draft-ietf-mmusic-trickle-ice-sip-11.txt   draft-ietf-mmusic-trickle-ice-sip-12.txt 
Network Working Group E. Ivov Network Working Group E. Ivov
Internet-Draft Jitsi Internet-Draft Jitsi
Intended status: Standards Track T. Stach Intended status: Standards Track T. Stach
Expires: May 17, 2018 Unaffiliated Expires: June 25, 2018 Unaffiliated
E. Marocco E. Marocco
Telecom Italia Telecom Italia
C. Holmberg C. Holmberg
Ericsson Ericsson
November 13, 2017 December 22, 2017
A Session Initiation Protocol (SIP) usage for Trickle ICE A Session Initiation Protocol (SIP) usage for Trickle ICE
draft-ietf-mmusic-trickle-ice-sip-11 draft-ietf-mmusic-trickle-ice-sip-12
Abstract Abstract
The Interactive Connectivity Establishment (ICE) protocol describes a The Interactive Connectivity Establishment (ICE) protocol describes a
Network Address Translator (NAT) traversal mechanism for UDP-based Network Address Translator (NAT) traversal mechanism for UDP-based
multimedia sessions established with the Offer/Answer model. The ICE multimedia sessions established with the Offer/Answer model. The ICE
extension for Incremental Provisioning of Candidates (Trickle ICE) extension for Incremental Provisioning of Candidates (Trickle ICE)
defines a mechanism that allows ICE Agents to shorten session defines a mechanism that allows ICE Agents to shorten session
establishment delays by making the candidate gathering and establishment delays by making the candidate gathering and
connectivity checking phases of ICE non-blocking and by executing connectivity checking phases of ICE non-blocking and by executing
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
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and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on May 17, 2018. This Internet-Draft will expire on June 25, 2018.
Copyright Notice Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of (https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 4 3. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 4
3.1. Discovery issues . . . . . . . . . . . . . . . . . . . . 5 3.1. Discovery issues . . . . . . . . . . . . . . . . . . . . 5
3.2. Relationship with the Offer/Answer Model . . . . . . . . 6 3.2. Relationship with the Offer/Answer Model . . . . . . . . 6
4. Incremental Signaling of ICE candidates . . . . . . . . . . . 7 4. Incremental Signaling of ICE candidates . . . . . . . . . . . 7
4.1. Initial Offer/Answer exchange . . . . . . . . . . . . . . 8 4.1. Initial Offer/Answer exchange . . . . . . . . . . . . . . 8
4.1.1. Sending the initial Offer . . . . . . . . . . . . . . 8 4.1.1. Sending the initial Offer . . . . . . . . . . . . . . 8
4.1.2. Receiving the initial Offer . . . . . . . . . . . . . 9 4.1.2. Receiving the initial Offer . . . . . . . . . . . . . 9
4.1.3. Sending the initial Answer . . . . . . . . . . . . . 9 4.1.3. Sending the initial Answer . . . . . . . . . . . . . 9
4.1.4. Receiving the initial Answer . . . . . . . . . . . . 9 4.1.4. Receiving the initial Answer . . . . . . . . . . . . 10
4.2. Establishing the dialog . . . . . . . . . . . . . . . . . 9 4.2. Subsequent Offer/Answer exchanges . . . . . . . . . . . . 10
4.2.1. Asserting dialog state through reliable Offer/Answer 4.3. Establishing the dialog . . . . . . . . . . . . . . . . . 10
delivery . . . . . . . . . . . . . . . . . . . . . . 10 4.3.1. Establishing dialog state through reliable
4.2.2. Asserting dialog state through unreliable Offer/Answer delivery . . . . . . . . . . . . . . . . 11
Offer/Answer delivery . . . . . . . . . . . . . . . . 10 4.3.2. Establishing dialog state through unreliable
4.2.3. Initiating Trickle ICE without an SDP Answer . . . . 12 Offer/Answer delivery . . . . . . . . . . . . . . . . 12
4.2.4. Considerations for 3PCC . . . . . . . . . . . . . . . 14 4.3.3. Initiating Trickle ICE without an SDP Answer . . . . 14
4.3. Delivering candidates in INFO messages . . . . . . . . . 15 4.3.4. Considerations for Third Party Call Control . . . . . 15
5. Initial discovery of Trickle ICE support . . . . . . . . . . 19 4.4. Delivering candidates in INFO messages . . . . . . . . . 17
5.1. Provisioning support for Trickle ICE . . . . . . . . . . 20 5. Initial discovery of Trickle ICE support . . . . . . . . . . 21
5.2. Trickle ICE discovery with GRUU . . . . . . . . . . . . . 20 5.1. Provisioning support for Trickle ICE . . . . . . . . . . 22
5.3. Trickle ICE discovery through other protocols . . . . . . 21 5.2. Trickle ICE discovery with Globally Routable User Agent
5.4. Fall-back to Half Trickle . . . . . . . . . . . . . . . . 21 URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 22
6. Considerations for RTP and RTCP multiplexing . . . . . . . . 23 5.3. Fall-back to Half Trickle . . . . . . . . . . . . . . . . 23
7. Considerations for Media Multiplexing . . . . . . . . . . . . 25 6. Considerations for RTP and RTCP multiplexing . . . . . . . . 24
8. SDP 'end-of-candidate' Attribute . . . . . . . . . . . . . . 27 7. Considerations for Media Multiplexing . . . . . . . . . . . . 26
8.1. Defintion . . . . . . . . . . . . . . . . . . . . . . . . 27 8. SDP 'end-of-candidate' Attribute . . . . . . . . . . . . . . 29
8.2. Offer/Answer procedures . . . . . . . . . . . . . . . . . 27 8.1. Definition . . . . . . . . . . . . . . . . . . . . . . . 29
9. Content Type 'application/trickle-ice-sdpfrag' . . . . . . . 28 8.2. Offer/Answer procedures . . . . . . . . . . . . . . . . . 30
9.1. Overall Description . . . . . . . . . . . . . . . . . . . 28 9. Content Type 'application/trickle-ice-sdpfrag' . . . . . . . 30
9.2. Grammar . . . . . . . . . . . . . . . . . . . . . . . . . 28 9.1. Overall Description . . . . . . . . . . . . . . . . . . . 30
10. Info Package . . . . . . . . . . . . . . . . . . . . . . . . 30 9.2. Grammar . . . . . . . . . . . . . . . . . . . . . . . . . 30
10.1. Rationale - Why INFO? . . . . . . . . . . . . . . . . . 30 10. Info Package . . . . . . . . . . . . . . . . . . . . . . . . 32
10.2. Overall Description . . . . . . . . . . . . . . . . . . 31 10.1. Rationale - Why INFO? . . . . . . . . . . . . . . . . . 32
10.3. Applicability . . . . . . . . . . . . . . . . . . . . . 31 10.2. Overall Description . . . . . . . . . . . . . . . . . . 33
10.4. Info Package Name . . . . . . . . . . . . . . . . . . . 31 10.3. Applicability . . . . . . . . . . . . . . . . . . . . . 33
10.5. Info Package Parameters . . . . . . . . . . . . . . . . 31 10.4. Info Package Name . . . . . . . . . . . . . . . . . . . 33
10.6. SIP Option Tags . . . . . . . . . . . . . . . . . . . . 31 10.5. Info Package Parameters . . . . . . . . . . . . . . . . 33
10.7. Info Message Body Parts . . . . . . . . . . . . . . . . 32 10.6. SIP Option Tags . . . . . . . . . . . . . . . . . . . . 33
10.8. Info Package Usage Restrictions . . . . . . . . . . . . 32 10.7. Info Request Body Parts . . . . . . . . . . . . . . . . 34
10.9. Rate of INFO Requests . . . . . . . . . . . . . . . . . 32 10.8. Info Package Usage Restrictions . . . . . . . . . . . . 34
10.10. Info Package Security Considerations . . . . . . . . . . 32 10.9. Rate of INFO Requests . . . . . . . . . . . . . . . . . 34
11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 32 10.10. Info Package Security Considerations . . . . . . . . . . 34
11.1. SDP 'end-of-candidate' Attribute . . . . . . . . . . . . 32 11. Deployment Considerations . . . . . . . . . . . . . . . . . . 34
11.2. application/trickle-ice-sdpfrag Media Type . . . . . . . 33 12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 34
11.3. SIP Info Package 'trickle-ice' . . . . . . . . . . . . . 35 12.1. SDP 'end-of-candidate' Attribute . . . . . . . . . . . . 35
11.4. SIP Option Tag 'trickle-ice' . . . . . . . . . . . . . . 35 12.2. application/trickle-ice-sdpfrag Media Type . . . . . . . 35
12. Security Considerations . . . . . . . . . . . . . . . . . . . 35 12.3. SIP Info Package 'trickle-ice' . . . . . . . . . . . . . 37
13. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 35 12.4. SIP Option Tag 'trickle-ice' . . . . . . . . . . . . . . 37
14. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 36 13. Security Considerations . . . . . . . . . . . . . . . . . . . 38
15. References . . . . . . . . . . . . . . . . . . . . . . . . . 38 14. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 38
15.1. Normative References . . . . . . . . . . . . . . . . . . 38 15. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 38
15.2. Informative References . . . . . . . . . . . . . . . . . 40 16. References . . . . . . . . . . . . . . . . . . . . . . . . . 41
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 41 16.1. Normative References . . . . . . . . . . . . . . . . . . 41
16.2. Informative References . . . . . . . . . . . . . . . . . 44
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 44
1. Introduction 1. Introduction
The Interactive Connectivity Establishment protocol The Interactive Connectivity Establishment (ICE) protocol
[I-D.ietf-mmusic-rfc5245bis] describes a mechanism for NAT traversal [I-D.ietf-ice-rfc5245bis] describes a mechanism for Network Address
that consists of three main phases: a phase where an agent gathers a Translator (NAT) traversal that consists of three main phases.
set of candidate transport addresses (source IP address, port and
transport protocol), a second phase where these candidates are sent
to a remote agent. There, this gathering procedure is repeated and,
finally, a third phase starts where connectivity between all
candidates in both sets is checked (connectivity checks). Once these
phases have been completed, and only then, both agents can begin
communication. According to [I-D.ietf-mmusic-rfc5245bis] the three
phases above happen consecutively, in a blocking way, which can
introduce undesirable latency during session establishment.
The Trickle ICE extension [I-D.ietf-ice-trickle] defines generic During the first phase an agent gathers a set of candidate transport
semantics required for these ICE phases to happen simultaneously, in addresses (source IP address, port and transport protocol). This is
a non-blocking way and hence speed up session establishment. followed by a second phase where these candidates are sent to a
remote agent. There, the gathering procedure is repeated and
candidates are sent to the first agent. Finally, a third phase
starts where connectivity between all candidates in both sets is
checked (connectivity checks). Once these phases have been
completed, and only then, both agents can begin communication.
According to [I-D.ietf-ice-rfc5245bis] the three phases above happen
consecutively, in a blocking way, which can introduce undesirable
setup delay during session establishment. The Trickle ICE extension
[I-D.ietf-ice-trickle] defines generic semantics required for these
ICE phases to happen in a parallel, non-blocking way and hence speed
up session establishment.
This specification defines a usage of Trickle ICE with the Session This specification defines a usage of Trickle ICE with the Session
Initiation Protocol (SIP)[RFC3261]. It describes how ICE candidates Initiation Protocol (SIP)[RFC3261]. It describes how ICE candidates
are to be exchanged incrementally with SIP INFO requests [RFC6086] are to be exchanged incrementally with SIP INFO requests [RFC6086]
and how the Half Trickle and Full Trickle modes defined in and how the Half Trickle and Full Trickle modes defined in
[I-D.ietf-ice-trickle] are to be used by SIP User Agents (UAs) [I-D.ietf-ice-trickle] are to be used by SIP User Agents (UAs)
depending on their expectations for support of Trickle ICE by a depending on their expectations for support of Trickle ICE by a
remote agent. remote agent.
This document defines a new Info Package as specified in [RFC6086] This document defines a new Info Package as specified in [RFC6086]
for use with Trickle ICE. for use with Trickle ICE.
2. Terminology 2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
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[I-D.ietf-ice-trickle] are to be used by SIP User Agents (UAs) [I-D.ietf-ice-trickle] are to be used by SIP User Agents (UAs)
depending on their expectations for support of Trickle ICE by a depending on their expectations for support of Trickle ICE by a
remote agent. remote agent.
This document defines a new Info Package as specified in [RFC6086] This document defines a new Info Package as specified in [RFC6086]
for use with Trickle ICE. for use with Trickle ICE.
2. Terminology 2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
document are to be interpreted as described in [RFC2119]. "OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119], [RFC8174] when, and only when, they appear in all
capitals, as shown here.
This specification makes use of all terminology defined by the This specification makes use of terminology defined by the protocol
protocol for Interactive Connectivity Establishment in for Interactive Connectivity Establishment in
[I-D.ietf-mmusic-rfc5245bis] and its Trickle ICE extension [I-D.ietf-ice-rfc5245bis] and its Trickle ICE extension
[I-D.ietf-ice-trickle]. It is assumed that the reader will be [I-D.ietf-ice-trickle]. It is assumed that the reader will be
familiar with the terminology from both documents. familiar with the terminology from both documents.
