendError occurs when a Message could not be 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 an the Connection's transport properties. The SendError contains an
implementation-specific reference to the Message to which it applies. implementation-specific reference to the Message to which it applies.
7.3. Message Context Parameters 7.3. Message Properties
Applications may need to annotate the Messages they send with extra Applications may need to annotate the Messages they send with extra
information to control how data is scheduled and processed by the information to control how data is scheduled and processed by the
transport protocols in the Connection. A MessageContext object transport protocols in the Connection. A MessageContext object
contains parameters for sending Messages, and can be passed to the contains properties for sending Messages, and can be passed to the
Send Action. Some of these parameters are properties as defined in Send Action. Note that these properties are per-Message, not per-
Section 12. Note that these properties are per-Message, not per-Send Send if partial Messages are sent (Section 7.4). All data blocks
if partial Messages are sent (Section 7.4). All data blocks
associated with a single Message share properties. For example, it associated with a single Message share properties. For example, it
would not make sense to have the beginning of a Message expire, but would not make sense to have the beginning of a Message expire, but
allow the end of a Message to still be sent. allow the end of a Message to still be sent.
messageData := "hello".octets() messageData := "hello".octets()
messageContext := NewMessageContext() messageContext := NewMessageContext()
messageContext.add(parameter, value) messageContext.add(parameter, value)
Connection.Send(messageData, messageContext) Connection.Send(messageData, messageContext)
The simpler form of Send that does not take any MessageContext is The simpler form of Send that does not take any messageContext is
equivalent to passing a default MessageContext with not values added. equivalent to passing a default MessageContext with not values added.
Message Properties share a single namespace with Transport Properties
(see Section 12). This allows the specification of per-Connection
Protocol Properties that can be overridden on a per-Message basis.
If an application wants to override Message Properties for a specific If an application wants to override Message Properties for a specific
message, it can acquire an empty messageContext Object and add all message, it can acquire an empty MessageContext Object and add all
desired Message Properties to that Object. It can then reuse the desired Message Properties to that Object. It can then reuse the
same messageContext Object for sending multiple Messages with the same messageContext Object for sending multiple Messages with the
same properties. same properties.
Parameters may be added to a messageContext object only before the Properties may be added to a MessageContext object only before the
context is used for sending. Once a messageContext has been used context is used for sending. Once a messageContext has been used
with a Send call, modifying any of its parameters is invalid. with a Send call, modifying any of its properties is invalid.
Message Properties may be inconsistent with the properties of the Message Properties may be inconsistent with the properties of the
Protocol Stacks underlying the Connection on which a given Message is Protocol Stacks underlying the Connection on which a given Message is
sent. For example, a Connection must provide reliability to allow sent. For example, a Connection must provide reliability to allow
setting an infinitie value for the lifetime property of a Message. setting an infinitie value for the lifetime property of a Message.
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.
The following Message Context Parameters are supported: The following Message Properties are supported:
[TODO: De-Duplicate with Properties in Section 12, find consensus on
which Section to put them]
7.3.1. Lifetime 7.3.1. Lifetime
[TODO: De-Duplicate with Section 12.3.28] Type: Integer
Lifetime specifies how long a particular Message can wait to be sent Lifetime specifies how long a particular Message can wait to be sent
to the remote endpoint before it is irrelevant and no longer needs to to the remote endpoint before it is irrelevant and no longer needs to
be (re-)transmitted. When a Message's Lifetime is infinite, it must be (re-)transmitted. When a Message's Lifetime is infinite, it must
be transmitted reliably. The type and units of Lifetime are be transmitted reliably. The type and units of Lifetime are
implementation-specific. implementation-specific.
7.3.2. Niceness 7.3.2. Niceness
[TODO: De-Duplicate with Section 12.3.21] Type: Integer (non-negative)
Niceness is a numeric (non-negative) value that represents an This property represents an unbounded hierarchy of priorities. It
unbounded hierarchy of priorities of Messages, relative to other can specify the priority of a Message, relative to other Messages
Messages sent over the same Connection and/or Connection Group (see sent over the same Connection.
Section 6.4). A Message with Niceness 0 will yield to a Message with
Niceness 1, which will yield to a Message with Niceness 2, and so on.
Niceness may be used as a sender-side scheduling construct only, or
be used to specify priorities on the wire for Protocol Stacks
supporting prioritization.
This encoding of the priority has a convenient property that the A Message with Niceness 0 will yield to a Message with Niceness 1,
priority increases as both Niceness and Lifetime decrease. which will yield to a Message with Niceness 2, and so on. Niceness
may be used as a sender-side scheduling construct only, or be used to
specify priorities on the wire for Protocol Stacks supporting
prioritization.
Note that this property is not a per-message override of the
connection Niceness - see Section 9.1.5. Both Niceness properties
may interact, but can be used independently and be realized by
different mechanisms.
7.3.3. Ordered 7.3.3. Ordered
[TODO: De-Duplicate with Section 12.3.6] Type: Boolean
Ordered is a boolean property. If true, this Message should be If true, it specifies that the receiver-side transport protocol stack
delivered after the last Message passed to the same Connection via only deliver the Message to the receiving application after the
the Send Action; if false, this Message may be delivered out of previous ordered Message which was passed to the same Connection via
order. the Send Action, when such a Message exists. If false, the Message
may be delivered to the receiving application out of order. This
property is used for protocols that support preservation of data
ordering, see Section 5.2.3, but allow out-of-order delivery for
certain messages.
7.3.4. Idempotent 7.3.4. Idempotent
[TODO: De-Duplicate with Section 12.3.9] Type: Boolean
Idempotent is a boolean property. If true, the application-layer If true, it specifies that a Message is safe to send to the remote
entity in the Message is safe to send to the remote endpoint more endpoint more than once for a single Send Action. It is used to mark
than once for a single Send Action. It is used to mark data safe for data safe for certain 0-RTT establishment techniques, where
certain 0-RTT establishment techniques, where retransmission of the retransmission of the 0-RTT data may cause the remote application to
0-RTT data may cause the remote application to receive the Message receive the Message multiple times.
multiple times.
7.3.5. Final 7.3.5. Final
[TODO: De-Duplicate with Section 12.3.1] Type: Boolean
Final is a boolean property. If true, this Message is the last one If true, this Message is the last one that the application will send
that the application will send on a Connection. This allows on a Connection. This allows underlying protocols to indicate to the
underlying protocols to indicate to the Remote Endpoint that the Remote Endpoint that the Connection has been effectively closed in
Connection has been effectively closed in the sending direction. For the sending direction. For example, TCP-based Connections can send a
example, TCP-based Connections can send a FIN once a Message marked FIN once a Message marked as Final has been completely sent,
as Final has been completely sent, indicated by marking endOfMessage. indicated by marking endOfMessage. Protocols that do not support
Protocols that do not support signalling the end of a Connection in a signalling the end of a Connection in a given direction will ignore
given direction will ignore this property. this property.
Note that a Final Message must always be sorted to the end of a list Note that a Final Message must always be sorted to the end of a list
of Messages. The Final property overrides Niceness and any other of Messages. The Final property overrides Niceness 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 new Message will report an error. Connection, the Send Action for the new Message will cause a
SendError Event.
7.3.6. Corruption Protection Length 7.3.6. Corruption Protection Length
[TODO: De-Duplicate with Section 12.3.15] Type: Integer (non-negative with -1 as special value)
This numeric property specifies the length of the section of the This property specifies the length of the section of the Message,
Message, starting from byte 0, that the application assumes will be starting from byte 0, that the application requires to be delivered
received without corruption due to lower layer errors. It is used to without corruption due to lower layer errors. It is used to specify
specify options for simple integrity protection via checksums. By options for simple integrity protection via checksums. By default,
default, the entire Message is protected by checksum. A value of 0 the entire Message is protected by a checksum. A value of 0 means
means that no checksum is required, and a special value (e.g. -1) can that no checksum is required, and a special value (e.g. -1) can be
be used to indicate the default. Only full coverage is guaranteed, used to indicate the default. Only full coverage is guaranteed, any
any other requests are advisory. other requests are advisory.
7.3.7. Transmission Profile 7.3.7. Reliable Data Transfer (Message)
[TODO: De-Duplicate with Section 12.3.19] Type: Boolean
This property specifies that a message should be sent in such a way
that the transport protocol ensures all data is received on the other
side without corruption. Changing the 'Reliable Data Transfer'
property on Messages is only possible if the Connection supports
reliability. When this is not the case, changing it will generate an
error.
7.3.8. Transmission Profile
Type: Enumeration
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 protocol and path selection property (see the Capacity Profile protocol and path selection property (see
Section 12.3.19). Section 9.1.12).
The following values are valid for Transmission Profile: The following values are valid for Transmission Profile:
Default: No special optimizations of the tradeoff between delay, Default: No special optimizations of the tradeoff between delay,
delay variation, and bandwidth efficiency should be made when delay variation, and bandwidth efficiency should be made when
sending this message. sending this message.
Low Latency: Response time (latency) should be optimized at the Low Latency: Response time (latency) should be optimized at the
expense of efficiently using the available capacity when sending expense of efficiently using the available capacity when sending
this message. This can be used by the system to disable the this message. This can be used by the system to disable the
coalescing of multiple small Messages into larger packets (Nagle's coalescing of multiple small Messages into larger packets (Nagle's
algorithm); to prefer immediate acknowledgment from the peer algorithm); to prefer immediate acknowledgment from the peer
endpoint when supported by the underlying transport; to signal a endpoint when supported by the underlying transport; to signal a
preference for lower-latency, higher-loss treatment; and so on. preference for lower-latency, higher-loss treatment; and so on.
