draft-ietf-taps-interface-13.txt   draft-ietf-taps-interface-14.txt 
TAPS Working Group B. Trammell, Ed. TAPS Working Group B. Trammell, Ed.
Internet-Draft Google Switzerland GmbH Internet-Draft Google Switzerland GmbH
Intended status: Standards Track M. Welzl, Ed. Intended status: Standards Track M. Welzl, Ed.
Expires: 13 January 2022 University of Oslo Expires: 7 July 2022 University of Oslo
T. Enghardt T. Enghardt
Netflix Netflix
G. Fairhurst G. Fairhurst
University of Aberdeen University of Aberdeen
M. Kuehlewind M. Kuehlewind
Ericsson Ericsson
C. Perkins C. Perkins
University of Glasgow University of Glasgow
P. Tiesel P. Tiesel
SAP SE SAP SE
C.A. Wood C.A. Wood
Cloudflare Cloudflare
T. Pauly T. Pauly
Apple Inc. Apple Inc.
K. Rose K. Rose
Akamai Technologies, Inc. Akamai Technologies, Inc.
12 July 2021 3 January 2022
An Abstract Application Layer Interface to Transport Services An Abstract Application Layer Interface to Transport Services
draft-ietf-taps-interface-13 draft-ietf-taps-interface-14
Abstract Abstract
This document describes an abstract application programming This document describes an abstract application programming
interface, API, to the transport layer that enables the selection of interface, API, to the transport layer that enables the selection of
transport protocols and network paths dynamically at runtime. This transport protocols and network paths dynamically at runtime. This
API enables faster deployment of new protocols and protocol features API enables faster deployment of new protocols and protocol features
without requiring changes to the applications. The specified API without requiring changes to the applications. The specified API
follows the Transport Services Architecture by providing follows the Transport Services architecture by providing
asynchronous, atomic transmission of messages. It is intended to asynchronous, atomic transmission of messages. It is intended to
replace the traditional BSD sockets API as the common interface to replace the BSD sockets API as the common interface to the transport
the transport layer, in an environment where endpoints could select layer, in an environment where endpoints could select from multiple
from multiple interfaces and potential transport protocols. interfaces and potential transport protocols.
Status of This Memo Status of This Memo
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Copyright Notice Copyright Notice
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Terminology and Notation . . . . . . . . . . . . . . . . 5 1.1. Terminology and Notation . . . . . . . . . . . . . . . . 5
1.2. Specification of Requirements . . . . . . . . . . . . . . 7 1.2. Specification of Requirements . . . . . . . . . . . . . . 7
2. Overview of Interface Design . . . . . . . . . . . . . . . . 7 2. Overview of the API Design . . . . . . . . . . . . . . . . . 7
3. API Summary . . . . . . . . . . . . . . . . . . . . . . . . . 8 3. API Summary . . . . . . . . . . . . . . . . . . . . . . . . . 8
3.1. Usage Examples . . . . . . . . . . . . . . . . . . . . . 9 3.1. Usage Examples . . . . . . . . . . . . . . . . . . . . . 9
3.1.1. Server Example . . . . . . . . . . . . . . . . . . . 10 3.1.1. Server Example . . . . . . . . . . . . . . . . . . . 9
3.1.2. Client Example . . . . . . . . . . . . . . . . . . . 10 3.1.2. Client Example . . . . . . . . . . . . . . . . . . . 10
3.1.3. Peer Example . . . . . . . . . . . . . . . . . . . . 12 3.1.3. Peer Example . . . . . . . . . . . . . . . . . . . . 12
4. Transport Properties . . . . . . . . . . . . . . . . . . . . 13 4. Transport Properties . . . . . . . . . . . . . . . . . . . . 13
4.1. Transport Property Names . . . . . . . . . . . . . . . . 13 4.1. Transport Property Names . . . . . . . . . . . . . . . . 14
4.2. Transport Property Types . . . . . . . . . . . . . . . . 14 4.2. Transport Property Types . . . . . . . . . . . . . . . . 15
5. Scope of the Interface Definition . . . . . . . . . . . . . . 15 5. Scope of the API Definition . . . . . . . . . . . . . . . . . 15
6. Pre-Establishment Phase . . . . . . . . . . . . . . . . . . . 16 6. Pre-Establishment Phase . . . . . . . . . . . . . . . . . . . 16
6.1. Specifying Endpoints . . . . . . . . . . . . . . . . . . 17 6.1. Specifying Endpoints . . . . . . . . . . . . . . . . . . 17
6.1.1. Using Multicast Endpoints . . . . . . . . . . . . . . 18 6.1.1. Using Multicast Endpoints . . . . . . . . . . . . . . 19
6.1.2. Endpoint Aliases . . . . . . . . . . . . . . . . . . 18 6.1.2. Constraining Interfaces for Endpoints . . . . . . . . 19
6.1.3. Endpoint Examples . . . . . . . . . . . . . . . . . . 19 6.1.3. Endpoint Aliases . . . . . . . . . . . . . . . . . . 20
6.2. Specifying Transport Properties . . . . . . . . . . . . . 20 6.1.4. Endpoint Examples . . . . . . . . . . . . . . . . . . 20
6.2.1. Reliable Data Transfer (Connection) . . . . . . . . . 23 6.1.5. Multicast Examples . . . . . . . . . . . . . . . . . 21
6.2.2. Preservation of Message Boundaries . . . . . . . . . 23 6.2. Specifying Transport Properties . . . . . . . . . . . . . 23
6.2.3. Configure Per-Message Reliability . . . . . . . . . . 24 6.2.1. Reliable Data Transfer (Connection) . . . . . . . . . 26
6.2.4. Preservation of Data Ordering . . . . . . . . . . . . 24 6.2.2. Preservation of Message Boundaries . . . . . . . . . 27
6.2.3. Configure Per-Message Reliability . . . . . . . . . . 27
6.2.4. Preservation of Data Ordering . . . . . . . . . . . . 27
6.2.5. Use 0-RTT Session Establishment with a Safely 6.2.5. Use 0-RTT Session Establishment with a Safely
Replayable Message . . . . . . . . . . . . . . . . . 24 Replayable Message . . . . . . . . . . . . . . . . . 27
6.2.6. Multistream Connections in Group . . . . . . . . . . 28
6.2.6. Multistream Connections in Group . . . . . . . . . . 24 6.2.7. Full Checksum Coverage on Sending . . . . . . . . . . 28
6.2.7. Full Checksum Coverage on Sending . . . . . . . . . . 25 6.2.8. Full Checksum Coverage on Receiving . . . . . . . . . 28
6.2.8. Full Checksum Coverage on Receiving . . . . . . . . . 25 6.2.9. Congestion control . . . . . . . . . . . . . . . . . 29
6.2.9. Congestion control . . . . . . . . . . . . . . . . . 25 6.2.10. Keep alive . . . . . . . . . . . . . . . . . . . . . 29
6.2.10. Keep alive . . . . . . . . . . . . . . . . . . . . . 26 6.2.11. Interface Instance or Type . . . . . . . . . . . . . 29
6.2.11. Interface Instance or Type . . . . . . . . . . . . . 26 6.2.12. Provisioning Domain Instance or Type . . . . . . . . 30
6.2.12. Provisioning Domain Instance or Type . . . . . . . . 27 6.2.13. Use Temporary Local Address . . . . . . . . . . . . . 31
6.2.13. Use Temporary Local Address . . . . . . . . . . . . . 28 6.2.14. Multipath Transport . . . . . . . . . . . . . . . . . 32
6.2.14. Multipath Transport . . . . . . . . . . . . . . . . . 28 6.2.15. Advertisement of Alternative Addresses . . . . . . . 33
6.2.15. Advertisement of Alternative Addresses . . . . . . . 29 6.2.16. Direction of communication . . . . . . . . . . . . . 33
6.2.16. Direction of communication . . . . . . . . . . . . . 30 6.2.17. Notification of ICMP soft error message arrival . . . 34
6.2.17. Notification of ICMP soft error message arrival . . . 30 6.2.18. Initiating side is not the first to write . . . . . . 34
6.2.18. Initiating side is not the first to write . . . . . . 31 6.3. Specifying Security Parameters and Callbacks . . . . . . 35
6.3. Specifying Security Parameters and Callbacks . . . . . . 31 6.3.1. Specifying Security Parameters on a Pre-Connection . 35
6.3.1. Specifying Security Parameters on a Pre-Connection . 31 6.3.2. Connection Establishment Callbacks . . . . . . . . . 37
6.3.2. Connection Establishment Callbacks . . . . . . . . . 33 7. Establishing Connections . . . . . . . . . . . . . . . . . . 37
7. Establishing Connections . . . . . . . . . . . . . . . . . . 33 7.1. Active Open: Initiate . . . . . . . . . . . . . . . . . . 37
7.1. Active Open: Initiate . . . . . . . . . . . . . . . . . . 34 7.2. Passive Open: Listen . . . . . . . . . . . . . . . . . . 39
7.2. Passive Open: Listen . . . . . . . . . . . . . . . . . . 35 7.3. Peer-to-Peer Establishment: Rendezvous . . . . . . . . . 40
7.3. Peer-to-Peer Establishment: Rendezvous . . . . . . . . . 36 7.4. Connection Groups . . . . . . . . . . . . . . . . . . . . 42
7.4. Connection Groups . . . . . . . . . . . . . . . . . . . . 38 7.5. Adding and Removing Endpoints on a Connection . . . . . . 43
8. Managing Connections . . . . . . . . . . . . . . . . . . . . 39 8. Managing Connections . . . . . . . . . . . . . . . . . . . . 44
8.1. Generic Connection Properties . . . . . . . . . . . . . . 41 8.1. Generic Connection Properties . . . . . . . . . . . . . . 46
8.1.1. Required Minimum Corruption Protection Coverage for 8.1.1. Required Minimum Corruption Protection Coverage for
Receiving . . . . . . . . . . . . . . . . . . . . . . 41 Receiving . . . . . . . . . . . . . . . . . . . . . . 46
8.1.2. Connection Priority . . . . . . . . . . . . . . . . . 42 8.1.2. Connection Priority . . . . . . . . . . . . . . . . . 46
8.1.3. Timeout for Aborting Connection . . . . . . . . . . . 42 8.1.3. Timeout for Aborting Connection . . . . . . . . . . . 47
8.1.4. Timeout for keep alive packets . . . . . . . . . . . 42 8.1.4. Timeout for keep alive packets . . . . . . . . . . . 47
8.1.5. Connection Group Transmission Scheduler . . . . . . . 43 8.1.5. Connection Group Transmission Scheduler . . . . . . . 47
8.1.6. Capacity Profile . . . . . . . . . . . . . . . . . . 43 8.1.6. Capacity Profile . . . . . . . . . . . . . . . . . . 48
8.1.7. Policy for using Multipath Transports . . . . . . . . 45 8.1.7. Policy for using Multipath Transports . . . . . . . . 49
8.1.8. Bounds on Send or Receive Rate . . . . . . . . . . . 46 8.1.8. Bounds on Send or Receive Rate . . . . . . . . . . . 50
8.1.9. Group Connection Limit . . . . . . . . . . . . . . . 46 8.1.9. Group Connection Limit . . . . . . . . . . . . . . . 51
8.1.10. Isolate Session . . . . . . . . . . . . . . . . . . . 46 8.1.10. Isolate Session . . . . . . . . . . . . . . . . . . . 51
8.1.11. Read-only Connection Properties . . . . . . . . . . . 47 8.1.11. Read-only Connection Properties . . . . . . . . . . . 51
8.2. TCP-specific Properties: User Timeout Option (UTO) . . . 48 8.2. TCP-specific Properties: User Timeout Option (UTO) . . . 52
8.2.1. Advertised User Timeout . . . . . . . . . . . . . . . 48 8.2.1. Advertised User Timeout . . . . . . . . . . . . . . . 53
8.2.2. User Timeout Enabled . . . . . . . . . . . . . . . . 48 8.2.2. User Timeout Enabled . . . . . . . . . . . . . . . . 53
8.2.3. Timeout Changeable . . . . . . . . . . . . . . . . . 49 8.2.3. Timeout Changeable . . . . . . . . . . . . . . . . . 53
8.3. Connection Lifecycle Events . . . . . . . . . . . . . . . 49 8.3. Connection Lifecycle Events . . . . . . . . . . . . . . . 54
8.3.1. Soft Errors . . . . . . . . . . . . . . . . . . . . . 49 8.3.1. Soft Errors . . . . . . . . . . . . . . . . . . . . . 54
8.3.2. Path change . . . . . . . . . . . . . . . . . . . . . 49 8.3.2. Path change . . . . . . . . . . . . . . . . . . . . . 54
9. Data Transfer . . . . . . . . . . . . . . . . . . . . . . . . 49 9. Data Transfer . . . . . . . . . . . . . . . . . . . . . . . . 54
9.1. Messages and Framers . . . . . . . . . . . . . . . . . . 50 9.1. Messages and Framers . . . . . . . . . . . . . . . . . . 54
9.1.1. Message Contexts . . . . . . . . . . . . . . . . . . 50 9.1.1. Message Contexts . . . . . . . . . . . . . . . . . . 55
9.1.2. Message Framers . . . . . . . . . . . . . . . . . . . 50 9.1.2. Message Framers . . . . . . . . . . . . . . . . . . . 55
9.1.3. Message Properties . . . . . . . . . . . . . . . . . 53 9.1.3. Message Properties . . . . . . . . . . . . . . . . . 57
9.2. Sending Data . . . . . . . . . . . . . . . . . . . . . . 58 9.2. Sending Data . . . . . . . . . . . . . . . . . . . . . . 63
9.2.1. Basic Sending . . . . . . . . . . . . . . . . . . . . 59 9.2.1. Basic Sending . . . . . . . . . . . . . . . . . . . . 63
9.2.2. Send Events . . . . . . . . . . . . . . . . . . . . . 59 9.2.2. Send Events . . . . . . . . . . . . . . . . . . . . . 64
9.2.3. Partial Sends . . . . . . . . . . . . . . . . . . . . 60 9.2.3. Partial Sends . . . . . . . . . . . . . . . . . . . . 65
9.2.4. Batching Sends . . . . . . . . . . . . . . . . . . . 61 9.2.4. Batching Sends . . . . . . . . . . . . . . . . . . . 66
9.2.5. Send on Active Open: InitiateWithSend . . . . . . . . 61 9.2.5. Send on Active Open: InitiateWithSend . . . . . . . . 66
9.2.6. Priority in TAPS . . . . . . . . . . . . . . . . . . 62 9.2.6. Priority and the Transport Services API . . . . . . . 67
9.3. Receiving Data . . . . . . . . . . . . . . . . . . . . . 63 9.3. Receiving Data . . . . . . . . . . . . . . . . . . . . . 67
9.3.1. Enqueuing Receives . . . . . . . . . . . . . . . . . 63 9.3.1. Enqueuing Receives . . . . . . . . . . . . . . . . . 67
9.3.2. Receive Events . . . . . . . . . . . . . . . . . . . 64 9.3.2. Receive Events . . . . . . . . . . . . . . . . . . . 68
9.3.3. Receive Message Properties . . . . . . . . . . . . . 66 9.3.3. Receive Message Properties . . . . . . . . . . . . . 71
10. Connection Termination . . . . . . . . . . . . . . . . . . . 67 10. Connection Termination . . . . . . . . . . . . . . . . . . . 72
11. Connection State and Ordering of Operations and Events . . . 69 11. Connection State and Ordering of Operations and Events . . . 73
12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 70 12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 75
13. Privacy and Security Considerations . . . . . . . . . . . . . 70 13. Privacy and Security Considerations . . . . . . . . . . . . . 75
14. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 72 14. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 77
15. References . . . . . . . . . . . . . . . . . . . . . . . . . 72 15. References . . . . . . . . . . . . . . . . . . . . . . . . . 77
15.1. Normative References . . . . . . . . . . . . . . . . . . 72 15.1. Normative References . . . . . . . . . . . . . . . . . . 77
15.2. Informative References . . . . . . . . . . . . . . . . . 73 15.2. Informative References . . . . . . . . . . . . . . . . . 78
Appendix A. Implementation Mapping . . . . . . . . . . . . . . . 76 Appendix A. Implementation Mapping . . . . . . . . . . . . . . . 81
A.1. Types . . . . . . . . . . . . . . . . . . . . . . . . . . 76 A.1. Types . . . . . . . . . . . . . . . . . . . . . . . . . . 82
A.2. Events and Errors . . . . . . . . . . . . . . . . . . . . 77 A.2. Events and Errors . . . . . . . . . . . . . . . . . . . . 82
A.3. Time Duration . . . . . . . . . . . . . . . . . . . . . . 77 A.3. Time Duration . . . . . . . . . . . . . . . . . . . . . . 82
Appendix B. Convenience Functions . . . . . . . . . . . . . . . 77 Appendix B. Convenience Functions . . . . . . . . . . . . . . . 83
B.1. Adding Preference Properties . . . . . . . . . . . . . . 77 B.1. Adding Preference Properties . . . . . . . . . . . . . . 83
B.2. Transport Property Profiles . . . . . . . . . . . . . . . 78 B.2. Transport Property Profiles . . . . . . . . . . . . . . . 83
B.2.1. reliable-inorder-stream . . . . . . . . . . . . . . . 78 B.2.1. reliable-inorder-stream . . . . . . . . . . . . . . . 83
B.2.2. reliable-message . . . . . . . . . . . . . . . . . . 78 B.2.2. reliable-message . . . . . . . . . . . . . . . . . . 84
B.2.3. unreliable-datagram . . . . . . . . . . . . . . . . . 79 B.2.3. unreliable-datagram . . . . . . . . . . . . . . . . . 84
Appendix C. Relationship to the Minimal Set of Transport Services Appendix C. Relationship to the Minimal Set of Transport Services
for End Systems . . . . . . . . . . . . . . . . . . . . . 80 for End Systems . . . . . . . . . . . . . . . . . . . . . 85
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 83 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 88
1. Introduction 1. Introduction
This document specifies a modern abstract application programming This document specifies an abstract application programming interface
interface (API) atop the high-level architecture for transport (API) that specifies the interface component of the high-level
services defined in [I-D.ietf-taps-arch]. The Transport Services Transport Services architecture defined in [I-D.ietf-taps-arch]. A
Architecture supports asynchronous, atomic transmission of messages Transport Services system supports asynchronous, atomic transmission
over transport protocols and network paths dynamically selected at of messages over transport protocols and network paths dynamically
runtime, in environments where an endpoint selects from multiple selected at runtime, in environments where an endpoint selects from
interfaces and potential transport protocols. multiple interfaces and potential transport protocols.
Applications that adopt this interface will benefit from a wide set Applications that adopt this API will benefit from a wide set of
of transport features that can evolve over time. This protocol- transport features that can evolve over time. This protocol-
independent API ensures that the system providing the interface can independent API ensures that the system providing the API can
optimize its behavior based on the application requirements and optimize its behavior based on the application requirements and
network conditions, without requiring changes to the applications. network conditions, without requiring changes to the applications.
This flexibility enables faster deployment of new features and This flexibility enables faster deployment of new features and
protocols, and can support applications by offering racing and protocols, and can support applications by offering racing and
fallback mechanisms, which otherwise need to be separately fallback mechanisms, which otherwise need to be separately
implemented in each application. implemented in each application.
This API derives specific path and protocol selection properties and The Transport Services system derives specific path and protocol
supported transport features from the analysis provided in [RFC8095], selection properties and supported transport features from the
[RFC8923], and [RFC8922]. The design encourages implementations analysis provided in [RFC8095], [RFC8923], and [RFC8922]. The
underneath the interface to dynamically choose a transport protocol Transport Services API enables an implementation to dynamically
depending on an application's choices rather than statically binding choose a transport protocol rather than statically binding
applications to a protocol at compile time. Nevertheless, the applications to a protocol at compile time. The Transport Services
Transport Services API also provides applications with a way to API also provides applications with a way to override transport
override transport selection and instantiate a specific stack, e.g., selection and instantiate a specific stack, e.g., to support servers
to support servers wishing to listen to a specific protocol. wishing to listen to a specific protocol. However, forcing a choice
However, forcing a specific transport stack choice is discouraged for to use a specific transport stack is discouraged for general use,
general use, because it can reduce portability. because it can reduce portability.
1.1. Terminology and Notation 1.1. Terminology and Notation
This API is described in terms of The Transport Services API is described in terms of
* Objects with which an application can interact; * Objects with which an application can interact;
* Actions the application can perform on these Objects; * Actions the application can perform on these Objects;
* Events, which an Object can send to an application to be processed * Events, which an Object can send to an application to be processed
aynchronously; and aynchronously; and
* Parameters associated with these Actions and Events. * Parameters associated with these Actions and Events.
skipping to change at page 6, line 11 skipping to change at page 6, line 13
* An Object sends an Event: * An Object sends an Event:
Object -> Event<> Object -> Event<>
* An Action takes a set of Parameters; an Event contains a set of * An Action takes a set of Parameters; an Event contains a set of
Parameters. Action and Event parameters whose names are suffixed Parameters. Action and Event parameters whose names are suffixed
with a question mark are optional. with a question mark are optional.
Action(param0, param1?, ...) / Event<param0, param1, ...> Action(param0, param1?, ...) / Event<param0, param1, ...>
Actions associated with no Object are Actions on the abstract Objects that are passed as parameters to Actions use call-by-value
interface itself; they are equivalent to Actions on a per-application behavior. Actions associated with no Object are Actions on the API;
global context. they are equivalent to Actions on a per-application global context.
Events are sent to the application or application-supplied code (e.g. Events are sent to the application or application-supplied code (e.g.
framers, see Section 9.1.2) for processing; the details of event framers, see Section 9.1.2) for processing; the details of event
processing are platform- and implementation-specific. processing are platform- and implementation-specific.
We also make use of the following basic types: We also make use of the following basic types:
* Boolean: Instances take the value "true" or "false". * Boolean: Instances take the value true or false.
* Integer: Instances take positive or negative numeric integer * Integer: Instances take positive or negative integer values.
values, or sometimes special non-numeric (symbolic) values.
* Numeric: Instances take positive or negative numeric values, or * Numeric: Instances take positive or negative real number values.
sometimes special non-numeric (symbolic) values.
* Enumeration: A family of types in which each instance takes one of * Enumeration: A family of types in which each instance takes one of
a fixed, predefined set of values specific to a given enumerated a fixed, predefined set of values specific to a given enumerated
type. type.