3. Protocol Overview 3. Protocol Overview
When using ICE for SIP according to [I-D.ietf-mmusic-ice-sip-sdp] the When using ICE for SIP according to [I-D.ietf-mmusic-ice-sip-sdp] the
ICE candidates are exchanged solely via SDP Offer/Answer as per ICE candidates are exchanged solely via SDP Offer/Answer as per
[RFC3264]. This specification defines an additional mechanism where [RFC3264]. This specification defines an additional mechanism where
candidates can be exchanged using SIP INFO messages and a newly candidates can be exchanged using SIP INFO messages and a newly
defined Info Package [RFC6086]. This allows ICE candidates also to defined Info Package [RFC6086]. This allows ICE candidates also to
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| |<=======================>| | | |<=======================>| |
| | | | | | | |
| | 200 OK | | | | 200 OK | |
| |<------------------------| | | |<------------------------| |
| | ACK | | | | ACK | |
| |------------------------>| | | |------------------------>| |
| | | | | | | |
| |<===== MEDIA FLOWS =====>| | | |<===== MEDIA FLOWS =====>| |
| | | | | | | |
Note: SRFLX denotes server-reflexive candidates
Figure 1: Sample Trickle ICE scenario with SIP Figure 1: Sample Trickle ICE scenario with SIP
3.1. Discovery issues 3.1. Discovery issues
In order to benefit from Trickle ICE's full potential and reduce In order to benefit from Trickle ICE's full potential and reduce
session establishment latency to a minimum, Trickle ICE agents need session establishment latency to a minimum, Trickle ICE agents need
to generate SDP Offers and Answers that contain incomplete, to generate SDP Offers and Answers that contain incomplete,
potentially empty sets of candidates. Such Offers and Answers can potentially empty sets of candidates. Such Offers and Answers can
only be handled meaningfully by agents that actually support only be handled meaningfully by agents that actually support
incremental candidate provisioning, which implies the need to confirm incremental candidate provisioning, which implies the need to confirm
such support before actually using it. such support before actually using it.
Contrary to other protocols, like XMPP [RFC6120], where "in advance" Contrary to other protocols, where "in advance" capability discovery
capability discovery is widely implemented, the mechanisms that allow is widely implemented, the mechanisms that allow this for SIP (i.e.,
this for SIP (i.e., a combination of UA Capabilities [RFC3840] and a combination of UA Capabilities [RFC3840] and GRUU [RFC5627]) have
GRUU [RFC5627]) have only seen low levels of adoption. This presents only seen low levels of adoption. This presents an issue for Trickle
an issue for Trickle ICE implementations as SIP UAs do not have an ICE implementations as SIP UAs do not have an obvious means of
obvious means of verifying that their peer will support incremental verifying that their peer will support incremental candidate
candidate provisioning. provisioning.
The Half Trickle mode of operation defined in the Trickle ICE The Half Trickle mode of operation defined in the Trickle ICE
specification [I-D.ietf-ice-trickle] provides one way around this, by specification [I-D.ietf-ice-trickle] provides one way around this, by
requiring the first Offer to contain a complete set of local ICE requiring the first Offer to contain a complete set of local ICE
candidates and only using incremental provisioning of remote candidates and only using incremental provisioning of remote
candidates for the rest of the session. candidates for the rest of the session.
While using Half Trickle does provide a working solution it also While using Half Trickle does provide a working solution it also
comes at the price of increased latency. Section 5 therefore makes comes at the price of increased latency. Section 5 therefore makes
several alternative suggestions that enable SIP UAs to engage in Full several alternative suggestions that enable SIP UAs to engage in Full
Trickle right from their first Offer: Section 5.1 discusses the use Trickle right from their first Offer: Section 5.1 discusses the use
of on-line provisioning as a means of allowing use of Trickle ICE for of on-line provisioning as a means of allowing use of Trickle ICE for
all endpoints in controlled environments. Section 5.2 describes all endpoints in controlled environments. Section 5.2 describes
anticipatory discovery for implementations that actually do support anticipatory discovery for implementations that actually do support
GRUU and UA Capabilities and Section 5.4 discusses the implementation GRUU and UA Capabilities and Section 5.3 discusses the implementation
and use of Half Trickle by SIP UAs where none of the above are an and use of Half Trickle by SIP UAs where none of the above are an
option. option.
3.2. Relationship with the Offer/Answer Model 3.2. Relationship with the Offer/Answer Model
From the perspective of all SIP middle boxes and proxies, and with From the perspective of SIP middle boxes and proxies the Offer/Answer
the exception of the actual INFO messages, signaling in general and exchange looks partly similar for Trickle ICE as it would for regular
Offer/Answer exchanges in particular would look the same way for ICE for SIP [I-D.ietf-mmusic-ice-sip-sdp]. However, in order to have
Trickle ICE as they would for ICE for SIP the full picture of the candidate exchange, the newly introduced INFO
[I-D.ietf-mmusic-ice-sip-sdp]. messages need to be considered as well.
+-------------------------------+ +-------------------------------+ +-------------------------------+ +-------------------------------+
| Alice +--------------+ | | +--------------+ Bob | | Alice +--------------+ | | +--------------+ Bob |
| | Offer/Answer | | | | Offer/Answer | | | | Offer/Answer | | | | Offer/Answer | |
| +-------+ | Module | | | | Module | +-------+ | | +--------+ | Module | | | | Module | +--------+ |
| | ICE | +--------------+ | | +--------------+ | ICE | | | | ICE | +--------------+ | | +--------------+ | ICE | |
| | Agent | | | | | | Agent | | | | Module | | | | | | Module | |
| +-------+ | | | | +-------+ | | +--------+ | | | | +--------+ |
+-------------------------------+ +-------------------------------+ +-------------------------------+ +-------------------------------+
| | | | | | | |
| | INVITE (Offer) | | | | INVITE (Offer) | |
| |--------------------->| | | |--------------------->| |
| | 183 (Answer) | | | | 183 (Answer) | |
| |<---------------------| | | |<---------------------| |
| | | | | | | |
| | | |
| SIP INFO (more candidates) | | SIP INFO (more candidates) |
|----------------------------------------------------->| |----------------------------------------------------->|
skipping to change at page 7, line 36 skipping to change at page 7, line 36
|----------------------------------------------------->| |----------------------------------------------------->|
| STUN Binding Requests/Responses | | STUN Binding Requests/Responses |
|<-----------------------------------------------------| |<-----------------------------------------------------|
| | | |
Figure 2: Distinguishing between Trickle ICE and traditional Figure 2: Distinguishing between Trickle ICE and traditional
signaling. signaling.
From an architectural viewpoint, as displayed in Figure 2, exchanging From an architectural viewpoint, as displayed in Figure 2, exchanging
candidates through SIP INFO requests could be represented as candidates through SIP INFO requests could be represented as
signaling between ICE Agents and not between Offer/Answer modules of signaling between ICE modules and not between Offer/Answer modules of
SIP User Agents. Then, such INFO requests do not impact the state of SIP User Agents. Then, such INFO requests do not impact the state of
the Offer/Answer transaction other than providing additional the Offer/Answer transaction other than providing additional
candidates. Consequently, INFO requests are not considered Offers or candidates. Consequently, INFO requests are not considered Offers or
Answers. Nevertheless, candidates that have been exchanged using Answers. Nevertheless, candidates that have been exchanged using
INFO SHALL be included in subsequent Offers or Answers. The version INFO requests SHALL be included in subsequent Offers or Answers. The
number in the "o=" line of that subsequent offer would need to be version number in the "o=" line of that subsequent Offer would need
incremented by 1 per the rules in [RFC3264]. to be incremented by 1 per the rules in [RFC3264].
4. Incremental Signaling of ICE candidates 4. Incremental Signaling of ICE candidates
Trickle ICE Agents will construct Offers and Answers with ICE Trickle ICE Agents will exchange ICE descriptions compliant to
descriptions compliant to [I-D.ietf-ice-trickle] and the following [I-D.ietf-ice-trickle] via Offer/Answer procedures and/or INFO
additional SIP-specific additions: request bodies. This requires the following SIP-specific extensions:
1. Trickle ICE Agents MUST indicate support for Trickle ICE by 1. Trickle ICE Agents MUST indicate support for Trickle ICE by
including the SIP option-tag 'trickle-ice' in a SIP Supported: including the SIP option-tag 'trickle-ice' in a SIP Supported:
header field within all SIP INVITE requests and responses. header field within all SIP INVITE requests and responses.
2. Trickle ICE Agents MUST indicate support for Trickle ICE by 2. Trickle ICE Agents MUST indicate support for Trickle ICE by
including the ice-option 'trickle' within all SDP Offers and including the ice-option 'trickle' within all SDP Offers and
Answers in accordance to [I-D.ietf-ice-trickle]. Answers in accordance to [I-D.ietf-ice-trickle].
3. Trickle ICE Agents MAY include any number of ICE candidates, i.e. 3. Trickle ICE Agents MAY include any number of ICE candidates, i.e.
from zero to the complete set of candidates, in their initial from zero to the complete set of candidates, in their initial
Offer or Answer. If the complete candidate set is included Offer or Answer. If the complete candidate set is included
already in the initial Offer, this is called Half-Trickle. already in the initial Offer, this is called Half-Trickle.
4. Trickle ICE Agents MAY exchange additional ICE candidates using 4. Trickle ICE Agents MAY exchange additional ICE candidates using
INFO requests within an existing INVITE dialog usage (including INFO requests within an existing INVITE dialog usage (including
an early dialog) as specified in [RFC6086]. The INFO requests an early dialog) as specified in [RFC6086]. The INFO requests
carry an Info-Package: trickle-ice. Trickle ICE Agents MUST be carry an Info-Package: trickle-ice. Trickle ICE Agents MUST be
prepared to receive INFO requests within that same dialog usage, prepared to receive INFO requests within that same dialog usage,
containing additional candidates or an indication for the end of containing additional candidates and/or an indication that
such candidates. trickling of such candidates has ended.
5. Trickle ICE Agents MAY exchange additional ICE candidates before 5. Trickle ICE Agents MAY exchange additional ICE candidates before
the Answerer has sent the Answer provided that an invite dialog the Answerer has sent the Answer provided that an invite dialog
usage is established at both Trickle ICE Agents. Note that in usage is established at both Trickle ICE Agents. Note that in
case of forking multiple early dialogs will exist. case of forking multiple early dialogs may exist.
The following sections provide further details on how Trickle ICE The following sections provide further details on how Trickle ICE
Agents perform the initial Offers/Answers exchange and establish the Agents perform the initial Offers/Answers exchange (Section 4.1),
INVITE dialog usage such that they can trickle candidates. perform subsequent Offers/Answers exchanges (Section 4.2) and
establish the INVITE dialog usage (Section 4.3) such that they can
incrementally trickle candidates (Section 4.4).
4.1. Initial Offer/Answer exchange 4.1. Initial Offer/Answer exchange
4.1.1. Sending the initial Offer 4.1.1. Sending the initial Offer
If the Offerer includes candidates in its initial Offer, it MUST If the Offerer includes candidates in its initial Offer, it MUST
encode these candidates as specified in encode these candidates as specified in
[I-D.ietf-mmusic-ice-sip-sdp]. [I-D.ietf-mmusic-ice-sip-sdp].
If the Offerer wants to send its initial Offer before knowing any If the Offerer wants to send its initial Offer before knowing any
candidate of one or more media descriptions, it MUST include the candidate for one or more media descriptions, it MUST set the port to
following default values in the corresponding "m=" line. the default value '9' for these media descriptions. If the Offerer
does not want to include the host IP address in the corresponding
o The media field is set to 'audio'. c-line, e.g. due to privacy reasons, it SHOULD include a default
address in the c-line, which is set to the IPv4 address 0.0.0.0 or to
o The port value is set to '9'. the IPv6 equivalent ::.
o The proto value is set to 'RTP/AVP'.
In this case, the Offerer obviously cannot know the RTCP transport In this case, the Offerer obviously cannot know the RTCP transport
address and, thus, MUST NOT include the "a=rtcp" attribute [RFC6086]. address and, thus, MUST NOT include the "a=rtcp" attribute [RFC6086].
This avoids potential ICE mismatch (see This avoids potential ICE mismatch (see
[I-D.ietf-mmusic-ice-sip-sdp]) for the RTCP transport address. [I-D.ietf-mmusic-ice-sip-sdp]) for the RTCP transport address.
If the Offerer wants to use RTCP multiplexing [RFC5761] and/or If the Offerer wants to use RTCP multiplexing [RFC5761] and/or
exclusive RTCP multiplexing [I-D.ietf-mmusic-mux-exclusive], it still exclusive RTCP multiplexing [I-D.ietf-mmusic-mux-exclusive], it still
MUST include the "a=rtcp-mux" and/or "a=rctp-mux-only" attribute in will include the "a=rtcp-mux" and/or "a=rctp-mux-only" attribute in
the initial Offer. the initial Offer.
In any case, the Offerer MUST include the attribute a=ice- In any case, the Offerer MUST include the attribute "a=ice-
options:trickle in accordance to [I-D.ietf-ice-trickle]. options:trickle" in accordance to [I-D.ietf-ice-trickle] and MUST
include in each "m="-line a "a=mid:" attribute in accordance to
[RFC5888].
4.1.2. Receiving the initial Offer 4.1.2. Receiving the initial Offer
If the initial Offer included candidates, the Answerer MUST treat If the initial Offer included candidates, the Answerer uses these
these candidates as specified in [I-D.ietf-mmusic-ice-sip-sdp]. candidates to start ICE processing as specified in
[I-D.ietf-ice-trickle].