[TODO: This is inconsistent with {prop-cap-profile}} - needs to be
fixed]
7.3.9. Singular Transmission
Type: Boolean
This property specifies that a message should be sent and received as
a single packet without transport-layer segmentation or network-layer
fragmentation. Attempts to send a message with this property set
with a size greater to the transport's current estimate of its
maximum transmission segment size will result in a "SendError". When
used with transports supporting this functionality and running over
IP version 4, the Don't Fragment bit will be set.
7.4. Partial Sends 7.4. 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.
The following example sends a Message in two separate calls to Send. The following example sends a Message in two separate calls to Send.
messageContext := NewMessageContext() messageContext := NewMessageContext()
messageContext.add(parameter, value) messageContext.add(parameter, value)
messageData := "hel".octets() messageData := "hel".octets()
endOfMessage := false endOfMessage := false
Connection.Send(messageData, messageContext, endOfMessage) Connection.Send(messageData, messageContext, endOfMessage)
messageData := "lo".octets() messageData := "lo".octets()
endOfMessage := true endOfMessage := true
Connection.Send(messageData, messageContext, endOfMessage) Connection.Send(messageData, messageContext, endOfMessage)
All messageData sent with the same messageContext object will be All data sent with the same MessageContext object will be treated as
treated as belonging to the same Message, and will constitute an in- belonging to the same Message, and will constitute an in-order series
order series until the endOfMessage is marked. Once the end of the until the endOfMessage is marked. Once the end of the Message is
Message is marked, the messageContext object may be re-used as a new marked, the MessageContext object may be re-used as a new Message
Message with identical parameters. with identical parameters.
7.5. Batching Sends 7.5. Batching Sends
In order to reduce the overhead of sending multiple small Messages on In order to reduce the overhead of sending multiple small Messages on
a Connection, the application may want to batch several Send actions a Connection, the application may want to 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 should be coalesced when possible, and that sending these Messages should be coalesced when possible, and that sending
any of the batched Messages may be delayed until the last Message in any of the batched Messages may be delayed until the last Message in
the batch is enqueued. the batch is enqueued.
Connection.Batch( Connection.Batch(
Connection.Send(messageData) Connection.Send(messageData)
Connection.Send(messageData) Connection.Send(messageData)
) )
7.6. Sender-side Framing 7.6. Send on Active Open: InitiateWithIdempotentSend
For application-layer protocols where the Connection initiator also
sends the first message, the InitiateWithIdempotentSend() action
combines Connection initiation with a first Message sent, provided
that message is idempotent.
Without a message context (as in Section 7.1):
Connection := Preconnection.InitiateWithIdempotentSend(messageData)
With a message context (as in Section 7.3):
Connection := Preconnection.InitiateWithIdempotentSend(messageData, messageContext)
The message passed to InitiateWithIdempotentSend() is, as suggested
by the name, considered to be idempotent (see Section 7.3.4)
regardless of declared message properties or defaults. If protocol
stacks supporting 0-RTT establishment with idempotent data are
available on the Preconnection, then 0-RTT establishment may be used
with the given message when establishing candidate connections. For
a non-idemponent initial message, or when the selected stack(s) do
not support 0-RTT establishment, InitiateWithIdempotentSend is
identical to Initiate() followed by Send().
Neither partial sends nor send batching are supported by
InitiateWithIdempotentSend().
The Events that may be sent after InitiateWithIdempotentSend() are
equivalent to those that would be sent by an invocation of Initate()
followed immediately by an invocation of Send(), with the caveat that
a send failure that occurs because the Connection could not be
established will not result in a SendError separate from the
InitiateError signaling the failure of Connection establishment.
7.7. Sender-side Framing
Sender-side framing allows a caller to provide the interface with a Sender-side framing allows a caller to provide the interface with a
function that takes a Message of an appropriate application-layer function that takes a Message of an appropriate application-layer
type and returns an array of octets, the on-the-wire representation type and returns an array of octets, the on-the-wire representation
of the Message to be handed down to the Protocol Stack. It consists of the Message to be handed down to the Protocol Stack. It consists
of a Framer Object with a single Action, Frame. Since the Framer of a Framer Object with a single Action, Frame. Since the Framer
depends on the protocol used at the application layer, it is bound to depends on the protocol used at the application layer, it is bound to
the Preconnection during the pre-establishment phase: the Preconnection during the pre-establishment phase:
Preconnection.FrameWith(Framer) Preconnection.FrameWith(Framer)
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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 8.2.1). event (Section 8.2.1).
The application can set a minIncompleteLength value to indicates the The application can set a minIncompleteLength value to indicates 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. If this which means that only complete Messages should be delivered (see
value is set to some smaller value, the associated receive event will Section 8.2.2 and Section 8.4 for more information on how this is
be triggered only when at least that many bytes are available, or the accomplished). If this value is set to some smaller value, the
Message is complete with fewer bytes, or the system needs to free up associated receive event will be triggered only when at least that
memory. Applications should always check the length of the data many bytes are available, or the Message is complete with fewer
delivered to the receive event and not assume it will be as long as bytes, or the system needs to free up memory. Applications should
minIncompleteLength in the case of shorter complete Messages or always check the length of the data delivered to the receive event
memory issues. and not assume it will be as long as minIncompleteLength in the case
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 the application is currently prepared to receive. The default bytes the application is currently prepared to receive. The default
value for maxLength is infinite. If an incoming Message is larger value for maxLength is infinite. If an incoming Message is larger
than the minimum of this size and the maximum Message size on receive than the minimum of this size and the maximum Message size on receive
for the Connection's Protocol Stack, it will be delivered via for the Connection's Protocol Stack, it will be delivered via
ReceivedPartial events (Section 8.2.2). ReceivedPartial events (Section 8.2.2).
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 may receive that many bytes if they are available; the interface may
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8.2.2. ReceivedPartial 8.2.2. 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 may be delivered with a ReceivedPartial event. In order the Message may be delivered with a ReceivedPartial event. In order
to continue to receive more of the same Message, the application must to 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. All partial blocks of a single Message are flag is delivered or a ReceiveError occurs. All partial blocks of a
delivered in order without gaps. This event does not support single Message are delivered in order without gaps. This event does
delivering discontiguous partial Messages. not support delivering discontiguous partial Messages.
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:
o the underlying Protocol Stack supports message boundary o 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;
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deframing, all bytes received on the Connection will be represented deframing, all bytes received on the Connection will be represented
as one large message of indeterminate length. as one large message of indeterminate length.
8.2.3. ReceiveError 8.2.3. ReceiveError
Connection -> ReceiveError<messageContext> Connection -> ReceiveError<messageContext>
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 deframed, or when Protocol Stack that cannot be fully retrieved or deframed, or when
some other indication is received that reception has failed. Such some other indication is received that reception has failed. Such
conditions that irrevocably lead the the termination of the conditions that irrevocably lead to the termination of the Connection
Connection are signaled using ConnectionError instead (see are signaled using ConnectionError instead (see Section 10).
Section 10).
The ReceiveError event passes an optional associated messageContext. The ReceiveError event passes an optional associated MessageContext.
This may indicate that a Message that was being partially received This may indicate that a Message that was being partially received
previously, but had not completed, encountered and error and will not previously, but had not completed, encountered an error and will not
be completed. be completed.
8.3. Message Receive Context 8.3. Message Receive Context
Each Received Message Context may contain metadata from protocols in Each Received Message Context may contain metadata from protocols in
the Protocol Stack; which metadata is available is Protocol Stack the Protocol Stack; which metadata is available is Protocol Stack
dependent. The following metadata values are supported: dependent. The following metadata values are supported:
8.3.1. ECN 8.3.1. 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 purposes, and for building applications for logging and debugging purposes, and for building applications
which need access to information about the transport internals for which need access to information about the transport internals for
their own operation. their own operation.
8.3.2. Early Data 8.3.2. Early Data
In some cases it may be valuable to know whether data was read as In some cases it may be valuable to know whether data was read as
part of early data streams. This is useful if applications need to part of early data transfer (before connection establishment has
treat early data separately, e.g., if early data has different finished). This is useful if applications need to treat early data
security properties than data sent after connection establishment. separately, e.g., if early data has different security properties
In the case of TLS 1.3, client early data can be replayed maliciously than data sent after connection establishment. In the case of TLS
(see [I-D.ietf-tls-tls13]). Thus, receivers may wish to perform 1.3, client early data can be replayed maliciously (see
[I-D.ietf-tls-tls13]). Thus, receivers may wish to perform
additional checks for early data to ensure it is idempotent or not additional checks for early data to ensure it is idempotent or not
replayed. If TLS 1.3 is available and the recipient Message was sent replayed. If TLS 1.3 is available and the recipient Message was sent
as part of early data, the corresponding metadata carries a flag as part of early data, the corresponding metadata carries a flag
indicating as such. If early data is enabled, applications should indicating as such. If early data is enabled, applications should
check this metadata field for Messages received during connection check this metadata field for Messages received during connection
establishment and respond accordingly. establishment and respond accordingly.