* Tuple: An ordered grouping of multiple value types, represented as * Tuple: An ordered grouping of multiple value types, represented as
a comma-separated list in parentheses, e.g., "(Enumeration, a comma-separated list in parentheses, e.g., (Enumeration,
Preference)". Instances take a sequence of values each valid for Preference). Instances take a sequence of values each valid for
the corresponding value type. the corresponding value type.
* Array: Denoted []Type, an instance takes a value for each of zero * Array: Denoted []Type, an instance takes a value for each of zero
or more elements in a sequence of the given Type. An array may be or more elements in a sequence of the given Type. An array may be
of fixed or variable length. of fixed or variable length.
* Collection: An unordered grouping of one or more values of the * Collection: An unordered grouping of one or more values of the
same type. same type.
For guidance on how these abstract concepts may be implemented in For guidance on how these abstract concepts may be implemented in
skipping to change at page 7, line 13 skipping to change at page 7, line 13
platform features, see Appendix A. platform features, see Appendix A.
1.2. Specification of Requirements 1.2. Specification of Requirements
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP "OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
2. Overview of Interface Design 2. Overview of the API Design
The design of the interface specified in this document is based on a The design of the API specified in this document is based on a set of
set of principles, themselves an elaboration on the architectural principles, themselves an elaboration on the architectural design
design principles defined in [I-D.ietf-taps-arch]. The interface principles defined in [I-D.ietf-taps-arch]. The API defined in this
defined in this document provides: document provides:
* Access to a variety of transport protocols, independent of the * A Transport Services system can offer a variety of transport
Protocol Stacks that will be used at runtime. All common features protocols, independent of the Protocol Stacks that will be used at
of these protocol stacks are made available to the application in runtime. All common features of these protocol stacks are made
a transport-independent way to the degree possible. This enables available to the application in a transport-independent way to the
applications written to a single API to make use of transport degree possible. This enables applications written to a single
protocols in terms of the features they provide. API to make use of transport protocols in terms of the features
they provide.
* A unified interface to datagram and stream-oriented transports, * A unified API to datagram and stream-oriented transports, allowing
allowing use of a common API for connection establishment and use of a common API for connection establishment and closing.
closing.
* Message-orientation, as opposed to stream-orientation, using * Message-orientation, as opposed to stream-orientation, using
application-assisted framing and deframing where the underlying application-assisted framing and deframing where the underlying
transport does not provide these. transport does not provide these.
* Asynchronous Connection establishment, transmission, and * Asynchronous Connection establishment, transmission, and
reception. This allows concurrent operations during establishment reception. This allows concurrent operations during establishment
and event-driven application interactions with the transport and event-driven application interactions with the transport
layer, in line with developments in modern platforms and layer;
programming languages;
* Selection between alternate network paths, using additional * Selection between alternate network paths, using additional
information about the networks over which a connection can operate information about the networks over which a connection can operate
(e.g. Provisioning Domain (PvD) information [RFC7556]) where (e.g. Provisioning Domain (PvD) information [RFC7556]) where
available. available.
* Explicit support for transport-specific features to be applied, * Explicit support for transport-specific features to be applied,
should that particular transport be part of a chosen Protocol should that particular transport be part of a chosen Protocol
Stack. Stack.
* Explicit support for security properties as first-order transport * Explicit support for security properties as first-order transport
features. features.
* Explicit support for configuration of cryptographic identities and * Explicit support for configuration of cryptographic identities and
transport security parameters persistent across multiple transport security parameters persistent across multiple
Connections. Connections.
* Explicit support for multistreaming and multipath transport * Explicit support for multistreaming and multipath transport
protocols, and the grouping of related Connections into Connection protocols, and the grouping of related Connections into Connection
Groups through cloning of Connections. This allows applications Groups through "cloning" of Connections (see Section 7.4). This
to take full advantage of new transport protocols supporting these function allows applications to take full advantage of new
features. transport protocols supporting these features.
3. API Summary 3. API Summary
The Transport Services API is the basic common abstract application
programming interface to the Transport Services Architecture defined
in the TAPS Architecture [I-D.ietf-taps-arch].
An application primarily interacts with this API through two Objects: An application primarily interacts with this API through two Objects:
Preconnections and Connections. A Preconnection object (Section 6) Preconnections and Connections. A Preconnection object (Section 6)
represents a set of properties and constraints on the selection and represents a set of properties and constraints on the selection and
configuration of paths and protocols to establish a Connection with configuration of paths and protocols to establish a Connection with
an Endpoint. A Connection object represents an instance of a an Endpoint. A Connection object represents an instance of a
transport Protocol Stack on which data can be sent to and/or received transport Protocol Stack on which data can be sent to and/or received
from a Remote Endpoint (i.e., a logical connection that, depending on from a Remote Endpoint (i.e., a logical connection that, depending on
the kind of transport, can be bi-directional or unidirectional, and the kind of transport, can be bi-directional or unidirectional, and
that can use a stream protocol or a datagram protocol). Connections that can use a stream protocol or a datagram protocol). Connections
are presented consistently to the application, irrespective of are presented consistently to the application, irrespective of
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* by initiating the Preconnection (i.e., actively opening, as in a * by initiating the Preconnection (i.e., actively opening, as in a
client; Section 7.1), client; Section 7.1),
* through listening on the Preconnection (i.e., passively opening, * through listening on the Preconnection (i.e., passively opening,
as in a server Section 7.2), as in a server Section 7.2),
* or rendezvousing on the Preconnection (i.e., peer to peer * or rendezvousing on the Preconnection (i.e., peer to peer
establishment; Section 7.3). establishment; Section 7.3).
Once a Connection is established, data can be sent and received on it Once a Connection is established, data can be sent and received on it
in the form of Messages. The interface supports the preservation of in the form of Messages. The API supports the preservation of
message boundaries both via explicit Protocol Stack support, and via message boundaries both via explicit Protocol Stack support, and via
application support through a Message Framer that finds message application support through a Message Framer that finds message
boundaries in a stream. Messages are received asynchronously through boundaries in a stream. Messages are received asynchronously through
event handlers registered by the application. Errors and other event handlers registered by the application. Errors and other
notifications also happen asynchronously on the Connection. It is notifications also happen asynchronously on the Connection. It is
not necessary for an application to handle all Events; some Events not necessary for an application to handle all Events; some Events
may have implementation-specific default handlers. The application may have implementation-specific default handlers. The application
should not assume that ignoring Events (e.g., Errors) is always safe. should not assume that ignoring Events (e.g., Errors) is always safe.
Section 6, Section 7, Section 9.2, Section 9.3, and Section 10
describe the details of application interaction with Objects through
Actions and Events in each phase of a Connection, following the
phases (Pre-Establishment, Establishment, Data Transfer, and
Termination) described in Section 4.1 of [I-D.ietf-taps-arch].
3.1. Usage Examples 3.1. Usage Examples
The following usage examples illustrate how an application might use The following usage examples illustrate how an application might use
the Transport Services Interface to: the Transport Services API to:
* Act as a server, by listening for incoming connections, receiving * Act as a server, by listening for incoming connections, receiving
requests, and sending responses, see Section 3.1.1. requests, and sending responses, see Section 3.1.1.
* Act as a client, by connecting to a Remote Endpoint using * Act as a client, by connecting to a Remote Endpoint using
Initiate, sending requests, and receiving responses, see Initiate, sending requests, and receiving responses, see
Section 3.1.2. Section 3.1.2.
* Act as a peer, by connecting to a Remote Endpoint using Rendezvous * Act as a peer, by connecting to a Remote Endpoint using Rendezvous
while simultaneously waiting for incoming Connections, sending while simultaneously waiting for incoming Connections, sending
Messages, and receiving Messages, see Section 3.1.3. Messages, and receiving Messages, see Section 3.1.3.
The examples in this section presume that a transport protocol is The examples in this section presume that a transport protocol is
available between the Local and Remote Endpoints that provides available between the Local and Remote Endpoints that provides
Reliable Data Transfer, Preservation of data ordering, and Reliable Data Transfer, Preservation of Data Ordering, and
Preservation of Message Boundaries. In this case, the application Preservation of Message Boundaries. In this case, the application
can choose to receive only complete messages. can choose to receive only complete messages.
If none of the available transport protocols provides Preservation of If none of the available transport protocols provides Preservation of
Message Boundaries, but there is a transport protocol that provides a Message Boundaries, but there is a transport protocol that provides a
reliable ordered byte stream, an application could receive this byte reliable ordered byte stream, an application could receive this byte
stream as partial Messages and transform it into application-layer stream as partial Messages and transform it into application-layer
Messages. Alternatively, an application might provide a Message Messages. Alternatively, an application might provide a Message
Framer, which can transform a sequence of Messages into a byte stream Framer, which can transform a sequence of Messages into a byte stream
and vice versa (Section 9.1.2). and vice versa (Section 9.1.2).
3.1.1. Server Example 3.1.1. Server Example
This is an example of how an application might listen for incoming This is an example of how an application might listen for incoming
Connections using the Transport Services Interface, and receive a Connections using the Transport Services API, and receive a request,
request, and send a response. and send a response.
LocalSpecifier := NewLocalEndpoint() LocalSpecifier := NewLocalEndpoint()
LocalSpecifier.WithInterface("any") LocalSpecifier.WithInterface("any")
LocalSpecifier.WithService("https") LocalSpecifier.WithService("https")
TransportProperties := NewTransportProperties() TransportProperties := NewTransportProperties()
TransportProperties.Require(preserve-msg-boundaries) TransportProperties.Require(preserve-msg-boundaries)
// Reliable Data Transfer and Preserve Order are Required by default // Reliable Data Transfer and Preserve Order are Required by default
SecurityParameters := NewSecurityParameters() SecurityParameters := NewSecurityParameters()
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Connection.Close() Connection.Close()
// Stop listening for incoming Connections // Stop listening for incoming Connections
// (this example supports only one Connection) // (this example supports only one Connection)
Listener.Stop() Listener.Stop()
//---- Receive event handler end ---- //---- Receive event handler end ----
3.1.2. Client Example 3.1.2. Client Example
This is an example of how an application might open two Connections This is an example of how an application might open two Connections
to a remote application using the Transport Services Interface, and to a remote application using the Transport Services API, and send a
send a request as well as receive a response on each of them. request as well as receive a response on each of them.
RemoteSpecifier := NewRemoteEndpoint() RemoteSpecifier := NewRemoteEndpoint()
RemoteSpecifier.WithHostname("example.com") RemoteSpecifier.WithHostname("example.com")
RemoteSpecifier.WithService("https") RemoteSpecifier.WithService("https")
TransportProperties := NewTransportProperties() TransportProperties := NewTransportProperties()
TransportProperties.Require(preserve-msg-boundaries) TransportProperties.Require(preserve-msg-boundaries)
// Reliable Data Transfer and Preserve Order are Required by default // Reliable Data Transfer and Preserve Order are Required by default
SecurityParameters := NewSecurityParameters() SecurityParameters := NewSecurityParameters()
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Connection -> Received<messageDataResponse, messageContext> Connection -> Received<messageDataResponse, messageContext>
Connection2 -> Received<messageDataResponse, messageContext> Connection2 -> Received<messageDataResponse, messageContext>
// Close the Connection in a Receive event handler // Close the Connection in a Receive event handler
Connection.Close() Connection.Close()
Connection2.Close() Connection2.Close()
Preconnections are reusable after being used to initiate a Preconnections are reusable after being used to initiate a
Connection. Hence, for example, after the Connections were closed, Connection. Hence, for example, after the Connections were closed,
the following would be correct: ~~~ //.. carry out adjustments to the the following would be correct:
Preconnection, if desire Connection := Preconnection.Initiate() ~~~
//.. carry out adjustments to the Preconnection, if desire
Connection := Preconnection.Initiate()
3.1.3. Peer Example 3.1.3. Peer Example
This is an example of how an application might establish a connection This is an example of how an application might establish a connection
with a peer using Rendezvous(), send a Message, and receive a with a peer using Rendezvous(), send a Message, and receive a
Message. Message.
// Configure local candidates: a port on the Local Endpoint and via a STUN server // Configure local candidates: a port on the Local Endpoint
HostCandidate := NewLocalEndpoint() // and via a STUN server
HostCandidate.WithPort(9876) HostCandidate := NewLocalEndpoint()
HostCandidate.WithPort(9876)
StunCandidate := NewLocalEndpoint() StunCandidate := NewLocalEndpoint()
StunCandidate.WithStunServer(address, port, credentials) StunCandidate.WithStunServer(address, port, credentials)
LocalCandidates = [HostCandidate, StunCandidate] LocalCandidates = [HostCandidate, StunCandidate]
// Configure transport and security properties // Configure transport and security properties
TransportProperties := ... TransportProperties := ...
SecurityParameters := ... SecurityParameters := ...
Preconnection := NewPreconnection(LocalCandidates, Preconnection := NewPreconnection(LocalCandidates,
[], // No remote candidates yet [], // No remote candidates yet
TransportProperties, TransportProperties,
SecurityParameters) SecurityParameters)
// Resolve the LocalCandidates. The Preconnection.Resolve() call // Resolve the LocalCandidates. The Preconnection.Resolve() call
// resolves both local and remote candidates but, since the remote // resolves both local and remote candidates but, since the remote
// candidates have not yet been specified, the ResolvedRemote list // candidates have not yet been specified, the ResolvedRemote list
// returned will be empty and is not used. // returned will be empty and is not used.
ResolvedLocal, ResolvedRemote = Preconnection.Resolve() ResolvedLocal, ResolvedRemote = Preconnection.Resolve()
// ...Send the ResolvedLocal list to peer via signalling channel // ...Send the ResolvedLocal list to peer via signalling channel
// ...Receive a list of RemoteCandidates from peer via signalling channel // ...Receive a list of RemoteCandidates from peer via
// signalling channel
Preconnection.AddRemote(RemoteCandidates) Preconnection.AddRemote(RemoteCandidates)
Preconnection.Rendezvous() Preconnection.Rendezvous()
Preconnection -> RendezvousDone<Connection> Preconnection -> RendezvousDone<Connection>
//---- RendezvousDone event handler begin ---- //---- RendezvousDone event handler begin ----
Connection.Send(messageDataRequest) Connection.Send(messageDataRequest)
Connection.Receive() Connection.Receive()
//---- RendezvousDone event handler end ---- //---- RendezvousDone event handler end ----
Connection -> Received<messageDataResponse, messageContext> Connection -> Received<messageDataResponse, messageContext>
// If new remote endpoint candidates are received from the peer over
// the signalling channel, for example if using Trickle ICE, then add
// them to the Connection:
Connection.AddRemote(NewRemoteCandidates)
// On a PathChange<> events, resolve the local endpoints to see if a
// new local endpoint has become available and, if so, send to the peer
// as a new candidate and add to the connection:
Connection -> PathChange<>
//---- PathChange event handler begin ----
ResolvedLocal, ResolvedRemote = Preconnection.Resolve()
if ResolvedLocal has changed:
// ...Send the ResolvedLocal list to peer via signalling channel
// Add the new local endpoints to the connection:
Connection.AddLocal(ResolvedLocal)
//---- PathChange event handler end ----
// Close the Connection in a Receive event handler
Connection.Close()
// Close the Connection in a Receive event handler
Connection.Close()
4. Transport Properties 4. Transport Properties
Each application using the Transport Services Interface declares its Each application using the Transport Services API declares its
preferences for how the transport service should operate using preferences for how the Transport Services system should operate.
properties at each stage of the lifetime of a connection using This is done by using Transport Properties, as defined in
Transport Properties, as defined in [I-D.ietf-taps-arch]. [I-D.ietf-taps-arch], at each stage of the lifetime of a connection.
Transport Properties are divided into Selection, Connection, and Transport Properties are divided into Selection, Connection, and
Message Properties. Selection Properties (see Section 6.2) can only Message Properties. Selection Properties (see Section 6.2) can only
be set during pre-establishment. They are only used to specify which be set during pre-establishment. They are only used to specify which
paths and protocol stacks can be used and are preferred by the paths and protocol stacks can be used and are preferred by the
application. Although Connection Properties (see Section 8.1) can be application. Although Connection Properties (see Section 8.1) can be
set during pre-establishment, they may be changed later. They are set during pre-establishment, they may be changed later. They are
used to inform decisions made during establishment and to fine-tune used to inform decisions made during establishment and to fine-tune
the established connection. Calling Initiate on a Preconnection the established connection. Calling Initiate on a Preconnection
creates an outbound Connection or a Listener, and the Selection creates an outbound Connection or a Listener, and the Selection
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input to the selection process. Protocol Specific Properties, which input to the selection process. Protocol Specific Properties, which
enable configuration of specialized features of a specific protocol, enable configuration of specialized features of a specific protocol,
see Section 3.2 of [I-D.ietf-taps-arch], are not used as an input to see Section 3.2 of [I-D.ietf-taps-arch], are not used as an input to
the selection process, but only support configuration if the the selection process, but only support configuration if the
respective protocol has been selected. respective protocol has been selected.
4.1. Transport Property Names 4.1. Transport Property Names
Transport Properties are referred to by property names. For the Transport Properties are referred to by property names. For the
purposes of this document, these names are alphanumeric strings in purposes of this document, these names are alphanumeric strings in
which words may be separated by hyphens. These names serve two which words may be separated by hyphens. Specifically, the following
characters are allowed: lowercase letters a-z, uppercase letters A-Z,
digits 0-9, the hyphen -, and the underscore _. These names serve two
purposes: purposes:
* Allowing different components of a TAPS implementation to pass * Allowing different components of a Transport Services
Transport Properties, e.g., between a language frontend and a implementation to pass Transport Properties, e.g., between a
policy manager, or as a representation of properties retrieved language frontend and a policy manager, or as a representation of
from a file or other storage. properties retrieved from a file or other storage.
* Making the code of different TAPS implementations look similar. * Making the code of different Transport Services implementations
While individual programming languages may preclude strict look similar. While individual programming languages may preclude
adherence to the aforementioned naming convention (for instance, strict adherence to the aforementioned naming convention (for
by prohibiting the use of hyphens in symbols), users interacting instance, by prohibiting the use of hyphens in symbols), users
with multiple implementations will still benefit from the interacting with multiple implementations will still benefit from
consistency resulting from the use of visually similar symbols. the consistency resulting from the use of visually similar
symbols.
Transport Property Names are hierarchically organized in the form Transport Property Names are hierarchically organized in the form
[<Namespace>.]<PropertyName>. [<Namespace>.]<PropertyName>.
* The Namespace component MUST be empty for well-known, generic * The Namespace component MUST be empty for well-known, generic
properties, i.e., for properties that are not specific to a properties, i.e., for properties that are not specific to a
protocol and are defined in an RFC. protocol and are defined in an RFC.
* Protocol Specific Properties MUST use the protocol acronym as the * Protocol Specific Properties MUST use the protocol acronym as the
Namespace, e.g., "tcp" for TCP specific Transport Properties. For Namespace, e.g., tcp for TCP specific Transport Properties. For
IETF protocols, property names under these namespaces SHOULD be IETF protocols, property names under these namespaces SHOULD be
defined in an RFC. defined in an RFC.
* Vendor or implementation specific properties MUST use a string * Vendor or implementation specific properties MUST use a string
identifying the vendor or implementation as the Namespace. identifying the vendor or implementation as the Namespace.
Namespaces for each of the keywords provided in the IANA protocol Namespaces for each of the keywords provided in the IANA protocol
numbers registry (see https://www.iana.org/assignments/protocol- numbers registry (see https://www.iana.org/assignments/protocol-
numbers/protocol-numbers.xhtml), reformatted where necessary to numbers/protocol-numbers.xhtml) are reserved for Protocol Specific
conform to an implementation's naming conventions, are reserved for Properties and MUST NOT be used for vendor or implementation-specific
Protocol Specific Properties and MUST NOT be used for vendor or properties. Avoid using any of the terms listed as keywords in the
implementation-specific properties. protocol numbers registry as any part of a vendor- or implementation-
specific property name.
4.2. Transport Property Types 4.2. Transport Property Types
Each Transport Property has a one of the basic types described in Each Transport Property has a one of the basic types described in
Section 1.1. Section 1.1.
Most Selection Properties (see Section 6.2) are of the Enumeration Most Selection Properties (see Section 6.2) are of the Enumeration
type, and use the Preference Enumeration, which takes one of five type, and use the Preference Enumeration, which takes one of five
possible values (Prohibit, Avoid, Ignore, Prefer, or Require) possible values (Prohibit, Avoid, Ignore, Prefer, or Require)
denoting the level of preference for a given property during protocol denoting the level of preference for a given property during protocol
selection. selection.
5. Scope of the Interface Definition 5. Scope of the API Definition
This document defines a language- and platform-independent interface This document defines a language- and platform-independent API of a
to a Transport Services system. Given the wide variety of languages Transport Services system. Given the wide variety of languages and
and language conventions used to write applications that use the language conventions used to write applications that use the
transport layer to connect to other applications over the Internet, transport layer to connect to other applications over the Internet,
this independence makes this interface necessarily abstract. this independence makes this API necessarily abstract.
There is no interoperability benefit in tightly defining how the There is no interoperability benefit in tightly defining how the API
interface is presented to application programmers across diverse is presented to application programmers across diverse platforms.
platforms. However, maintaining the "shape" of the abstract However, maintaining the "shape" of the abstract API across different
interface across different platforms reduces the effort for platforms reduces the effort for programmers who learn to use the
programmers who learn the transport services interface to then apply Transport Services API to then apply their knowledge to another
their knowledge to another platform. platform.
We therefore make the following recommendations: We therefore make the following recommendations:
* Actions, Events, and Errors in implementations of this interface * Actions, Events, and Errors in implementations of the Transport
SHOULD use the names given for them in the document, subject to Services API SHOULD use the names given for them in the document,
capitalization, punctuation, and other typographic conventions in subject to capitalization, punctuation, and other typographic
the language of the implementation, unless the implementation conventions in the language of the implementation, unless the
itself uses different names for substantially equivalent objects implementation itself uses different names for substantially
for networking by convention. equivalent objects for networking by convention.