If the initial Offer included the attribute a=ice-options:trickle, If the initial Offer included the attribute a=ice-options:trickle,
the Answerer MUST be prepared for receiving trickled candidates later the Answerer MUST be prepared for receiving trickled candidates later
on. on.
In case of a "m=" lines with default values neither of the eventually In case of a "m/c=" line with default values none of the eventually
trickled candidates will match the default destination. This trickled candidates will match the default destination. This
situation MUST NOT cause an ICE mismatch (see situation MUST NOT cause an ICE mismatch (see
[I-D.ietf-mmusic-ice-sip-sdp]). [I-D.ietf-mmusic-ice-sip-sdp]).
4.1.3. Sending the initial Answer 4.1.3. Sending the initial Answer
Section Section 4.1.1 applies to the Answerer with the roles of If the Answerer includes candidates in its initial Answerer, it MUST
Offerer and Answer being swapped. encode these candidates as specified in
[I-D.ietf-mmusic-ice-sip-sdp].
If the Answerer wants to send its initial Answer before knowing any
candidate for one or more media descriptions, it MUST set the port to
the default value '9' for these media descriptions. If the Answerer
does not want to include the host IP address in the corresponding
c-line, e.g. due to privacy reasons, it SHOULD include a default
address in the c-line, which is set to the IPv4 address 0.0.0.0 or to
the IPv6 equivalent ::.
In this case, the Answerer obviously cannot know the RTCP transport
address and, thus, MUST NOT include the "a=rtcp" attribute [RFC6086].
This avoids potential ICE mismatch (see
[I-D.ietf-mmusic-ice-sip-sdp]) for the RTCP transport address.
If the Answerer accepts to use RTCP multiplexing [RFC5761] and/or
exclusive RTCP multiplexing [I-D.ietf-mmusic-mux-exclusive], it will
include the "a=rtcp-mux" attribute in the initial Answer.
In any case, the Answerer MUST include the attribute "a=ice-
options:trickle" in accordance to [I-D.ietf-ice-trickle] and MUST
include in each "m="-line a "a=mid:" attribute in accordance to
[RFC5888].
4.1.4. Receiving the initial Answer 4.1.4. Receiving the initial Answer
Section Section 4.1.2 applies to the Answerer with the roles of If the initial Answer included candidates, the Offerer uses these
Offerer and Answer being swapped. candidates to start ICE processing as specified in
[I-D.ietf-ice-trickle].
4.2. Establishing the dialog If the initial Answer included the attribute a=ice-options:trickle,
the Offerer MUST be prepared for receiving trickled candidates later
on.
In case of a "m/c=" line with default values none of the eventually
trickled candidates will match the default destination. This
situation MUST NOT cause an ICE mismatch (see
[I-D.ietf-mmusic-ice-sip-sdp]).
4.2. Subsequent Offer/Answer exchanges
Subsequent Offer/Answer exchanges are handled as for regular ICE (see
section 4.2 of [I-D.ietf-mmusic-ice-sip-sdp]).
If an Offer or Answer needs to be sent while the ICE agents are in
the middle of trickling section 4.2.1.2.1 of
[I-D.ietf-mmusic-ice-sip-sdp]) applies. This means that an ICE agent
includes candidate attributes for all local candidates it had
trickled previously for a specific media stream.
[RFC EDITOR NOTE: The section 4.2.1.2.1 in above sentence is correct
for version 16 of said I-D. Authors need to cross-check during
Auth48 since it could have have changed in the meantime.]
4.3. Establishing the dialog
In order to be able to start trickling, the following two conditions In order to be able to start trickling, the following two conditions
need to be satisfied at the SIP UAs: need to be satisfied at the SIP UAs:
o Trickle ICE support at the peer agent MUST be confirmed. o Trickle ICE support at the peer agent MUST be confirmed.
o The dialog at both peers MUST be in early or confirmed state. o The dialog at both peers MUST be in early or confirmed state.
Section 5 discusses in detail the various options for satisfying the Section 5 discusses in detail the various options for satisfying the
first of the above conditions. Regardless of those mechanisms, first of the above conditions. Regardless of those mechanisms,
however, agents are certain to have a clear understanding of whether however, agents are certain to have a clear understanding of whether
their peers support trickle ICE once an Offer and an Answer have been their peers support trickle ICE once an Offer and an Answer have been
exchanged, which also allows for ICE processing to commence (see exchanged, which also allows for ICE processing to commence (see
Figure 3). Figure 3).
4.2.1. Asserting dialog state through reliable Offer/Answer delivery 4.3.1. Establishing dialog state through reliable Offer/Answer delivery
Alice Bob Alice Bob
| | | |
| INVITE (Offer) | | INVITE (Offer) |
|------------------------>| |------------------------>|
| 183 (Answer) | | 183 (Answer) |
|<------------------------| |<------------------------|
| PRACK/OK | | PRACK/OK |
|------------------------>| |------------------------>|
| | | |
skipping to change at page 10, line 32 skipping to change at page 11, line 35
|and know that the dialog is in the early| |and know that the dialog is in the early|
|state. Send INFO! | |state. Send INFO! |
+----------------------------------------+ +----------------------------------------+
| | | |
| INFO/OK (+SRFLX Cand.) | | INFO/OK (+SRFLX Cand.) |
|------------------------>| |------------------------>|
| INFO/OK (+SRFLX Cand.) | | INFO/OK (+SRFLX Cand.) |
|<------------------------| |<------------------------|
| | | |
Note: SRFLX denotes server-reflexive candidates
Figure 3: SIP Offerer can freely trickle as soon as it receives an Figure 3: SIP Offerer can freely trickle as soon as it receives an
Answer. Answer.
As shown in Figure 3 satisfying both conditions is relatively trivial As shown in Figure 3 satisfying both conditions is relatively trivial
for ICE Agents that have sent an Offer in an INVITE and that have for ICE Agents that have sent an Offer in an INVITE and that have
received an Answer in a reliable provisional response. It is received an Answer in a reliable provisional response. It is
guaranteed to have confirmed support for Trickle ICE at the Answerer guaranteed to have confirmed support for Trickle ICE at the Answerer
(or lack thereof) and to have fully initialized the SIP dialog at (or lack thereof) and to have fully initialized the SIP dialog at
both ends. Offerers and Answerers (after receipt of the PRACK both ends. Offerers and Answerers (after receipt of the PRACK
request) in the above situation can therefore freely commence request) in the above situation can therefore freely commence
trickling within the newly established dialog. trickling within the newly established dialog.
4.2.2. Asserting dialog state through unreliable Offer/Answer delivery 4.3.2. Establishing dialog state through unreliable Offer/Answer
delivery
The situation is a bit more delicate for agents that have received an The situation is a bit more delicate for agents that have received an
Offer in an INVITE request and have sent an Answer in an unreliable Offer in an INVITE request and have sent an Answer in an unreliable
provisional response because, once the response has been sent, the provisional response because, once the response has been sent, the
Answerer does not know when or if it has been received (Figure 4). Answerer does not know when or if it has been received (Figure 4).
Alice Bob Alice Bob
| | | |
| INVITE (Offer) | | INVITE (Offer) |
|------------------------>| |------------------------>|
skipping to change at page 11, line 34 skipping to change at page 12, line 42
In order to clear this ambiguity as soon as possible, the Answerer In order to clear this ambiguity as soon as possible, the Answerer
needs to retransmit the provisional response with the exponential needs to retransmit the provisional response with the exponential
back-off timers described in [RFC3262]. These retransmissions MUST back-off timers described in [RFC3262]. These retransmissions MUST
cease on receipt of an INFO request or on transmission of the Answer cease on receipt of an INFO request or on transmission of the Answer
in a 2xx response. This is similar to the procedure described in in a 2xx response. This is similar to the procedure described in
section 8.1.1 of [I-D.ietf-mmusic-ice-sip-sdp] except that the STUN section 8.1.1 of [I-D.ietf-mmusic-ice-sip-sdp] except that the STUN
binding Request is replaced by the INFO request. binding Request is replaced by the INFO request.
[RFC EDITOR NOTE: The section 8.1.1 in above sentence is correct for [RFC EDITOR NOTE: The section 8.1.1 in above sentence is correct for
version 14 of said I-D. Please cross-check since it could have have version 16 of said I-D. Authors need to cross-check during Auth48
changed in the meantime.] since it could have have changed in the meantime.]
The Offerer MUST send a Trickle ICE INFO request as soon as it The Offerer MUST send a Trickle ICE INFO request as soon as it
receives an SDP Answer in an unreliable provisional response. This receives an SDP Answer in an unreliable provisional response. This
INFO request MUST repeat the candidates that were already provided in INFO request MUST repeat the candidates that were already provided in
the Offer (as would be the case when Half Trickle is performed or the Offer (as would be the case when Half Trickle is performed or
when new candidates have not been learned since then) and/or they MAY when new candidates have not been learned since then).
also deliver newly learned candidates (if available). The Offerer
MAY include an end-of-candidates attribute in case candidate If available, the Offerer SHOULD also deliver newly learned
discovery has ended in the mean time. candidates in this INFO request, unless it wants to hold back some
candidates in reserve, e.g. in case that these candidates are
expensive to use and would only be trickled if all other candidates
failed.
The Offerer SHOULD include an end-of-candidates attribute in case
candidate discovery has ended in the mean time and no further
candidates are to be trickled.
As soon as an Answerer has received such an INFO request, the As soon as an Answerer has received such an INFO request, the
Answerer has an indication that a dialog is established at both ends Answerer has an indication that a dialog is established at both ends
and MAY begin trickling (Figure 5). and can begin trickling (Figure 5).
Note: The +SRFLX in Figure 5 indicates that additionally newly Note: The +SRFLX in Figure 5 indicates that additionally newly
learned server-reflexive candidates are included. learned server-reflexive candidates are included.
Alice Bob Alice Bob
| | | |
| INVITE (Offer) | | INVITE (Offer) |
|------------------------>| |------------------------>|
| 183 (Answer) | | 183 (Answer) |
|<------------------------| |<------------------------|
skipping to change at page 12, line 24 skipping to change at page 13, line 38
| +----------------------+ | +----------------------+
| |Bob: Now I know Alice| | |Bob: Now I know Alice|
| | is ready. Send INFO! | | | is ready. Send INFO! |
| +----------------------+ | +----------------------+
| INFO/OK (+SRFLX Cand.) | | INFO/OK (+SRFLX Cand.) |
|<------------------------| |<------------------------|
| | | |
| 200/ACK (Answer) | | 200/ACK (Answer) |
|<------------------------| |<------------------------|
Note: SRFLX denotes server-reflexive candidates
Figure 5: A SIP UA that received an INFO request after sending an Figure 5: A SIP UA that received an INFO request after sending an
unreliable provisional response knows that the dialog at the side of unreliable provisional response knows that the dialog at the side of
the receiver has entered the early state the receiver has entered the early state
When sending the Answer in the 200 OK response to the INVITE request, When sending the Answer in the 200 OK response to the INVITE request,
the Answerer MUST repeat exactly the same Answer that was previously the Answerer needs to repeat exactly the same Answer that was
sent in the unreliable provisional response in order to fulfill the previously sent in the unreliable provisional response in order to
corresponding requirements in [RFC3264]. Thus, the Offerer needs to fulfill the corresponding requirements in [RFC3264]. Thus, the
be prepared for receiving a different number of candidates in that Offerer needs to be prepared for receiving a different number of
repeated Answer than previously exchanged via trickling and MUST candidates in that repeated Answer than previously exchanged via
ignore the candidate information in that 200 OK response. trickling and MUST ignore the candidate information in that 200 OK
response.
4.2.3. Initiating Trickle ICE without an SDP Answer 4.3.3. Initiating Trickle ICE without an SDP Answer
The possibility to convey arbitrary candidates in INFO message bodies The ability to convey arbitrary candidates in INFO message bodies
allows ICE Agents to initiate trickling without actually sending an allows ICE Agents to initiate trickling without actually sending an
Answer. Trickle ICE Agents MAY therefore respond to an INVITE Answer. Trickle ICE Agents can therefore respond to an INVITE
request with provisional responses without an SDP Answer. Such request with provisional responses without an SDP Answer [RFC3261].
provisional responses serve for establishing an early dialog. Such provisional responses serve for establishing an early dialog.
Agents that choose to establish the dialog in this way, MUST Agents that choose to establish the dialog in this way, MUST
retransmit these responses with the exponential back-off timers retransmit these responses with the exponential back-off timers
described in [RFC3262]. These retransmissions MUST cease on receipt described in [RFC3262]. These retransmissions MUST cease on receipt
of an INFO request or on transmission of the Answer in a 2xx of an INFO request or on transmission of the Answer in a 2xx
response. This is again similar to the procedure described in response. This is again similar to the procedure described in
section 8.1.1 of [I-D.ietf-mmusic-ice-sip-sdp] except that an Answer section 8.1.1 of [I-D.ietf-mmusic-ice-sip-sdp] except that an Answer
is not yet provided. is not yet provided.
[RFC EDITOR NOTE: The section 8.1.1 in above sentence is correct for [RFC EDITOR NOTE: The section 8.1.1 in above sentence is correct for
version 14 of said I-D. Please cross-check since it could have have version 16 of said I-D. Authors need to cross-check during Auth48
changed in the meantime.] since it could have have changed in the meantime.]
Note: The +SRFLX in Figure 6 indicates that additionally newly Note: The +SRFLX in Figure 6 indicates that additionally newly
learned server-reflexive candidates are included. learned server-reflexive candidates are included.