8.3.3. Receiving Final Messages 8.3.3. Receiving Final Messages
The Received Message Context can indicate whether or not this Message The Received Message Context can indicate whether or not this Message
is the Final Message on a Connection. For any Message that is marked is the Final Message on a Connection. For any Message that is marked
as Final, the application can assume that there will be no more as Final, the application can assume that there will be no more
Messages received on the Connection once the Message has been Messages received on the Connection once the Message has been
completely delivered. This corresponds to the Final property that completely delivered. This corresponds to the Final property that
may be marked on a sent Message Section 12.3.1. may be marked on a sent Message Section 7.3.5.
Some transport protocols and peers may not support signaling of the Some transport protocols and peers may 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 other endpoint is done a Message marked Final to know that the other 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.
8.4. Receiver-side De-framing over Stream Protocols 8.4. Receiver-side De-framing over Stream Protocols
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an appropriate type for the application and platform, and leaves the an appropriate type for the application and platform, and leaves the
octet stream at the start of the next Message to deframe. It octet stream at the start of the next Message to deframe. It
consists of a Deframer Object with a single Action, Deframe. Since consists of a Deframer Object with a single Action, Deframe. Since
the Deframer depends on the protocol used at the application layer, the Deframer depends on the protocol used at the application layer,
it is bound to the Preconnection during the pre-establishment phase: it is bound to the Preconnection during the pre-establishment phase:
Preconnection.DeframeWith(Deframer) Preconnection.DeframeWith(Deframer)
{messageData} := Deframer.Deframe(OctetStream, ...) {messageData} := Deframer.Deframe(OctetStream, ...)
9. Setting and Querying Connection Properties 9. Managing Connections
At any point, the application can query Connection Properties. It After establishment, connections can be configured and queried using
can also set per-connection Protocol Properties. Connection Properties, and asynchronous information may be available
about the state of the connection via Soft Errors.
ConnectionProperties := Connection.GetProperties() Connection Properties represent the configuration and state of the
selected Protocol Stack(s) backing a Connection. These Connection
Properties may be Generic, applying regardless of transport protocol,
or Specific, applicable to a single implementation of a single
transport protocol stack. Generic Connection Properties are defined
in Section 9.1 below. Specific Protocol Properties are defined in a
transport- and implementation-specific way, and must not be assumed
to apply across different protocols. Attempts to set Specific
Protocol Properties on a protocol stack not containing that specific
protocol are simply ignored, and do not raise an error; however, too
much reliance by an application on Specific Protocol Properties may
significantly reduce the flexibility of a transport services
implementation.
Connection.SetProperty(property, value) The application can set and query Connection Properties on a per-
Connection basis. Connection Properties that are not read-only can
be set during pre-establishment (see Section 5.2), as well as on
connections directly using the SetProperty action: ~~~
Connection.SetProperty(property, value) ~~~
At any point, the application can query Connection Properties. ~~~
ConnectionProperties := Connection.GetProperties() ~~~
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:
o The status of the connection, which can be one of the following: o The connection state, which can be one of the following:
Establishing, Established, Closing, or Closed. Establishing, Established, Closing, or Closed.
o Whether the connection can be used to send data. A connection can o 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 "Unidirectional Receive" or if a Message marked Selection Property "Direction of Communication" set to
as "Final" was sent over this connection, see Section 12.3.1. "unidirectional receive" or if a Message marked as "Final" was
sent over this connection, see Section 7.3.5.
o Whether the connection can be used to receive data. A connection o Whether the connection can be used to receive data. A connection
can not be used for reading if the connection was created with the can not be used for reading if the connection was created with the
Selection Property "Unidirectional: Send" or if a Message marked Selection Property "Direction of Communication" set to
as "Final" was received, see Section 8.3.3. The latter is only "unidirectional send" or if a Message marked as "Final" was
supported by certain transport protocols, e.g., by TCP as half- received, see Section 8.3.3. The latter is only supported by
closed connection. certain transport protocols, e.g., by TCP as half-closed
connection.
o For Connections that are Establishing: Transport Properties that o For Connections that are Establishing: Transport Properties that
the application specified on the Preconnection, see Section 5.2. the application specified on the Preconnection, see Section 5.2.
Selection Properties of a Connection can only be queried, not set.
o For Connections that are Established, Closing, or Closed (TODO:
double-check if closed belongs here): Transport Properties of the
actual protocols that were selected and instantiated. These
features correspond to the properties given in Section 12 and
include Selection Properties and Protocol Properties.
* Selection Properties indicate whether or not the Connection has
or offers a certain Selection Property. Note that the actually
instantiated protocol stack may not match all Protocol
Selection Properties that the application specified on the
Preconnection. For example, a certain Protocol Selection
Property that an application specified as Preferred may not
actually be present in the chosen protocol stack because none
of the currently available transport protocols had this
feature. Selection Properties of a Connection can only be
queried.
* Protocol Properties of the protocol stack in use (see
Section 12.2.2 below). These can be queried and set. Certain
specific Procotol Properties may be read-only, on a protocol-
and property-specific basis.
o For Connections that are Established, properties of the path(s) in
use. These properties can be derived from the local provisioning
domain [RFC7556], measurements by the Protocol Stack, or other
sources. They can only be queried.
10. Connection Termination
Close terminates a Connection after satisfying all the requirements
that were specified regarding the delivery of Messages that the
application has already given to the transport system. For example,
if reliable delivery was requested for a Message handed over before
calling Close, the transport system will ensure that this Message is
indeed delivered. If the Remote Endpoint still has data to send, it
cannot be received after this call.
Connection.Close()
The Closed Event can inform the application that the Remote Endpoint
has closed the Connection; however, there is no guarantee that a
remote close will be signaled.
Connection -> Closed<>
Abort terminates a Connection without delivering remaining data:
Connection.Abort()
A ConnectionError can inform the application that the other side has
aborted the Connection; however, there is no guarantee that an abort
will be signaled:
Connection -> ConnectionError<>
A SoftError can inform the application about the receipt of an ICMP
error message that does not force termination of the connection, if
the underlying protocol stack supports access to soft errors;
however, even if the underlying stack supports it, there is no
guarantee that a soft error will be signaled.
Connection -> SoftError<>
11. Ordering of Operations and Events
As this interface is designed to be independent of concurrency model,
the details of how exactly actions are handled, and on which threads/
callbacks events are dispatched, are implementation dependent.
However, the interface does provide the following guarantees about
the ordering of operations:
o Received<> will never occur on a Connection before a Ready<> event
on that Connection, or a ConnectionReceived<> or RendezvousDone<>
containing that Connection.
o No events will occur on a Connection after a Closed<> event, an
InitiateError<> or ConnectionError<> on that connection. To
ensure this ordering, Closed<> will not occur on a Connection
while other events on the Connection are still locally outstanding
(i.e., known to the interface and waiting to be dealt with by the
application). ConnectionError<> may occur after Closed<>, but the
interface must gracefully handle the application ignoring these
errors.
o 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
network interface, depending on implementation).
12. Transport Properties
Transport Properties allow an application to control and introspect
most aspects of the transport system and transport protocols.
Properties are structured in two ways:
o By how they influence the transport system, which leads to a
classification into "Selection Properties", "Protocol Properties",
"Control Properties" and "Intents".
o By the object they can be applied to: Preconnections, see
Section 5.2, Connections, see Section 9, and Messages, see
Section 7.3.
Because some properties can be applied or queried on multiple
objects, all Transport Properties are organized within a single
namespace.
Note that it is possible for a set of specified Transport Properties
to be internally inconsistent, or to be inconsistent with the later
use of the API by the application. Application developers can reduce
inconsistency by only using the most stringent preference levels when
failure to meet the property would break the application's
functionality. For example, it can set the Selection Property
"Reliable Data Transfer", which is a core assumption of many
application protocols, as Required. Implementations of this
interface should also raise any detected errors in configuration as
early as possible, to help ensure that inconsistencies are caught
early in the development process.
12.1. Transport Property Types
Each Transport Property takes a value of a property-specific type.
12.1.1. Boolean
A boolean is a data type that can be either "true" or "false".
Boolean transport properties should only be used for properties that
can not be used in an optional way or to query the state of the
transport implementation. For optional features, especially in
Selection Properties, the usage of the Preference type (see
Section 12.1.4) is preferred.
12.1.2. Enumeration
Enumeration types are used for transport properties that can take one
value out of a limited set of choices. The representation is
implementation dependent.
12.1.3. Integer
Integer types are used to represent integer numbers. The
representation is implementation dependent.
12.1.4. Preference
The Preference type is used in most Selection properties on a
Preconnection object to constrain Path Selection and Protocol
Selection. It is a specific instance of the "Enum" type and has five
different preference levels:
+------------+------------------------------------------------------+
| Preference | Effect |
+------------+------------------------------------------------------+
| Require | Select only protocols/paths providing the property, |
| | fail otherwise |
| | |
| Prefer | Prefer protocols/paths providing the property, |
| | proceed otherwise |
| | |
| Ignore | Cancel any default preference for this property |
| | |
| Avoid | Prefer protocols/paths not providing the property, |
| | proceed otherwise |
| | |
| Prohibit | Select only protocols/paths not providing the |
| | property, fail otherwise |
+------------+------------------------------------------------------+
When used on a Connection, this type becomes a (read-only) Boolean
representing whether the selected transport supports the requested
feature.
12.2. Transport Property Classification
Note: This section is subject to WG discussion on IETF-102.
Transport Properties - whether they apply to connections,
preconnections, or messages - differ in the way they affect the
transport system and protocols exposed through the transport system.