* Implementations of this interface SHOULD implement each Selection * Transport Services systems SHOULD implement each Selection
Property, Connection Property, and Message Context Property Property, Connection Property, and Message Context Property
specified in this document. Each interface SHOULD be implemented specified in this document. The Transport Services API SHOULD be
even when in a specific implementation/platform it will always implemented even when in a specific implementation/platform it
result in no operation, e.g. there is no action when the API will always result in no operation, e.g. there is no action when
specifies a Property that is not available in a transport protocol the API specifies a Property that is not available in a transport
implemented on a specific platform. For example, if TCP is the protocol implemented on a specific platform. For example, if TCP
only underlying transport protocol, the Message Property is the only underlying transport protocol, the Message Property
"msgOrdered" can be implemented (trivially, as a no-op) as msgOrdered can be implemented (trivially, as a no-op) as disabling
disabling the requirement for ordering will not have any effect on the requirement for ordering will not have any effect on delivery
delivery order for Connections over TCP. Similarly, the "msg- order for Connections over TCP. Similarly, the msg-lifetime
lifetime" Message Property can be implemented but ignored, as the Message Property can be implemented but ignored, as the
description of this Property states that "it is not guaranteed description of this Property states that "it is not guaranteed
that a Message will not be sent when its Lifetime has expired". that a Message will not be sent when its Lifetime has expired".
* Implementations may use other representations for Transport * Implementations may use other representations for Transport
Property Names, e.g., by providing constants, but should provide a Property Names, e.g., by providing constants, but should provide a
straight-forward mapping between their representation and the straight-forward mapping between their representation and the
property names specified here. property names specified here.
6. Pre-Establishment Phase 6. Pre-Establishment Phase
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If more than one Local Endpoint is specified on a Preconnection, then If more than one Local Endpoint is specified on a Preconnection, then
all the Local Endpoints on the Preconnection MUST represent the same all the Local Endpoints on the Preconnection MUST represent the same
host. For example, they might correspond to different interfaces on host. For example, they might correspond to different interfaces on
a multi-homed host, of they might correspond to local interfaces and a multi-homed host, of they might correspond to local interfaces and
a STUN server that can be resolved to a server reflexive address for a STUN server that can be resolved to a server reflexive address for
a Preconnection used to make a peer-to-peer Rendezvous(). a Preconnection used to make a peer-to-peer Rendezvous().
If more than one Remote Endpoint is specified on the Preconnection, If more than one Remote Endpoint is specified on the Preconnection,
then all the Remote Endpoints on the Preconnection SHOULD represent then all the Remote Endpoints on the Preconnection SHOULD represent
the same host. For example, the Remote Endpoints might represent the same service. For example, the Remote Endpoints might represent
various network interfaces of a host, or a server reflexive address various network interfaces of a host, or a server reflexive address
that can be used to reach a host, or a set of hosts that provide that can be used to reach a host, or a set of hosts that provide
equivalent local balanced service. equivalent local balanced service.
In most cases, it is expected that a single Remote Endpoint will be In most cases, it is expected that a single Remote Endpoint will be
specified by name, and a later call to Initiate() on the specified by name, and a later call to Initiate() on the
Preconnection (see Section 7.1) will internally resolve that name to Preconnection (see Section 7.1) will internally resolve that name to
a list of concrete endpoints. Specifying multiple Remote Endpoints a list of concrete endpoints. Specifying multiple Remote Endpoints
on a Preconnection allows applications to override this for more on a Preconnection allows applications to override this for more
detailed control. detailed control.
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identifiers are set. For example, an Endpoint that only specifies a identifiers are set. For example, an Endpoint that only specifies a
hostname may in fact end up corresponding to several different IP hostname may in fact end up corresponding to several different IP
addresses on different hosts. addresses on different hosts.
An Endpoint Object can be configured with the following identifiers: An Endpoint Object can be configured with the following identifiers:
* Hostname (string): * Hostname (string):
RemoteSpecifier.WithHostname("example.com") RemoteSpecifier.WithHostname("example.com")
* Port (a 16-bit integer) or a Service (string) that maps to a port: * Port (a 16-bit integer):
RemoteSpecifier.WithPort(443) RemoteSpecifier.WithPort(443)
* Service (an identifier that maps to a port; either a the name of a
well-known service, or a DNS SRV service name to be resolved):
RemoteSpecifier.WithService("https") RemoteSpecifier.WithService("https")
* IP address (IPv4 or IPv6 address): * IP address (IPv4 or IPv6 address):
RemoteSpecifier.WithIPv4Address(192.0.2.21) RemoteSpecifier.WithIPv4Address(192.0.2.21)
RemoteSpecifier.WithIPv6Address(2001:db8:4920:e29d:a420:7461:7073:0a) RemoteSpecifier.WithIPv6Address(2001:db8:4920:e29d:a420:7461:7073:0a)
* Interface name (string): * Interface name (string), e.g., to qualify link-local or multicast
addresses (see Section 6.1.2 for details):
LocalSpecifier.WithInterface("en0") LocalSpecifier.WithInterface("en0")
Note that an IPv6 address specified with a scope (e.g.
2001:db8:4920:e29d:a420:7461:7073:0a%en0) is equivalent to
WithIPv6Address with an unscoped address and WithInterface together.
An Endpoint cannot have multiple identifiers of a same type set. An Endpoint cannot have multiple identifiers of a same type set.
That is, an endpoint cannot have two IP addresses specified. Two That is, an endpoint cannot have two IP addresses specified. Two
separate IP addresses are represented as two Endpoint Objects. If a separate IP addresses are represented as two Endpoint Objects. If a
Preconnection specifies a Remote Endpoint with a specific IP address Preconnection specifies a Remote Endpoint with a specific IP address
set, it will only establish Connections to that IP address. If, on set, it will only establish Connections to that IP address. If, on
the other hand, the Remote Endpoint specifies a hostname but no the other hand, the Remote Endpoint specifies a hostname but no
addresses, the Connection can perform name resolution and attempt addresses, the Connection can perform name resolution and attempt
using any address derived from the original hostname of the Remote using any address derived from the original hostname of the Remote
Endpoint. Endpoint. Note that multiple Remote Endpoints can be added to a
Preconnection, as discussed in Section 7.5.
The Transport Services API resolves names internally, when the The Transport Services system resolves names internally, when the
Initiate(), Listen(), or Rendezvous() method is called to establish a Initiate(), Listen(), or Rendezvous() method is called to establish a
Connection. Privacy considerations for the timing of this resolution Connection. Privacy considerations for the timing of this resolution
are given in Section 13. are given in Section 13.
The Resolve() action on a Preconnection can be used by the The Resolve() action on a Preconnection can be used by the
application to force early binding when required, for example with application to force early binding when required, for example with
some Network Address Translator (NAT) traversal protocols (see some Network Address Translator (NAT) traversal protocols (see
Section 7.3). Section 7.3).
6.1.1. Using Multicast Endpoints 6.1.1. Using Multicast Endpoints
Specifying a multicast group address on a Local Endpoint will Specifying a multicast group address on a Local Endpoint will
indicate to the transport system that the resulting connection will indicate to the Transport Services system that the resulting
be used to receive multicast messages. The Remote Endpoint can be connection will be used to receive multicast messages. The Remote
used to filter incoming multicast from specific senders. Such a Endpoint can be used to filter incoming multicast from specific
Preconnection will only support calling Listen(), not Initiate(). senders. Such a Preconnection will only support calling Listen(),
The accepted Connections are receive-only. not Initiate(). Calling Listen() will cause the Transport Services
system to register for receiving multicast, such as issuing an IGMP
join [RFC3376] or using MLD for IPV6 [RFC4604]. Any Connections that
are accepted from this Listener are receive-only.
Similarly, specifying a multicast group address on the Remote Similarly, specifying a multicast group address on the Remote
Endpoint will indicate that the resulting connection will be used to Endpoint will indicate that the resulting connection will be used to
send multicast messages. send multicast messages, and that the Preconnection will support
Initiate() but not Listen(). Any Connections created this way are
send-only.
6.1.2. Endpoint Aliases A Rendezvous() call on Preconnections containing group addresses
results in an EstablishmentError as described in Section 7.3.
See Section 6.1.5 for more examples.
6.1.2. Constraining Interfaces for Endpoints
Note that this API has multiple ways to constrain and prioritize
endpoint candidates based on the network interface:
* Specifying an interface on a RemoteEndpoint qualifies the scope of
the remote endpoint, e.g., for link-local addresses.
* Specifying an interface on a LocalEndpoint explicitly binds all
candidates derived from this endpoint to use the specified
interface.
* Specifying an interface using the interface Selection Property
(Section 6.2.11) or indirectly via the pvd Selection Property
(Section 6.2.12) influences the selection among the available
candidates.
While specifying an interface on an endpoint restricts the candidates
available for connection establishment in the Pre-Establishment
Phase, the Selection Properties prioritize and constrain the
connection establishment.
6.1.3. Endpoint Aliases
An Endpoint can have an alternative definition when using different An Endpoint can have an alternative definition when using different
protocols. For example, a server that supports both TLS/TCP and QUIC protocols. For example, a server that supports both TLS/TCP and QUIC
may be accessible on two different port numbers depending on which may be accessible on two different port numbers depending on which
protocol is used. protocol is used.
To support this, Endpoint Objects can specify "aliases". An Endpoint To support this, Endpoint Objects can specify "aliases". An Endpoint
can have multiple aliases set. can have multiple aliases set.
RemoteSpecifier.AddAlias(AlternateRemoteSpecifier) RemoteSpecifier.AddAlias(AlternateRemoteSpecifier)
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RemoteSpecifier.WithHostname("example.com") RemoteSpecifier.WithHostname("example.com")
RemoteSpecifier.WithPort(443) RemoteSpecifier.WithPort(443)
QUICRemoteSpecifier := NewRemoteEndpoint() QUICRemoteSpecifier := NewRemoteEndpoint()
QUICRemoteSpecifier.WithHostname("example.com") QUICRemoteSpecifier.WithHostname("example.com")
QUICRemoteSpecifier.WithPort(8443) QUICRemoteSpecifier.WithPort(8443)
QUICRemoteSpecifier.WithProtocol(QUIC) QUICRemoteSpecifier.WithProtocol(QUIC)
RemoteSpecifier.AddAlias(QUICRemoteSpecifier) RemoteSpecifier.AddAlias(QUICRemoteSpecifier)
6.1.3. Endpoint Examples 6.1.4. Endpoint Examples
The following examples of Endpoints show common usage patterns. The following examples of Endpoints show common usage patterns.
Specify a Remote Endpoint using a hostname and service name: Specify a Remote Endpoint using a hostname and service name:
RemoteSpecifier := NewRemoteEndpoint() RemoteSpecifier := NewRemoteEndpoint()
RemoteSpecifier.WithHostname("example.com") RemoteSpecifier.WithHostname("example.com")
RemoteSpecifier.WithService("https") RemoteSpecifier.WithService("https")
Specify a Remote Endpoint using an IPv6 address and remote port: Specify a Remote Endpoint using an IPv6 address and remote port:
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RemoteSpecifier.WithPort(443) RemoteSpecifier.WithPort(443)
Specify a Local Endpoint using a local interface name and local port: Specify a Local Endpoint using a local interface name and local port:
LocalSpecifier := NewLocalEndpoint() LocalSpecifier := NewLocalEndpoint()
LocalSpecifier.WithInterface("en0") LocalSpecifier.WithInterface("en0")
LocalSpecifier.WithPort(443) LocalSpecifier.WithPort(443)
As an alternative to specifying an interface name for the Local As an alternative to specifying an interface name for the Local
Endpoint, an application can express more fine-grained preferences Endpoint, an application can express more fine-grained preferences
using the "Interface Instance or Type" Selection Property, see using the Interface Instance or Type Selection Property, see
Section 6.2.11. However, if the application specifies Selection Section 6.2.11. However, if the application specifies Selection
Properties that are inconsistent with the Local Endpoint, this will Properties that are inconsistent with the Local Endpoint, this will
result in an Error once the application attempts to open a result in an Error once the application attempts to open a
Connection. Connection.
Specify a Local Endpoint using a STUN server: Specify a Local Endpoint using a STUN server:
LocalSpecifier := NewLocalEndpoint() LocalSpecifier := NewLocalEndpoint()
LocalSpecifier.WithStunServer(address, port, credentials) LocalSpecifier.WithStunServer(address, port, credentials)
6.1.5. Multicast Examples
Specify a Local Endpoint using an Any-Source Multicast group to join Specify a Local Endpoint using an Any-Source Multicast group to join
on a named local interface: on a named local interface:
LocalSpecifier := NewLocalEndpoint() LocalSpecifier := NewLocalEndpoint()
LocalSpecifier.WithIPv4Address(233.252.0.0) LocalSpecifier.WithIPv4Address(233.252.0.0)
LocalSpecifier.WithInterface("en0") LocalSpecifier.WithInterface("en0")
Source-Specific Multicast requires setting both a Local and Remote Source-Specific Multicast requires setting both a Local and Remote
Endpoint: Endpoint:
LocalSpecifier := NewLocalEndpoint() LocalSpecifier := NewLocalEndpoint()
LocalSpecifier.WithIPv4Address(232.1.1.1) LocalSpecifier.WithIPv4Address(232.1.1.1)
LocalSpecifier.WithInterface("en0") LocalSpecifier.WithInterface("en0")
RemoteSpecifier := NewRemoteEndpoint() RemoteSpecifier := NewRemoteEndpoint()
RemoteSpecifier.WithIPv4Address(192.0.2.22) RemoteSpecifier.WithIPv4Address(192.0.2.22)
One common pattern for multicast is to both send and receive
multicast. For such cases, an application can set up both a Listener
and a Connection. The Listener is only used to accept Connections
that receive inbound multicast. The initiated Connection is only
used to send multicast.
// Prepare multicast Listener
LocalMulticastSpecifier := NewLocalEndpoint()
LocalMulticastSpecifier.WithIPv4Address(233.252.0.0)
LocalMulticastSpecifier.WithPort(5353)
LocalMulticastSpecifier.WithInterface("en0")
TransportProperties := NewTransportProperties()
TransportProperties.Require(preserve-msg-boundaries)
// Reliable Data Transfer and Preserve Order are Required by default
// Specifying a Remote Endpoint is optional when using Listen()
Preconnection := NewPreconnection(LocalMulticastSpecifier,
TransportProperties,
SecurityParameters)
MulticastListener := Preconnection.Listen()
// Handle inbound messages sent to the multicast group
MulticastListener -> ConnectionReceived<MulticastReceiverConnection>
MulticastReceiverConnection.Receive()
MulticastReceiverConnection -> Received<messageDataRequest, messageContext>
// Prepare Connection to send multicast
LocalSpecifier := NewLocalEndpoint()
LocalSpecifier.WithPort(5353)
LocalSpecifier.WithInterface("en0")
RemoteMulticastSpecifier := NewRemoteEndpoint()
RemoteMulticastSpecifier.WithIPv4Address(233.252.0.0)
RemoteMulticastSpecifier.WithPort(5353)
RemoteMulticastSpecifier.WithInterface("en0")
Preconnection2 := NewPreconnection(LocalSpecifier,
RemoteMulticastSpecifier,
TransportProperties,
SecurityParameters)
// Send outbound messages to the multicast group
MulticastSenderConnection := Preconnection.Initiate()
MulticastSenderConnection.Send(messageData)
6.2. Specifying Transport Properties 6.2. Specifying Transport Properties
A Preconnection Object holds properties reflecting the application's A Preconnection Object holds properties reflecting the application's
requirements and preferences for the transport. These include requirements and preferences for the transport. These include
Selection Properties for selecting protocol stacks and paths, as well Selection Properties for selecting protocol stacks and paths, as well
as Connection Properties for configuration of the detailed operation as Connection Properties and Message Properties for configuration of
of the selected Protocol Stacks. the detailed operation of the selected Protocol Stacks on a per-
Connection and Message level.
The protocol(s) and path(s) selected as candidates during The protocol(s) and path(s) selected as candidates during
establishment are determined and configured using these properties. establishment are determined and configured using these properties.
Since there could be paths over which some transport protocols are Since there could be paths over which some transport protocols are
unable to operate, or remote endpoints that support only specific unable to operate, or remote endpoints that support only specific
network addresses or transports, transport protocol selection is network addresses or transports, transport protocol selection is
necessarily tied to path selection. This may involve choosing necessarily tied to path selection. This may involve choosing
between multiple local interfaces that are connected to different between multiple local interfaces that are connected to different
access networks. access networks.
When additional information (such as Provisioning Domain (PvD) When additional information (such as Provisioning Domain (PvD)
information Path information can include network segment PMTU, set of information [RFC7556]) is available about the networks over which an
supported DSCPs, expected usage, cost, etc. The usage of this endpoint can operate, this can inform the selection between alternate
information by the Transport Services System is generally independent network paths.
of the specific mechanism/protocol used to receive the information Path information can include network segment PMTU, set of supported
(e.g. zero-conf, DHCP, or IPv6 RA).[RFC7556]) is available about the DSCPs, expected usage, cost, etc. The usage of this information by
networks over which an endpoint can operate, this can inform the the Transport Services System is generally independent of the
selection between alternate network paths. specific mechanism/protocol used to receive the information (e.g.
zero-conf, DHCP, or IPv6 RA).
Most Selection Properties are represented as Preferences, which can Most Selection Properties are represented as Preferences, which can
take one of five values: take one of five values:
+============+========================================+ +============+========================================+
| Preference | Effect | | Preference | Effect |
+============+========================================+ +============+========================================+
| Require | Select only protocols/paths providing | | Require | Select only protocols/paths providing |
| | the property, fail otherwise | | | the property, fail otherwise |
+------------+----------------------------------------+ +------------+----------------------------------------+
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A Connection gets its Transport Properties either by being explicitly A Connection gets its Transport Properties either by being explicitly
configured via a Preconnection, by configuration after establishment, configured via a Preconnection, by configuration after establishment,
or by inheriting them from an antecedent via cloning; see Section 7.4 or by inheriting them from an antecedent via cloning; see Section 7.4
for more. for more.
Section 8.1 provides a list of Connection Properties, while Selection Section 8.1 provides a list of Connection Properties, while Selection
Properties are listed in the subsections below. Many properties are Properties are listed in the subsections below. Many properties are
only considered during establishment, and can not be changed after a only considered during establishment, and can not be changed after a
Connection is established; however, they can still be queried. The Connection is established; however, they can still be queried. The
return type of a queried Selection Property is Boolean, where "true" return type of a queried Selection Property is Boolean, where true
means that the Selection Property has been applied and "false" means means that the Selection Property has been applied and false means
that the Selection Property has not been applied. Note that "true" that the Selection Property has not been applied. Note that true
does not mean that a request has been honored. For example, if does not mean that a request has been honored. For example, if
"Congestion control" was requested with preference level "Prefer", Congestion control was requested with preference level Prefer, but
but congestion control could not be supported, querying the congestion control could not be supported, querying the
"congestionControl" property yields the value "false". If the congestionControl property yields the value false. If the preference
preference level "Avoid" was used for "Congestion control", and, as level Avoid was used for Congestion control, and, as requested, the
requested, the Connection is not congestion controlled, querying the Connection is not congestion controlled, querying the
"congestionControl" property also yields the value "false". congestionControl property also yields the value false.
An implementation of this interface must provide sensible defaults An implementation of the Transport Services API must provide sensible
for Selection Properties. The default values for each property below defaults for Selection Properties. The default values for each
represent a configuration that can be implemented over TCP. If these property below represent a configuration that can be implemented over
default values are used and TCP is not supported by a Transport TCP. If these default values are used and TCP is not supported by a
Services implementation, then an application using the default set of Transport Services system, then an application using the default set
Properties might not succeed in establishing a connection. Using the of Properties might not succeed in establishing a connection. Using
same default values for independent Transport Services the same default values for independent Transport Services
implementations can be beneficial when applications are ported implementations can be beneficial when applications are ported
between different implementations/platforms, even if this default between different implementations/platforms, even if this default
could lead to a connection failure when TCP is not available. If could lead to a connection failure when TCP is not available. If
default values other than those suggested below are used, it is default values other than those suggested below are used, it is
RECOMMENDED to clearly document any differences. RECOMMENDED to clearly document any differences.
6.2.1. Reliable Data Transfer (Connection) 6.2.1. Reliable Data Transfer (Connection)
Name: reliability Name: reliability
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received multiple times (i.e., multiple copies of the message data received multiple times (i.e., multiple copies of the message data
may be passed to the Remote Endpoint). See also Section 9.1.3.4. may be passed to the Remote Endpoint). See also Section 9.1.3.4.
6.2.6. Multistream Connections in Group 6.2.6. Multistream Connections in Group
Name: multistreaming Name: multistreaming
Type: Preference Type: Preference
Default: Prefer Default: Prefer
This property specifies that the application would prefer multiple This property specifies that the application would prefer multiple
Connections within a Connection Group to be provided by streams of a Connections within a Connection Group to be provided by streams of a
single underlying transport connection where possible. single underlying transport connection where possible.
6.2.7. Full Checksum Coverage on Sending 6.2.7. Full Checksum Coverage on Sending
Name: FullChecksumSend Name: fullChecksumSend
Type: Preference Type: Preference
Default: Require Default: Require
This property specifies the application's need for protection against This property specifies the application's need for protection against
corruption for all data transmitted on this Connection. Disabling corruption for all data transmitted on this Connection. Disabling
this property could enable later control of the sender checksum this property could enable later control of the sender checksum
coverage (see Section 9.1.3.6). coverage (see Section 9.1.3.6).
6.2.8. Full Checksum Coverage on Receiving 6.2.8. Full Checksum Coverage on Receiving
Name: FullChecksumRecv Name: fullChecksumRecv
Type: Preference Type: Preference
Default: Require Default: Require
This property specifies the application's need for protection against This property specifies the application's need for protection against
corruption for all data received on this Connection. Disabling this corruption for all data received on this Connection. Disabling this
property could enable later control of the required minimum receiver property could enable later control of the required minimum receiver
checksum coverage (see Section 8.1.1). checksum coverage (see Section 8.1.1).
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period for generation of the keep alive-packets. (See also period for generation of the keep alive-packets. (See also
Section 8.1.4). Section 8.1.4).
6.2.11. Interface Instance or Type 6.2.11. Interface Instance or Type
Name: interface Name: interface
Type: Collection of (Preference, Enumeration) Type: Collection of (Preference, Enumeration)
Default: Empty (not setting a preference for any interface) Default: Empty (not setting a preference for any interface)
This property allows the application to select any specific network This property allows the application to select any specific network
interfaces or categories of interfaces it wants to "Require", interfaces or categories of interfaces it wants to Require, Prohibit,
"Prohibit", "Prefer", or "Avoid". Note that marking a specific Prefer, or Avoid. Note that marking a specific interface as Require
interface as "Require" strictly limits path selection to that single strictly limits path selection to that single interface, and often
interface, and often leads to less flexible and resilient connection leads to less flexible and resilient connection establishment.
establishment.