Alice Bob Alice Bob
| | | |
| INVITE (Offer) | | INVITE (Offer) |
|------------------------>| |------------------------>|
| 183 (-) | | 183 (-) |
|<------------------------| |<------------------------|
skipping to change at page 13, line 35 skipping to change at page 15, line 28
| +----------------------+ | +----------------------+
| INFO/OK (SRFLX Cand.) | | INFO/OK (SRFLX Cand.) |
|<------------------------| |<------------------------|
| 183 (Answer) opt. | | 183 (Answer) opt. |
|<------------------------| |<------------------------|
| INFO/OK (SRFLX Cand.) | | INFO/OK (SRFLX Cand.) |
|<------------------------| |<------------------------|
| 200/ACK (Answer) | | 200/ACK (Answer) |
|<------------------------| |<------------------------|
Note: SRFLX denotes server-reflexive candidates
Figure 6: A SIP UA sends an unreliable provisional response without Figure 6: A SIP UA sends an unreliable provisional response without
an Answer for establishing an early dialog an Answer for establishing an early dialog
When sending the Answer, the agent MUST repeat all currently known When sending the Answer, the agent MUST repeat all currently known
and used candidates, if any, and MAY include all newly gathered and used candidates, if any, and MAY include all newly gathered
candidates since the last INFO request was sent. If that Answer was candidates since the last INFO request was sent. However, if that
sent in a unreliable provisional response, the Answerers MUST repeat Answer was already sent in a unreliable provisional response, the
exactly the same Answer in the 200 OK response to the INVITE request Answerers MUST repeat exactly the same Answer in the 200 OK response
in order to fulfill the corresponding requirements in [RFC3264]. In to the INVITE request in order to fulfill the corresponding
case that trickling continued, an Offerer needs to be prepared for requirements in [RFC3264]. In case that trickling continued, an
receiving fewer candidates in that repeated Answer than previously Offerer needs to be prepared for receiving fewer candidates in that
exchanged via trickling and MUST ignore the candidate information in repeated Answer than previously exchanged via trickling and MUST
that 200 OK response. ignore the candidate information in that 200 OK response.
4.2.4. Considerations for 3PCC 4.3.4. Considerations for Third Party Call Control
Agents that have sent an Offer in a reliable provisional response and Third Party Call Control (3PCC) for SIP can be performed using
that receive an Answer in a PRACK are also in a situation where several signaling variants as described in [RFC3725]. We give
support for Trickle ICE is confirmed and the SIP dialog is guaranteed specific consideration for 3PCC that starts with an offerless INVITE
to be in a state that would allow in-dialog INFO requests (see request [RFC3261]. Then, a User Agent Client (UAC) has the option to
Figure 7). send its Offer in a reliable provisional response [RFC3262] or in the
200 OK response to the INVITE request.
Agents that had sent an Offer in a reliable provisional response and
that received an Answer in a PRACK request [RFC3262] are also in a
situation where support for Trickle ICE is confirmed and the SIP
dialog is guaranteed to be in a state that would allow in-dialog INFO
requests (see Figure 7).
Alice Bob Alice Bob
| | | |
| INVITE | | INVITE |
|------------------------>| |------------------------>|
| 183 (Offer) | | 183 (Offer) |
|<------------------------| |<------------------------|
| PRACK (Answer) | | PRACK (Answer) |
|------------------------>| |------------------------>|
| | | |
skipping to change at page 14, line 37 skipping to change at page 16, line 35
| +----------------------+ | +----------------------+
| | | |
| INFO/OK (SRFLX Cand.) | | INFO/OK (SRFLX Cand.) |
|<------------------------| |<------------------------|
| | | |
| INFO/OK (SRFLX Cand.) | | INFO/OK (SRFLX Cand.) |
|------------------------>| |------------------------>|
| 200 OK/ACK | | 200 OK/ACK |
|<------------------------| |<------------------------|
Note: SRFLX denotes server-reflexive candidates
Figure 7: A SIP Offerer in a 3PCC scenario can also freely start Figure 7: A SIP Offerer in a 3PCC scenario can also freely start
trickling as soon as it receives an Answer. trickling as soon as it receives an Answer.
Trickle Agents that send an Offer in a 200 OK and receive an Answer Trickle ICE Agents that send an Offer in a 200 OK response and
in an ACK can still create a dialog and confirm support for Trickle receive an Answer in an ACK message can still create a dialog and
ICE by sending an unreliable provisional response similar to confirm support for Trickle ICE by sending an unreliable provisional
Section 4.2.3. According to [RFC3261], this unreliable response MUST response similar to Section 4.3.3. According to [RFC3261], this
NOT contain an Offer. unreliable response cannot contain an Offer.
The Trickle Agent (at the UAS) retransmits the provisional response The Trickle ICE Agent, i.e. the user Agent server (UAS), retransmits
with the exponential back-off timers described in [RFC3262]. the provisional response with the exponential back-off timers
Retransmits MUST cease on receipt of an INFO request or on described in [RFC3262]. Retransmits MUST cease on receipt of an INFO
transmission of the Answer in a 2xx response. The peer Trickle Agent request or on transmission of the Answer in a 2xx response. The peer
(at the UAC) MUST send a Trickle ICE INFO request as soon as they Trickle ICE Agent (the UAC) MUST send a Trickle ICE INFO request as
receive an unreliable provisional response (see Figure 8). soon as they receive an unreliable provisional response (see
Figure 8).
Alice Bob Alice Bob
| | | |
| INVITE | | INVITE |
|------------------------>| |------------------------>|
| 183 (-) | | 183 (-) |
|<------------------------| |<------------------------|
| INFO/OK (SRFLX Cand.) | | INFO/OK (SRFLX Cand.) |
|------------------------>| |------------------------>|
| | | |
skipping to change at page 15, line 31 skipping to change at page 17, line 33
| | | |
| INFO/OK (SRFLX Cand.) | | INFO/OK (SRFLX Cand.) |
|<------------------------| |<------------------------|
| | | |
| 200 (Offer) | | 200 (Offer) |
|<------------------------| |<------------------------|
| ACK (Answer) | | ACK (Answer) |
|------------------------>| |------------------------>|
| | | |
Note: SRFLX denotes server-reflexive candidates
Figure 8: A SIP UAC in a 3PCC scenario can also freely start Figure 8: A SIP UAC in a 3PCC scenario can also freely start
trickling as soon as it receives an unreliable provisional response. trickling as soon as it receives an unreliable provisional response.
4.3. Delivering candidates in INFO messages 4.4. Delivering candidates in INFO messages
Whenever new ICE candidates become available for sending, agents Whenever new ICE candidates become available for sending, agents
would encode them in "a=candidate" lines as described by would encode them in "a=candidate" attributes as described by
[I-D.ietf-mmusic-ice-sip-sdp]. For example: [I-D.ietf-mmusic-ice-sip-sdp]. For example:
a=candidate:2 1 UDP 1694498815 2001:db8:a0b:12f0::3 5000 typ srflx a=candidate:2 1 UDP 1694498815 2001:db8:a0b:12f0::3 5000 typ srflx
raddr 2001:db8:a0b:12f0::1 rport 8998 raddr 2001:db8:a0b:12f0::1 rport 8998
The use of SIP INFO requests happens within the context of the Info The use of SIP INFO requests happens within the context of the Info
Package as defined Section 10. The Media Type [RFC6838] for their Package as defined Section 10. The Media Type [RFC6838] for their
payload MUST be set to 'application/trickle-ice-sdpfrag' as defined payload MUST be set to 'application/trickle-ice-sdpfrag' as defined
in Section 9. in Section 9.
Since neither the "a=candidate" nor the "a=end-of-candidates" Since neither the "a=candidate" nor the "a=end-of-candidates"
attributes contain information that would allow correlating them to a attributes contain information that would allow correlating them to a
specific "m=" line, this is handled through the use of pseudo "m=" specific "m=" line, this is handled through the use of pseudo "m="
lines and identification tags in "a=mid:" attributes as defined in lines and identification tags in "a=mid:" attributes as defined in
skipping to change at page 16, line 26 skipping to change at page 18, line 32
Trickle-ICE might be decoupled from the Offer/Answer negotiation this Trickle-ICE might be decoupled from the Offer/Answer negotiation this
content might be unknown to the agent. In this case, the agent MUST content might be unknown to the agent. In this case, the agent MUST
include the following default values. include the following default values.
o The media field is set to 'audio'. o The media field is set to 'audio'.
o The port value is set to '9'. o The port value is set to '9'.
o The proto value is set to 'RTP/AVP'. o The proto value is set to 'RTP/AVP'.
o The fmt SHOULD appear only once and is set to '0' o The fmt field MUST appear only once and is set to '0'
Agents MUST include a pseudo "m=" line and an identification tag in a Agents MUST include a pseudo "m=" line and an identification tag in a
"a=mid:" attribute for every "m=" line whose candidate list they "a=mid:" attribute for every "m=" line whose candidate list they
intend to update. Such "a=mid:" attributes MUST immediately precede intend to update. Such "a=mid:" attributes MUST immediately precede
the list of candidates for that specific "m=" line. All the list of candidates for that specific "m=" line. All
"a=candidate" or "a=end-of-candidates" attributes following an "a=candidate" or "a=end-of-candidates" attributes following an
"a=mid:" attribute, up until (and excluding) the next occurrence of a "a=mid:" attribute, up until (and excluding) the next occurrence of a
pseudo "m=" line, pertain to the "m=" line identified by that pseudo "m=" line, pertain to the "m=" line identified by that
identification tag. An "a=end-of-candidates" attribute, preceding identification tag. An "a=end-of-candidates" attribute, preceding
any pseudo "m=" line, indicates the end of all trickling from that any pseudo "m=" line, indicates the end of all trickling from that
skipping to change at page 17, line 24 skipping to change at page 19, line 29
The "a=ice-pwd:" and "a=ice-ufrag:" attributes MUST appear at the The "a=ice-pwd:" and "a=ice-ufrag:" attributes MUST appear at the
same level as the ones in the Offer/Answer exchange. In other words, same level as the ones in the Offer/Answer exchange. In other words,
if they were present as session-level attributes, they will also if they were present as session-level attributes, they will also
appear at the beginning of all INFO request payloads, i.e. preceding appear at the beginning of all INFO request payloads, i.e. preceding
all pseudo "m=" lines. If they were originally exchanged as media all pseudo "m=" lines. If they were originally exchanged as media
level attributes, potentially overriding session-level values, then level attributes, potentially overriding session-level values, then
they will also be included in INFO request payloads following the they will also be included in INFO request payloads following the
corresponding pseudo "m=" lines. corresponding pseudo "m=" lines.
Note that [I-D.ietf-ice-trickle] requires that when candidates are Note that [I-D.ietf-ice-trickle] requires that when candidates are
trickled, each candidate MUST be delivered to the receiving Trickle trickled, each candidate must be delivered to the receiving Trickle
ICE implementation not more than once and in the same order as it was ICE implementation not more than once and in the same order as it was
conveyed. If the signaling protocol provides any candidate conveyed. If the signaling protocol provides any candidate
retransmissions, they need to be hidden from the ICE implementation. retransmissions, they need to be hidden from the ICE implementation.
This requirement is fulfilled as follows. This requirement is fulfilled as follows.
Since the agent is not fully aware of the state of the ICE Since the agent is not fully aware of the state of the ICE
Negotiation Session at its peer it MUST include all currently known Negotiation Session at its peer it MUST include all currently known
and used local candidates in every INFO request. I.e. the agent MUST and used local candidates in every INFO request. I.e. the agent MUST
repeat in the INFO request body all candidates that were previously repeat in the INFO request body all candidates that were previously
sent under the same combination of "a=ice-pwd:" and "a=ice-ufrag:" in sent under the same combination of "a=ice-pwd:" and "a=ice-ufrag:" in
skipping to change at page 18, line 9 skipping to change at page 20, line 13
the Offer/Answer exchange preceding them. Two candidates are the Offer/Answer exchange preceding them. Two candidates are
considered to be equal if their IP address port, transport and considered to be equal if their IP address port, transport and
component ID are the same. After identifying and discarding known component ID are the same. After identifying and discarding known
candidates, the agents MUST forward the actually new candidates to candidates, the agents MUST forward the actually new candidates to
the ICE Agents in the same order as they were received in the INFO the ICE Agents in the same order as they were received in the INFO
request body. The ICE Agents will then process the new candidates request body. The ICE Agents will then process the new candidates
according to the rules described in [I-D.ietf-ice-trickle]. according to the rules described in [I-D.ietf-ice-trickle].
Receiving an "a=end-of-candidates" attribute in an INFO request body Receiving an "a=end-of-candidates" attribute in an INFO request body
- with the "a=ice-ufrag" and "a=ice-pwd" attributes matching the - with the "a=ice-ufrag" and "a=ice-pwd" attributes matching the
current ICE generation - is an indication of the peer agent that it current ICE generation - is an indication from the peer agent that it
will not send any further candidates. When included at session will not send any further candidates. When included at session
level, i.e. before any pseudo "m=" line, this indication applies to level, i.e. before any pseudo "m=" line, this indication applies to
the whole session; when included at media level the indication the whole session; when included at media level the indication
applies only to the corresponding "m=" line. Handling of such end- applies only to the corresponding "m=" line. Handling of such end-
of-candidate indications is defined in [I-D.ietf-ice-trickle]. of-candidate indications is defined in [I-D.ietf-ice-trickle].