The classification proposed below emphasizes two aspects of how
properties affect the transport system, so applications know what to
expect:
o Whether properties affect protocols exposed through the transport
system (Protocol Properties) or the transport system itself
(Control Properties)
o Whether properties have a clearly defined behavior that is likely
to be invariant across implementations and environments (Protocol
Properties and Control Properties) or whether the properties are
interpreted by the transport system to provide a best effort
service that matches the applications needs as well as possible
(Intents).
Note: in I-D.ietf-taps-interface-00, we had a classification into
Connection Properties and Message Properties, whereby Connection
Properties where itself were sub-classified in Protocol-Selection,
Path-Selection and Protocol properties.
The classification in this version of the draft emphasizes the way
the property affects the transport system and protocols. It
treats the aspect of whether properties are used on a connection,
preconnection or message as an orthogonal dimension of
classification.
The "Message Properties" from I-D.ietf-taps-interface-00 therefore
have been split into "Protocol Properties" - emphasizing that they
affect the protocol configurations - and "Control Properties" -
emphasizing that they control the local transport system itself.
12.2.1. Selection Properties
Selection Properties influence protocol and path selection. Their
value usually is or includes a Preference that constrains (in case of
Require or Prohibit) or influences (Prefer, Ignore, Avoid) the
selection of transport protocols and paths used.
An implementation of this interface must provide sensible defaults
for Selection Properties. The defaults given for each property below
represent a configuration that can be implemented over TCP. An
alternate set of default Protocol Selection Properties would
represent a configuration that can be implemented over UDP.
Protocol Selection Properties can only be set on Preconnections, see o For Connections that are Established, Closing, or Closed:
Section 5.2. Path Selection Properties are usually used on Selection (Section 5.2) and Connection Properties (Section 9.1) of
Preconnections, but might also be used on messages to assist per- the actual protocols that were selected and instantiated.
message path selection for multipath aware protocols. Selection Properties indicate whether or not the Connection has or
offers a certain Selection Property. Note that the actually
12.2.2. Protocol Properties instantiated protocol stack may not match all Protocol Selection
Properties that the application specified on the Preconnection.
For example, a certain Protocol Selection Property that an
application specified as Preferred may not actually be present in
the chosen protocol stack because none of the currently available
transport protocols had this feature.
Protocol Properties represent the configuration of the selected o For Connections that are Established, additional properties of the
Protocol Stacks backing a Connection. Some properties apply path(s) in use. These properties can be derived from the local
generically across multiple transport protocols, while other provisioning domain [RFC7556], measurements by the Protocol Stack,
properties only apply to specific protocols. Generic properties will or other sources.
be passed to the selected candidate Protocol Stack(s) to configure
them before candidate Connection establishment. The default settings
of these properties will vary based on the specific protocols being
used and the system's configuration.
Most Protocol Properties can be set on a Preconnection during pre- 9.1. Generic Connection Properties
establishment to preconfigure Protocol Stacks during establishment.
In order to specify Specific Protocol Properties, Transport System The Connection Properties defined as independent, and available on
implementations may offer applications to attach a set of options to all Connections are defined in the subsections below.
the Preconnection Object, associated with a specific protocol. For
example, an application could specify a set of TCP Options to use if
and only if TCP is selected by the system. Such properties must not
be assumed to apply across different protocols. Attempts to set
specific protocol properties on a protocol stack not containing that
specific protocol are simply ignored, and do not raise an error.
Note that many protocol properties have a corresponding selection Note that many protocol properties have a corresponding selection
property which asks for a protocol providing a specific transport property, which prefers protocols providing a specific transport
feature that is controlled by the protocol property. feature that controlled by that protocol property. [EDITOR'S NOTE:
todo: add these cross-references up to Section 5.2]
12.2.3. Control Properties
[TODO: Discuss]
Control properties manage the local transport system behavior or
request state changes in the local transport system. Depending on
the protocols used, setting these properties might also influence the
protocol state machine. See Section 12.3.1 for an example.
12.2.4. Intents
[TODO: Discuss]
Intents are hints to the transport system that do not directly map to
a single protocol/transport feature or behavior of the transport
system, but express a presumed application behavior or generic
application needs.
The application can expect the transport system to take appropriate
actions involving protocol selection, path selection and, setting of
protocol flags. For example, if an application sets the "Capacity
Profile" to "bulk" on a Preconnection, this will likely influence
path selection, DSCP flags in the IP header as well as niceness for
multi-streaming connections. When using Intents, the application
must not expect consistent behavior across different environments,
implementations or versions of the same implementation.
12.3. Mandatory Transport Properties
The following properties are mandatory to implement in a transport
system:
12.3.1. Final
See Section 7.3.5.
[TODO: Decide whether this is a property or a parameter]
12.3.2. Reliable Data Transfer (Connection)
Classification: Selection Property
Type: Preference
Applicability: Preconnection, Connection (read only)
This property specifies whether the application wishes to use a
transport protocol that ensures that all data is received on the
other side without corruption. This also entails being notified when
a Connection is closed or aborted. The default is to enable Reliable
Data Transfer.
12.3.3. Configure per-Message reliability
Classification: Selection Property
Type: Preference
Applicability: Preconnection, Connection (read only)
This property specifies whether an application considers it useful to
indicate its reliability requirements on a per-Message basis. This
property applies to Connections and Connection Groups. The default
is to not have this option.
12.3.4. Reliable Data Transfer (Message)
Classification: Protocol Property (Generic)
Type: Boolean
Applicability: Message
This property specifies that a message should be sent in such a way
that the transport protocol ensures all data is received on the other
side without corruption. Changing the 'Reliable Data Transfer'
property on Messages is only possible if the transport protocol
supports partial reliability (see Section 12.3.3). Therefore, for
protocols that always transfer data reliably, this property is always
true and for protocols that always transfer data unreliably, this
flag is always false. Changing it may generate an error.
12.3.5. Preservation of data ordering
Classification: Selection Property
Type: Preference
Applicability: Preconnection, Connection (read only)
This property specifies whether the application wishes to use a
transport protocol that ensures that data is received by the
application on the other end in the same order as it was sent. The
default is to preserve data ordering.
12.3.6. Ordered
Classification: Protocol Property (Generic)
Type: Boolean
Applicability: Message
This property specifies that a Message should be delivered to the
other side after the previous Message which was passed to the same
Connection via the Send Action. It us used for protocols that
support preservation of data ordering, see Section 12.3.5, but allow
out-of-order delivery for certain messages.
12.3.7. Direction of communication
Classification: Selection Property, Control Property [TODO: Discuss]
Type: Enumeration
Applicability: Preconnection, Connection (read only)
This property specifies whether an application wants to use the
connection for sending and/or receiving data. Possible values are:
Bidirectional (default): The connection must support sending and
receiving data
unidirectional send: The connection must support sending data.
unidirectional receive: The connection must support receiving data
In case a unidirectional connection is requested, but unidirectional
connections are not supported by the transport protocol, the system
should fall back to bidirectional transport.
12.3.8. Use 0-RTT session establishment with an idempotent Message
Classification: Selection Property
Type: Preference
Applicability: Preconnection, Connection (read only)
This property specifies whether an application would like to supply a
Message to the transport protocol before Connection establishment,
which will then be reliably transferred to the other side before or
during Connection establishment, potentially multiple times. See
also Section 12.3.9. The default is to not have this option.
12.3.9. Idempotent
Classification: Control Property
Type: Boolean
Applicability: Message
This property specifies that a Message is safe to send to the remote
endpoint more than once for a single Send Action. It is used to mark
data safe for certain 0-RTT establishment techniques, where
retransmission of the 0-RTT data may cause the remote application to
receive the Message multiple times.
The application can query the maximum size of a message that can be
sent idempotent, see Section 12.3.24.
12.3.10. Multistream Connections in Group
Classification: Selection Property
Type: Preference
Applicability: Preconnection, Connection (read only)
This property specifies that the application would prefer multiple
Connections within a Connection Group to be provided by streams of a
single underlying transport connection where possible. The default
is to not have this option.
12.3.11. Notification of excessive retransmissions
Classification: Control Property [TODO: Discuss] 9.1.1. Notification of excessive retransmissions
Type: Boolean Type: Boolean
Applicability: Preconnection, Connection
This property specifies whether an application considers it useful to This property specifies whether an application considers it useful to
be informed in case sent data was retransmitted more often than a be informed in case sent data was retransmitted more often than a
certain threshold. When set to true, the effect is twofold: The certain threshold. When set to true, the effect is twofold: The
application may receive events in case excessive retransmissions. In application may receive events in case excessive retransmissions. In
addition, the transport system considers this as a preference to use addition, the transport system considers this as a preference to use
transports stacks that can provide this notification. This is not a transports stacks that can provide this notification. This is not a
strict requirement. If set to false, no notification of excessive strict requirement. If set to false, no notification of excessive
retransmissions will be sent and this transport feature is ignored retransmissions will be sent and this transport feature is ignored
for protocol selection. for protocol selection.
The default is to have this option. The recommended default is to have this option.
12.3.12. Retransmission threshold before excessive retransmission
notification
Classification: Control Property [TODO: Discuss] 9.1.2. Retransmission threshold before excessive retransmission
notification
Type: Integer Type: Integer
Applicability: Preconnection, Connection
This property specifies after how many retransmissions to inform the This property specifies after how many retransmissions to inform the
application about "Excessive Retransmissions". application about "Excessive Retransmissions".