In contrast to other Selection Properties, this property is a tuple In contrast to other Selection Properties, this property is a tuple
of an (Enumerated) interface identifier and a preference, and can of an (Enumerated) interface identifier and a preference, and can
either be implemented directly as such, or for making one preference either be implemented directly as such, or for making one preference
available for each interface and interface type available on the available for each interface and interface type available on the
system. system.
The set of valid interface types is implementation- and system- The set of valid interface types is implementation- and system-
specific. For example, on a mobile device, there may be "Wi-Fi" and specific. For example, on a mobile device, there may be Wi-Fi and
"Cellular" interface types available; whereas on a desktop computer, Cellular interface types available; whereas on a desktop computer,
"Wi-Fi" and "Wired Ethernet" interface types might be available. An Wi-Fi and Wired Ethernet interface types might be available. An
implementation should provide all types that are supported on the implementation should provide all types that are supported on the
local system, to allow applications to be written generically. For local system, to allow applications to be written generically. For
example, if a single implementation is used on both mobile devices example, if a single implementation is used on both mobile devices
and desktop devices, it should define the "Cellular" interface type and desktop devices, it should define the Cellular interface type for
for both systems, since an application might wish to always prohibit both systems, since an application might wish to always prohibit
cellular. cellular.
The set of interface types is expected to change over time as new The set of interface types is expected to change over time as new
access technologies become available. The taxonomy of interface access technologies become available. The taxonomy of interface
types on a given Transport Services system is implementation- types on a given Transport Services system is implementation-
specific. specific.
Interface types should not be treated as a proxy for properties of Interface types should not be treated as a proxy for properties of
interfaces such as metered or unmetered network access. If an interfaces such as metered or unmetered network access. If an
application needs to prohibit metered interfaces, this should be application needs to prohibit metered interfaces, this should be
specified via Provisioning Domain attributes (see Section 6.2.12) or specified via Provisioning Domain attributes (see Section 6.2.12) or
another specific property. another specific property.
Note that this property is not used to specify an interface scope for
a particular endpoint. Section 6.1.2 provides details about how to
qualify endpoint candidates on a per-interface basis.
6.2.12. Provisioning Domain Instance or Type 6.2.12. Provisioning Domain Instance or Type
Name: pvd Name: pvd
Type: Collection of (Preference, Enumeration) Type: Collection of (Preference, Enumeration)
Default: Empty (not setting a preference for any PvD) Default: Empty (not setting a preference for any PvD)
Similar to interface instances and types (see Section 6.2.11), this Similar to interface instances and types (see Section 6.2.11), this
property allows the application to control path selection by property allows the application to control path selection by
selecting which specific Provisioning Domain (PvD) or categories of selecting which specific Provisioning Domain (PvD) or categories of
PVDs it wants to "Require", "Prohibit", "Prefer", or "Avoid". PVDs it wants to Require, Prohibit, Prefer, or Avoid. Provisioning
Provisioning Domains define consistent sets of network properties Domains define consistent sets of network properties that may be more
that may be more specific than network interfaces [RFC7556]. specific than network interfaces [RFC7556].
As with interface instances and types, this property is a tuple of an As with interface instances and types, this property is a tuple of an
(Enumerated) PvD identifier and a preference, and can either be (Enumerated) PvD identifier and a preference, and can either be
implemented directly as such, or for making one preference available implemented directly as such, or for making one preference available
for each interface and interface type available on the system. for each interface and interface type available on the system.
The identification of a specific PvD is implementation- and system- The identification of a specific PvD is implementation- and system-
specific, because there is currently no portable standard format for specific, because there is currently no portable standard format for
a PvD identifier. For example, this identifier might be a string a PvD identifier. For example, this identifier might be a string
name or an integer. As with requiring specific interfaces, requiring name or an integer. As with requiring specific interfaces, requiring
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established, even if the chosen transport supports using multiple established, even if the chosen transport supports using multiple
paths. paths.
Active: The connection will negotiate the use of multiple paths if Active: The connection will negotiate the use of multiple paths if
the chosen transport supports this. the chosen transport supports this.
Passive: The connection will support the use of multiple paths if Passive: The connection will support the use of multiple paths if
the Remote Endpoint requests it. the Remote Endpoint requests it.
The policy for using multiple paths is specified using the separate The policy for using multiple paths is specified using the separate
"multipath-policy" property, see Section 8.1.7 below. To enable the multipath-policy property, see Section 8.1.7 below. To enable the
peer endpoint to initiate additional paths towards a local address peer endpoint to initiate additional paths towards a local address
other than the one initially used, it is necessary to set the other than the one initially used, it is necessary to set the
Alternative Addresses property (see Section 6.2.15 below). Alternative Addresses property (see Section 6.2.15 below).
Setting this property to "Active", can have privacy implications: It Setting this property to "Active", can have privacy implications: It
enables the transport to establish connectivity using alternate paths enables the transport to establish connectivity using alternate paths
that might result in users being linkable across the multiple paths, that might result in users being linkable across the multiple paths,
even if the Advertisement of Alternative Addresses property (see even if the Advertisement of Alternative Addresses property (see
Section 6.2.15 below) is set to false. Section 6.2.15 below) is set to false.
Note that Multipath Transport has no corresponding Selection Property Note that Multipath Transport has no corresponding Selection Property
of type Preference. Enumeration values other than "Disabled" are of type Preference. Enumeration values other than "Disabled" are
interpreted as a preference for choosing protocols that can make use interpreted as a preference for choosing protocols that can make use
of multiple paths. The "Disabled" value implies a requirement not to of multiple paths. The "Disabled" value implies a requirement not to
use multiple paths in parallel but does not prevent choosing a use multiple paths in parallel but does not prevent choosing a
protocol that is capable of using multiple paths, e.g., it does not protocol that is capable of using multiple paths, e.g., it does not
prevent choosing TCP, but prevents sending the "MP_CAPABLE" option in prevent choosing TCP, but prevents sending the MP_CAPABLE option in
the TCP handshake. the TCP handshake.
6.2.15. Advertisement of Alternative Addresses 6.2.15. Advertisement of Alternative Addresses
Name: advertises-altaddr Name: advertises-altaddr
Type: Boolean Type: Boolean
Default: False Default: False
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will necessarily be delivered, so applications cannot rely upon will necessarily be delivered, so applications cannot rely upon
receiving them [RFC8085]. receiving them [RFC8085].
6.2.18. Initiating side is not the first to write 6.2.18. Initiating side is not the first to write
Name: activeReadBeforeSend Name: activeReadBeforeSend
Type: Preference Type: Preference
Default: Ignore Default: Ignore
The most common client-server communication pattern involves the The most common client-server communication pattern involves the
client actively opening a connection, then sending data to the client actively opening a connection, then sending data to the
server. The server listens (passive open), reads, and then answers. server. The server listens (passive open), reads, and then answers.
This property specifies whether an application wants to diverge from This property specifies whether an application wants to diverge from
this pattern - either by actively opening with Initiate(), this pattern -- either by actively opening with Initiate(),
immediately followed by reading, or passively opening with Listen(), immediately followed by reading, or passively opening with Listen(),
immediately followed by writing. This property is ignored when immediately followed by writing. This property is ignored when
establishing connections using Rendezvous(). Requiring this property establishing connections using Rendezvous(). Requiring this property
limits the choice of mappings to underlying protocols, which can limits the choice of mappings to underlying protocols, which can
reduce efficiency. For example, it prevents the Transport Services reduce efficiency. For example, it prevents the Transport Services
system from mapping Connections to SCTP streams, where the first system from mapping Connections to SCTP streams, where the first
transmitted data takes the role of an active open signal transmitted data takes the role of an active open signal
[I-D.ietf-taps-impl]. [I-D.ietf-taps-impl].
6.3. Specifying Security Parameters and Callbacks 6.3. Specifying Security Parameters and Callbacks
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Security configuration parameters and sample usage follow: Security configuration parameters and sample usage follow:
* Local identity and private keys: Used to perform private key * 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 hardware security modules (HSMs), handshake callbacks stored in hardware security modules (HSMs), handshake callbacks
must be used. See below for details.) must be used. See below for details.)
SecurityParameters.Set(identity, myIdentity) SecurityParameters.Set(identity, myIdentity)
SecurityParameters.Set(key-pair, myPrivateKey, myPublicKey) SecurityParameters.Set(key-pair, myPrivateKey, myPublicKey)
* Supported algorithms: Used to restrict what parameters are used by * 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 use known and safe defaults for the these algorithms should use known and safe defaults for the
system. Parameters include: ciphersuites, supported groups, and system. Parameters include: ciphersuites, supported groups, and
signature algorithms. These parameters take a collection of signature algorithms. These parameters take a collection of
supported algorithms as parameter. supported algorithms as parameter.
SecurityParameters.Set(supported-group, "secp256k1") SecurityParameters.Set(supported-group, "secp256r1")
SecurityParameters.Set(ciphersuite, "TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305_SHA256") SecurityParameters.Set(ciphersuite, "TLS_AES_128_GCM_SHA256")
SecurityParameters.Set(signature-algorithm, "ed25519") SecurityParameters.Set(signature-algorithm, "ecdsa_secp256r1_sha256")
* Pre-Shared Key import: Used to install pre-shared keying material * Pre-Shared Key import: Used to install pre-shared keying material
established out-of-band. Each pre-shared keying material is established out-of-band. Each pre-shared keying material is
associated with some identity that typically identifies its use or associated with some identity that typically identifies its use or
has some protocol-specific meaning to the Remote Endpoint. has some protocol-specific meaning to the Remote Endpoint.
SecurityParameters.Set(pre-shared-key, key, identity) SecurityParameters.Set(pre-shared-key, key, identity)
* Session cache management: Used to tune session cache capacity, * Session cache management: Used to tune session cache capacity,
lifetime, and other policies. lifetime, and other policies.
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Establishment may be active, using the Initiate() Action; passive, Establishment may be active, using the Initiate() Action; passive,
using the Listen() Action; or simultaneous for peer-to-peer, using using the Listen() Action; or simultaneous for peer-to-peer, using
the Rendezvous() Action. These Actions are described in the the Rendezvous() Action. These Actions are described in the
subsections below. subsections below.
7.1. Active Open: Initiate 7.1. Active Open: Initiate
Active open is the Action of establishing a Connection to a Remote Active open is the Action of establishing a Connection to a Remote
Endpoint presumed to be listening for incoming Connection requests. Endpoint presumed to be listening for incoming Connection requests.
Active open is used by clients in client-server interactions. Active Active open is used by clients in client-server interactions. Active
open is supported by this interface through the Initiate Action: open is supported by the Transport Services API through the Initiate
Action:
Connection := Preconnection.Initiate(timeout?) Connection := Preconnection.Initiate(timeout?)
The timeout parameter specifies how long to wait before aborting The timeout parameter specifies how long to wait before aborting
Active open. Before calling Initiate, the caller must have populated Active open. Before calling Initiate, the caller must have populated
a Preconnection Object with a Remote Endpoint specifier, optionally a 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. necessary for candidate selection.
The Initiate() Action returns a Connection object. Once Initiate() The Initiate() Action returns a Connection object. Once Initiate()
has been called, any changes to the Preconnection MUST NOT have any has been called, any changes to the Preconnection MUST NOT have any
effect on the Connection. However, the Preconnection can be reused, effect on the Connection. However, the Preconnection can be reused,
e.g., to Initiate another Connection. e.g., to Initiate another Connection.
Once Initiate is called, the candidate Protocol Stack(s) may cause Once Initiate is called, the candidate Protocol Stack(s) may cause
one or more candidate transport-layer connections to be created to one or more candidate transport-layer connections to be created to
the specified Remote Endpoint. The caller may immediately begin the specified Remote Endpoint. The caller may immediately begin
sending Messages on the Connection (see Section 9.2) after calling sending Messages on the Connection (see Section 9.2) after calling
Initiate(); note that any data marked "Safely Replayable" that is Initiate(); note that any data marked Safely Replayable that is sent
sent while the Connection is being established may be sent multiple while the Connection is being established may be sent multiple times
times or on multiple candidates. or on multiple candidates.
The following Events may be sent by the Connection after Initiate() The following Events may be sent by the Connection after Initiate()
is called: is called:
Connection -> Ready<> Connection -> Ready<>
The Ready Event occurs after Initiate has established a transport- The Ready Event occurs after Initiate has established a transport-
layer connection on at least one usable candidate Protocol Stack over layer connection on at least one usable candidate Protocol Stack over
at least one candidate Path. No Receive Events (see Section 9.3) at least one candidate Path. No Receive Events (see Section 9.3)
will occur before the Ready Event for Connections established using will occur before the Ready Event for Connections established using
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Connection by the operating system, or the establishment attempt has Connection by the operating system, or the establishment attempt has
timed out for any other reason). timed out for any other reason).
Connection establishment and transmission of the first message can be Connection establishment and transmission of the first message can be
combined in a single action Section 9.2.5. combined in a single action Section 9.2.5.
7.2. Passive Open: Listen 7.2. Passive Open: Listen
Passive open is the Action of waiting for Connections from Remote Passive open is the Action of waiting for Connections from Remote
Endpoints, commonly used by servers in client-server interactions. Endpoints, commonly used by servers in client-server interactions.
Passive open is supported by this interface through the Listen Action Passive open is supported by the Transport Services API through the
and returns a Listener object: Listen Action and returns a Listener object:
Listener := Preconnection.Listen() Listener := Preconnection.Listen()
Before calling Listen, the caller must have initialized the Before calling Listen, the caller must have initialized the
Preconnection during the pre-establishment phase with a Local Preconnection during the pre-establishment phase with a Local
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. constrain what Connections are accepted.
The Listen() Action returns a Listener object. Once Listen() has The Listen() Action returns a Listener object. Once Listen() has
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If the endpoints are suspected to be behind a NAT, Rendezvous() can If the endpoints are suspected to be behind a NAT, Rendezvous() can
be initiated using Local Endpoints that support a method of be initiated using Local Endpoints that support a method of
discovering NAT bindings such as Session Traversal Utilities for NAT discovering NAT bindings such as Session Traversal Utilities for NAT
(STUN) [RFC8489] or Traversal Using Relays around NAT (TURN) (STUN) [RFC8489] or Traversal Using Relays around NAT (TURN)
[RFC5766]. In this case, the Local Endpoint will resolve to a [RFC5766]. In this case, the Local Endpoint will resolve to a
mixture of local and server reflexive addresses. The Resolve() mixture of local and server reflexive addresses. The Resolve()
action on the Preconnection can be used to discover these bindings: action on the Preconnection can be used to discover these bindings:
[]LocalEndpoint, []RemoteEndpoint := Preconnection.Resolve() []LocalEndpoint, []RemoteEndpoint := Preconnection.Resolve()
The Resolve() call returns lists of Local Endpoints and Remote The Resolve() call returns lists of Local Endpoints and Remote
Endpoints, that represent the concrete addresses, local and server Endpoints, that represent the concrete addresses, local and server
reflexive, on which a Rendezvous() for the Preconnection will listen reflexive, on which a Rendezvous() for the Preconnection will listen
for incoming Connections, and to which it will attempt to establish for incoming Connections, and to which it will attempt to establish
connections. connections.
Note that the set of LocalEndpoints returned by Resolve() might or
might not contain information about all possible local interfaces; it
is valid only for a Rendezvous happening at the same time as the
resolution. Care should be taken in using these values in any other
context.
An application that uses Rendezvous() to establish a peer-to-peer An application that uses Rendezvous() to establish a peer-to-peer
connection in the presence of NATs will configure the Preconnection connection in the presence of NATs will configure the Preconnection
object with at least one a Local Endpoint that supports NAT binding object with at least one a Local Endpoint that supports NAT binding
discovery. It will then Resolve() the Preconnection, and pass the discovery. It will then Resolve() the Preconnection, and pass the
resulting list of Local Endpoint candidates to the peer via a resulting list of Local Endpoint candidates to the peer via a
signalling protocol, for example as part of an ICE [RFC5245] exchange signalling protocol, for example as part of an ICE [RFC5245] exchange
within SIP [RFC3261] or WebRTC [RFC7478]. The peer will then, via within SIP [RFC3261] or WebRTC [RFC7478]. The peer will then, via
the same signalling channel, return the Remote Endpoint candidates. the same signalling channel, return the Remote Endpoint candidates.
The set of Remote Endpoint candidates are then configured onto the The set of Remote Endpoint candidates are then configured onto the
Preconnection: Preconnection:
skipping to change at page 38, line 26 skipping to change at page 42, line 26
Connection Groups can be created using the Clone Action: Connection Groups can be created using the Clone Action:
Connection := Connection.Clone(framer?) Connection := Connection.Clone(framer?)
Calling Clone on a Connection yields a Connection Group containing Calling Clone on a Connection yields a Connection Group containing
two Connections: the parent Connection on which Clone was called, and two Connections: the parent Connection on which Clone was called, and
a resulting cloned Connection. The new Connection is actively a resulting cloned Connection. The new Connection is actively
openend, and it will send a Ready Event or an EstablishmentError openend, and it will send a Ready Event or an EstablishmentError
Event. Calling Clone on any of these Connections adds another Event. Calling Clone on any of these Connections adds another
Connection to the Connection Group. Connections in a Connection Connection to the Connection Group. Connections in a Connection
Group share all Connection Properties except "Connection Priority" Group share all Connection Properties except Connection Priority (see
(see Section 8.1.2), and these Connection Properties are entangled: Section 8.1.2), and these Connection Properties are entangled:
Changing one of the Connection Properties on one Connection in the Changing one of the Connection Properties on one Connection in the
Connection Group automatically changes the Connection Property for Connection Group automatically changes the Connection Property for
all others. For example, changing "Timeout for aborting Connection" all others. For example, changing Timeout for aborting Connection
(see Section 8.1.3) on one Connection in a Connection Group will (see Section 8.1.3) on one Connection in a Connection Group will
automatically make the same change to this Connection Property for automatically make the same change to this Connection Property for
all other Connections in the Connection Group. Like all other all other Connections in the Connection Group. Like all other
Properties, "Connection Priority" is copied to the new Connection Properties, Connection Priority is copied to the new Connection when
when calling Clone(), but in this case, a later change to the calling Clone(), but in this case, a later change to the Connection
"Connection Priority" on one Connection does not change it on the Priority on one Connection does not change it on the other
other Connections in the same Connection Group. Connections in the same Connection Group.
Message Properties are also not entangled. For example, changing Message Properties set on a Connection also apply only to that
"Lifetime" (see Section 9.1.3.1) of a Message will only affect a Connection.
single Message on a single Connection.
A new Connection created by Clone can have a Message Framer assigned A new Connection created by Clone can have a Message Framer assigned
via the optional "framer" parameter of the Clone Action. If this via the optional framer parameter of the Clone Action. If this
parameter is not supplied, the stack of Message Framers associated parameter is not supplied, the stack of Message Framers associated
with a Connection is copied to the cloned Connection when calling with a Connection is copied to the cloned Connection when calling
Clone. Then, a cloned Connection has the same stack of Message Clone. Then, a cloned Connection has the same stack of Message
Framers as the Connection from which they are Cloned, but these Framers as the Connection from which they are Cloned, but these
Framers may internally maintain per-Connection state. Framers may internally maintain per-Connection state.
It is also possible to check which Connections belong to the same It is also possible to check which Connections belong to the same
Connection Group. Calling GroupedConnections() on a specific Connection Group. Calling GroupedConnections() on a specific
Connection returns a set of all Connections in the same group. Connection returns a set of all Connections in the same group.
[]Connection := Connection.GroupedConnections() []Connection := Connection.GroupedConnections()
Connections will belong to the same group if the application Connections will belong to the same group if the application
previously called Clone. Passive Connections can also be added to previously called Clone. Passive Connections can also be added to
the same group - e.g., when a Listener receives a new Connection that the same group -- e.g., when a Listener receives a new Connection
is just a new stream of an already active multi-streaming protocol that is just a new stream of an already active multi-streaming
instance. protocol instance.
If the underlying protocol supports multi-streaming, it is natural to If the underlying protocol supports multi-streaming, it is natural to
use this functionality to implement Clone. In that case, Connections use this functionality to implement Clone. In that case, Connections
in a Connection Group are multiplexed together, giving them similar in a Connection Group are multiplexed together, giving them similar
treatment not only inside endpoints, but also across the end-to-end treatment not only inside endpoints, but also across the end-to-end
Internet path. Internet path.
Note that calling Clone() can result in on-the-wire signaling, e.g., Note that calling Clone() can result in on-the-wire signaling, e.g.,
to open a new transport connection, depending on the underlying to open a new transport connection, depending on the underlying
Protocol Stack. When Clone() leads to the opening of multiple such Protocol Stack. When Clone() leads to the opening of multiple such
connections, the Transport Services system will ensure consistency of connections, the Transport Services system will ensure consistency of
Connection Properties by uniformly applying them to all underlying Connection Properties by uniformly applying them to all underlying
connections in a group. Even in such a case, there are possibilities connections in a group. Even in such a case, there are possibilities
for a Transport Services system to implement prioritization within a for a Transport Services system to implement prioritization within a
Connection Group [TCP-COUPLING] [RFC8699]. Connection Group [TCP-COUPLING] [RFC8699].
Attempts to clone a Connection can result in a CloneError: Attempts to clone a Connection can result in a CloneError:
Connection -> CloneError<reason?> Connection -> CloneError<reason?>
The "Connection Priority" Connection Property operates on Connections The Connection Priority Connection Property operates on Connections
in a Connection Group using the same approach as in Section 9.1.3.2: in a Connection Group using the same approach as in Section 9.1.3.2:
when allocating available network capacity among Connections in a when allocating available network capacity among Connections in a
Connection Group, sends on Connections with lower Priority values Connection Group, sends on Connections with higher Priority values
will be prioritized over sends on Connections with higher Priority will be prioritized over sends on Connections that have lower
values. Capacity will be shared among these Connections according to Priority values. Capacity will be shared among these Connections
the Connection Group Transmission Scheduler property (Section 8.1.5). according to the Connection Group Transmission Scheduler property
See Section 9.2.6 for more. (Section 8.1.5). See Section 9.2.6 for more.