Note: At the time of writing this specification there were ongoing Note: At the time of writing this specification there were ongoing
discussions if a functionality for removing already exchanged discussions if a functionality for removing already exchanged
candidates would be useful. Such a functionality is out of the scope candidates would be useful. Such a functionality is out of the scope
of this specification and most likely needs to be signaled by means of this specification and most likely needs to be signaled by means
of a yet to be defined ICE extension, although it could in principle of a yet to be defined ICE extension, although it could in principle
be achieved quite easily, e.g. without anticipating any solution by be achieved quite easily, e.g. without anticipating any solution by
simply omitting a previously sent candidate from a subsequent INFO simply omitting a previously sent candidate from a subsequent INFO
request. However, if an implementation according to this request. However, if an implementation according to this
specification receives such an INFO request with a missing candidate specification receives such an INFO request with a missing candidate
it MAY treat that as an exceptional case. Implementing appropriate it would have to treat that as an exceptional case. Implementing
recovery procedures at the receiving side is RECOMMENDED for this appropriate recovery procedures at the receiving side is advisable
situation. Ignoring that a candidate was missing might be a sensible for this situation. Ignoring that a candidate was missing might be a
strategy. sensible strategy.
The following example shows the content of one sample candidate The example in Figure 9 shows the content of a candidate delivering
delivering INFO request: INFO request. In the example the "a=end-of-candidates" attributes
indicate that the candidate gathering is finished and that no further
INFO requests follow.
INFO sip:alice@example.com SIP/2.0 INFO sip:alice@example.com SIP/2.0
... ...
Info-Package: trickle-ice Info-Package: trickle-ice
Content-type: application/trickle-ice-sdpfrag Content-type: application/trickle-ice-sdpfrag
Content-Disposition: Info-Package Content-Disposition: Info-Package
Content-length: ... Content-length: 862
a=ice-pwd:asd88fgpdd777uzjYhagZg a=ice-pwd:asd88fgpdd777uzjYhagZg
a=ice-ufrag:8hhY a=ice-ufrag:8hhY
m=audio 9 RTP/AVP 0 m=audio 9 RTP/AVP 0
a=mid:1 a=mid:1
a=candidate:1 1 UDP 2130706431 2001:db8:a0b:12f0::1 5000 typ host a=candidate:1 1 UDP 2130706431 2001:db8:a0b:12f0::1 5000 typ host
a=candidate:1 2 UDP 2130706431 2001:db8:a0b:12f0::1 5001 typ host a=candidate:1 2 UDP 2130706431 2001:db8:a0b:12f0::1 5001 typ host
a=candidate:2 1 UDP 1694498815 2001:db8:a0b:12f0::3 5000 typ srflx a=candidate:2 1 UDP 1694498815 2001:db8:a0b:12f0::3 5000 typ srflx
raddr 2001:db8:a0b:12f0::1 rport 8998 raddr 2001:db8:a0b:12f0::1 rport 8998
a=candidate:2 2 UDP 1694498815 2001:db8:a0b:12f0::3 5001 typ srflx a=candidate:2 2 UDP 1694498815 2001:db8:a0b:12f0::3 5001 typ srflx
skipping to change at page 19, line 33 skipping to change at page 21, line 33
m=audio 9 RTP/AVP 0 m=audio 9 RTP/AVP 0
a=mid:2 a=mid:2
a=candidate:1 1 UDP 2130706431 2001:db8:a0b:12f0::1 6000 typ host a=candidate:1 1 UDP 2130706431 2001:db8:a0b:12f0::1 6000 typ host
a=candidate:1 2 UDP 2130706431 2001:db8:a0b:12f0::1 6001 typ host a=candidate:1 2 UDP 2130706431 2001:db8:a0b:12f0::1 6001 typ host
a=candidate:2 1 UDP 1694498815 2001:db8:a0b:12f0::3 6000 typ srflx a=candidate:2 1 UDP 1694498815 2001:db8:a0b:12f0::3 6000 typ srflx
raddr 2001:db8:a0b:12f0::1 rport 9998 raddr 2001:db8:a0b:12f0::1 rport 9998
a=candidate:2 2 UDP 1694498815 2001:db8:a0b:12f0::3 6001 typ srflx a=candidate:2 2 UDP 1694498815 2001:db8:a0b:12f0::3 6001 typ srflx
raddr 2001:db8:a0b:12f0::1 rport 9998 raddr 2001:db8:a0b:12f0::1 rport 9998
a=end-of-candidates a=end-of-candidates
Note: In a real INFO request there would be no line breaks
in the a=candidate: attributes
Figure 9: An Example for the Content of an INFO Request Figure 9: An Example for the Content of an INFO Request
5. Initial discovery of Trickle ICE support 5. Initial discovery of Trickle ICE support
SIP User Agents (UAs) that support and intend to use trickle ICE are SIP User Agents (UAs) that support and intend to use trickle ICE are
REQUIRED by [I-D.ietf-ice-trickle] to indicate that in their Offers required by [I-D.ietf-ice-trickle] to indicate that in their Offers
and Answers using the following attribute: "a=ice-options:trickle". and Answers using the following attribute: "a=ice-options:trickle".
This makes discovery fairly straightforward for Answerers or for This makes discovery fairly straightforward for Answerers or for
cases where Offers need to be generated within existing dialogs cases where Offers need to be generated within existing dialogs
(i.e., when sending re-INVITE requests). In both scenarios prior SDP (i.e., when sending UPDATE or re-INVITE requests). In both scenarios
would have provided the necessary information. prior SDP would have provided the necessary information.
Obviously, prior SDP is not available at the time a first Offer is Obviously, prior SDP is not available at the time a first Offer is
being constructed and it is therefore impossible for ICE Agents to being constructed and it is therefore impossible for ICE Agents to
determine support for incremental provisioning that way. The determine support for incremental provisioning that way. The
following options are suggested as ways of addressing this issue. following options are suggested as ways of addressing this issue.
5.1. Provisioning support for Trickle ICE 5.1. Provisioning support for Trickle ICE
In certain situations it may be possible for integrators deploying In certain situations it may be possible for integrators deploying
Trickle ICE to know in advance that some or all endpoints reachable Trickle ICE to know in advance that some or all endpoints reachable
from within the deployment will support Trickle ICE. This is likely from within the deployment will support Trickle ICE. This is the
to be the case, for example, for WebRTC clients that will always be case, for example, if Session Border Controllers (SBC) with support
communicating with other WebRTC clients or known Session Border for this specification are used to connect to UAs that do not support
Controllers (SBC) with support for this specification. Trickle ICE.
While the exact mechanism for allowing such provisioning is out of While the exact mechanism for allowing such provisioning is out of
scope here, this specification encourages trickle ICE implementations scope here, this specification encourages trickle ICE implementations
to allow the option in the way they find most appropriate. to allow the option in the way they find most appropriate.
5.2. Trickle ICE discovery with GRUU 5.2. Trickle ICE discovery with Globally Routable User Agent URIs
[RFC3840] provides a way for SIP User Agents to query for support of [RFC3840] provides a way for SIP User Agents to query for support of
specific capabilities using, among others, OPTIONS requests. GRUU specific capabilities using, among others, OPTIONS requests. Support
support on the other hand allows SIP requests to be addressed to for Globally Routable User Agent URIs (GRUU) according to [RFC5627]
specific UAs (as opposed to arbitrary instances of an address of on the other hand allows SIP requests to be addressed to specific UAs
record). Combining the two and using the "trickle-ice" option tag (as opposed to arbitrary instances of an address of record).
defined in Section 10.6 provides SIP UAs with a way of learning the Combining the two and using the "trickle-ice" option tag defined in
capabilities of specific US instances and then addressing them Section 10.6 provides SIP UAs with a way of learning the capabilities
directly with INVITE requests that require SIP support. of specific SIP UA instances and then addressing them directly with
INVITE requests that require Trickle ICE support.
Such targeted trickling may happen in different ways. One option Such learning of capabilities may happen in different ways. One
would be for a SIP UA to learn the GRUU instance ID of a peer through option for a SIP UA would be to learn the GRUU instance ID of a peer
presence and to then query its capabilities direction with an OPTIONS through presence and then to query its capabilities with an OPTIONS
request. Alternately, it can also just send an OPTIONS request to request. Alternatively, it can also just send an OPTIONS request to
the AOR it intends to contact and then inspect the returned the AOR it intends to contact and then inspect the returned
response(s) for support of both GRUU and Trickle ICE (Figure 10). response(s) for support of both GRUU and Trickle ICE (Figure 10). It
is noted that using the GRUU means that the INVITE request can go
only to that particular device. This circumvents to use of forking
for that request.
Alice Bob Alice Bob
| | | |
| OPTIONS sip:b1@example.com SIP/2.0 | | OPTIONS sip:b1@example.com SIP/2.0 |
|-------------------------------------------------->| |-------------------------------------------------->|
| | | |
| 200 OK | | 200 OK |
| Contact: sip:b1@example.com;gr=hha9s8d-999a | | Contact: sip:b1@example.com;gr=hha9s8d-999a |
| ;audio;video|;trickle-ice;... | | ;audio;video|;trickle-ice;... |
|<--------------------------------------------------| |<--------------------------------------------------|
skipping to change at page 21, line 32 skipping to change at page 23, line 32
| | | |
| ... | | ... |
| | | |
Figure 10: Trickle ICE support discovery with OPTIONS and GRUU Figure 10: Trickle ICE support discovery with OPTIONS and GRUU
Confirming support for Trickle ICE through [RFC3840] gives SIP UAs Confirming support for Trickle ICE through [RFC3840] gives SIP UAs
the options to engage in Full Trickle negotiation (as opposed to the the options to engage in Full Trickle negotiation (as opposed to the
more lengthy Half Trickle) from the very first Offer they send. more lengthy Half Trickle) from the very first Offer they send.
5.3. Trickle ICE discovery through other protocols 5.3. Fall-back to Half Trickle
Protocols like XMPP [RFC6120] define advanced discovery mechanisms
that allow specific features to be queried priory to actually
attempting to use them. Solutions like [RFC7081] define ways of
using SIP and XMPP together which also provides a way for dual stack
SIP+XMPP endpoints to make use of such features and verify Trickle
ICE support for a specific SIP endpoint through XMPP. However, such
discovery mechanisms are out of the scope of this document.
5.4. Fall-back to Half Trickle
In cases where none of the other mechanisms in this section are In cases where none of the other mechanisms in this section are
acceptable, SIP UAs should use the Half Trickle mode defined in acceptable, SIP UAs should use the Half Trickle mode defined in
[I-D.ietf-ice-trickle]. With Half Trickle, agents initiate sessions [I-D.ietf-ice-trickle]. With Half Trickle, agents initiate sessions
the same way they would when using ICE for SIP the same way they would when using ICE for SIP
[I-D.ietf-mmusic-ice-sip-sdp]. This means that, prior to actually [I-D.ietf-mmusic-ice-sip-sdp]. This means that, prior to actually
sending an Offer, agents would first gather ICE candidates in a sending an Offer, agents would first gather ICE candidates in a
blocking way and then send them all in that Offer. The blocking blocking way and then send them all in that Offer. The blocking
nature of the process would likely imply that some amount of latency nature of the process would likely imply that some amount of latency
will be accumulated and it is advised that agents try to anticipate will be accumulated and it is advised that agents try to anticipate
skipping to change at page 23, line 16 skipping to change at page 25, line 7
use the Full Trickle mode of operation. use the Full Trickle mode of operation.
6. Considerations for RTP and RTCP multiplexing 6. Considerations for RTP and RTCP multiplexing
The following consideration describe options for Trickle-ICE in order The following consideration describe options for Trickle-ICE in order
to give some guidance to implementors on how trickling can be to give some guidance to implementors on how trickling can be
optimized with respect to providing RTCP candidates. optimized with respect to providing RTCP candidates.
Handling of the "a=rtcp" attribute [RFC3605] and the "a=rtcp-mux" Handling of the "a=rtcp" attribute [RFC3605] and the "a=rtcp-mux"
attribute for RTP/RTCP multiplexing [RFC5761] is already considered attribute for RTP/RTCP multiplexing [RFC5761] is already considered
in section 5.6.1. of [I-D.ietf-mmusic-rfc5245bis] and as well in in section 5.1.1.1. of [I-D.ietf-ice-rfc5245bis] and as well in
[RFC5761] itself. These considerations are still valid for Trickle [RFC5761] itself. These considerations are still valid for Trickle
ICE, however, trickling provides more flexibility for the sequence of ICE, however, trickling provides more flexibility for the sequence of
candidate exchange in case of RTCP multiplexing. candidate exchange in case of RTCP multiplexing.
[RFC EDITOR NOTE: The section 5.6.1 in above sentence is correct for [RFC EDITOR NOTE: The section 5.1.1.1 in above sentence is correct
version 05 of said I-D. Please cross-check since it could have have for version 15 of said I-D. Authors need to cross-check during
changed in the meantime.] Auth48 since it could have have changed in the meantime.]
If the Offerer supports RTP/RTCP multiplexing exclusively as If the Offerer supports RTP/RTCP multiplexing exclusively as
specified in [I-D.ietf-mmusic-mux-exclusive], the procedures in that specified in [I-D.ietf-mmusic-mux-exclusive], the procedures in that
document apply for the handling of the "a=rtcp-mux-only", "a=rtcp" document apply for the handling of the "a=rtcp-mux-only", "a=rtcp"
and the "a=rtcp-mux" attributes. and the "a=rtcp-mux" attributes.