12.3.13. Notification of ICMP soft error message arrival 9.1.3. Notification of ICMP soft error message arrival
Classification: Control Property [TODO: Discuss]
Type: Boolean Type: Boolean
Applicability: Preconnection, Connection
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
will be available as SoftErrors. Note that even if a protocol will be available as SoftErrors. Note that even if a protocol
supporting this property is selected, not all ICMP errors will supporting this property is selected, not all ICMP errors will
necessarily be delivered, so applications cannot rely on receiving necessarily be delivered, so applications cannot rely on receiving
them. Setting this option also implies a preference to prefer them. Setting this option also implies a preference to prefer
transports stacks that can provide this notification. If not set, no transports stacks that can provide this notification. If not set, no
events will be sent for ICMP soft error message and this transport events will be sent for ICMP soft error message and this transport
feature is ignored for protocol selection. feature is ignored for protocol selection.
This property applies to Connections and Connection Groups. The This property applies to Connections and Connection Groups. The
default is not to have this option. recommended default is not to have this option.
12.3.14. Control checksum coverage on sending or receiving
Classification: Selection Property
Type: Preference
Applicability: Preconnection, Connection (read only)
This property specifies whether the application considers it useful
to enable, disable, or configure a checksum when sending a Message,
or configure whether to require a checksum or not when receiving.
The default is full checksum coverage without the option to configure
it, and requiring a checksum when receiving.
12.3.15. Corruption Protection Length
Classification: Protocol Property (Generic)
Type: Integer
Applicability: Message
This numeric property specifies the length of the section of the
Message, starting from byte 0, that the application assumes will be
received without corruption due to lower layer errors. It is used to
specify options for simple integrity protection via checksums. By
default, the entire Message is protected by the checksum. A value of
0 means that no checksum is required, and a special value (e.g. -1)
can be used to indicate the default. Only full coverage is
guaranteed, any other requests are advisory.
12.3.16. Required minimum coverage of the checksum for receiving
Classification: Protocol Property (Generic) 9.1.4. Required minimum coverage of the checksum for receiving
Type: Integer Type: Integer
Applicability: Connection
This property specifies the part of the received data that needs to This property specifies the part of the received data that needs to
be covered by a checksum. It is given in Bytes. A value of 0 means be covered by a checksum. It is given in Bytes. A value of 0 means
that no checksum is required, and a special value (e.g., -1) that no checksum is required, and a special value (e.g., -1)
indicates full checksum coverage. indicates full checksum coverage.
12.3.17. Interface Instance or Type 9.1.5. Niceness (Connection)
Classification: Selection Property Type: Integer
Type: Tuple (Enumeration, Preference) This Property is a non-negative integer representing the relative
inverse priority of this Connection relative to other Connections in
the same Connection Group. It has no effect on Connections not part
of a Connection Group. As noted in Section 6.4, this property is not
entangled when Connections are cloned.
Applicability: Preconnection, Connection (read only) 9.1.6. Timeout for aborting Connection
This property allows the application to select which specific network Type: Integer
interfaces or categories of interfaces it wants to "Require",
"Prohibit", "Prefer", or "Avoid".
If a system supports discovery of specific interface identifiers, This property specifies how long to wait before aborting a Connection
such as "en0" or "eth0" on Unix-style systems, an implemention should during establishment, or before deciding that a Connection has failed
allow using these identifiers to define path preferences. Note that after establishment. It is given in seconds.
marking a specific interface as "Required" strictly limits path
selection to a single interface, and leads to less flexible and
resilient connection establishment.
The set of valid interface types is implementation- and system- 9.1.7. Connection group transmission scheduler
specific. For example, on a mobile device, there may be "Wi-Fi" and
"Cellular" interface types available; whereas on a desktop computer,
there may be "Wi-Fi" and "Wired Ethernet" interface types available.
Implementations should provide all types that are supported on some
system to all systems, in order to allow applications to write
generic code. For example, if a single implementation is used on
both mobile devices and desktop devices, it should define the
"Cellular" interface type for both systems, since an application may
want to always "Prohibit Cellular". Note that marking a specific
interface type as "Required" limits path selection to a small set of
interfaces, and leads to less flexible and resilient connection
establishment.
The set of interface types is expected to change over time as new Type: Enum
access technologies become available.
Interface types should not be treated as a proxy for properties of This property specifies which scheduler should be used among
interfaces such as metered or unmetered network access. If an Connections within a Connection Group, see Section 6.4. The set of
application needs to prohibit metered interfaces, this should be schedulers can be taken from [I-D.ietf-tsvwg-sctp-ndata].
specified via Provisioning Domain attributes Section 12.3.18 or
another specific property.
12.3.18. Provisioning Domain Instance or Type 9.1.8. Maximum message size concurrent with Connection establishment
Classification: Selection Property Type: Integer (read only)
Type: Tuple (Enumeration, Preference) This property represents the maximum Message size that can be sent
before or during Connection establishment, see also Section 7.3.4.
It is given in Bytes.
Applicability: Preconnection, Connection (read only) 9.1.9. Maximum Message size before fragmentation or segmentation
Similar to interface instances and types Section 12.3.17, this Type: Integer (read only)
property allows the application to control path selection by
selecting which specific Provisioning Domains or categories of
Provisioning Domains it wants to "Require", "Prohibit", "Prefer", or
"Avoid". Provisioning Domains define consistent sets of network
properties that may be more specific than network interfaces
[RFC7556].
The identification of a specific Provisioning Domain (PvD) is defined This property, if applicable, represents the maximum Message size
to be implementation- and system-specific, since there is not a that can be sent without incurring network-layer fragmentation or
portable standard format for a PvD identitfier. For example, this transport layer segmentation at the sender.
identifier may be a string name or an integer. As with requiring
specific interfaces, requiring a specific PvD strictly limits path
selection.
Categories or types of PvDs are also defined to be implementation- 9.1.10. Maximum Message size on send
and system-specific. These may be useful to identify a service that
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
can use the relevant PvD type to require some PvD that provides this
service, without needing to look up a particular instance. While
this does restrict path selection, it is more broad than requiring
specific PvD instances or interface instances, and should be
preferred over those options.
12.3.19. Capacity Profile Type: Integer (read only)
Classification: Intent [TODO: Discuss] This property represents the maximum Message size that can be sent.
Type: Enumeration 9.1.11. Maximum Message size on receive
Applicability: Preconnection, Connection, Message Type: Integer (read only)
This property specifies the application's expectation of the This numeric property represents the maximum Message size that can be
dominating traffic pattern for this Connection. This implies that received.
the transport system should optimize for the capacity profile
specified. This can influence path and protocol selection. The 9.1.12. Capacity Profile
following values are valid for the Capacity Profile:
This property specifies the desired network treatment for traffic
sent by the application and the tradeoffs the application is prepared
to make in path and protocol selection to receive that desired
treatment. When the capacity profile is set to a value other than
Default, the transport system should select paths and profiles to
optimize for the capacity profile specified. The following values
are valid for the Capacity Profile:
Default: The application makes no representation about its expected Default: The application makes no representation about its expected
capacity profile. No special optimizations of the tradeoff capacity profile. No special optimizations of the tradeoff
between delay, delay variation, and bandwidth efficiency should be between delay, delay variation, and bandwidth efficiency should be
made when selecting and configuring stacks. made when selecting and configuring transport protocol stacks.
Transport system implementations that map the requested capacity
profile onto per-connection DSCP signaling without multiplexing
SHOULD assign the DSCP Default Forwarding [RFC2474] PHB; when the
Connection is multiplexed, the guidelines in section 6 of
[RFC7657] apply.
Low Latency: Response time (latency) should be optimized at the Scavenger: The application is not interactive. It expects to send
expense of bandwidth efficiency and delay variation when sending and/or receive data without any urgency. This can, for example,
this message. This can be used by the system to disable the be used to select protocol stacks with scavenger transmission
control and/or to assign the traffic to a lower-effort service.
Transport system implementations that map the requested capacity
profile onto per-connection DSCP signaling without multiplexing
SHOULD assign the DSCP Less than Best Effort [LE-PHB] PHB; when
the Connection is multiplexed, the guidelines in section 6 of
[RFC7657] apply.
Low Latency/Interactive: The application is interactive, and prefers
loss to latency. Response time should be optimized at the expense
of bandwidth efficiency and delay variation when sending on this
connection. This can be used by the system to disable the
coalescing of multiple small Messages into larger packets (Nagle's coalescing of multiple small Messages into larger packets (Nagle's
algorithm); to prefer immediate acknowledgment from the peer algorithm); to prefer immediate acknowledgment from the peer
endpoint when supported by the underlying transport; to signal a endpoint when supported by the underlying transport; and so on.
preference for lower-latency, higher-loss treatment; and so on. Transport system implementations that map the requested capacity
profile onto per-connection DSCP signaling without multiplexing
SHOULD assign the DSCP Expedited Forwarding [RFC3246] PHB; when
the Connection is multiplexed, the guidelines in section 6 of
[RFC7657] apply.
Constant Rate: The application expects to send/receive data at a Low Latency/Non-Interactive: The application prefers loss to latency
constant rate after Connection establishment. Delay and delay but is not interactive. Response time should be optimized at the
variation should be minimized at the expense of bandwidth expense of bandwidth efficiency and delay variation when sending
on this connection.Transport system implementations that map the
requested capacity profile onto per-connection DSCP signaling
without multiplexing SHOULD assign a DSCP Assured Forwarding
(AF21,AF22,AF23,AF24) [RFC2597] PHB; when the Connection is
multiplexed, the guidelines in section 6 of [RFC7657] apply.