7.5. Adding and Removing Endpoints on a Connection
Transport protocols that are explicitly multipath aware are expected
to automatically manage the set of Remote Endpoints that they are
communicating with, and the paths to those endpoints. A PathChange<>
event, described in Section 8.3.2, will be generated when the path
changes.
In some cases, however, it is necessary to explicitly indicate to a
Connection that a new remote endpoint has become available for use,
or to indicate that some remote endpoint is no longer available.
This is most common in the case of peer to peer connections using
Trickle ICE [RFC8838].
The AddRemote() action can be used to add one or more new remote
endpoints to a Connection:
Connection.AddRemote([]RemoteEndpoint)
Endpoints that are already known to the Connection are ignored. A
call to AddRemote() makes the new remote endpoints available to the
connection, but whether the Connection makes use of those endpoints
will depend on the underlying transport protocol.
Similarly, the RemoveRemote() action can be used to tell a connection
to stop using one or more remote endpoints:
Connection.RemoveRemote([]RemoteEndpoint)
Removing all known remote endpoints can have the effect of aborting
the connection. The effect of removing the active remote endpoint(s)
depends on the underlying transport: multipath aware transports might
be able to switch to a new path if other reachable remote endpoints
exist, or the connection might abort.
Similarly, the AddLocal() and RemoveLocal() actions can be used to
add and remove local endpoints to/from a Connection.
8. Managing Connections 8. Managing Connections
During pre-establishment and after establishment, connections can be During pre-establishment and after establishment, connections can be
configured and queried using Connection Properties, and asynchronous configured and queried using Connection Properties, and asynchronous
information may be available about the state of the connection via information may be available about the state of the connection via
Soft Errors. Soft Errors.
Connection Properties represent the configuration and state of the Connection Properties represent the configuration and state of the
selected Protocol Stack(s) backing a Connection. These Connection selected Protocol Stack(s) backing a Connection. These Connection
Properties may be Generic, applying regardless of transport protocol, Properties may be Generic, applying regardless of transport protocol,
or Specific, applicable to a single implementation of a single or Specific, applicable to a single implementation of a single
transport protocol stack. Generic Connection Properties are defined transport protocol stack. Generic Connection Properties are defined
in Section 8.1 below. in Section 8.1 below.
Protocol Specific Properties are defined in a transport- and Protocol Specific Properties are defined in a transport- and
implementation-specific way, and MUST NOT apply across different implementation-specific way to permit more specialized protocol
protocols. Too much reliance by an application on Protocol Specific features to be used. Too much reliance by an application on Protocol
Properties can significantly reduce the flexibility of a transport Specific Properties can significantly reduce the flexibility of a
services implementation. transport services implementation to make appropriate selection and
configuration choices. Therefore, it is RECOMMENDED that Protocol
Properties are used for properties common across different protocols
and that Protocol Specific Properties are only used where specific
protocols or properties are necessary.
The application can set and query Connection Properties on a per- The application can set and query Connection Properties on a per-
Connection basis. Connection Properties that are not read-only can Connection basis. Connection Properties that are not read-only can
be set during pre-establishment (see Section 6.2), as well as on be set during pre-establishment (see Section 6.2), as well as on
connections directly using the SetProperty action: connections directly using the SetProperty action:
Connection.SetProperty(property, value) Connection.SetProperty(property, value)
Note that changing one of the Connection Properties on one Connection Note that changing one of the Connection Properties on one Connection
in a Connection Group will also change it for all other Connections in a Connection Group will also change it for all other Connections
skipping to change at page 40, line 43 skipping to change at page 45, line 35
if ConnectionProperties.Has(boolean_or_preference_property) then ... if ConnectionProperties.Has(boolean_or_preference_property) then ...
Depending on the status of the connection, the queried Connection Depending on the status of the connection, the queried Connection
Properties will include different information: Properties will include different information:
* The connection state, which can be one of the following: * The connection state, which can be one of the following:
Establishing, Established, Closing, or Closed. Establishing, Established, Closing, or Closed.
* Whether the connection can be used to send data. A connection can * Whether the connection can be used to send data. A connection can
not be used for sending if the connection was created with the not be used for sending if the connection was created with the
Selection Property "Direction of Communication" set to Selection Property Direction of Communication set to
"unidirectional receive" or if a Message marked as "Final" was unidirectional receive or if a Message marked as Final was sent
sent over this connection. See also Section 9.1.3.5. over this connection. See also Section 9.1.3.5.
* Whether the connection can be used to receive data. A connection * Whether the connection can be used to receive data. A connection
cannot be used for reading if the connection was created with the cannot be used for reading if the connection was created with the
Selection Property "Direction of Communication" set to Selection Property Direction of Communication set to
"unidirectional send" or if a Message marked as "Final" was unidirectional send or if a Message marked as Final was received.
received. See Section 9.3.3.3. The latter is only supported by See Section 9.3.3.3. The latter is only supported by certain
certain transport protocols, e.g., by TCP as half-closed transport protocols, e.g., by TCP as half-closed connection.
connection.
* For Connections that are Established, Closing, or Closed: * For Connections that are Established, Closing, or Closed:
Connection Properties (Section 8.1) of the actual protocols that Connection Properties (Section 8.1) of the actual protocols that
were selected and instantiated, and Selection Properties that the were selected and instantiated, and Selection Properties that the
application specified on the Preconnection. Selection Properties application specified on the Preconnection. Selection Properties
of type "Preference" will be exposed as boolean values indicating of type Preference will be exposed as boolean values indicating
whether or not the property applies to the selected transport. whether or not the property applies to the selected transport.
Note that the instantiated protocol stack might not match all Note that the instantiated protocol stack might not match all
Protocol Selection Properties that the application specified on Protocol Selection Properties that the application specified on
the Preconnection. the Preconnection.
* For Connections that are Established, additional properties of the * For Connections that are Established: information concerning the
path(s) in use. These properties can be derived from the local path(s) used by the Protocol Stack. This can be derived from
provisioning domain [RFC7556], measurements by the Protocol Stack, local PVD information, measurements by the Protocol Stack, or
or other sources. other sources. For example, a TAPS system that is configured to
receive and process PVD information [RFC7556] could also provide
network configuration information for the chosen path(s).
8.1. Generic Connection Properties 8.1. Generic Connection Properties
Generic Connection Properties are defined independent of the chosen Generic Connection Properties are defined independent of the chosen
protocol stack and therefore available on all Connections. protocol stack and therefore available on all Connections.
Many Connection Properties have a corresponding Selection Property Many Connection Properties have a corresponding Selection Property
that enables applications to express their preference for protocols that enables applications to express their preference for protocols
providing a supporting transport feature. providing a supporting transport feature.
8.1.1. Required Minimum Corruption Protection Coverage for Receiving 8.1.1. Required Minimum Corruption Protection Coverage for Receiving
Name: recvChecksumLen Name: recvChecksumLen
Type: Integer (non-negative with special value "Full Coverage") Type: Integer or Full Coverage
Default: Full Coverage Default: Full Coverage
This property specifies the minimum number of bytes in a received If this property is an Integer, it specifies the minimum number of
message that need to be covered by a checksum. A special value of 0 bytes in a received message that need to be covered by a checksum. A
means that a received packet does not need to have a non-zero receiving endpoint will not forward messages that have less coverage
checksum field. A receiving endpoint will not forward messages that to the application. The application is responsible for handling any
have less coverage to the application. The application is corruption within the non-protected part of the message [RFC8085]. A
responsible for handling any corruption within the non-protected part special value of 0 means that a received packet may also have a zero
of the message [RFC8085]. checksum field.
8.1.2. Connection Priority 8.1.2. Connection Priority
Name: connPrio Name: connPriority
Type: Integer Type: Integer (non-negative)
Default: 100 Default: 100
This Property is a non-negative integer representing the relative This Property is a non-negative integer representing the priority of
inverse priority (i.e., a lower value reflects a higher priority) of
this Connection relative to other Connections in the same Connection this Connection relative to other Connections in the same Connection
Group. It has no effect on Connections not part of a Connection Group. A higher value reflects a higher priority. It has no effect
Group. As noted in Section 7.4, this property is not entangled when on Connections not part of a Connection Group. As noted in
Connections are cloned, i.e., changing the Priority on one Connection Section 7.4, this property is not entangled when Connections are
in a Connection Group does not change it on the other Connections in cloned, i.e., changing the Priority on one Connection in a Connection
the same Connection Group. No guarantees of a specific behavior Group does not change it on the other Connections in the same
regarding Connection Priority are given; a Transport Services system Connection Group. No guarantees of a specific behavior regarding
may ignore this property. See Section 9.2.6 for more details. Connection Priority are given; a Transport Services system may ignore
this property. See Section 9.2.6 for more details.
8.1.3. Timeout for Aborting Connection 8.1.3. Timeout for Aborting Connection
Name: connTimeout Name: connTimeout
Type: Numeric, with special value "Disabled" Type: Numeric or Disabled
Default: Disabled Default: Disabled
This property specifies how long to wait before deciding that an If this property is Numeric, it specifies how long to wait before
active Connection has failed when trying to reliably deliver data to deciding that an active Connection has failed when trying to reliably
the Remote Endpoint. Adjusting this Property will only take effect deliver data to the Remote Endpoint. Adjusting this Property will
when the underlying stack supports reliability. The special value only take effect when the underlying stack supports reliability. If
"Disabled" means that no timeout is scheduled. this property has the enumerated value Disabled, it means that no
timeout is scheduled.
8.1.4. Timeout for keep alive packets 8.1.4. Timeout for keep alive packets
Name: keepAliveTimeout Name: keepAliveTimeout
Type: Numeric, with special value "Disabled" Type: Numeric or Disabled
Default: Implementation-defined Default: Implementation-defined
A Transport Services system can request a protocol that supports A Transport Services API can request a protocol that supports sending
sending keep alive packets Section 6.2.10. This property specifies keep alive packets Section 6.2.10. If this property is an Integer,
the maximum length of time an idle connection (one for which no it specifies the maximum length of time an idle connection (one for
transport packets have been sent) should wait before the Local which no transport packets have been sent) should wait before the
Endpoint sends a keep-alive packet to the Remote Endpoint. Adjusting Local Endpoint sends a keep-alive packet to the Remote Endpoint.
this Property will only take effect when the underlying stack Adjusting this Property will only take effect when the underlying
supports sending keep-alive packets. Guidance on setting this value stack supports sending keep-alive packets. Guidance on setting this
for datagram transports is provided in [RFC8085]. A value greater value for datagram transports is provided in [RFC8085]. A value
than the connection timeout (Section 8.1.3), or the special value greater than the connection timeout (Section 8.1.3) or the enumerated
"Disabled", will disable the sending of keep-alive packets. value Disabled will disable the sending of keep-alive packets.
8.1.5. Connection Group Transmission Scheduler 8.1.5. Connection Group Transmission Scheduler
Name: connScheduler Name: connScheduler
Type: Enumeration Type: Enumeration
Default: Weighted Fair Queueing (see Section 3.6 in [RFC8260]) Default: Weighted Fair Queueing (see Section 3.6 in [RFC8260])
This property specifies which scheduler should be used among This property specifies which scheduler should be used among
Connections within a Connection Group, see Section 7.4. The set of Connections within a Connection Group, see Section 7.4. The set of
schedulers can be taken from [RFC8260]. schedulers can be taken from [RFC8260].
8.1.6. Capacity Profile 8.1.6. Capacity Profile
Name: connCapacityProfile Name: connCapacityProfile
Type: Enumeration
Default: Default Profile (Best Effort)
This property specifies the desired network treatment for traffic This property specifies the desired network treatment for traffic
sent by the application and the tradeoffs the application is prepared sent by the application and the tradeoffs the application is prepared
to make in path and protocol selection to receive that desired to make in path and protocol selection to receive that desired
treatment. When the capacity profile is set to a value other than treatment. When the capacity profile is set to a value other than
Default, the Transport Services system SHOULD select paths and Default, z Transport Services system SHOULD select paths and
configure protocols to optimize the tradeoff between delay, delay configure protocols to optimize the tradeoff between delay, delay
variation, and efficient use of the available capacity based on the variation, and efficient use of the available capacity based on the
capacity profile specified. How this is realized is implementation- capacity profile specified. How this is realized is implementation-
specific. The Capacity Profile MAY also be used to set markings on specific. The Capacity Profile MAY also be used to set markings on
the wire for Protocol Stacks supporting this. Recommendations for the wire for Protocol Stacks supporting this. Recommendations for
use with DSCP are provided below for each profile; note that when a use with DSCP are provided below for each profile; note that when a
Connection is multiplexed, the guidelines in Section 6 of [RFC7657] Connection is multiplexed, the guidelines in Section 6 of [RFC7657]
apply. apply.
The following values are valid for the Capacity Profile: The following values are valid for the Capacity Profile:
Default: The application provides no information about its expected Default: The application provides no information about its expected
capacity profile. Transport Services system implementations that capacity profile. Transport Services implementations that map the
map the requested capacity profile onto per-connection DSCP requested capacity profile onto per-connection DSCP signaling
signaling SHOULD assign the DSCP Default Forwarding [RFC2474] Per SHOULD assign the DSCP Default Forwarding [RFC2474] Per Hop
Hop Behaviour (PHB). Behaviour (PHB).
Scavenger: The application is not interactive. It expects to send Scavenger: The application is not interactive. It expects to send
and/or receive data without any urgency. This can, for example, and/or receive data without any urgency. This can, for example,
be used to select protocol stacks with scavenger transmission be used to select protocol stacks with scavenger transmission
control and/or to assign the traffic to a lower-effort service. control and/or to assign the traffic to a lower-effort service.
Transport Services system implementations that map the requested Transport Services implementations that map the requested capacity
capacity profile onto per-connection DSCP signaling SHOULD assign profile onto per-connection DSCP signaling SHOULD assign the DSCP
the DSCP Less than Best Effort [RFC8622] PHB. Less than Best Effort [RFC8622] PHB.
Low Latency/Interactive: The application is interactive, and prefers Low Latency/Interactive: The application is interactive, and prefers
loss to latency. Response time should be optimized at the expense loss to latency. Response time should be optimized at the expense
of delay variation and efficient use of the available capacity of delay variation and efficient use of the available capacity
when sending on this connection. This can be used by the system when sending on this connection. This can be used by the system
to disable the coalescing of multiple small Messages into larger to disable the coalescing of multiple small Messages into larger
packets (Nagle's algorithm); to prefer immediate acknowledgment packets (Nagle's algorithm); to prefer immediate acknowledgment
from the peer endpoint when supported by the underlying transport; from the peer endpoint when supported by the underlying transport;
and so on. Transport Services system implementations that map the and so on. Transport Services implementations that map the
requested capacity profile onto per-connection DSCP signaling requested capacity profile onto per-connection DSCP signaling
without multiplexing SHOULD assign a DSCP Assured Forwarding without multiplexing SHOULD assign a DSCP Assured Forwarding
(AF41,AF42,AF43,AF44) [RFC2597] PHB. Inelastic traffic that is (AF41,AF42,AF43,AF44) [RFC2597] PHB. Inelastic traffic that is
expected to conform to the configured network service rate could expected to conform to the configured network service rate could
be mapped to the DSCP Expedited Forwarding [RFC3246] or [RFC5865] be mapped to the DSCP Expedited Forwarding [RFC3246] or [RFC5865]
PHBs. PHBs.
Low Latency/Non-Interactive: The application prefers loss to Low Latency/Non-Interactive: The application prefers loss to
latency, but is not interactive. Response time should be latency, but is not interactive. Response time should be
optimized at the expense of delay variation and efficient use of optimized at the expense of delay variation and efficient use of
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might fail if the Path is unable to maintain the desired rate. A might fail if the Path is unable to maintain the desired rate. A
transport can interpret this capacity profile as preferring a transport can interpret this capacity profile as preferring a
circuit breaker [RFC8084] to a rate-adaptive congestion circuit breaker [RFC8084] to a rate-adaptive congestion
controller. Transport system implementations that map the controller. Transport system implementations that map the
requested capacity profile onto per-connection DSCP signaling requested capacity profile onto per-connection DSCP signaling
without multiplexing SHOULD assign a DSCP Assured Forwarding without multiplexing SHOULD assign a DSCP Assured Forwarding
(AF31,AF32,AF33,AF34) [RFC2597] PHB. (AF31,AF32,AF33,AF34) [RFC2597] PHB.
Capacity-Seeking: The application expects to send/receive data at Capacity-Seeking: The application expects to send/receive data at
the maximum rate allowed by its congestion controller over a the maximum rate allowed by its congestion controller over a
relatively long period of time. Transport Services system relatively long period of time. Transport Services
implementations that map the requested capacity profile onto per- implementations that map the requested capacity profile onto per-
connection DSCP signaling without multiplexing SHOULD assign a connection DSCP signaling without multiplexing SHOULD assign a
DSCP Assured Forwarding (AF11,AF12,AF13,AF14) [RFC2597] PHB per DSCP Assured Forwarding (AF11,AF12,AF13,AF14) [RFC2597] PHB per
Section 4.8 of [RFC4594]. Section 4.8 of [RFC4594].
The Capacity Profile for a selected protocol stack may be modified on The Capacity Profile for a selected protocol stack may be modified on
a per-Message basis using the Transmission Profile Message Property; a per-Message basis using the Transmission Profile Message Property;
see Section 9.1.3.8. see Section 9.1.3.8.
8.1.7. Policy for using Multipath Transports 8.1.7. Policy for using Multipath Transports
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capacity limitations of the individual paths. The actual strategy capacity limitations of the individual paths. The actual strategy
is implementation specific. is implementation specific.
Note that this is a local choice - the Remote Endpoint can choose a Note that this is a local choice - the Remote Endpoint can choose a
different policy. different policy.
8.1.8. Bounds on Send or Receive Rate 8.1.8. Bounds on Send or Receive Rate
Name: minSendRate / minRecvRate / maxSendRate / maxRecvRate Name: minSendRate / minRecvRate / maxSendRate / maxRecvRate
Type: Numeric (with special value "Unlimited") / Numeric (with Type: Numeric or Unlimited / Numeric or Unlimited / Numeric or
special value "Unlimited") / Numeric (with special value Unlimited / Numeric or Unlimited
"Unlimited") / Numeric (with special value "Unlimited")
Default: Unlimited / Unlimited / Unlimited / Unlimited Default: Unlimited / Unlimited / Unlimited / Unlimited
This property specifies an upper-bound rate that a transfer is not Integer values of this property specify an upper-bound rate that a
expected to exceed (even if flow control and congestion control allow transfer is not expected to exceed (even if flow control and
higher rates), and/or a lower-bound rate below which the application congestion control allow higher rates), and/or a lower-bound rate
does not deem it will be useful. These are specified in bits per below which the application does not deem it will be useful. These
second. The special value "Unlimited" indicates that no bound is are specified in bits per second. The enumerated value Unlimited
specified. indicates that no bound is specified.
8.1.9. Group Connection Limit 8.1.9. Group Connection Limit
Name: groupConnLimit Name: groupConnLimit
Type: Numeric (with special value "Unlimited") Type: Numeric or Unlimited
Default: Unlimited Default: Unlimited
This property controls the number of Connections that can be accepted If this property is an Integer, it controls the number of Connections
from a peer as new members of the Connection's group. Similar to that can be accepted from a peer as new members of the Connection's
SetNewConnectionLimit(), this limits the number of ConnectionReceived group. Similar to SetNewConnectionLimit(), this limits the number of
Events that will occur, but constrained to the group of the ConnectionReceived Events that will occur, but constrained to the
Connection associated with this property. For a multi-streaming group of the Connection associated with this property. For a multi-
transport, this limits the number of allowed streams. streaming transport, this limits the number of allowed streams.
8.1.10. Isolate Session 8.1.10. Isolate Session
Name: isolateSession Name: isolateSession
Type: Boolean Type: Boolean
Default: false Default: false
When set to true, this property will initiate new Connections using When set to true, this property will initiate new Connections using
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application can receive. application can receive.
8.2. TCP-specific Properties: User Timeout Option (UTO) 8.2. TCP-specific Properties: User Timeout Option (UTO)
These properties specify configurations for the User Timeout Option These properties specify configurations for the User Timeout Option
(UTO), in the case that TCP becomes the chosen transport protocol. (UTO), in the case that TCP becomes the chosen transport protocol.
Implementation is optional and useful only if TCP is implemented in Implementation is optional and useful only if TCP is implemented in
the Transport Services system. the Transport Services system.
These TCP-specific properties are included here because the feature These TCP-specific properties are included here because the feature
"Suggest timeout to the peer" is part of the minimal set of transport Suggest timeout to the peer is part of the minimal set of transport
services [RFC8923], where this feature was categorized as services [RFC8923], where this feature was categorized as
"functional". This means that when an implementation offers this "functional". This means that when an Transport Services
feature, it has to expose an interface to it to the application. implementation offers this feature, the Transport Services API has to
Otherwise, the implementation might violate assumptions by the expose an interface to the application. Otherwise, the
application, which could cause the application to fail. implementation might violate assumptions by the application, which
could cause the application to fail.
All of the below properties are optional (e.g., it is possible to All of the below properties are optional (e.g., it is possible to
specify "User Timeout Enabled" as true, but not specify an Advertised specify User Timeout Enabled as true, but not specify an Advertised
User Timeout value; in this case, the TCP default will be used). User Timeout value; in this case, the TCP default will be used).
These properties reflect the API extension specified in Section 3 of These properties reflect the API extension specified in Section 3 of
[RFC5482]. [RFC5482].
8.2.1. Advertised User Timeout 8.2.1. Advertised User Timeout
Name: tcp.userTimeoutValue Name: tcp.userTimeoutValue
Type: Integer Type: Integer
Default: the TCP default Default: the TCP default
This time value is advertised via the TCP User Timeout Option (UTO) This time value is advertised via the TCP User Timeout Option (UTO)
[RFC5482] at the Remote Endpoint to adapt its own "Timeout for [RFC5482] at the Remote Endpoint to adapt its own Timeout for
aborting Connection" (see Section 8.1.3) value. aborting Connection (see Section 8.1.3) value.