While a Half Trickle Offerer would have to send an offer compliant to While a Half Trickle Offerer would have to send an Offer compliant to
[I-D.ietf-mmusic-ice-sip-sdp] and [RFC5761] including candidates for [I-D.ietf-mmusic-ice-sip-sdp] and [RFC5761] including candidates for
all components, this flexibility allows a Full Trickle Offerer to all components, this flexibility allows a Full Trickle Offerer to
send only RTP candidates (component 1) in the initial Offer if it send only RTP candidates (component 1) in the initial Offer if it
assumes that RTCP multiplexing is supported by the Answerer. A Full assumes that RTCP multiplexing is supported by the Answerer. A Full
Trickle Offerer would need to start gathering and trickling RTCP Trickle Offerer would need to start gathering and trickling RTCP
candidates (component 2) only after having received an indication in candidates (component 2) only after having received an indication in
the Answer that the Answerer unexpectedly does not support RTCP the Answer that the Answerer unexpectedly does not support RTCP
multiplexing. multiplexing.
A Trickle Answerer MAY include an "a=rtcp-mux" attribute [RFC5761] in A Trickle Answerer MAY include an "a=rtcp-mux" attribute [RFC5761] in
the application/trickle-ice-sdpfrag body if it supports and uses RTP the application/trickle-ice-sdpfrag body if it supports and uses RTP
and RTCP multiplexing. The Trickle Answerer MUST follow the guidance and RTCP multiplexing. The Trickle Answerer needs to follow the
on the usage of the "a=rtcp" attribute as given in guidance on the usage of the "a=rtcp" attribute as given in
[I-D.ietf-mmusic-ice-sip-sdp] and [RFC3605]. Receipt of this [I-D.ietf-mmusic-ice-sip-sdp] and [RFC3605]. Receipt of this
attribute at the Offerer in an INFO request prior to the Answer attribute at the Offerer in an INFO request prior to the Answer
indicates that the Answerer supports and uses RTP and RTCP indicates that the Answerer supports and uses RTP and RTCP
multiplexing. The Offerer can use this information e.g. for stopping multiplexing. The Offerer can use this information e.g. for stopping
gathering of RTCP candidates and/or for freeing corresponding gathering of RTCP candidates and/or for freeing corresponding
resources. resources.
This behavior is illustrated by the following example offer that This behavior is illustrated by the following example Offer that
indicates support for RTP and RTCP multiplexing. indicates support for RTP and RTCP multiplexing.
v=0 v=0
o=alice 2890844526 2890844526 IN IP4 atlanta.example.com o=alice 2890844526 2890844526 IN IP6 atlanta.example.com
s= s=
c=IN IP4 atlanta.example.com c=IN IP6 2001:db8:a0b:12f0::3
t=0 0 t=0 0
a=ice-pwd:777uzjYhagZgasd88fgpdd a=ice-pwd:777uzjYhagZgasd88fgpdd
a=ice-ufrag:Yhh8 a=ice-ufrag:Yhh8
m=audio 10000 RTP/AVP 0 m=audio 5000 RTP/AVP 0
a=mid:1 a=mid:1
a=rtcp-mux a=rtcp-mux
a=candidate:1 1 UDP 1658497328 2001:db8:a0b:12f0::3 5000 typ host a=candidate:1 1 UDP 1658497328 2001:db8:a0b:12f0::3 5000 typ host
Once the dialog is established as described in section Section 4.2 Once the dialog is established as described in section Section 4.3
the Answerer sends the following INFO request. the Answerer sends the following INFO request.
INFO sip:alice@example.com SIP/2.0 INFO sip:alice@example.com SIP/2.0
... ...
Info-Package: trickle-ice Info-Package: trickle-ice
Content-type: application/sdp Content-type: application/sdp
Content-Disposition: Info-Package Content-Disposition: Info-Package
Content-length: ... Content-length: 161
a=ice-pwd:asd88fgpdd777uzjYhagZg a=ice-pwd:asd88fgpdd777uzjYhagZg
a=ice-ufrag:8hhY a=ice-ufrag:8hhY
m=audio 9 RTP/AVP 0 m=audio 9 RTP/AVP 0
a=mid:1 a=mid:1
a=rtcp-mux a=rtcp-mux
a=candidate:1 1 UDP 1658497328 2001:db8:a0b:12f0::3 5000 typ host a=candidate:1 1 UDP 1658497382 2001:db8:a0b:12f0::4 6000 typ host
This INFO request indicates that the Answerer supports and uses RTP This INFO request indicates that the Answerer supports and uses RTP
and RTCP multiplexing as well. It allows the Offerer to omit and RTCP multiplexing as well. It allows the Offerer to omit
gathering of RTCP candidates or releasing already gathered RTCP gathering of RTCP candidates or releasing already gathered RTCP
candidates. If the INFO request did not contain the a=rtcp-mux candidates. If the INFO request did not contain the a=rtcp-mux
attribute, the Offerer would have to gather RTCP candidates unless it attribute, the Offerer would have to gather RTCP candidates unless it
wants to wait until receipt of an Answer that eventually confirms wants to wait until receipt of an Answer that eventually confirms
support or non-support for RTP and RTCP multiplexing. support or non-support for RTP and RTCP multiplexing.
7. Considerations for Media Multiplexing 7. Considerations for Media Multiplexing
skipping to change at page 25, line 21 skipping to change at page 27, line 12
that the reader is familiar with that the reader is familiar with
[I-D.ietf-mmusic-sdp-bundle-negotiation]. [I-D.ietf-mmusic-sdp-bundle-negotiation].
ICE candidate exchange is already considered in section 11 of ICE candidate exchange is already considered in section 11 of
[I-D.ietf-mmusic-sdp-bundle-negotiation]. These considerations are [I-D.ietf-mmusic-sdp-bundle-negotiation]. These considerations are
still valid for Trickle ICE, however, trickling provides more still valid for Trickle ICE, however, trickling provides more
flexibility for the sequence of candidate exchange, especially in flexibility for the sequence of candidate exchange, especially in
Full Trickle mode. Full Trickle mode.
Except for bundle-only "m=" lines, a Half Trickle Offerer would have Except for bundle-only "m=" lines, a Half Trickle Offerer would have
to send an offer with candidates for all bundled "m=" lines. The to send an Offer with candidates for all bundled "m=" lines. The
additional flexibility, however, allows a Full Trickle Offerer to additional flexibility, however, allows a Full Trickle Offerer to
initially send only candidates for the "m=" line with the suggested initially send only candidates for the "m=" line with the suggested
Offerer BUNDLE address. Offerer BUNDLE address.
Latest on receipt of the Answer, the Offerer will detect if BUNDLE is On receipt of the Answer, the Offerer will detect if BUNDLE is
supported by the Answerer and if the suggested Offerer BUNDLE address supported by the Answerer and if the suggested Offerer BUNDLE address
was selected. In this case, the Offerer does not need to trickle was selected. In this case, the Offerer does not need to trickle
further candidates for the remaining "m=" lines in a bundle. further candidates for the remaining "m=" lines in a bundle.
However, if BUNDLE is not supported, the Full Trickle Offerer needs However, if BUNDLE is not supported, the Full Trickle Offerer needs
to gather and trickle candidates for the remaining "m=" lines as to gather and trickle candidates for the remaining "m=" lines as
necessary. If the Answerer selects an Offerer BUNDLE address necessary. If the Answerer selects an Offerer BUNDLE address
different from the suggested Offerer BUNDLE address, the Full Trickle different from the suggested Offerer BUNDLE address, the Full Trickle
Offerer needs to gather and trickle candidates for the "m=" line that Offerer needs to gather and trickle candidates for the "m=" line that
carries the selected Offerer BUNDLE address. carries the selected Offerer BUNDLE address.
skipping to change at page 25, line 49 skipping to change at page 27, line 40
ice-sdpfrag body if it supports and uses bundling. When doing so, ice-sdpfrag body if it supports and uses bundling. When doing so,
the Answerer MUST include all identification-tags in the same order the Answerer MUST include all identification-tags in the same order
that is used or will be used in the Answer. that is used or will be used in the Answer.
Receipt of this attribute at the Offerer in an INFO request prior to Receipt of this attribute at the Offerer in an INFO request prior to
the Answer indicates that the Answerer supports and uses bundling. the Answer indicates that the Answerer supports and uses bundling.
The Offerer can use this information e.g. for stopping the gathering The Offerer can use this information e.g. for stopping the gathering
of candidates for the remaining "m=" lines in a bundle and/or for of candidates for the remaining "m=" lines in a bundle and/or for
freeing corresponding resources. freeing corresponding resources.
This behaviour is illustrated by the following example offer that This behaviour is illustrated by the following example Offer that
indicates support for Media Multiplexing. indicates support for Media Multiplexing.
v=0 v=0
o=alice 2890844526 2890844526 IN IP6 atlanta.example.com o=alice 2890844526 2890844526 IN IP6 atlanta.example.com
s= s=
c=IN IP6 atlanta.example.com c=IN IP6 2001:db8:a0b:12f0::3
t=0 0 t=0 0
a=group:BUNDLE foo bar a=group:BUNDLE foo bar
a=ice-pwd:777uzjYhagZgasd88fgpdd a=ice-pwd:777uzjYhagZgasd88fgpdd
a=ice-ufrag:Yhh8 a=ice-ufrag:Yhh8
m=audio 10000 RTP/AVP 0 m=audio 10000 RTP/AVP 0
a=mid:foo a=mid:foo
a=rtpmap:0 PCMU/8000 a=rtcp-mux
a=extmap 1 urn:ietf:params:rtp-hdrext:sdes:mid a=rtpmap:0 PCMU/8000
m=video 10002 RTP/AVP 31 a=extmap 1 urn:ietf:params:rtp-hdrext:sdes:mid
a=mid:bar a=candidate:1 1 UDP 1658497328 2001:db8:a0b:12f0::3 10000 typ host
a=rtpmap:31 H261/90000 m=video 10002 RTP/AVP 31
a=extmap 1 urn:ietf:params:rtp-hdrext:sdes:mid a=mid:bar
a=rtcp-mux
a=rtpmap:31 H261/90000
a=extmap 1 urn:ietf:params:rtp-hdrext:sdes:mid
Once the dialog is established as described in section Section 4.2 The example Offer indicates support for RTP and RTCP multiplexing and
the Answerer sends the following INFO request. contains a "a=candidate" attribute only for the m-line with the
suggested Offerer bundle address. Once the dialog is established as
described in Section 4.3 the Answerer sends the following INFO
request.
INFO sip:alice@example.com SIP/2.0 INFO sip:alice@example.com SIP/2.0
... ...
Info-Package: trickle-ice Info-Package: trickle-ice
Content-type: application/sdp Content-type: application/sdp
Content-Disposition: Info-Package Content-Disposition: Info-Package
Content-length: ... Content-length: 219
a=group:BUNDLE foo bar a=group:BUNDLE foo bar
a=ice-pwd:asd88fgpdd777uzjYhagZg a=ice-pwd:asd88fgpdd777uzjYhagZg
a=ice-ufrag:8hhY a=ice-ufrag:8hhY
m=audio 9 RTP/AVP 0 m=audio 9 RTP/AVP 0
a=mid:foo a=mid:foo
a=rtcp-mux a=rtcp-mux
a=candidate:1 1 UDP 1658497328 2001:db8:a0b:12f0::3 5000 typ host a=candidate:1 1 UDP 1658497328 2001:db8:a0b:12f0::3 5000 typ host
m=audio 9 RTP/AVP 0 m=audio 9 RTP/AVP 0
a=mid:bar a=mid:bar
This INFO request indicates that the Answerer supports and uses Media This INFO request indicates that the Answerer supports and uses Media
Multiplexing as well. Note, that the second "m=" line shows the Multiplexing as well. Note, that the second "m=" line shows the
default values as specified in section Section 4.3, e.g. media set default values as specified in section Section 4.4, e.g. media set
'audio' although 'video' was offered. The receiving ICE Agents MUST 'audio' although 'video' was offered. The receiving ICE Agents MUST
ignore these default values in the pseudo "m=" lines. ignore these default values in the pseudo "m=" lines.
The INFO request also indicates that the Answerer accepted the The INFO request also indicates that the Answerer accepted the
suggested Offerer Bundle Address. This allows the Offerer to omit suggested Offerer Bundle Address. This allows the Offerer to omit
gathering of RTP and RTCP candidates for the other "m=" lines or gathering of RTP and RTCP candidates for the other "m=" lines or
releasing already gathered candidates. If the INFO request did not releasing already gathered candidates. If the INFO request did not
contain the a=group:BUNDLE attribute, the Offerer would have to contain the a=group:BUNDLE attribute, the Offerer would have to
gather RTP and RTCP candidates for the other "m=" lines unless it gather RTP and RTCP candidates for the other "m=" lines unless it
wants to wait until receipt of an Answer that eventually confirms wants to wait until receipt of an Answer that eventually confirms
support or non-support for Media Multiplexing. support or non-support for Media Multiplexing.
Independent of using Full Trickle or Half Trickle mode, the rules Independent of using Full Trickle or Half Trickle mode, the rules
from [I-D.ietf-mmusic-sdp-mux-attributes] apply to both, Offerer and from [I-D.ietf-mmusic-sdp-mux-attributes] apply to both, Offerer and
Answerer, when putting attributes as specified in Section 9.2 in the Answerer, when putting attributes as specified in Section 9.2 in the
application/trickle-ice-sdpfrag body. application/trickle-ice-sdpfrag body.