Constant-Rate Streaming: The application expects to send/receive
data at a constant rate after Connection establishment. Delay and
delay variation should be minimized at the expense of bandwidth
efficiency. This implies that the Connection may fail if the efficiency. This implies that the Connection may fail if the
desired rate cannot be maintained across the Path. A transport desired rate cannot be maintained across the Path. A transport
may interpret this capacity profile as preferring a circuit may interpret this capacity profile as preferring a circuit
breaker [RFC8084] to a rate-adaptive congestion controller. breaker [RFC8084] to a rate-adaptive congestion controller.
Transport system implementations that map the requested capacity
profile onto per-connection DSCP signaling without multiplexing
SHOULD assign a DSCP Assured Forwarding (AF31,AF32,AF33,AF34)
[RFC2597] PHB; when the Connection is multiplexed, the guidelines
in section 6 of [RFC7657] apply.
Scavenger/Bulk: The application is not interactive. It expects to High Throughput Data: The application expects to send/receive data
send/receive a large amount of data, without any urgency. This at the maximum rate allowed by its congestion controller over a
can, for example, be used to select protocol stacks with scavenger relatively long period of time. Transport system implementations
transmission control, to signal a preference for less-than-best- that map the requested capacity profile onto per-connection DSCP
effort treatment, or to assign the traffic to a lower-effort signaling without multiplexing SHOULD assign a DSCP Assured
service. Forwarding (AF11,AF12,AF13,AF14) [RFC2597] PHB per section 4.8 of
[RFC4594]. When the Connection is multiplexed, the guidelines in
12.3.20. Congestion control section 6 of [RFC7657] apply.
Classification: Selection Property
Type: Preference
Applicability: Preconnection, Connection (read only)
This property specifies whether the application would like the
Connection to be congestion controlled or not. Note that if a
Connection is not congestion controlled, an application using such a
Connection should itself perform congestion control in accordance
with [RFC2914]. Also note that reliability is usually combined with
congestion control in protocol implementations, rendering "reliable
but not congestion controlled" a request that is unlikely to succeed.
The default is that the Connection is congestion controlled.
12.3.21. Niceness
Classification: Protocol Property (Generic)
Type: Integer
Applicability: Connection, Message
This property is a numeric (non-negative) value that represents an
unbounded hierarchy of priorities. It can specify the priority of a
Message, relative to other Messages sent over the same Connection
and/or Connection Group (see Section 6.4), or the priority of a
Connection, relative to other Connections in the same Connection
Group.
A Message with Niceness 0 will yield to a Message with Niceness 1,
which will yield to a Message with Niceness 2, and so on. Niceness
may be used as a sender-side scheduling construct only, or be used to
specify priorities on the wire for Protocol Stacks supporting
prioritization.
This encoding of the priority has a convenient property that the
priority increases as both Niceness and Lifetime decrease.
As noted in Section 6.4, when set on a Connection, this property is
not entangled when Connections are cloned.
12.3.22. Timeout for aborting Connection
Classification: Control Property [TODO: Discuss]
Type: Integer
Applicability: Preconnection, Connection
This property specifies how long to wait before aborting a Connection
during establishment, or before deciding that a Connection has failed
after establishment. It is given in seconds.
12.3.23. Connection group transmission scheduler
Classification: Protocol Property (Generic) / Control Property
[TODO: Discuss]
Type: Enum
Applicability: Preconnection, Connection
This property specifies which scheduler should be used among
Connections within a Connection Group, see Section 6.4. The set of
schedulers can be taken from [I-D.ietf-tsvwg-sctp-ndata].
12.3.24. Maximum message size concurrent with Connection establishment
Classification: Protocol Property (Generic)
Type: Integer The Capacity Profile for a selected protocol stack may be modified on
a per-Message basis using the Transmission Profile Message Property;
see Section 7.3.8.
Applicability: Connection (read only) 9.2. Soft Errors
This property represents the maximum Message size that can be sent Asynchronous introspection is also possible, via the SoftError Event.
before or during Connection establishment, see also Section 12.3.9. This event informing the application about the receipt of an ICMP
It is given in Bytes. This property is read-only. error message related to the Connection. This will only happen if
the underlying protocol stack supports access to soft errors;
however, even if the underlying stack supports it, there is no
guarantee that a soft error will be signaled.
12.3.25. Maximum Message size before fragmentation or segmentation Connection -> SoftError<>
Classification: Protocol Property (Generic) 10. Connection Termination
Type: Integer Close terminates a Connection after satisfying all the requirements
that were specified regarding the delivery of Messages that the
application has already given to the transport system. For example,
if reliable delivery was requested for a Message handed over before
calling Close, the transport system will ensure that this Message is
indeed delivered. If the Remote Endpoint still has data to send, it
cannot be received after this call.
Applicability: Connection (read only) Connection.Close()
This property, if applicable, represents the maximum Message size The Closed Event can inform the application that the Remote Endpoint
that can be sent without incurring network-layer fragmentation and/or has closed the Connection; however, there is no guarantee that a
transport layer segmentation at the sender. This property is read- remote Close will indeed be signaled.
only.
12.3.26. Maximum Message size on send Connection -> Closed<>
Classification: Protocol Property (Generic) Abort terminates a Connection without delivering remaining data:
Type: Integer Connection.Abort()
Applicability: Connection (read only)
This property represents the maximum Message size that can be sent. A ConnectionError can inform the application that the other side has
This property is read-only. aborted the Connection; however, there is no guarantee that an Abort
will indeed be signaled.
12.3.27. Maximum Message size on receive Connection -> ConnectionError<>
Classification: Protocol Property (Generic) 11. Connection State and Ordering of Operations and Events
Type: Integer As this interface is designed to be independent of an
implementation's concurrency model, the details of how exactly
actions are handled, and on which threads/callbacks events are
dispatched, are implementation dependent.
Applicability: Connection (read only) Each transition of connection state is associated with one of more
events:
This numeric property represents the maximum Message size that can be o Ready<> occurs when a Connection created with Initiate() or
received. This property is read-only. InitiateWithIdempotentData() transitions to Established state.
12.3.28. Lifetime o ConnectionReceived<> occurs when a Connection created with
Listen() transitions to Established state.
Classification: Protocol Property (Generic) o RendezvousDone<> occurs when a Connection created with
Rendezvous() transitions to Established state.
Type: Integer o Closed<> occurs when a Connection transitions to Closed state
without error.
Applicability: Message o InitiateError<> occurs when a Connection created with Initiate()
transitions from Establishing state to Closed state due to an
error.
Lifetime specifies how long a particular Message can wait to be sent o ConnectionError<> occurs when a Connection transitions to Closed
to the remote endpoint before it is irrelevant and no longer needs to state due to an error in all other circumstances.
be (re-)transmitted. When a Message's Lifetime is infinite, it must
be transmitted reliably. The type and units of Lifetime are
implementation-specific.
12.4. Optional Transport Properties The interface provides the following guarantees about the ordering of
operations:
TODO: Maybe move some of the above properties here. o 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
network interface, depending on implementation).
12.5. Experimental Transport Properties o Received<> will never occur on a Connection before it is
Established; i.e. before a Ready<> event on that Connection, or a
ConnectionReceived<> or RendezvousDone<> containing that
Connection.
TODO: Move Appendix A here. o No events will occur on a Connection after it is Closed; i.e.,
after a Closed<> event, an InitiateError<> or ConnectionError<> on
that connection. To ensure this ordering, Closed<> will not occur
on a Connection while other events on the Connection are still
locally outstanding (i.e., known to the interface and waiting to
be dealt with by the application). ConnectionError<> may occur
after Closed<>, but the interface must gracefully handle all cases
where application ignores these errors.
13. 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. This document has no Actions for IANA.
14. Security Considerations 13. 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 Section 5.3. It does not recommend use (or disuse) of in Section 5.3. It does not recommend use (or disuse) of specific
specific algorithms or protocols. Any API-compatible transport algorithms or protocols. Any API-compatible transport security
security protocol should work in a TAPS system. protocol should work in a TAPS system.
15. 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
Sciences Research Council under grant EP/R04144X/1. Sciences Research Council under grant EP/R04144X/1.
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. which this work has evolved.
16. References 15. References
16.1. 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., and C. Wood, "An Architecture for
Transport Services", draft-ietf-taps-arch-01 (work in Transport Services", draft-ietf-taps-arch-01 (work in
progress), July 2018. progress), July 2018.
[I-D.ietf-taps-minset] [I-D.ietf-taps-minset]
Welzl, M. and S. Gjessing, "A Minimal Set of Transport Welzl, M. and S. Gjessing, "A Minimal Set of Transport
Services for End Systems", draft-ietf-taps-minset-04 (work Services for End Systems", draft-ietf-taps-minset-11 (work
in progress), June 2018. in progress), September 2018.
[I-D.ietf-tls-tls13] [I-D.ietf-tls-tls13]
Rescorla, E., "The Transport Layer Security (TLS) Protocol Rescorla, E., "The Transport Layer Security (TLS) Protocol
Version 1.3", draft-ietf-tls-tls13-28 (work in progress), Version 1.3", draft-ietf-tls-tls13-28 (work in progress),
March 2018. March 2018.