8.2.2. User Timeout Enabled 8.2.2. User Timeout Enabled
Name: tcp.userTimeout Name: tcp.userTimeoutEnabled
Type: Boolean Type: Boolean
Default: false Default: false
This property controls whether the UTO option is enabled for a This property controls whether the UTO option is enabled for a
connection. This applies to both sending and receiving. connection. This applies to both sending and receiving.
8.2.3. Timeout Changeable 8.2.3. Timeout Changeable
Name: tcp.userTimeoutRecv Name: tcp.userTimeoutChangeable
Type: Boolean Type: Boolean
Default: true Default: true
This property controls whether the Timeout for aborting Connection
This property controls whether the "Timeout for aborting Connection"
(see Section 8.1.3) may be changed based on a UTO option received (see Section 8.1.3) may be changed based on a UTO option received
from the remote peer. This boolean becomes false when "Timeout for from the remote peer. This boolean becomes false when Timeout for
aborting Connection" (see Section 8.1.3) is used. aborting Connection (see Section 8.1.3) is used.
8.3. Connection Lifecycle Events 8.3. Connection Lifecycle Events
During the lifetime of a connection there are events that can occur During the lifetime of a connection there are events that can occur
when configured. when configured.
8.3.1. Soft Errors 8.3.1. Soft Errors
Asynchronous introspection is also possible, via the SoftError Event. Asynchronous introspection is also possible, via the SoftError Event.
This event informs the application about the receipt and contents of This event informs the application about the receipt and contents of
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errors; however, even if the underlying stack supports it, there is errors; however, even if the underlying stack supports it, there is
no guarantee that a soft error will be signaled. no guarantee that a soft error will be signaled.
Connection -> SoftError<> Connection -> SoftError<>
8.3.2. Path change 8.3.2. Path change
This event notifies the application when at least one of the paths This event notifies the application when at least one of the paths
underlying a Connection has changed. Changes occur on a single path underlying a Connection has changed. Changes occur on a single path
when the PMTU changes as well as when multiple paths are used and when the PMTU changes as well as when multiple paths are used and
paths are added or removed, or a handover has been performed. paths are added or removed, the set of local endpoints changes, or a
handover has been performed.
Connection -> PathChange<> Connection -> PathChange<>
9. Data Transfer 9. Data Transfer
Data is sent and received as Messages, which allows the application Data is sent and received as Messages, which allows the application
to communicate the boundaries of the data being transferred. to communicate the boundaries of the data being transferred.
9.1. Messages and Framers 9.1. Messages and Framers
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equivalent to passing a default MessageContext without adding any equivalent to passing a default MessageContext without adding any
Message Properties. Message Properties.
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.
Properties can be added to a MessageContext object only before the Properties can 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, it is invalid to modify any of its properties. with a Send call, further modifications to the MessageContext object
do not have any effect on this Send call.
The Message Properties could be inconsistent with the properties of The Message Properties could be inconsistent with the properties of
the Protocol Stacks underlying the Connection on which a given the Protocol Stacks underlying the Connection on which a given
Message is sent. For example, a Protocol Stack must be able to Message is sent. For example, a Protocol Stack must be able to
provide ordering if the msgOrdered property of a Message is enabled. provide ordering if the msgOrdered property of a Message is enabled.
Sending a Message with Message Properties inconsistent with the Sending a Message with Message Properties inconsistent with the
Selection Properties of the Connection yields an error. Selection Properties of the Connection yields an error.
Connection Properties describe the default behavior for all Messages If a Message Property contradicts a Connection Property, and if this
on a Connection. If a Message Property contradicts a Connection per-Message behavior can be supported, it overrides the Connection
Property, and if this per-Message behavior can be supported, it Property for the specific Message. For example, if Reliable Data
overrides the Connection Property for the specific Message. For Transfer (Connection) is set to Require and a protocol with
example, if "Reliable Data Transfer (Connection)" is set to "Require" configurable per-Message reliability is used, setting Reliable Data
and a protocol with configurable per-Message reliability is used, Transfer (Message) to false for a particular Message will allow this
setting "Reliable Data Transfer (Message)" to "false" for a Message to be sent without any reliability guarantees. Changing the
particular Message will allow this Message to be sent without any Reliable Data Transfer property on Messages is only possible for
reliability guarantees. Changing the Reliable Data Transfer property Connections that were established enabling the Selection Property
on Messages is only possible for Connections that were established Configure Per-Message Reliability.
enabling the Selection Property "Configure Per-Message Reliability".
The following Message Properties are supported: The following Message Properties are supported:
9.1.3.1. Lifetime 9.1.3.1. Lifetime
Name: msgLifetime Name: msgLifetime
Type: Numeric Type: Numeric
Default: infinite Default: infinite
The Lifetime specifies how long a particular Message can wait to be The Lifetime specifies how long a particular Message can wait to be
sent to the Remote Endpoint before it is irrelevant and no longer sent to the Remote Endpoint before it is irrelevant and no longer
needs to be (re-)transmitted. This is a hint to the Transport needs to be (re-)transmitted. This is a hint to the Transport
Services system - it is not guaranteed that a Message will not be Services implementation -- it is not guaranteed that a Message will
sent when its Lifetime has expired. not be sent when its Lifetime has expired.
Setting a Message's Lifetime to infinite indicates that the Setting a Message's Lifetime to infinite indicates that the
application does not wish to apply a time constraint on the application does not wish to apply a time constraint on the
transmission of the Message, but it does not express a need for transmission of the Message, but it does not express a need for
reliable delivery; reliability is adjustable per Message via the reliable delivery; reliability is adjustable per Message via the
"Reliable Data Transfer (Message)" property (see Section 9.1.3.7). Reliable Data Transfer (Message) property (see Section 9.1.3.7). The
The type and units of Lifetime are implementation-specific. type and units of Lifetime are implementation-specific.
9.1.3.2. Priority 9.1.3.2. Priority
Name: msgPrio Name: msgPriority
Type: Integer (non-negative) Type: Integer (non-negative)
Default: 100 Default: 100
This property specifies the priority of a Message, relative to other This property specifies the priority of a Message, relative to other
Messages sent over the same Connection. Messages sent over the same Connection.
A Message with Priority 0 will yield to a Message with Priority 1, A Message with Priority 0 will yield to a Message with Priority 1,
which will yield to a Message with Priority 2, and so on. Priorities which will yield to a Message with Priority 2, and so on. Priorities
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interact, but can be used independently and be realized by different interact, but can be used independently and be realized by different
mechanisms; see Section 9.2.6. mechanisms; see Section 9.2.6.
9.1.3.3. Ordered 9.1.3.3. Ordered
Name: msgOrdered Name: msgOrdered
Type: Boolean Type: Boolean
Default: the queried Boolean value of the Selection Property Default: the queried Boolean value of the Selection Property
"preserveOrder" (Section 6.2.4) preserveOrder (Section 6.2.4)
The order in which Messages were submitted for transmission via the The order in which Messages were submitted for transmission via the
Send Action will be preserved on delivery via Receive<> events for Send Action will be preserved on delivery via Receive<> events for
all Messages on a Connection that have this Message Property set to all Messages on a Connection that have this Message Property set to
true. true.
If false, the Message is delivered to the receiving application If false, the Message is delivered to the receiving application
without preserving the ordering. This property is used for protocols without preserving the ordering. This property is used for protocols
that support preservation of data ordering, see Section 6.2.4, but that support preservation of data ordering, see Section 6.2.4, but
allow out-of-order delivery for certain messages, e.g., by allow out-of-order delivery for certain messages, e.g., by
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Default: false Default: false
If true, Safely Replayable specifies that a Message is safe to send If true, Safely Replayable specifies that a Message is safe to send
to the Remote Endpoint more than once for a single Send Action. It to the Remote Endpoint more than once for a single Send Action. It
marks the data as safe for certain 0-RTT establishment techniques, marks the data as safe for certain 0-RTT establishment techniques,
where retransmission of the 0-RTT data may cause the remote where retransmission of the 0-RTT data may cause the remote
application to receive the Message multiple times. application to receive the Message multiple times.
For protocols that do not protect against duplicated messages, e.g., For protocols that do not protect against duplicated messages, e.g.,
UDP, all messages need to be marked as "Safely Replayable". To UDP, all messages need to be marked as Safely Replayable. To enable
enable protocol selection to choose such a protocol, "Safely protocol selection to choose such a protocol, Safely Replayable needs
Replayable" needs to be added to the TransportProperties passed to to be added to the TransportProperties passed to the Preconnection.
the Preconnection. If such a protocol was chosen, disabling "Safely If such a protocol was chosen, disabling Safely Replayable on
Replayable" on individual messages MUST result in a SendError. individual messages MUST result in a SendError.
9.1.3.5. Final 9.1.3.5. Final
Name: final Name: final
Type: Boolean Type: Boolean
Default: false Default: false
If true, this indicates a Message is the last that the application If true, this indicates a Message is the last that the application
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Messages. The Final property overrides Priority and any other Messages. The Final property overrides Priority and any other
property that would re-order Messages. If another Message is sent property that would re-order Messages. If another Message is sent
after a Message marked as Final has already been sent on a after a Message marked as Final has already been sent on a
Connection, the Send Action for the new Message will cause a Connection, the Send Action for the new Message will cause a
SendError Event. SendError Event.
9.1.3.6. Sending Corruption Protection Length 9.1.3.6. Sending Corruption Protection Length
Name: msgChecksumLen Name: msgChecksumLen
Type: Integer (non-negative with special value "Full Coverage") Type: Integer or Full Coverage
Default: Full Coverage Default: Full Coverage
This property specifies the minimum length of the section of a sent If this property is an Integer, it specifies the minimum length of
Message, starting from byte 0, that the application requires to be the section of a sent Message, starting from byte 0, that the
delivered without corruption due to lower layer errors. It is used application requires to be delivered without corruption due to lower
to specify options for simple integrity protection via checksums. A layer errors. It is used to specify options for simple integrity
value of 0 means that no checksum needs to be calculated, and "Full protection via checksums. A value of 0 means that no checksum needs
Coverage" means that the entire Message needs to be protected by a to be calculated, and the enumerated value Full Coverage means that
checksum. Only "Full Coverage" is guaranteed, any other requests are the entire Message needs to be protected by a checksum. Only Full
advisory, which may result in "Full Coverage" being applied. Coverage is guaranteed, any other requests are advisory, which may
result in Full Coverage being applied.
9.1.3.7. Reliable Data Transfer (Message) 9.1.3.7. Reliable Data Transfer (Message)
Name: msgReliable Name: msgReliable
Type: Boolean Type: Boolean
Default: the queried Boolean value of the Selection Property Default: the queried Boolean value of the Selection Property
"reliability" (Section 6.2.1) reliability (Section 6.2.1)
When true, this property specifies that a Message should be sent in When true, this property specifies that a Message should be sent in
such a way that the transport protocol ensures all data is received such a way that the transport protocol ensures all data is received
on the other side without corruption. Changing the "Reliable Data on the other side without corruption. Changing the Reliable Data
Transfer" property on Messages is only possible for Connections that Transfer property on Messages is only possible for Connections that
were established enabling the Selection Property "Configure Per- were established enabling the Selection Property Configure Per-
Message Reliability". When this is not the case, changing Message Reliability. When this is not the case, changing msgReliable
"msgReliable" will generate an error. will generate an error.
Disabling this property indicates that the Transport Services system Disabling this property indicates that the Transport Services system
may disable retransmissions or other reliability mechanisms for this may disable retransmissions or other reliability mechanisms for this
particular Message, but such disabling is not guaranteed. particular Message, but such disabling is not guaranteed.
9.1.3.8. Message Capacity Profile Override 9.1.3.8. Message Capacity Profile Override
Name: msgCapacityProfile Name: msgCapacityProfile
Type: Enumeration Type: Enumeration
Default: inherited from the Connection Property Default: inherited from the Connection Property connCapacityProfile
"connCapacityProfile" (Section 8.1.6) (Section 8.1.6)
This enumerated property specifies the application's preferred This enumerated property specifies the application's preferred
tradeoffs for sending this Message; it is a per-Message override of tradeoffs for sending this Message; it is a per-Message override of
the Capacity Profile connection property (see Section 8.1.6). the Capacity Profile connection property (see Section 8.1.6).
9.1.3.9. No Network-Layer Fragmentation 9.1.3.9. No Network-Layer Fragmentation
Name: noFragmentation Name: noFragmentation
Type: Boolean Type: Boolean
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prefered. prefered.
This only takes effect when the transport uses a network layer that This only takes effect when the transport uses a network layer that
supports this functionality. When it does take effect, setting this supports this functionality. When it does take effect, setting this
property to true will cause the sender to avoid network-layer source property to true will cause the sender to avoid network-layer source
frgementation. When using IPv4, this will result in the Don't frgementation. When using IPv4, this will result in the Don't
Fragment bit being set in the IP header. Fragment bit being set in the IP header.
Attempts to send a message with this property that result in a size Attempts to send a message with this property that result in a size
greater than the transport's current estimate of its maximum packet greater than the transport's current estimate of its maximum packet
size ("singularTransmissionMsgMaxLen") can result in transport size (singularTransmissionMsgMaxLen) can result in transport
segmentation when permitted, or in a "SendError". segmentation when permitted, or in a SendError.
Note: noSegmentation should be used when it is desired to only send a Note: noSegmentation should be used when it is desired to only send a
message within a single network packet. message within a single network packet.
9.1.3.10. No Segmentation 9.1.3.10. No Segmentation
Name: noSegmentation Name: noSegmentation
Type: Boolean Type: Boolean
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query the Connection Property "Maximum Message size on send" query the Connection Property "Maximum Message size on send"
(Section 8.1.11.3) to determine the maximum size allowed for a single (Section 8.1.11.3) to determine the maximum size allowed for a single
Message. If a Message is too large to fit in the Maximum Message Message. If a Message is too large to fit in the Maximum Message
Size for the Connection, the Send will fail with a SendError event Size for the Connection, the Send will fail with a SendError event
(Section 9.2.2.3). For example, it is invalid to send a Message over (Section 9.2.2.3). For example, it is invalid to send a Message over
a UDP connection that is larger than the available datagram sending a UDP connection that is larger than the available datagram sending
size. size.
9.2.2. Send Events 9.2.2. Send Events
Like all Actions in this interface, the Send Action is asynchronous. Like all Actions in Transport Services API, the Send Action is
There are several Events that can be delivered in response to Sending asynchronous. There are several Events that can be delivered in
a Message. Exactly one Event (Sent, Expired, or SendError) will be response to Sending a Message. Exactly one Event (Sent, Expired, or
delivered in response to each call to Send. SendError) will be delivered in response to each call to Send.
Note that if partial Sends are used (Section 9.2.3), there will still Note that if partial Sends are used (Section 9.2.3), there will still
be exactly one Send Event delivered for each call to Send. For be exactly one Send Event delivered for each call to Send. For
example, if a Message expired while two requests to Send data for example, if a Message expired while two requests to Send data for
that Message are outstanding, there will be two Expired events that Message are outstanding, there will be two Expired events
delivered. delivered.
The interface should allow the application to correlate which Send The Transport Services API should allow the application to correlate
Action resulted in a particular Send Event. The manner in which this which Send Action resulted in a particular Send Event. The manner in
correlation is indicated is implementation-specific. which this correlation is indicated is implementation-specific.
9.2.2.1. Sent 9.2.2.1. Sent
Connection -> Sent<messageContext> Connection -> Sent<messageContext>
The Sent Event occurs when a previous Send Action has completed, The Sent Event occurs when a previous Send Action has completed,
i.e., when the data derived from the Message has been passed down or i.e., when the data derived from the Message has been passed down or
through the underlying Protocol Stack and is no longer the through the underlying Protocol Stack and is no longer the
responsibility of this interface. The exact disposition of the responsibility of the Transport Services API. The exact disposition
Message (i.e., whether it has actually been transmitted, moved into a of the Message (i.e., whether it has actually been transmitted, moved
buffer on the network interface, moved into a kernel buffer, and so into a buffer on the network interface, moved into a kernel buffer,
on) when the Sent Event occurs is implementation-specific. The Sent and so on) when the Sent Event occurs is implementation-specific.
Event contains a reference to the Message Context of the Message to The Sent Event contains a reference to the Message Context of the
which it applies. Message to which it applies.
Sent Events allow an application to obtain an understanding of the Sent Events allow an application to obtain an understanding of the
amount of buffering it creates. That is, if an application calls the amount of buffering it creates. That is, if an application calls the
Send Action multiple times without waiting for a Sent Event, it has Send Action multiple times without waiting for a Sent Event, it has
created more buffer inside the Transport Services system than an created more buffer inside the Transport Services system than an
application that always waits for the Sent Event before calling the application that always waits for the Sent Event before calling the
next Send Action. next Send Action.
9.2.2.2. Expired 9.2.2.2. Expired
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Connection.Send(messageData) Connection.Send(messageData)
Connection.EndBatch() Connection.EndBatch()
9.2.5. Send on Active Open: InitiateWithSend 9.2.5. Send on Active Open: InitiateWithSend
For application-layer protocols where the Connection initiator also For application-layer protocols where the Connection initiator also
sends the first message, the InitiateWithSend() action combines sends the first message, the InitiateWithSend() action combines
Connection initiation with a first Message sent: Connection initiation with a first Message sent:
Connection := Preconnection.InitiateWithSend(messageData, messageContext?, timeout?) Connection := Preconnection.InitiateWithSend(messageData, messageContext?, timeout?)
Whenever possible, a messageContext should be provided to declare the Whenever possible, a messageContext should be provided to declare the
Message passed to InitiateWithSend as "Safely Replayable". This Message passed to InitiateWithSend as Safely Replayable. This allows
allows the Transport Services system to make use of 0-RTT the Transport Services system to make use of 0-RTT establishment in
establishment in case this is supported by the available protocol case this is supported by the available protocol stacks. When the
stacks. When the selected stack(s) do not support transmitting data selected stack(s) do not support transmitting data upon connection
upon connection establishment, InitiateWithSend is identical to establishment, InitiateWithSend is identical to Initiate() followed
Initiate() followed by Send(). by Send().
Neither partial sends nor send batching are supported by Neither partial sends nor send batching are supported by
InitiateWithSend(). InitiateWithSend().
The Events that may be sent after InitiateWithSend() are equivalent The Events that may be sent after InitiateWithSend() are equivalent
to those that would be sent by an invocation of Initiate() followed to those that would be sent by an invocation of Initiate() followed
immediately by an invocation of Send(), with the caveat that a send immediately by an invocation of Send(), with the caveat that a send
failure that occurs because the Connection could not be established failure that occurs because the Connection could not be established
will not result in a SendError separate from the EstablishmentError will not result in a SendError separate from the EstablishmentError
signaling the failure of Connection establishment. signaling the failure of Connection establishment.
9.2.6. Priority in TAPS 9.2.6. Priority and the Transport Services API
The Transport Services interface provides two properties to allow a The Transport Services API provides two properties to allow a sender
sender to signal the relative priority of data transmission: the to signal the relative priority of data transmission: the Priority
Priority Message Property Section 9.1.3.2, and the Connection Message Property Section 9.1.3.2, and the Connection Priority
Priority Connection Property Section 8.1.2. These properties are Connection Property Section 8.1.2. These properties are designed to
designed to allow the expression and implementation of a wide variety allow the expression and implementation of a wide variety of
of approaches to transmission priority in the transport and approaches to transmission priority in the transport and application
application layer, including those which do not appear on the wire layer, including those which do not appear on the wire (affecting
(affecting only sender-side transmission scheduling) as well as those only sender-side transmission scheduling) as well as those that do
that do (e.g. [I-D.ietf-httpbis-priority]. (e.g. [I-D.ietf-httpbis-priority].
A Transport Services system gives no guarantees about how its A Transport Services system gives no guarantees about how its
expression of relative priorities will be realized. However, the expression of relative priorities will be realized. However, the
Transport Services system will seek to ensure that performance of Transport Services system will seek to ensure that performance of
relatively-prioritized connections and messages is not worse with relatively-prioritized connections and messages is not worse with
respect to those connections and messages than an equivalent respect to those connections and messages than an equivalent
configuration in which all prioritization properties are left at configuration in which all prioritization properties are left at
their defaults. their defaults.
The Transport Services interface does order Connection Priority over The Transport Services API does order Connection Priority over the
the Priority Message Property. In the absense of other externalities Priority Message Property. In the absense of other externalities
(e.g., transport-layer flow control), a priority 1 Message on a (e.g., transport-layer flow control), a priority 1 Message on a
priority 0 Connection will be sent before a priority 0 Message on a priority 0 Connection will be sent before a priority 0 Message on a
priority 1 Connection in the same group. priority 1 Connection in the same group.
9.3. Receiving Data 9.3. Receiving Data
Once a Connection is established, it can be used for receiving data Once a Connection is established, it can be used for receiving data
(unless the "Direction of Communication" property is set to (unless the Direction of Communication property is set to
"unidirectional send"). As with sending, the data is received in unidirectional send). As with sending, the data is received in
Messages. Receiving is an asynchronous operation, in which each call Messages. Receiving is an asynchronous operation, in which each call
to Receive enqueues a request to receive new data from the to Receive enqueues a request to receive new data from the
connection. Once data has been received, or an error is encountered, connection. Once data has been received, or an error is encountered,
an event will be delivered to complete any pending Receive requests an event will be delivered to complete any pending Receive requests
(see Section 9.3.2). If Messages arrive at the Transport Services (see Section 9.3.2). If Messages arrive at the Transport Services
system before Receive requests are issued, ensuing Receive requests system before Receive requests are issued, ensuing Receive requests
will first operate on these Messages before awaiting any further will first operate on these Messages before awaiting any further
Messages. Messages.
9.3.1. Enqueuing Receives 9.3.1. Enqueuing Receives
skipping to change at page 63, line 51 skipping to change at page 68, line 28
of shorter complete Messages or memory issues. of shorter complete Messages or memory issues.
The maxLength argument indicates the maximum size of a Message in The maxLength argument indicates the maximum size of a Message in
bytes that the application is currently prepared to receive. The bytes that the application is currently prepared to receive. The
default value for maxLength is infinite. If an incoming Message is default value for maxLength is infinite. If an incoming Message is
larger than the minimum of this size and the maximum Message size on larger than the minimum of this size and the maximum Message size on
receive for the Connection's Protocol Stack, it will be delivered via receive for the Connection's Protocol Stack, it will be delivered via
ReceivedPartial events (Section 9.3.2.2). ReceivedPartial events (Section 9.3.2.2).