8. SDP 'end-of-candidate' Attribute 8. SDP 'end-of-candidate' Attribute
8.1. Defintion 8.1. Definition
This section defines a new SDP media-level and session-level This section defines a new SDP media-level and session-level
attribute [RFC4566] 'end-of-candidate'. 'end-of-candidate' is a attribute [RFC4566] 'end-of-candidate'. 'end-of-candidate' is a
property attribute [RFC4566], and hence has no value. By including property attribute [RFC4566], and hence has no value. By including
this attribute in an Offer or Answer the sending agent indicates that this attribute in an Offer or Answer the sending agent indicates that
it will not trickle further candidates. When included at session it will not trickle further candidates. When included at session
level this indication applies to the whole session, when included at level this indication applies to the whole session, when included at
media level the indication applies only to the corresponding media media level the indication applies only to the corresponding media
desciption. description.
Name: end-of-candidate Name: end-of-candidate
Value: N/A Value: N/A
Usage Level: media and session-level Usage Level: media and session-level
Charset Dependent: no Charset Dependent: no
Mux Category: IDENTICAL Mux Category: IDENTICAL
skipping to change at page 28, line 8 skipping to change at page 30, line 17
The Offerer or Answerer MAY include an "a=end-of-candidates" The Offerer or Answerer MAY include an "a=end-of-candidates"
attribute in case candidate discovery has ended and no further attribute in case candidate discovery has ended and no further
candidates are to be trickled. The Offerer or Answerer MUST provide candidates are to be trickled. The Offerer or Answerer MUST provide
the "a=end-of-candidates" attribute together with the "a=ice-ufrag" the "a=end-of-candidates" attribute together with the "a=ice-ufrag"
and "a=ice-pwd" attributes of the current ICE generation as required and "a=ice-pwd" attributes of the current ICE generation as required
by [I-D.ietf-ice-trickle]. When included at session level this by [I-D.ietf-ice-trickle]. When included at session level this
indication applies to the whole session; when included at media level indication applies to the whole session; when included at media level
the indication applies only to the corresponding media description. the indication applies only to the corresponding media description.
Receipt of an "a=end-of-candidates" attribute at an Offerer or Receipt of an "a=end-of-candidates" attribute at an Offerer or
Anwerer - with the "a=ice-ufrag" and "a=ice-pwd" attributes matching Answerer - with the "a=ice-ufrag" and "a=ice-pwd" attributes matching
the current ICE generation - indicates that gathering of candidates the current ICE generation - indicates that gathering of candidates
has ended at the peer, either for the session or only for the has ended at the peer, either for the session or only for the
corresponding media description as specified above. The receiving corresponding media description as specified above. The receiving
agent forwards an end-of-candidates indication to the ICE Agent, agent forwards an end-of-candidates indication to the ICE Agent,
which in turn acts as specified in [I-D.ietf-ice-trickle]. which in turn acts as specified in [I-D.ietf-ice-trickle].
9. Content Type 'application/trickle-ice-sdpfrag' 9. Content Type 'application/trickle-ice-sdpfrag'
9.1. Overall Description 9.1. Overall Description
A application/trickle-ice-sdpfrag body is used by the 'trickle-ice' A application/trickle-ice-sdpfrag body is used exclusively by the
Info Package. It uses a subset of the possible SDP lines as defined 'trickle-ice' Info Package. Other SDP related applications need to
by the grammar defined in [RFC4566]. A valid body uses only pseudo define their own media type. The INFO request body uses a subset of
"m=" lines and certain attributes that are needed and/or useful for the possible SDP lines as defined by the grammar defined in
trickling candidates. The content adheres to the following grammar. [RFC4566]. A valid body uses only pseudo "m=" lines and certain
attributes that are needed and/or useful for trickling candidates.
The content adheres to the following grammar.
9.2. Grammar 9.2. Grammar
The grammar of an 'application/trickle-ice-sdpfrag' body is based on The grammar of an 'application/trickle-ice-sdpfrag' body is based on
the following ABNF [RFC5234]. It specifies the subset of existing the following ABNF [RFC5234]. It specifies the subset of existing
SDP attributes, that are needed or useful for trickling candidates. SDP attributes, that is needed or useful for trickling candidates.
The grammar uses the indicator for case-sensitivity %s is defined in The grammar uses the indicator for case-sensitivity %s as defined in
[RFC7405], but also imports grammars for other SDP attributes that [RFC7405], but also imports grammars for other SDP attributes that
precede the production of that RFC. A sender SHOULD stick to lower- precede the production of [RFC7405]. A sender SHOULD stick to lower-
case for such grammars, but a receiver SHOULD treat them case- case for such grammars, but a receiver MUST treat them case-
insensitive. insensitive.
; Syntax ; Syntax
trickle-ice-sdpfrag = session-level-fields trickle-ice-sdpfrag = session-level-fields
pseudo-media-descriptions pseudo-media-descriptions
session-level-fields = [bundle-group-attribute CRLF] session-level-fields = [bundle-group-attribute CRLF]
[ice-lite-attribute CRLF] [ice-lite-attribute CRLF]
ice-pwd-attribute CRLF ice-pwd-attribute CRLF
ice-ufrag-attribute CRLF ice-ufrag-attribute CRLF
[ice-options-attribute CRLF] [ice-options-attribute CRLF]
skipping to change at page 30, line 16 skipping to change at page 32, line 16
grammar in their corresponding RFC and are reproduced here. grammar in their corresponding RFC and are reproduced here.
An Agent MUST ignore any received unknown extension-attribute-fields. An Agent MUST ignore any received unknown extension-attribute-fields.
10. Info Package 10. Info Package
10.1. Rationale - Why INFO? 10.1. Rationale - Why INFO?
The decision to use SIP INFO requests as a candidate transport method The decision to use SIP INFO requests as a candidate transport method
is based primarily on their lightweight nature. Once a dialog has is based primarily on their lightweight nature. Once a dialog has
been established, INFO messages can be exchanged both ways with no been established, INFO requests can be exchanged both ways with no
restrictions on timing and frequency and no risk of collision. restrictions on timing and frequency and no risk of collision.
On the other hand, using Offer/Answer and UPDATE requests [RFC3311] On the other hand, using Offer/Answer and UPDATE requests [RFC3311]
introduces the following complications: would introduce the following complications:
Blocking of messages: [RFC3264] defines Offer/Answer as a strictly Blocking of messages: [RFC3264] defines Offer/Answer as a strictly
sequential mechanism. There can only be a maximum of one exchange sequential mechanism. There can only be a maximum of one active
at any point of time. Both sides cannot simultaneously send exchange at any point of time. Both sides cannot simultaneously
Offers nor can they generate multiple Offers prior to receiving an send Offers nor can they generate multiple Offers prior to
Answer. Using UPDATE requests for candidate transport would receiving an Answer. Using UPDATE requests for candidate
therefore imply the implementation of a candidate pool at every transport would therefore imply the implementation of a candidate
agent where candidates can be stored until it is once again that pool at every agent where candidates can be stored until it is
agent's "turn" to emit an Answer or a new Offer. Such an approach once again that agent's "turn" to emit an Answer or a new Offer.
would introduce non-negligible complexity for no additional value. Such an approach would introduce non-negligible complexity for no
additional value.
Elevated risk of glare: The sequential nature of Offer/Answer also Elevated risk of glare: The sequential nature of Offer/Answer also
makes it impossible for both sides to send Offers simultaneously. makes it impossible for both sides to send Offers simultaneously.
What's worse is that there are no mechanisms in SIP to actually What's worse is that there are no mechanisms in SIP to actually
prevent that. [RFC3261], where the situation of Offers crossing prevent that. [RFC3261], where the situation of Offers crossing
on the wire is described as "glare", only defines a procedure for on the wire is described as "glare", only defines a procedure for
addressing the issue after it has occurred. According to that addressing the issue after it has occurred. According to that
procedure both Offers are invalidated and both sides need to retry procedure both Offers are invalidated and both sides need to retry
the negotiation after a period between 0 and 4 seconds. The high the negotiation after a period between 0 and 4 seconds. The high
likelihood for glare to occur and the average two second back-off likelihood for glare to occur and the average two second back-off
skipping to change at page 32, line 9 skipping to change at page 34, line 9
option-tag /= "trickle-ice" option-tag /= "trickle-ice"
SIP entities that support this specification MUST place the 'trickle- SIP entities that support this specification MUST place the 'trickle-
ice' option-tag in a SIP Supported: header field within all SIP ice' option-tag in a SIP Supported: header field within all SIP
INVITE requests and responses. INVITE requests and responses.
When responding to, or generating a SIP OPTIONS request a SIP entity When responding to, or generating a SIP OPTIONS request a SIP entity
MUST also include the 'trickle-ice' option-tag in a SIP Supported: MUST also include the 'trickle-ice' option-tag in a SIP Supported:
header field. header field.
10.7. Info Message Body Parts 10.7. Info Request Body Parts
Entities implementing this specification MUST include a payload of Entities implementing this specification MUST include a payload of
type 'application/trickle-ice-sdpfrag' as defined in Section 9.2 all type 'application/trickle-ice-sdpfrag' as defined in Section 9.2 in
SIP INFO requests. The payload is used to convey SDP encoded ICE SIP INFO requests. The payload is used to convey SDP-encoded ICE
candidates. candidates.
10.8. Info Package Usage Restrictions 10.8. Info Package Usage Restrictions
This document does not define any Info Package Usage Restrictions. This document does not define any Info Package Usage Restrictions.
10.9. Rate of INFO Requests 10.9. Rate of INFO Requests
A Trickle ICE Agent with many network interfaces might create a high A Trickle ICE Agent with many network interfaces might create a high
rate of INFO requests if every newly detected candidate is trickled rate of INFO requests if every newly detected candidate is trickled
individually without aggregation. Implementors that are concerned individually without aggregation. Implementors that are concerned
about loss of packets in such a case might consider aggregating ICE about loss of packets in such a case might consider aggregating ICE
candidates and sending INFOs only at some configurable intervals. candidates and sending INFOs only at some configurable intervals.
10.10. Info Package Security Considerations 10.10. Info Package Security Considerations
See Section 12 See Section 13
11. IANA Considerations 11. Deployment Considerations
Trickle ICE uses two mechanism for exchange of candidate information.
This imposes new requirements to certain middleboxes that are used in
some networks, e.g. for monitoring purposes. While the first
mechanism, SDP Offers and Answers, is already used by regular ICE and
is assumed to be supported, the second mechanism, INFO request
bodies, needs to be considered by such middleboxes as well when
trickle ICE is used. Such middleboxes need to make sure that they
remain in the signaling path of the INFO requests and need to
understand the INFO request body.
12. IANA Considerations
[RFC EDITOR NOTE: Please replace RFCXXXX with the RFC number of this [RFC EDITOR NOTE: Please replace RFCXXXX with the RFC number of this
document. ] document. ]
11.1. SDP 'end-of-candidate' Attribute 12.1. SDP 'end-of-candidate' Attribute
This section defines a new SDP media-level and session-level This section defines a new SDP media-level and session-level
attribute [RFC4566] , 'end-of-candidate'. 'end-of-candidate' is a attribute [RFC4566] , 'end-of-candidate'. 'end-of-candidate' is a
property attribute [RFC4566] , and hence has no value. property attribute [RFC4566] , and hence has no value.
Name: end-of-candidate Name: end-of-candidate
Value: N/A Value: N/A
Usage Level: media and session Usage Level: media and session
Charset Dependent: no Charset Dependent: no
Purpose: The sender indicates that it will not trickle Purpose: The sender indicates that it will not trickle
further candidates. further ICE candidates.
O/A Procedures: RFCXXX defines the detailed O/A Procedures: RFCXXX defines the detailed
SDP Offer/Answer procedures for SDP Offer/Answer procedures for
the 'end-of-candidate' attribute. the 'end-of-candidate' attribute.
Mux Category: IDENTICAL Mux Category: IDENTICAL
Reference: RFCXXXX Reference: RFCXXXX
Example: Example:
a=end-of-candidate a=end-of-candidate
11.2. application/trickle-ice-sdpfrag Media Type 12.2. application/trickle-ice-sdpfrag Media Type
This section defines a new Media Type 'application/trickle-ice-
sdpfrag' in accordance with [RFC6838].
Type name: application Type name: application
Subtype name: trickle-ice-sdpfrag Subtype name: trickle-ice-sdpfrag
Required parameters: None. Required parameters: None.
Optional parameters: None. Optional parameters: None.
Encoding considerations: Encoding considerations:
skipping to change at page 34, line 5 skipping to change at page 36, line 16
initially defined content of a trickle-ice-sdpfrag body does initially defined content of a trickle-ice-sdpfrag body does
only include ASCII characters, UTF-8 encoded content might be only include ASCII characters, UTF-8 encoded content might be
introduced via extension attributes. The "a=charset:" introduced via extension attributes. The "a=charset:"
attribute may be used to signal the presence of other character attribute may be used to signal the presence of other character
sets in certain parts of a trickle-ice-sdpfrag body (see sets in certain parts of a trickle-ice-sdpfrag body (see
[RFC4566]). Arbitrary binary content cannot be directly [RFC4566]). Arbitrary binary content cannot be directly
represented in SDP or a trickle-ice-sdpfrag body. represented in SDP or a trickle-ice-sdpfrag body.