[I-D.ietf-tsvwg-rtcweb-qos] [I-D.ietf-tsvwg-rtcweb-qos]
Jones, P., Dhesikan, S., Jennings, C., and D. Druta, "DSCP Jones, P., Dhesikan, S., Jennings, C., and D. Druta, "DSCP
Packet Markings for WebRTC QoS", draft-ietf-tsvwg-rtcweb- Packet Markings for WebRTC QoS", draft-ietf-tsvwg-rtcweb-
qos-18 (work in progress), August 2016. qos-18 (work in progress), August 2016.
skipping to change at page 46, line 25 skipping to change at page 43, line 5
[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>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
16.2. Informative References 15.2. Informative References
[I-D.ietf-taps-transport-security] [I-D.ietf-taps-transport-security]
Pauly, T., Perkins, C., Rose, K., and C. Wood, "A Survey Pauly, T., Perkins, C., Rose, K., and C. Wood, "A Survey
of Transport Security Protocols", draft-ietf-taps- of Transport Security Protocols", draft-ietf-taps-
transport-security-02 (work in progress), June 2018. transport-security-02 (work in progress), June 2018.
[LE-PHB] Bless, R., "A Lower Effort Per-Hop Behavior (LE PHB)",
draft-ietf-tsvwg-le-phb-06 (work in progress), October
2018.
[RFC0793] Postel, J., "Transmission Control Protocol", STD 7, [RFC0793] Postel, J., "Transmission Control Protocol", STD 7,
RFC 793, DOI 10.17487/RFC0793, September 1981, RFC 793, DOI 10.17487/RFC0793, September 1981,
<https://www.rfc-editor.org/info/rfc793>. <https://www.rfc-editor.org/info/rfc793>.
[RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black,
"Definition of the Differentiated Services Field (DS
Field) in the IPv4 and IPv6 Headers", RFC 2474,
DOI 10.17487/RFC2474, December 1998,
<https://www.rfc-editor.org/info/rfc2474>.
[RFC2597] Heinanen, J., Baker, F., Weiss, W., and J. Wroclawski,
"Assured Forwarding PHB Group", RFC 2597,
DOI 10.17487/RFC2597, June 1999,
<https://www.rfc-editor.org/info/rfc2597>.
[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>.
[RFC3246] Davie, B., Charny, A., Bennet, J., Benson, K., Le Boudec,
J., Courtney, W., Davari, S., Firoiu, V., and D.
Stiliadis, "An Expedited Forwarding PHB (Per-Hop
Behavior)", RFC 3246, DOI 10.17487/RFC3246, March 2002,
<https://www.rfc-editor.org/info/rfc3246>.
[RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
A., Peterson, J., Sparks, R., Handley, M., and E. A., Peterson, J., Sparks, R., Handley, M., and E.
Schooler, "SIP: Session Initiation Protocol", RFC 3261, Schooler, "SIP: Session Initiation Protocol", RFC 3261,
DOI 10.17487/RFC3261, June 2002, DOI 10.17487/RFC3261, June 2002,
<https://www.rfc-editor.org/info/rfc3261>. <https://www.rfc-editor.org/info/rfc3261>.
[RFC4594] Babiarz, J., Chan, K., and F. Baker, "Configuration
Guidelines for DiffServ Service Classes", RFC 4594,
DOI 10.17487/RFC4594, August 2006,
<https://www.rfc-editor.org/info/rfc4594>.
[RFC5245] Rosenberg, J., "Interactive Connectivity Establishment [RFC5245] Rosenberg, J., "Interactive Connectivity Establishment
(ICE): A Protocol for Network Address Translator (NAT) (ICE): A Protocol for Network Address Translator (NAT)
Traversal for Offer/Answer Protocols", RFC 5245, Traversal for Offer/Answer Protocols", RFC 5245,
DOI 10.17487/RFC5245, April 2010, DOI 10.17487/RFC5245, April 2010,
<https://www.rfc-editor.org/info/rfc5245>. <https://www.rfc-editor.org/info/rfc5245>.
[RFC7478] Holmberg, C., Hakansson, S., and G. Eriksson, "Web Real- [RFC7478] Holmberg, C., Hakansson, S., and G. Eriksson, "Web Real-
Time Communication Use Cases and Requirements", RFC 7478, Time Communication Use Cases and Requirements", RFC 7478,
DOI 10.17487/RFC7478, March 2015, DOI 10.17487/RFC7478, March 2015,
<https://www.rfc-editor.org/info/rfc7478>. <https://www.rfc-editor.org/info/rfc7478>.
[RFC7556] Anipko, D., Ed., "Multiple Provisioning Domain [RFC7556] Anipko, D., Ed., "Multiple Provisioning Domain
Architecture", RFC 7556, DOI 10.17487/RFC7556, June 2015, Architecture", RFC 7556, DOI 10.17487/RFC7556, June 2015,
<https://www.rfc-editor.org/info/rfc7556>. <https://www.rfc-editor.org/info/rfc7556>.
[RFC7657] Black, D., Ed. and P. Jones, "Differentiated Services
(Diffserv) and Real-Time Communication", RFC 7657,
DOI 10.17487/RFC7657, November 2015,
<https://www.rfc-editor.org/info/rfc7657>.
[RFC8084] Fairhurst, G., "Network Transport Circuit Breakers", [RFC8084] Fairhurst, G., "Network Transport Circuit Breakers",
BCP 208, RFC 8084, DOI 10.17487/RFC8084, March 2017, BCP 208, RFC 8084, DOI 10.17487/RFC8084, March 2017,
<https://www.rfc-editor.org/info/rfc8084>. <https://www.rfc-editor.org/info/rfc8084>.
[RFC8095] Fairhurst, G., Ed., Trammell, B., Ed., and M. Kuehlewind, [RFC8095] Fairhurst, G., Ed., Trammell, B., Ed., and M. Kuehlewind,
Ed., "Services Provided by IETF Transport Protocols and Ed., "Services Provided by IETF Transport Protocols and
Congestion Control Mechanisms", RFC 8095, Congestion Control Mechanisms", RFC 8095,
DOI 10.17487/RFC8095, March 2017, DOI 10.17487/RFC8095, March 2017,
<https://www.rfc-editor.org/info/rfc8095>. <https://www.rfc-editor.org/info/rfc8095>.
skipping to change at page 47, line 49 skipping to change at page 45, line 11
used to enhance transport protocol and/or path selection, or the used to enhance transport protocol and/or path selection, or the
transmission of messages given a Protocol Stack that implements them. transmission of messages given a Protocol Stack that implements them.
These are not part of the interface, and may be removed from the These are not part of the interface, and may be removed from the
final document, but are presented here to support discussion within final document, but are presented here to support discussion within
the TAPS working group as to whether they should be added to a future the TAPS working group as to whether they should be added to a future
revision of the base specification. revision of the base specification.
A.1. Experimental Transport Properties A.1. Experimental Transport Properties
The following Transport Properties might be made available in The following Transport Properties might be made available in
addition to those specified in Section 12: addition to those specified in Section 5.2, Section 9.1, and
Section 7.3.
A.1.1. Suggest a timeout to the Remote Endpoint A.1.1. Direction of communication
Classification: Selection Property, Control Property [TODO: Discuss]
Type: Enumeration
Applicability: Preconnection, Connection (read only)
This property specifies whether an application wants to use the
connection for sending and/or receiving data. Possible values are:
Bidirectional (default): The connection must support sending and
receiving data
unidirectional send: The connection must support sending data.
unidirectional receive: The connection must support receiving data
In case a unidirectional connection is requested, but unidirectional
connections are not supported by the transport protocol, the system
should fall back to bidirectional transport.
A.1.2. Suggest a timeout to the Remote Endpoint
Classification: Selection Property Classification: Selection Property
Type: Preference Type: Preference
Applicability: Preconnection Applicability: Preconnection
This property specifies whether an application considers it useful to This property specifies whether an application considers it useful to
propose a timeout until the Connection is assumed to be lost. The propose a timeout until the Connection is assumed to be lost. The
default is to have this option. default is to have this option.
[EDITOR'S NOTE: For discussion of this option, see [EDITOR'S NOTE: For discussion of this option, see
https://github.com/taps-api/drafts/issues/109] https://github.com/taps-api/drafts/issues/109]
A.1.2. Abort timeout to suggest to the Remote Endpoint A.1.3. Abort timeout to suggest to the Remote Endpoint
Classification: Protocol Property Classification: Protocol Property
Type: Integer Type: Integer
Applicability: Preconnection, Connection Applicability: Preconnection, Connection
This numeric property specifies the timeout to propose to the Remote This numeric property specifies the timeout to propose to the Remote
Endpoint. It is given in seconds. Endpoint. It is given in seconds.
[EDITOR'S NOTE: For discussion of this property, see [EDITOR'S NOTE: For discussion of this property, see
https://github.com/taps-api/drafts/issues/109] https://github.com/taps-api/drafts/issues/109]
A.1.3. Request not to delay acknowledgment of Message
Classification: Selection Property
Type: Preference
Applicability: Preconnection
This property specifies whether an application considers it useful to
be able to request for a Message that its acknowledgment be sent out
as early as possible instead of potentially being bundled with other
acknowledgments. The default is to not have this option.