Note that maxLength does not guarantee that the application will Note that maxLength does not guarantee that the application will
receive that many bytes if they are available; the interface could receive that many bytes if they are available; the Transport Services
return ReceivedPartial events with less data than maxLength according API could return ReceivedPartial events with less data than maxLength
to implementation constraints. Note also that maxLength and according to implementation constraints. Note also that maxLength
minIncompleteLength are intended only to manage buffering, and are and minIncompleteLength are intended only to manage buffering, and
not interpreted as a receiver preference for message reordering. are not interpreted as a receiver preference for message reordering.
9.3.2. Receive Events 9.3.2. Receive Events
Each call to Receive will be paired with a single Receive Event, Each call to Receive will be paired with a single Receive Event,
which can be a success or an error. This allows an application to which can be a success or an error. This allows an application to
provide backpressure to the transport stack when it is temporarily provide backpressure to the transport stack when it is temporarily
not ready to receive messages. not ready to receive messages.
The interface should allow the application to correlate which call to The Transport Services API should allow the application to correlate
Receive resulted in a particular Receive Event. The manner in which which call to Receive resulted in a particular Receive Event. The
this correlation is indicated is implementation-specific. manner in which this correlation is indicated is implementation-
specific.
9.3.2.1. Received 9.3.2.1. Received
Connection -> Received<messageData, messageContext> Connection -> Received<messageData, messageContext>
A Received event indicates the delivery of a complete Message. It A Received event indicates the delivery of a complete Message. It
contains two objects, the received bytes as messageData, and the contains two objects, the received bytes as messageData, and the
metadata and properties of the received Message as messageContext. metadata and properties of the received Message as messageContext.
The messageData object provides access to the bytes that were The messageData object provides access to the bytes that were
received for this Message, along with the length of the byte array. received for this Message, along with the length of the byte array.
The messageContext is provided to enable retrieving metadata about The messageContext is provided to enable retrieving metadata about
the message and referring to the message, e.g., to send replies and the message and referring to the message. The messageContext object
map responses to their requests. See Section 9.1.1 for details. ist described in Section 9.1.1.
See Section 9.1.2 for handling Message framing in situations where See Section 9.1.2 for handling Message framing in situations where
the Protocol Stack only provides a byte-stream transport. the Protocol Stack only provides a byte-stream transport.
9.3.2.2. ReceivedPartial 9.3.2.2. ReceivedPartial
Connection -> ReceivedPartial<messageData, messageContext, endOfMessage> Connection -> ReceivedPartial<messageData, messageContext, endOfMessage>
If a complete Message cannot be delivered in one event, one part of If a complete Message cannot be delivered in one event, one part of
the Message can be delivered with a ReceivedPartial event. To the Message can be delivered with a ReceivedPartial event. To
skipping to change at page 65, line 32 skipping to change at page 70, line 13
available; or available; or
* the underlying Protocol Stack does not support message boundary * the underlying Protocol Stack does not support message boundary
preservation, and no Message Framer was supplied by the preservation, and no Message Framer was supplied by the
application application
Note that in the absence of message boundary preservation or a Note that in the absence of message boundary preservation or a
Message Framer, all bytes received on the Connection will be Message Framer, all bytes received on the Connection will be
represented as one large Message of indeterminate length. represented as one large Message of indeterminate length.
In the following example, an application only wants to receive up to
1000 bytes at a time from a Connection. If a 1500-byte message
arrives, it would receive the message in two separate ReceivedPartial
events.
Connection.Receive(1, 1000)
// Receive first 1000 bytes, message is incomplete
Connection -> ReceivedPartial<messageData(1000 bytes), messageContext, false>
Connection.Receive(1, 1000)
// Receive last 500 bytes, message is now complete
Connection -> ReceivedPartial<messageData(500 bytes), messageContext, true>
9.3.2.3. ReceiveError 9.3.2.3. ReceiveError
Connection -> ReceiveError<messageContext, reason?> Connection -> ReceiveError<messageContext, reason?>
A ReceiveError occurs when data is received by the underlying A ReceiveError occurs when data is received by the underlying
Protocol Stack that cannot be fully retrieved or parsed, and when it Protocol Stack that cannot be fully retrieved or parsed, and when it
is useful for the application to be notified of such errors. For is useful for the application to be notified of such errors. For
example, a ReceiveError can indicate that a Message (identified via example, a ReceiveError can indicate that a Message (identified via
the MessageContext) that was being partially received previously, but the MessageContext) that was being partially received previously, but
had not completed, encountered an error and will not be completed. had not completed, encountered an error and will not be completed.
skipping to change at page 69, line 7 skipping to change at page 73, line 47
A ConnectionError informs the application that: 1) data could not be A ConnectionError informs the application that: 1) data could not be
delivered to the peer after a timeout, or 2) the Connection has been delivered to the peer after a timeout, or 2) the Connection has been
aborted (e.g., because the peer has called Abort). There is no aborted (e.g., because the peer has called Abort). There is no
guarantee that an Abort from the peer will be signaled. guarantee that an Abort from the peer will be signaled.
Connection -> ConnectionError<reason?> Connection -> ConnectionError<reason?>
11. Connection State and Ordering of Operations and Events 11. Connection State and Ordering of Operations and Events
This interface is designed to be independent of an implementation's This Transport Services API is designed to be independent of an
concurrency model. The details of how exactly actions are handled, implementation's concurrency model. The details of how exactly
and how events are dispatched, are implementation dependent. actions are handled, and how events are dispatched, are
implementation dependent.
Each transition of connection state is associated with one of more Each transition of connection state is associated with one of more
events: events:
* Ready<> occurs when a Connection created with Initiate() or * Ready<> occurs when a Connection created with Initiate() or
InitiateWithSend() transitions to Established state. InitiateWithSend() transitions to Established state.
* ConnectionReceived<> occurs when a Connection created with * ConnectionReceived<> occurs when a Connection created with
Listen() transitions to Established state. Listen() transitions to Established state.
skipping to change at page 69, line 48 skipping to change at page 74, line 42
| ^ | ^
| | | |
+---------------------------------------------------+ +---------------------------------------------------+
EstablishmentError<> EstablishmentError<>
(*) Ready<>, ConnectionReceived<>, RendezvousDone<> (*) Ready<>, ConnectionReceived<>, RendezvousDone<>
(**) Closed<>, ConnectionError<> (**) Closed<>, ConnectionError<>
Figure 2: Connection State Diagram Figure 2: Connection State Diagram
The interface provides the following guarantees about the ordering of The Transport Services API provides the following guarantees about
operations: the ordering of operations:
* Sent<> events will occur on a Connection in the order in which the * Sent<> events will occur on a Connection in the order in which the
Messages were sent (i.e., delivered to the kernel or to the Messages were sent (i.e., delivered to the kernel or to the
network interface, depending on implementation). network interface, depending on implementation).
* Received<> will never occur on a Connection before it is * Received<> will never occur on a Connection before it is
Established; i.e. before a Ready<> event on that Connection, or a Established; i.e. before a Ready<> event on that Connection, or a
ConnectionReceived<> or RendezvousDone<> containing that ConnectionReceived<> or RendezvousDone<> containing that
Connection. Connection.
* No events will occur on a Connection after it is Closed; i.e., * No events will occur on a Connection after it is Closed; i.e.,
after a Closed<> event, an EstablishmentError<> or after a Closed<> event, an EstablishmentError<> or
ConnectionError<> will not occur on that connection. To ensure ConnectionError<> will not occur on that connection. To ensure
this ordering, Closed<> will not occur on a Connection while other this ordering, Closed<> will not occur on a Connection while other
events on the Connection are still locally outstanding (i.e., events on the Connection are still locally outstanding (i.e.,
known to the interface and waiting to be dealt with by the known to the Transport Services API and waiting to be dealt with
application). by the application).
12. IANA Considerations 12. IANA Considerations
RFC-EDITOR: Please remove this section before publication. RFC-EDITOR: Please remove this section before publication.
This document has no Actions for IANA. Later versions of this This document has no Actions for IANA. Later versions of this
document may create IANA registries for generic transport property document may create IANA registries for generic transport property
names and transport property namespaces (see Section 4.1). names and transport property namespaces (see Section 4.1).
13. Privacy and Security Considerations 13. Privacy and Security Considerations
This document describes a generic API for interacting with a This document describes a generic API for interacting with a
transport services (TAPS) system. Part of this API includes Transport Services system. Part of this API includes configuration
configuration details for transport security protocols, as discussed details for transport security protocols, as discussed in
in Section 6.3. It does not recommend use (or disuse) of specific Section 6.3. It does not recommend use (or disuse) of specific
algorithms or protocols. Any API-compatible transport security algorithms or protocols. Any API-compatible transport security
protocol ought to work in a TAPS system. Security considerations for protocol ought to work in a Transport Services system. Security
these protocols are discussed in the respective specifications. considerations for these protocols are discussed in the respective
specifications.
The described API is used to exchange information between an The described API is used to exchange information between an
application and the Transport Services system. While it is not application and the Transport Services system. While it is not
necessarily expected that both systems are implemented by the same necessarily expected that both systems are implemented by the same
authority, it is expected that the Transport Services system authority, it is expected that the Transport Services system
implementation is either provided as a library that is selected by implementation is either provided as a library that is selected by
the application from a trusted party, or that it is part of the the application from a trusted party, or that it is part of the
operating system that the application also relies on for other tasks. operating system that the application also relies on for other tasks.
In either case, the Transport Services API is an internal interface In either case, the Transport Services API is an internal interface
skipping to change at page 71, line 38 skipping to change at page 76, line 33
path fails and fallback or re-establishment is supported in the path fails and fallback or re-establishment is supported in the
Transport Services system. Transport Services system.
Applications should also take care to not assume that all data Applications should also take care to not assume that all data
received using the Transport Services API is always complete or well- received using the Transport Services API is always complete or well-
formed. Specifically, messages that are received partially formed. Specifically, messages that are received partially
Section 9.3.2.2 could be a source of truncation attacks if Section 9.3.2.2 could be a source of truncation attacks if
applications do not distinguish between partial messages and complete applications do not distinguish between partial messages and complete
messages. messages.
The interface explicitly does not require the application to resolve The Transport Services API explicitly does not require the
names, though there is a tradeoff between early and late binding of application to resolve names, though there is a tradeoff between
addresses to names. Early binding allows the API implementation to early and late binding of addresses to names. Early binding allows
reduce connection setup latency, at the cost of potentially limited the API implementation to reduce connection setup latency, at the
scope for alternate path discovery during Connection establishment, cost of potentially limited scope for alternate path discovery during
as well as potential additional information leakage about application Connection establishment, as well as potential additional information
interest when used with a resolution method (such as DNS without TLS) leakage about application interest when used with a resolution method
which does not protect query confidentiality. (such as DNS without TLS) which does not protect query
confidentiality.
These communication activities are not different from what is used These communication activities are not different from what is used
today. However, the goal of a Transport Services system is to today. However, the goal of a Transport Services system is to
support such mechanisms as a generic service within the transport support such mechanisms as a generic service within the transport
layer. This enables applications to more dynamically benefit from layer. This enables applications to more dynamically benefit from
innovations and new protocols in the transport, although it reduces innovations and new protocols in the transport, although it reduces
transparency of the underlying communication actions to the transparency of the underlying communication actions to the
application itself. The TAPS API is designed such that protocol and application itself. The Transport Services API is designed such that
path selection can be limited to a small and controlled set if protocol and path selection can be limited to a small and controlled
required by the application for functional or security purposes. set if required by the application for functional or security
Further, TAPS implementations should provide an interface to poll purposes. Further, A Transport Services system should provide an
information about which protocol and path is currently in use as well interface to poll information about which protocol and path is
as provide logging about the communication events of each connection. currently in use as well as provide logging about the communication
events of each connection.
14. 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).
skipping to change at page 72, line 44 skipping to change at page 77, line 40
contributing text, e.g., on multicast. contributing text, e.g., on multicast.
15. References 15. References
15.1. 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. S., and C. A. Wood, "An Perkins, C., Tiesel, P. S., and C. A. Wood, "An
Architecture for Transport Services", Work in Progress, Architecture for Transport Services", Work in Progress,
Internet-Draft, draft-ietf-taps-arch-10, 30 April 2021, Internet-Draft, draft-ietf-taps-arch-11, 12 July 2021,
<https://www.ietf.org/archive/id/draft-ietf-taps-arch- <https://datatracker.ietf.org/doc/html/draft-ietf-taps-
10.txt>. arch-11>.
[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/rfc/rfc2119>.
[RFC2914] Floyd, S., "Congestion Control Principles", BCP 41, [RFC2914] Floyd, S., "Congestion Control Principles", BCP 41,
RFC 2914, DOI 10.17487/RFC2914, September 2000, RFC 2914, DOI 10.17487/RFC2914, September 2000,
<https://www.rfc-editor.org/info/rfc2914>. <https://www.rfc-editor.org/rfc/rfc2914>.
[RFC4941] Narten, T., Draves, R., and S. Krishnan, "Privacy [RFC4941] Narten, T., Draves, R., and S. Krishnan, "Privacy
Extensions for Stateless Address Autoconfiguration in Extensions for Stateless Address Autoconfiguration in
IPv6", RFC 4941, DOI 10.17487/RFC4941, September 2007, IPv6", RFC 4941, DOI 10.17487/RFC4941, September 2007,
<https://www.rfc-editor.org/info/rfc4941>. <https://www.rfc-editor.org/rfc/rfc4941>.
[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/rfc/rfc8084>.
[RFC8085] Eggert, L., Fairhurst, G., and G. Shepherd, "UDP Usage [RFC8085] Eggert, L., Fairhurst, G., and G. Shepherd, "UDP Usage
Guidelines", BCP 145, RFC 8085, DOI 10.17487/RFC8085, Guidelines", BCP 145, RFC 8085, DOI 10.17487/RFC8085,
March 2017, <https://www.rfc-editor.org/info/rfc8085>. March 2017, <https://www.rfc-editor.org/rfc/rfc8085>.
[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/rfc/rfc8174>.
[RFC8303] Welzl, M., Tuexen, M., and N. Khademi, "On the Usage of [RFC8303] Welzl, M., Tuexen, M., and N. Khademi, "On the Usage of
Transport Features Provided by IETF Transport Protocols", Transport Features Provided by IETF Transport Protocols",
RFC 8303, DOI 10.17487/RFC8303, February 2018, RFC 8303, DOI 10.17487/RFC8303, February 2018,
<https://www.rfc-editor.org/info/rfc8303>. <https://www.rfc-editor.org/rfc/rfc8303>.
[RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol [RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol
Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018, Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
<https://www.rfc-editor.org/info/rfc8446>. <https://www.rfc-editor.org/rfc/rfc8446>.
15.2. Informative References 15.2. Informative References
[I-D.ietf-httpbis-priority] [I-D.ietf-httpbis-priority]
Oku, K. and L. Pardue, "Extensible Prioritization Scheme Oku, K. and L. Pardue, "Extensible Prioritization Scheme
for HTTP", Work in Progress, Internet-Draft, draft-ietf- for HTTP", Work in Progress, Internet-Draft, draft-ietf-
httpbis-priority-03, 11 January 2021, httpbis-priority-11, 8 December 2021,
<https://www.ietf.org/archive/id/draft-ietf-httpbis- <https://datatracker.ietf.org/doc/html/draft-ietf-httpbis-
priority-03.txt>. priority-11>.
[I-D.ietf-taps-impl] [I-D.ietf-taps-impl]
Brunstrom, A., Pauly, T., Enghardt, T., Grinnemo, K., Brunstrom, A., Pauly, T., Enghardt, T., Grinnemo, K.,
Jones, T., Tiesel, P. S., Perkins, C., and M. Welzl, Jones, T., Tiesel, P. S., Perkins, C., and M. Welzl,
"Implementing Interfaces to Transport Services", Work in "Implementing Interfaces to Transport Services", Work in
Progress, Internet-Draft, draft-ietf-taps-impl-09, 30 Progress, Internet-Draft, draft-ietf-taps-impl-10, 12 July
April 2021, <https://www.ietf.org/archive/id/draft-ietf- 2021, <https://datatracker.ietf.org/doc/html/draft-ietf-
taps-impl-09.txt>. taps-impl-10>.
[RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black, [RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black,
"Definition of the Differentiated Services Field (DS "Definition of the Differentiated Services Field (DS
Field) in the IPv4 and IPv6 Headers", RFC 2474, Field) in the IPv4 and IPv6 Headers", RFC 2474,
DOI 10.17487/RFC2474, December 1998, DOI 10.17487/RFC2474, December 1998,
<https://www.rfc-editor.org/info/rfc2474>. <https://www.rfc-editor.org/rfc/rfc2474>.
[RFC2597] Heinanen, J., Baker, F., Weiss, W., and J. Wroclawski, [RFC2597] Heinanen, J., Baker, F., Weiss, W., and J. Wroclawski,
"Assured Forwarding PHB Group", RFC 2597, "Assured Forwarding PHB Group", RFC 2597,
DOI 10.17487/RFC2597, June 1999, DOI 10.17487/RFC2597, June 1999,
<https://www.rfc-editor.org/info/rfc2597>. <https://www.rfc-editor.org/rfc/rfc2597>.
[RFC3246] Davie, B., Charny, A., Bennet, J.C.R., Benson, K., Le [RFC3246] Davie, B., Charny, A., Bennet, J.C.R., Benson, K., Le
Boudec, J.Y., Courtney, W., Davari, S., Firoiu, V., and D. Boudec, J.Y., Courtney, W., Davari, S., Firoiu, V., and D.
Stiliadis, "An Expedited Forwarding PHB (Per-Hop Stiliadis, "An Expedited Forwarding PHB (Per-Hop
Behavior)", RFC 3246, DOI 10.17487/RFC3246, March 2002, Behavior)", RFC 3246, DOI 10.17487/RFC3246, March 2002,
<https://www.rfc-editor.org/info/rfc3246>. <https://www.rfc-editor.org/rfc/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/rfc/rfc3261>.
[RFC3376] Cain, B., Deering, S., Kouvelas, I., Fenner, B., and A.
Thyagarajan, "Internet Group Management Protocol, Version
3", RFC 3376, DOI 10.17487/RFC3376, October 2002,
<https://www.rfc-editor.org/rfc/rfc3376>.
[RFC4594] Babiarz, J., Chan, K., and F. Baker, "Configuration [RFC4594] Babiarz, J., Chan, K., and F. Baker, "Configuration
Guidelines for DiffServ Service Classes", RFC 4594, Guidelines for DiffServ Service Classes", RFC 4594,
DOI 10.17487/RFC4594, August 2006, DOI 10.17487/RFC4594, August 2006,
<https://www.rfc-editor.org/info/rfc4594>. <https://www.rfc-editor.org/rfc/rfc4594>.
[RFC4604] Holbrook, H., Cain, B., and B. Haberman, "Using Internet
Group Management Protocol Version 3 (IGMPv3) and Multicast
Listener Discovery Protocol Version 2 (MLDv2) for Source-
Specific Multicast", RFC 4604, DOI 10.17487/RFC4604,
August 2006, <https://www.rfc-editor.org/rfc/rfc4604>.
[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/rfc/rfc5245>.
[RFC5482] Eggert, L. and F. Gont, "TCP User Timeout Option", [RFC5482] Eggert, L. and F. Gont, "TCP User Timeout Option",
RFC 5482, DOI 10.17487/RFC5482, March 2009, RFC 5482, DOI 10.17487/RFC5482, March 2009,
<https://www.rfc-editor.org/info/rfc5482>. <https://www.rfc-editor.org/rfc/rfc5482>.
[RFC5766] Mahy, R., Matthews, P., and J. Rosenberg, "Traversal Using [RFC5766] Mahy, R., Matthews, P., and J. Rosenberg, "Traversal Using
Relays around NAT (TURN): Relay Extensions to Session Relays around NAT (TURN): Relay Extensions to Session
Traversal Utilities for NAT (STUN)", RFC 5766, Traversal Utilities for NAT (STUN)", RFC 5766,
DOI 10.17487/RFC5766, April 2010, DOI 10.17487/RFC5766, April 2010,
<https://www.rfc-editor.org/info/rfc5766>. <https://www.rfc-editor.org/rfc/rfc5766>.
[RFC5865] Baker, F., Polk, J., and M. Dolly, "A Differentiated [RFC5865] Baker, F., Polk, J., and M. Dolly, "A Differentiated
Services Code Point (DSCP) for Capacity-Admitted Traffic", Services Code Point (DSCP) for Capacity-Admitted Traffic",
RFC 5865, DOI 10.17487/RFC5865, May 2010, RFC 5865, DOI 10.17487/RFC5865, May 2010,
<https://www.rfc-editor.org/info/rfc5865>. <https://www.rfc-editor.org/rfc/rfc5865>.
[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/rfc/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/rfc/rfc7556>.
[RFC7657] Black, D., Ed. and P. Jones, "Differentiated Services [RFC7657] Black, D., Ed. and P. Jones, "Differentiated Services
(Diffserv) and Real-Time Communication", RFC 7657, (Diffserv) and Real-Time Communication", RFC 7657,
DOI 10.17487/RFC7657, November 2015, DOI 10.17487/RFC7657, November 2015,
<https://www.rfc-editor.org/info/rfc7657>. <https://www.rfc-editor.org/rfc/rfc7657>.
[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/rfc/rfc8095>.
[RFC8229] Pauly, T., Touati, S., and R. Mantha, "TCP Encapsulation [RFC8229] Pauly, T., Touati, S., and R. Mantha, "TCP Encapsulation
of IKE and IPsec Packets", RFC 8229, DOI 10.17487/RFC8229, of IKE and IPsec Packets", RFC 8229, DOI 10.17487/RFC8229,
August 2017, <https://www.rfc-editor.org/info/rfc8229>. August 2017, <https://www.rfc-editor.org/rfc/rfc8229>.
[RFC8260] Stewart, R., Tuexen, M., Loreto, S., and R. Seggelmann, [RFC8260] Stewart, R., Tuexen, M., Loreto, S., and R. Seggelmann,
"Stream Schedulers and User Message Interleaving for the "Stream Schedulers and User Message Interleaving for the
Stream Control Transmission Protocol", RFC 8260, Stream Control Transmission Protocol", RFC 8260,
DOI 10.17487/RFC8260, November 2017, DOI 10.17487/RFC8260, November 2017,
<https://www.rfc-editor.org/info/rfc8260>. <https://www.rfc-editor.org/rfc/rfc8260>.