Security considerations: Security considerations:
See [RFC4566]) and RFCXXXX See [RFC4566] and RFCXXXX
Interoperability considerations: Interoperability considerations:
See RFCXXXX See RFCXXXX
Published specification: Published specification:
See RFCXXXX See RFCXXXX
Applications which use this Media Type: Applications which use this Media Type:
Voice over IP, video teleconferencing, streaming media, instant Trickle-ICE
messaging, Trickle-ICE among others.
Fragment identifier considerations: N/A Fragment identifier considerations: N/A
Additional information: Additional information:
Magic number(s): N/A Deprecated alias names for this type: N/A
File extension(s): N/A Magic number(s): N/A
Macintosh File Type Code(s): N/A File extension(s): N/A
Macintosh File Type Code(s): N/A
Person and email address to contact for further information: Person and email address to contact for further information:
IETF MMUSIC working group mmusic@ietf.org The IESG (iesg@ietf.org)
Intended usage: Intended usage:
Trickle-ICE for SIP as specified in RFCXXXX. Trickle-ICE for SIP as specified in RFCXXXX.
Restrictions on usage: N/A Restrictions on usage: N/A
Author/Change controller: Author/Change controller:
IETF MMUSIC working group mmusic@ietf.org The IESG (iesg@ietf.org)
Provisional registration? (standards tree only): N/A Provisional registration? (standards tree only): N/A
11.3. SIP Info Package 'trickle-ice' 12.3. SIP Info Package 'trickle-ice'
This document defines a new SIP Info Package named 'trickle-ice' and This document defines a new SIP Info Package named 'trickle-ice' and
updates the Info Packages Registry with the following entry. updates the Info Packages Registry with the following entry.
+-------------+-----------+ +-------------+-----------+
| Name | Reference | | Name | Reference |
+-------------+-----------+ +-------------+-----------+
| trickle-ice | [RFCXXXX] | | trickle-ice | [RFCXXXX] |
| | | | | |
+-------------+-----------+ +-------------+-----------+
11.4. SIP Option Tag 'trickle-ice' 12.4. SIP Option Tag 'trickle-ice'
This specification registers a new SIP option tag 'trickle-ice' as This specification registers a new SIP option tag 'trickle-ice' as
per the guidelines in Section 27.1 of [RFC3261] and updates the per the guidelines in Section 27.1 of [RFC3261] and updates the
"Option Tags" section of the SIP Parameter Registry with the "Option Tags" section of the SIP Parameter Registry with the
following entry: following entry:
+-------------+-------------------------------------+-----------+ +-------------+-------------------------------------+-----------+
| Name | Description | Reference | | Name | Description | Reference |
+-------------+-------------------------------------+-----------+ +-------------+-------------------------------------+-----------+
| trickle-ice | This option tag is used to indicate | [RFCXXXX] | | trickle-ice | This option tag is used to indicate | [RFCXXXX] |
| | that a UA supports and understands | | | | that a UA supports and understands | |
| | Trickle-ICE. | | | | Trickle-ICE. | |
+-------------+-------------------------------------+-----------+ +-------------+-------------------------------------+-----------+
12. Security Considerations 13. Security Considerations
The Security Considerations of [I-D.ietf-mmusic-ice-sip-sdp], The Security Considerations of [I-D.ietf-mmusic-ice-sip-sdp],
[RFC6086] and [I-D.ietf-ice-trickle] apply. This document clarifies [RFC6086] and [I-D.ietf-ice-trickle] apply. This document clarifies
how the above specifications are used together for trickling how the above specifications are used together for trickling
candidates and does not create addtitional security risks. candidates and does not create additional security risks.
13. Acknowledgements The new Info Package 'trickle-ice' and the new Media Type
'application/trickle-ice-sdpfrag' do not introduce additional
security considerations when used in the context of Trickle ICE.
Both are not intended to be used for other applications, so any
security considerations for its use in other contexts is out of the
scope of this document
14. Acknowledgements
The authors would like to thank Flemming Andreasen, Ayush Jain, Paul The authors would like to thank Flemming Andreasen, Ayush Jain, Paul
Kyzivat, Jonathan Lennox, Simon Perreault, Roman Shpount and Martin Kyzivat, Jonathan Lennox, Simon Perreault, Roman Shpount and Martin
Thomson for reviewing and/or making various suggestions for Thomson for reviewing and/or making various suggestions for
improvements and optimizations. improvements and optimizations.
14. Change Log The authors would also like to thank Flemming Andreasen for
shepherding this document and Ben Campbell for his AD review and
suggestions.
15. Change Log
[RFC EDITOR NOTE: Please remove this section when publishing]. [RFC EDITOR NOTE: Please remove this section when publishing].
Changes from draft-ietf-mmusic-trickle-ice-sip-01 Changes from draft-ietf-mmusic-trickle-ice-sip-01
o Editorial Clean up o Editorial Clean up
o IANA Consideration added o IANA Consideration added
o Security Consideration added o Security Consideration added
skipping to change at page 38, line 39 skipping to change at page 41, line 15
o replaced remaining IPv4 adresses with IPv6 o replaced remaining IPv4 adresses with IPv6
o Added text for handling a=rtcp in case of default RTP address o Added text for handling a=rtcp in case of default RTP address
0.0.0.0:9 based on comment from Roman Shpount. 0.0.0.0:9 based on comment from Roman Shpount.
Changes from draft-ietf-mmusic-trickle-ice-sip-10 Changes from draft-ietf-mmusic-trickle-ice-sip-10
o editorial fixes due to idnits output o editorial fixes due to idnits output
15. References Changes from draft-ietf-mmusic-trickle-ice-sip-11
15.1. Normative References o addressing comments from Ben Campell's AD review and Christer's
review
o Numerous editorial improvements/corrections
o Added [RFC8174] boiler plate and adapted usage of normative
language
o Clarified terminology ICE modules .vs. ICE agent
o Added more detailed OA procedures
o Corrected default values in m-line and usage of "a=mid:" attribute
explicitly mentioned for offer/answer
o Removed explicit mentioning of XMPP
o Added Deployment Considerations section
o Fixed ref for rfc5245bis
16. References
16.1. Normative References
[I-D.ietf-ice-rfc5245bis]
Keranen, A., Holmberg, C., and J. Rosenberg, "Interactive
Connectivity Establishment (ICE): A Protocol for Network
Address Translator (NAT) Traversal", draft-ietf-ice-
rfc5245bis-15 (work in progress), November 2017.
[I-D.ietf-ice-trickle] [I-D.ietf-ice-trickle]
Ivov, E., Rescorla, E., Uberti, J., and P. Saint-Andre, Ivov, E., Rescorla, E., Uberti, J., and P. Saint-Andre,
"Trickle ICE: Incremental Provisioning of Candidates for "Trickle ICE: Incremental Provisioning of Candidates for
the Interactive Connectivity Establishment (ICE) the Interactive Connectivity Establishment (ICE)
Protocol", draft-ietf-ice-trickle-14 (work in progress), Protocol", draft-ietf-ice-trickle-15 (work in progress),
September 2017. November 2017.
[I-D.ietf-mmusic-ice-sip-sdp] [I-D.ietf-mmusic-ice-sip-sdp]
Petit-Huguenin, M., Keranen, A., and S. Nandakumar, Petit-Huguenin, M., Keranen, A., and S. Nandakumar,
"Session Description Protocol (SDP) Offer/Answer "Session Description Protocol (SDP) Offer/Answer
procedures for Interactive Connectivity Establishment procedures for Interactive Connectivity Establishment
(ICE)", draft-ietf-mmusic-ice-sip-sdp-14 (work in (ICE)", draft-ietf-mmusic-ice-sip-sdp-16 (work in
progress), October 2017. progress), November 2017.
[I-D.ietf-mmusic-mux-exclusive] [I-D.ietf-mmusic-mux-exclusive]
Holmberg, C., "Indicating Exclusive Support of RTP/RTCP Holmberg, C., "Indicating Exclusive Support of RTP/RTCP
Multiplexing using SDP", draft-ietf-mmusic-mux- Multiplexing using SDP", draft-ietf-mmusic-mux-
exclusive-12 (work in progress), May 2017. exclusive-12 (work in progress), May 2017.
[I-D.ietf-mmusic-rfc5245bis]
Keranen, A. and J. Rosenberg, "Interactive Connectivity
Establishment (ICE): A Protocol for Network Address
Translator (NAT) Traversal", draft-ietf-mmusic-
rfc5245bis-05 (work in progress), September 2015.
[I-D.ietf-mmusic-sdp-bundle-negotiation] [I-D.ietf-mmusic-sdp-bundle-negotiation]
Holmberg, C., Alvestrand, H., and C. Jennings, Holmberg, C., Alvestrand, H., and C. Jennings,
"Negotiating Media Multiplexing Using the Session "Negotiating Media Multiplexing Using the Session
Description Protocol (SDP)", draft-ietf-mmusic-sdp-bundle- Description Protocol (SDP)", draft-ietf-mmusic-sdp-bundle-
negotiation-39 (work in progress), August 2017. negotiation-43 (work in progress), December 2017.
[I-D.ietf-mmusic-sdp-mux-attributes] [I-D.ietf-mmusic-sdp-mux-attributes]
Nandakumar, S., "A Framework for SDP Attributes when Nandakumar, S., "A Framework for SDP Attributes when
Multiplexing", draft-ietf-mmusic-sdp-mux-attributes-16 Multiplexing", draft-ietf-mmusic-sdp-mux-attributes-16
(work in progress), December 2016. (work in progress), December 2016.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
skipping to change at page 40, line 48 skipping to change at page 43, line 48
[RFC6838] Freed, N., Klensin, J., and T. Hansen, "Media Type [RFC6838] Freed, N., Klensin, J., and T. Hansen, "Media Type
Specifications and Registration Procedures", BCP 13, Specifications and Registration Procedures", BCP 13,
RFC 6838, DOI 10.17487/RFC6838, January 2013, RFC 6838, DOI 10.17487/RFC6838, January 2013,
<https://www.rfc-editor.org/info/rfc6838>. <https://www.rfc-editor.org/info/rfc6838>.
[RFC7405] Kyzivat, P., "Case-Sensitive String Support in ABNF", [RFC7405] Kyzivat, P., "Case-Sensitive String Support in ABNF",
RFC 7405, DOI 10.17487/RFC7405, December 2014, RFC 7405, DOI 10.17487/RFC7405, December 2014,
<https://www.rfc-editor.org/info/rfc7405>. <https://www.rfc-editor.org/info/rfc7405>.
15.2. Informative References [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
16.2. Informative References
[RFC3311] Rosenberg, J., "The Session Initiation Protocol (SIP) [RFC3311] Rosenberg, J., "The Session Initiation Protocol (SIP)
UPDATE Method", RFC 3311, DOI 10.17487/RFC3311, October UPDATE Method", RFC 3311, DOI 10.17487/RFC3311, October
2002, <https://www.rfc-editor.org/info/rfc3311>. 2002, <https://www.rfc-editor.org/info/rfc3311>.
[RFC3725] Rosenberg, J., Peterson, J., Schulzrinne, H., and G.
Camarillo, "Best Current Practices for Third Party Call
Control (3pcc) in the Session Initiation Protocol (SIP)",
BCP 85, RFC 3725, DOI 10.17487/RFC3725, April 2004,
<https://www.rfc-editor.org/info/rfc3725>.
[RFC3840] Rosenberg, J., Schulzrinne, H., and P. Kyzivat, [RFC3840] Rosenberg, J., Schulzrinne, H., and P. Kyzivat,
"Indicating User Agent Capabilities in the Session "Indicating User Agent Capabilities in the Session
Initiation Protocol (SIP)", RFC 3840, Initiation Protocol (SIP)", RFC 3840,
DOI 10.17487/RFC3840, August 2004, DOI 10.17487/RFC3840, August 2004,
<https://www.rfc-editor.org/info/rfc3840>. <https://www.rfc-editor.org/info/rfc3840>.
[RFC5627] Rosenberg, J., "Obtaining and Using Globally Routable User [RFC5627] Rosenberg, J., "Obtaining and Using Globally Routable User
Agent URIs (GRUUs) in the Session Initiation Protocol Agent URIs (GRUUs) in the Session Initiation Protocol
(SIP)", RFC 5627, DOI 10.17487/RFC5627, October 2009, (SIP)", RFC 5627, DOI 10.17487/RFC5627, October 2009,
<https://www.rfc-editor.org/info/rfc5627>. <https://www.rfc-editor.org/info/rfc5627>.
[RFC6120] Saint-Andre, P., "Extensible Messaging and Presence
Protocol (XMPP): Core", RFC 6120, DOI 10.17487/RFC6120,
March 2011, <https://www.rfc-editor.org/info/rfc6120>.
[RFC7081] Ivov, E., Saint-Andre, P., and E. Marocco, "CUSAX:
Combined Use of the Session Initiation Protocol (SIP) and
the Extensible Messaging and Presence Protocol (XMPP)",
RFC 7081, DOI 10.17487/RFC7081, November 2013,
<https://www.rfc-editor.org/info/rfc7081>.
Authors' Addresses Authors' Addresses
Emil Ivov Emil Ivov
Jitsi Jitsi
Strasbourg 67000 Strasbourg 67000
France France
Phone: +33 6 72 81 15 55 Phone: +33 6 72 81 15 55
Email: emcho@jitsi.org Email: emcho@jitsi.org
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