[EDITOR'S NOTE: For discussion of this option, see
https://github.com/taps-api/drafts/issues/90]
A.1.4. Traffic Category A.1.4. Traffic Category
Classification: Intent Classification: Intent
Type: Enumeration Type: Enumeration
Applicability: Preconnection Applicability: Preconnection
This property specifies what the application expect the dominating This property specifies what the application expects the dominating
traffic pattern to be. Possible values are: traffic pattern to be. Possible values are:
Query: Single request / response style workload, latency bound Query: Single request / response style workload, latency bound
Control: Long lasting low bandwidth control channel, not bandwidth Control: Long lasting low bandwidth control channel, not bandwidth
bound bound
Stream: Stream of data with steady data rate Stream: Stream of data with steady data rate
Bulk: Bulk transfer of large Messages, presumably bandwidth bound Bulk: Bulk transfer of large Messages, presumably bandwidth bound
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A.1.6. Duration A.1.6. Duration
Classification: Intent Classification: Intent
Type: Integer Type: Integer
Applicability: Preconnection Applicability: Preconnection
This Intent specifies what the application expects the lifetime of a This Intent specifies what the application expects the lifetime of a
connection to be. It is given in milliseconds. Connection to be. It is given in milliseconds.
A.1.7. Send or Receive Bit-rate A.1.7. Send or Receive Bit-rate
Classification: Intent Classification: Intent
Type: Integer Type: Integer
Applicability: Preconnection, Message Applicability: Preconnection, Message
This Intent specifies what the application expects the bit-rate of a This Intent specifies what the application expects the bit-rate of a
transfer to be. It is given in Bytes per second. transfer to be. It is given in Bytes per second.
On a message, this property specifies at what bitrate the application On a Message, this property specifies at what bitrate the application
wishes the Message to be sent. A transport system supporting this wishes the Message to be sent. A transport system supporting this
feature will not exceed the requested Send Bitrate even if flow- feature will not exceed the requested Send Bitrate even if flow-
control and congestion control allow higher bitrates. This helps to control and congestion control allow higher bitrates. This helps to
avoid bursty traffic pattern on busy video streaming servers. avoid a bursty traffic pattern on busy streaming video servers.
A.1.8. Cost Preferences A.1.8. Cost Preferences
Classification: Intent Classification: Intent
Type: Enumeration Type: Enumeration
Applicability: Preconnection, Message Applicability: Preconnection, Message
This property describes what an application prefers regarding This property describes what an application prefers regarding
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Optimize Cost: Prefer inexpensive transports and accept service Optimize Cost: Prefer inexpensive transports and accept service
degradation degradation
Balance Cost: Use system policy to balance cost and other criteria Balance Cost: Use system policy to balance cost and other criteria
Ignore Cost: Ignore cost, choose transport solely based on other Ignore Cost: Ignore cost, choose transport solely based on other
criteria criteria
The default is "Balance Cost". The default is "Balance Cost".
A.1.9. Immediate
Classification: Protocol Property (Generic)
Type: Boolean
Applicability: Message
This property specifies whether the caller prefers immediacy to
efficient capacity usage for this Message. For example, this means
that the Message should not be bundled with other Message into the
same transmission by the underlying Protocol Stack.
Appendix B. Sample API definition in Go Appendix B. Sample API definition in Go
This document defines an abstract interface. To illustrate how this This document defines an abstract interface. To illustrate how this
would map concretely into a programming language, an API interface would map concretely into a programming language, an API interface
definition in Go is available online at https://github.com/mami- definition in Go is available online at https://github.com/mami-
project/postsocket. Documentation for this API - an illustration of project/postsocket. Documentation for this API - an illustration of
the documentation an application developer would see for an instance the documentation an application developer would see for an instance
of this interface - is available online at of this interface - is available online at
https://godoc.org/github.com/mami-project/postsocket. This API https://godoc.org/github.com/mami-project/postsocket. This API
definition will be kept largely in sync with the development of this definition will be kept largely in sync with the development of this
abstract interface definition. abstract interface definition.
Authors' Addresses Appendix C. Relationship to the Minimal Set of Transport Services for
End Systems
[I-D.ietf-taps-minset] identifies a minimal set of transport services
that end systems should offer. These services make all transport
features offered by TCP, MPTCP, UDP, UDP-Lite, SCTP and LEDBAT
available that 1) require interaction with the application, and 2) do
not get in the way of a possible implementation over TCP or, with
limitations, UDP. The following text explains how this minimal set
is reflected in the present API. For brevity, this uses the list in
Section 4.1 of [I-D.ietf-taps-minset], updated according to the
discussion in Section 5 of [I-D.ietf-taps-minset].
[EDITOR'S NOTE: This is early text. In the future, this section will
contain backward references, which we currently avoid because things
are still being moved around and names / categories etc. are
changing. Also, clearly, the intention is for the full minset to be
reflected by the API at some point.]
o Connect:
"Initiate" Action.
o Listen:
"Listen" Action.
o Specify number of attempts and/or timeout for the first
establishment message:
TODO.
o Disable MPTCP:
TODO.
o Hand over a message to reliably transfer (possibly multiple times)
before connection establishment:
"InitiateWithIdempotentSend" Action.
o Hand over a message to reliably transfer during connection
establishment:
TODO.
o Change timeout for aborting connection (using retransmit limit or
time value):
"Timeout for aborting Connection" property, using a time value in
seconds.
o Timeout event when data could not be delivered for too long:
TODO: this should probably be covered by the "ConnectionError"
Event, but the text above it currently reads: "...can inform the
application that the other side has aborted the Connection". In
this case, it is the local side.
o Suggest timeout to the peer:
"Suggest a timeout to the Remote Endpoint" and "Abort timeout to
suggest to the Remote Endpoint" Selection property. [EDITOR'S
NOTE: For discussion of this option, see https://github.com/taps-
api/drafts/issues/109].
o Notification of Excessive Retransmissions (early warning below
abortion threshold):
"Notification of excessive retransmissions" property.
o Notification of ICMP error message arrival:
"Notification of ICMP soft error message arrival" property.
o Choose a scheduler to operate between streams of an association:
"Connection group transmission scheduler" property.
o Configure priority or weight for a scheduler:
"Niceness (Connection)" property.
o "Specify checksum coverage used by the sender" and "Disable
checksum when sending":
"Corruption Protection Length" property (value 0 to disable).
o "Specify minimum checksum coverage required by receiver" and
"Disable checksum requirement when receiving":
"Required minimum coverage of the checksum for receiving" property
(value 0 to disable).
o "Specify DF" field and "Request not to bundle messages:"
The "Singular Transmission" Message property combines both of
these requests, i.e. if a request not to bundle messages is made,
this also turns off DF in case of protocols that allow this (only
UDP and UDP-Lite, which cannot bundle messages anyway).
o Get max. transport-message size that may be sent using a non-
fragmented IP packet from the configured interface:
"Maximum Message size before fragmentation or segmentation"
property.
o Get max. transport-message size that may be received from the
configured interface:
"Maximum Message size on receive" property.
o Obtain ECN field:
"ECN" is a defined metadata value as part of the Message Receive
Context.
o "Specify DSCP field", "Disable Nagle algorithm", "Enable and
configure a 'Low Extra Delay Background Transfer'":
As suggested in Section 5.5 of [I-D.ietf-taps-minset], these
transport features are collectively offered via the "Capacity
profile" property.
o Close after reliably delivering all remaining data, causing an
event informing the application on the other side:
This is offered by the "Close" Action with slightly changed
semantics in line with the discussion in Section 5.2 of
[I-D.ietf-taps-minset].
o "Abort without delivering remaining data, causing an event
informing the application on the other side" and "Abort without
delivering remaining data, not causing an event informing the
application on the other side":
This is offered by the "Abort" action without promising that this
is signaled to the other side. If it is, a "ConnectionError"
Event will fire at the peer.
o "Reliably transfer data, with congestion control", "Reliably
transfer a message, with congestion control" and "Unreliably
transfer a message":
Reliability is controlled via the "Reliable Data Transfer
(Message)" Message property. Transmitting data without delimiters
is done by not using a Framer. The choice of congestion control
is provided via the "Congestion control" property.
o Configurable Message Reliability:
The "Lifetime" Message Property implements a time-based way to
configure message reliability.
o "Ordered message delivery (potentially slower than unordered)" and
"Unordered message delivery (potentially faster than ordered)":
The two transport features are controlled via the Message property
"Ordered".
o Request not to delay the acknowledgement (SACK) of a message:
Should the protocol support it, this is one of the transport
features the transport system can use when an application uses the
Capacity Profile Property with value "Low Latency/Interactive".
o Receive data (with no message delimiting):
"Received" Event without using a Deframer.
o Receive a message:
"Received" Event. Section 5.1 of [I-D.ietf-taps-minset] discusses
how messages can be obtained from a bytestream in case of
implementation over TCP. Here, this is dealt with by Framers and
Deframers.
o Information about partial message arrival:
"ReceivedPartial" Event.
o Notification of send failures:
"Expired" and "SendError" Events.
o Notification that the stack has no more user data to send:
Applications can obtain this information via the "Sent" Event.
o Notification to a receiver that a partial message delivery has
been aborted:
"ReceiveError" Event.
Authors' Addresses
Brian Trammell (editor) Brian Trammell (editor)
ETH Zurich ETH Zurich
Gloriastrasse 35 Gloriastrasse 35
8092 Zurich 8092 Zurich
Switzerland Switzerland
Email: ietf@trammell.ch Email: ietf@trammell.ch
Michael Welzl (editor) Michael Welzl (editor)
University of Oslo University of Oslo
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