[RFC8293] Ghanwani, A., Dunbar, L., McBride, M., Bannai, V., and R. [RFC8293] Ghanwani, A., Dunbar, L., McBride, M., Bannai, V., and R.
Krishnan, "A Framework for Multicast in Network Krishnan, "A Framework for Multicast in Network
Virtualization over Layer 3", RFC 8293, Virtualization over Layer 3", RFC 8293,
DOI 10.17487/RFC8293, January 2018, DOI 10.17487/RFC8293, January 2018,
<https://www.rfc-editor.org/info/rfc8293>. <https://www.rfc-editor.org/rfc/rfc8293>.
[RFC8489] Petit-Huguenin, M., Salgueiro, G., Rosenberg, J., Wing, [RFC8489] Petit-Huguenin, M., Salgueiro, G., Rosenberg, J., Wing,
D., Mahy, R., and P. Matthews, "Session Traversal D., Mahy, R., and P. Matthews, "Session Traversal
Utilities for NAT (STUN)", RFC 8489, DOI 10.17487/RFC8489, Utilities for NAT (STUN)", RFC 8489, DOI 10.17487/RFC8489,
February 2020, <https://www.rfc-editor.org/info/rfc8489>. February 2020, <https://www.rfc-editor.org/rfc/rfc8489>.
[RFC8546] Trammell, B. and M. Kuehlewind, "The Wire Image of a [RFC8546] Trammell, B. and M. Kuehlewind, "The Wire Image of a
Network Protocol", RFC 8546, DOI 10.17487/RFC8546, April Network Protocol", RFC 8546, DOI 10.17487/RFC8546, April
2019, <https://www.rfc-editor.org/info/rfc8546>. 2019, <https://www.rfc-editor.org/rfc/rfc8546>.
[RFC8622] Bless, R., "A Lower-Effort Per-Hop Behavior (LE PHB) for [RFC8622] Bless, R., "A Lower-Effort Per-Hop Behavior (LE PHB) for
Differentiated Services", RFC 8622, DOI 10.17487/RFC8622, Differentiated Services", RFC 8622, DOI 10.17487/RFC8622,
June 2019, <https://www.rfc-editor.org/info/rfc8622>. June 2019, <https://www.rfc-editor.org/rfc/rfc8622>.
[RFC8699] Islam, S., Welzl, M., and S. Gjessing, "Coupled Congestion [RFC8699] Islam, S., Welzl, M., and S. Gjessing, "Coupled Congestion
Control for RTP Media", RFC 8699, DOI 10.17487/RFC8699, Control for RTP Media", RFC 8699, DOI 10.17487/RFC8699,
January 2020, <https://www.rfc-editor.org/info/rfc8699>. January 2020, <https://www.rfc-editor.org/rfc/rfc8699>.
[RFC8838] Ivov, E., Uberti, J., and P. Saint-Andre, "Trickle ICE:
Incremental Provisioning of Candidates for the Interactive
Connectivity Establishment (ICE) Protocol", RFC 8838,
DOI 10.17487/RFC8838, January 2021,
<https://www.rfc-editor.org/rfc/rfc8838>.
[RFC8899] Fairhurst, G., Jones, T., Tüxen, M., Rüngeler, I., and T. [RFC8899] Fairhurst, G., Jones, T., Tüxen, M., Rüngeler, I., and T.
Völker, "Packetization Layer Path MTU Discovery for Völker, "Packetization Layer Path MTU Discovery for
Datagram Transports", RFC 8899, DOI 10.17487/RFC8899, Datagram Transports", RFC 8899, DOI 10.17487/RFC8899,
September 2020, <https://www.rfc-editor.org/info/rfc8899>. September 2020, <https://www.rfc-editor.org/rfc/rfc8899>.
[RFC8922] Enghardt, T., Pauly, T., Perkins, C., Rose, K., and C. [RFC8922] Enghardt, T., Pauly, T., Perkins, C., Rose, K., and C.
Wood, "A Survey of the Interaction between Security Wood, "A Survey of the Interaction between Security
Protocols and Transport Services", RFC 8922, Protocols and Transport Services", RFC 8922,
DOI 10.17487/RFC8922, October 2020, DOI 10.17487/RFC8922, October 2020,
<https://www.rfc-editor.org/info/rfc8922>. <https://www.rfc-editor.org/rfc/rfc8922>.
[RFC8923] Welzl, M. and S. Gjessing, "A Minimal Set of Transport [RFC8923] Welzl, M. and S. Gjessing, "A Minimal Set of Transport
Services for End Systems", RFC 8923, DOI 10.17487/RFC8923, Services for End Systems", RFC 8923, DOI 10.17487/RFC8923,
October 2020, <https://www.rfc-editor.org/info/rfc8923>. October 2020, <https://www.rfc-editor.org/rfc/rfc8923>.
[TCP-COUPLING] [TCP-COUPLING]
Islam, S., Welzl, M., Hiorth, K., Hayes, D., Armitage, G., Islam, S., Welzl, M., Hiorth, K., Hayes, D., Armitage, G.,
and S. Gjessing, "ctrlTCP: Reducing Latency through and S. Gjessing, "ctrlTCP: Reducing Latency through
Coupled, Heterogeneous Multi-Flow TCP Congestion Control", Coupled, Heterogeneous Multi-Flow TCP Congestion Control",
IEEE INFOCOM Global Internet Symposium (GI) workshop (GI IEEE INFOCOM Global Internet Symposium (GI) workshop (GI
2018) , 2018. 2018) , 2018.
Appendix A. Implementation Mapping Appendix A. Implementation Mapping
The way the concepts from this abstract interface map into concrete The way the concepts from this abstract API map into concrete APIs in
APIs in a given language on a given platform largely depends on the a given language on a given platform largely depends on the features
features and norms of the language and the platform. Actions could and norms of the language and the platform. Actions could be
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 event queues, handler functions or classes, could be implemented via event queues, handler functions or classes,
communicating sequential processes, or other asynchronous calling communicating sequential processes, or other asynchronous calling
conventions. conventions.
A.1. Types A.1. Types
The basic types mentioned in Section 1.1 typically have natural The basic types mentioned in Section 1.1 typically have natural
correspondences in practical programming languages, perhaps correspondences in practical programming languages, perhaps
constrained by implementation-specific limitations. For example: constrained by implementation-specific limitations. For example:
* An Integer can typically be represented in C by an "int" or * An Integer can typically be represented in C by an int or long,
"long", subject to the underlying platform's ranges for each. To subject to the underlying platform's ranges for each.
accommodate special values, a C function that returns a non-
negative "int" on success may return -1 on failure. In Python,
such a function might return "None" or raise an exception.
* In C, a Tuple may be represented as a "struct" with one member for * In C, a Tuple may be represented as a struct with one member for
each of the value types in the ordered grouping. In Python, by each of the value types in the ordered grouping. In Python, by
contrast, a Tuple may be represented natively as a "tuple", a contrast, a Tuple may be represented natively as a tuple, a
sequence of dynamically-typed elements. sequence of dynamically-typed elements.
* A Collection may be represented as a "std::set" in C++ or as a * A Collection may be represented as a std::set in C++ or as a set
"set" in Python. In C, it may be represented as an array or as a in Python. In C, it may be represented as an array or as a
higher-level data structure with appropriate accessors defined. higher-level data structure with appropriate accessors defined.
The objects described in Section 1.1 can similarly be represented in The objects described in Section 1.1 can similarly be represented in
different ways depending on which programming language is used. different ways depending on which programming language is used.
Objects like Preconnections, Connections, and Listeners can be long- Objects like Preconnections, Connections, and Listeners can be long-
lived, and benefit from using object-oriented constructs. Note that lived, and benefit from using object-oriented constructs. Note that
in C, these objects may need to provide a way to release or free in C, these objects may need to provide a way to release or free
their underlying memory when the application is done using them. For their underlying memory when the application is done using them. For
example, since a Preconnection can be used to initiate multiple example, since a Preconnection can be used to initiate multiple
Connections, it is the responsibility of the application to clean up Connections, it is the responsibility of the application to clean up
the Preconnection memory if necessary. the Preconnection memory if necessary.
A.2. Events and Errors A.2. Events and Errors
This specification treats Events and Errors similarly. Errors, just This specification treats Events and Errors similarly. Errors, just
as any other Events, may occur asynchronously in network as any other Events, may occur asynchronously in network
applications. However, implementations of this interface may report applications. However, implementations of this API may report Errors
Errors synchronously, according to the error handling idioms of the synchronously, according to the error handling idioms of the
implementation platform, where they can be immediately detected, such implementation platform, where they can be immediately detected, such
as by generating an exception when attempting to initiate a as by generating an exception when attempting to initiate a
connection with inconsistent Transport Properties. An error can connection with inconsistent Transport Properties. An error can
provide an optional reason to the application with further details provide an optional reason to the application with further details
about why the error occurred. about why the error occurred.
A.3. Time Duration A.3. Time Duration
Time duration types are implementation-specific. For instance, it Time duration types are implementation-specific. For instance, it
could be a number of seconds, number of milliseconds, or a "struct could be a number of seconds, number of milliseconds, or a struct
timeval" in C or a user-defined "Duration" class in C++. timeval in C or a user-defined Duration class in C++.
Appendix B. Convenience Functions Appendix B. Convenience Functions
B.1. Adding Preference Properties B.1. Adding Preference Properties
As Selection Properties of type "Preference" will be set on a As Selection Properties of type Preference will be set on a
TransportProperties object quite frequently, implementations can TransportProperties object quite frequently, implementations can
provide special actions for adding each preference level i.e, provide special actions for adding each preference level i.e,
"TransportProperties.Set(some_property, avoid)" is equivalent to TransportProperties.Set(some_property, avoid) is equivalent to
"TransportProperties.Avoid(some_property)": TransportProperties.Avoid(some_property):
TransportProperties.Require(property) TransportProperties.Require(property)
TransportProperties.Prefer(property) TransportProperties.Prefer(property)
TransportProperties.Ignore(property) TransportProperties.Ignore(property)
TransportProperties.Avoid(property) TransportProperties.Avoid(property)
TransportProperties.Prohibit(property) TransportProperties.Prohibit(property)
B.2. Transport Property Profiles B.2. Transport Property Profiles
To ease the use of the interface specified by this document, To ease the use of the Transport Services API specified by this
implementations can provide a mechanism to create Transport Property document, implementations can provide a mechanism to create Transport
objects (see Section 6.2) that are pre-configured with frequently Property objects (see Section 6.2) that are pre-configured with
used sets of properties; the following are in common use in current frequently used sets of properties; the following are in common use
applications: in current applications:
B.2.1. reliable-inorder-stream B.2.1. reliable-inorder-stream
This profile provides reliable, in-order transport service with This profile provides reliable, in-order transport service with
congestion control. TCP is an example of a protocol that provides congestion control. TCP is an example of a protocol that provides
this service. It should consist of the following properties: this service. It should consist of the following properties:
+=======================+=========+ +=======================+=========+
| Property | Value | | Property | Value |
+=======================+=========+ +=======================+=========+
skipping to change at page 80, line 17 skipping to change at page 85, line 22
[RFC8923] identifies a minimal set of transport services that end [RFC8923] identifies a minimal set of transport services that end
systems should offer. These services make all non-security-related systems should offer. These services make all non-security-related
transport features of TCP, MPTCP, UDP, UDP-Lite, SCTP and LEDBAT transport features of TCP, MPTCP, UDP, UDP-Lite, SCTP and LEDBAT
available that 1) require interaction with the application, and 2) do available that 1) require interaction with the application, and 2) do
not get in the way of a possible implementation over TCP (or, with not get in the way of a possible implementation over TCP (or, with
limitations, UDP). The following text explains how this minimal set limitations, UDP). The following text explains how this minimal set
is reflected in the present API. For brevity, it is based on the is reflected in the present API. For brevity, it is based on the
list in Section 4.1 of [RFC8923], updated according to the discussion list in Section 4.1 of [RFC8923], updated according to the discussion
in Section 5 of [RFC8923]. The present API covers all elements of in Section 5 of [RFC8923]. The present API covers all elements of
this section except "Notification of Excessive Retransmissions (early this section. This list is a subset of the transport features in
warning below abortion threshold)". This list is a subset of the Appendix A of [RFC8923], which refers to the primitives in "pass 2"
transport features in Appendix A of [RFC8923], which refers to the (Section 4) of [RFC8303] for further details on the implementation
primitives in "pass 2" (Section 4) of [RFC8303] for further details with TCP, MPTCP, UDP, UDP-Lite, SCTP and LEDBAT.
on the implementation with TCP, MPTCP, UDP, UDP-Lite, SCTP and
LEDBAT.
* Connect: "Initiate" Action (Section 7.1). * Connect: Initiate Action (Section 7.1).
* Listen: "Listen" Action (Section 7.2). * Listen: Listen Action (Section 7.2).
* Specify number of attempts and/or timeout for the first * Specify number of attempts and/or timeout for the first
establishment message: "timeout" parameter of "Initiate" establishment message: timeout parameter of Initiate (Section 7.1)
(Section 7.1) or "InitiateWithSend" Action (Section 9.2.5). or InitiateWithSend Action (Section 9.2.5).
* Disable MPTCP: "Multipath Transport" Property (Section 6.2.14). * Disable MPTCP: multipath Property (Section 6.2.14).
* Hand over a message to reliably transfer (possibly multiple times) * Hand over a message to reliably transfer (possibly multiple times)
before connection establishment: "InitiateWithSend" Action before connection establishment: InitiateWithSend Action
(Section 9.2.5). (Section 9.2.5).
* Change timeout for aborting connection (using retransmit limit or * Change timeout for aborting connection (using retransmit limit or
time value): "Timeout for Aborting Connection" property, using a time value): connTimeout property, using a time value
time value (Section 8.1.3). (Section 8.1.3).
* Timeout event when data could not be delivered for too long: * Timeout event when data could not be delivered for too long:
"ConnectionError" Event (Section 10). ConnectionError Event (Section 10).
* Suggest timeout to the peer: "TCP-specific Properties: User * Suggest timeout to the peer: See "TCP-specific Properties: User
Timeout Option (UTO)" (Section 8.2). Timeout Option (UTO)" (Section 8.2).
* Notification of ICMP error message arrival: "Notification of ICMP * Notification of ICMP error message arrival: softErrorNotify
soft error message arrival" property (Section 6.2.17). (Section 6.2.17) and SoftError Event (Section 8.3.1).
* Choose a scheduler to operate between streams of an association: * Choose a scheduler to operate between streams of an association:
"Connection Group Transmission Scheduler" property connScheduler property (Section 8.1.5).
(Section 8.1.5).
* Configure priority or weight for a scheduler: "Connection * Configure priority or weight for a scheduler: connPriority
Priority" property (Section 8.1.2). property (Section 8.1.2).
* "Specify checksum coverage used by the sender" and "Disable * "Specify checksum coverage used by the sender" and "Disable
checksum when sending": "Sending Corruption Protection Length" checksum when sending": msgChecksumLen property (Section 9.1.3.6)
property (Section 9.1.3.6) and "Full Checksum Coverage on Sending" and fullChecksumSend property (Section 6.2.7).
property (Section 6.2.7).
* "Specify minimum checksum coverage required by receiver" and * "Specify minimum checksum coverage required by receiver" and
"Disable checksum requirement when receiving": "Required Minimum "Disable checksum requirement when receiving": recvChecksumLen
Corruption Protection Coverage for Receiving" property property (Section 8.1.1) and fullChecksumRecv property
(Section 8.1.1) and "Full Checksum Coverage on Receiving" property
(Section 6.2.8). (Section 6.2.8).
* "Specify DF field": "No Network-Layer Fragmentation" property * "Specify DF field": noFragmentation property (Section 9.1.3.9).
(Section 9.1.3.9).
* Get max. transport-message size that may be sent using a non- * Get max. transport-message size that may be sent using a non-
fragmented IP packet from the configured interface: "Maximum fragmented IP packet from the configured interface:
Message Size Before Fragmentation or Segmentation" property singularTransmissionMsgMaxLen property (Section 8.1.11.2).
(Section 8.1.11.2).
* Get max. transport-message size that may be received from the * Get max. transport-message size that may be received from the
configured interface: "Maximum Message Size on Receive" property configured interface: recvMsgMaxLen property (Section 8.1.11.4).
(Section 8.1.11.4).
* Obtain ECN field: "UDP(-Lite)-specific Property: ECN" is a read- * Obtain ECN field: This is a read-only Message Property of the
only Message Property of the MessageContext object MessageContext object (see "UDP(-Lite)-specific Property: ECN"
(Section 9.3.3.1). Section 9.3.3.1).
* "Specify DSCP field", "Disable Nagle algorithm", "Enable and * "Specify DSCP field", "Disable Nagle algorithm", "Enable and
configure a "Low Extra Delay Background Transfer"": as suggested configure a Low Extra Delay Background Transfer": as suggested in
in Section 5.5 of [RFC8923], these transport features are Section 5.5 of [RFC8923], these transport features are
collectively offered via the "Capacity Profile" property collectively offered via the connCapacityProfile property
(Section 8.1.6). Per-Message control ("Request not to bundle (Section 8.1.6). Per-Message control ("Request not to bundle
messages") is offered via the "Message Capacity Profile Override" messages") is offered via the msgCapacityProfile property
property (Section 9.1.3.8). (Section 9.1.3.8).
* Close after reliably delivering all remaining data, causing an * Close after reliably delivering all remaining data, causing an
event informing the application on the other side: this is offered event informing the application on the other side: this is offered
by the "Close" Action with slightly changed semantics in line with by the Close Action with slightly changed semantics in line with
the discussion in Section 5.2 of [RFC8923] (Section 10). the discussion in Section 5.2 of [RFC8923] (Section 10).
* "Abort without delivering remaining data, causing an event * "Abort without delivering remaining data, causing an event
informing the application on the other side" and "Abort without informing the application on the other side" and "Abort without
delivering remaining data, not causing an event informing the delivering remaining data, not causing an event informing the
application on the other side": this is offered by the "Abort" application on the other side": this is offered by the Abort
action without promising that this is signaled to the other side. action without promising that this is signaled to the other side.
If it is, a "ConnectionError" Event will fire at the peer If it is, a ConnectionError Event will be invoked at the peer
(Section 10). (Section 10).
* "Reliably transfer data, with congestion control", "Reliably * "Reliably transfer data, with congestion control", "Reliably
transfer a message, with congestion control" and "Unreliably transfer a message, with congestion control" and "Unreliably
transfer a message": data is transferred via the "Send" action transfer a message": data is transferred via the Send action
(Section 9.2). Reliability is controlled via the "Reliable Data (Section 9.2). Reliability is controlled via the reliability
Transfer (Connection)" (Section 6.2.1) property and the "Reliable (Section 6.2.1) property and the msgReliable Message Property
Data Transfer (Message)" Message Property (Section 9.1.3.7). (Section 9.1.3.7). Transmitting data as a message or without
Transmitting data as a message or without delimiters is controlled delimiters is controlled via Message Framers (Section 9.1.2). The
via Message Framers (Section 9.1.2). The choice of congestion choice of congestion control is provided via the congestionControl
control is provided via the "Congestion control" property property (Section 6.2.9).
(Section 6.2.9).
* Configurable Message Reliability: the "Lifetime" Message Property * Configurable Message Reliability: the msgLifetime Message Property
implements a time-based way to configure message reliability implements a time-based way to configure message reliability
(Section 9.1.3.1). (Section 9.1.3.1).
* "Ordered message delivery (potentially slower than unordered)" and * "Ordered message delivery (potentially slower than unordered)" and
"Unordered message delivery (potentially faster than ordered)": "Unordered message delivery (potentially faster than ordered)":
these two transport features are controlled via the Message these two transport features are controlled via the Message
Property "Ordered" (Section 9.1.3.3). Property msgOrdered (Section 9.1.3.3).
* Request not to delay the acknowledgement (SACK) of a message: * Request not to delay the acknowledgement (SACK) of a message:
should the protocol support it, this is one of the transport should the protocol support it, this is one of the transport
features the Transport Services system can apply when an features the Transport Services system can apply when an
application uses the "Capacity Profile" Property (Section 8.1.6) application uses the connCapacityProfile Property (Section 8.1.6)
or the "Message Capacity Profile Override" Message Property or the msgCapacityProfile Message Property (Section 9.1.3.8) with
(Section 9.1.3.8) with value "Low Latency/Interactive". value Low Latency/Interactive.
* Receive data (with no message delimiting): "Receive" Action * Receive data (with no message delimiting): Receive Action
(Section 9.3) and "Received" Event (Section 9.3.2.1). (Section 9.3) and Received Event (Section 9.3.2.1).
* Receive a message: "Receive" Action (Section 9.3) and "Received" * Receive a message: Receive Action (Section 9.3) and Received Event
Event (Section 9.3.2.1), using Message Framers (Section 9.1.2). (Section 9.3.2.1), using Message Framers (Section 9.1.2).
* Information about partial message arrival: "Receive" Action * Information about partial message arrival: Receive Action
(Section 9.3) and "ReceivedPartial" Event (Section 9.3.2.2). (Section 9.3) and ReceivedPartial Event (Section 9.3.2.2).
* Notification of send failures: "Expired" Event (Section 9.2.2.2) * Notification of send failures: Expired Event (Section 9.2.2.2) and
and "SendError" Event (Section 9.2.2.3). SendError Event (Section 9.2.2.3).
* Notification that the stack has no more user data to send: * Notification that the stack has no more user data to send:
applications can obtain this information via the "Sent" Event applications can obtain this information via the Sent Event
(Section 9.2.2.1). (Section 9.2.2.1).
* Notification to a receiver that a partial message delivery has * Notification to a receiver that a partial message delivery has
been aborted: "ReceiveError" Event (Section 9.3.2.3). been aborted: ReceiveError Event (Section 9.3.2.3).
* Notification of Excessive Retransmissions (early warning below
abortion threshold): SoftError Event (Section 8.3.1).
Authors' Addresses Authors' Addresses
Brian Trammell (editor) Brian Trammell (editor)
Google Switzerland GmbH Google Switzerland GmbH
Gustav-Gull-Platz 1 Gustav-Gull-Platz 1
CH- 8004 Zurich CH- 8004 Zurich
Switzerland Switzerland
Email: ietf@trammell.ch Email: ietf@trammell.ch
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