draft-ietf-mmusic-ice-sip-sdp-18.txt   draft-ietf-mmusic-ice-sip-sdp-19.txt 
MMUSIC M. Petit-Huguenin MMUSIC M. Petit-Huguenin
Internet-Draft Impedance Mismatch Internet-Draft Impedance Mismatch
Obsoletes: 5245 (if approved) S. Nandakumar Obsoletes: 5245 (if approved) S. Nandakumar
Intended status: Standards Track Cisco Systems Intended status: Standards Track Cisco Systems
Expires: October 1, 2018 A. Keranen Expires: October 3, 2018 A. Keranen
Ericsson Ericsson
March 30, 2018 April 1, 2018
Session Description Protocol (SDP) Offer/Answer procedures for Session Description Protocol (SDP) Offer/Answer procedures for
Interactive Connectivity Establishment (ICE) Interactive Connectivity Establishment (ICE)
draft-ietf-mmusic-ice-sip-sdp-18 draft-ietf-mmusic-ice-sip-sdp-19
Abstract Abstract
This document describes Session Description Protocol (SDP) Offer/ This document describes Session Description Protocol (SDP) Offer/
Answer procedures for carrying out Interactive Connectivity Answer procedures for carrying out Interactive Connectivity
Establishment (ICE) between the agents. Establishment (ICE) between the agents.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
skipping to change at page 1, line 36 skipping to change at page 1, line 36
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on October 1, 2018. This Internet-Draft will expire on October 3, 2018.
Copyright Notice Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the Copyright (c) 2018 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://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
skipping to change at page 2, line 46 skipping to change at page 2, line 46
3.3.4. Concluding ICE . . . . . . . . . . . . . . . . . . . 8 3.3.4. Concluding ICE . . . . . . . . . . . . . . . . . . . 8
3.4. Subsequent Offer/Answer Exchanges . . . . . . . . . . . . 9 3.4. Subsequent Offer/Answer Exchanges . . . . . . . . . . . . 9
3.4.1. Sending Subsequent Offer . . . . . . . . . . . . . . 9 3.4.1. Sending Subsequent Offer . . . . . . . . . . . . . . 9
3.4.2. Sending Subsequent Answer . . . . . . . . . . . . . . 11 3.4.2. Sending Subsequent Answer . . . . . . . . . . . . . . 11
3.4.3. Receiving Answer for a Subsequent Offer . . . . . . . 13 3.4.3. Receiving Answer for a Subsequent Offer . . . . . . . 13
4. Grammar . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 4. Grammar . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
4.1. "candidate" Attribute . . . . . . . . . . . . . . . . . . 15 4.1. "candidate" Attribute . . . . . . . . . . . . . . . . . . 15
4.2. "remote-candidates" Attribute . . . . . . . . . . . . . . 18 4.2. "remote-candidates" Attribute . . . . . . . . . . . . . . 18
4.3. "ice-lite" and "ice-mismatch" Attributes . . . . . . . . 18 4.3. "ice-lite" and "ice-mismatch" Attributes . . . . . . . . 18
4.4. "ice-ufrag" and "ice-pwd" Attributes . . . . . . . . . . 19 4.4. "ice-ufrag" and "ice-pwd" Attributes . . . . . . . . . . 19
4.5. "ice-pacing" Attribute . . . . . . . . . . . . . . . . . 20 4.5. "ice-pacing" Attribute . . . . . . . . . . . . . . . . . 19
4.6. "ice-options" Attribute . . . . . . . . . . . . . . . . . 20 4.6. "ice-options" Attribute . . . . . . . . . . . . . . . . . 20
5. Keepalives . . . . . . . . . . . . . . . . . . . . . . . . . 21 5. Keepalives . . . . . . . . . . . . . . . . . . . . . . . . . 21
6. SIP Considerations . . . . . . . . . . . . . . . . . . . . . 21 6. SIP Considerations . . . . . . . . . . . . . . . . . . . . . 21
6.1. Latency Guidelines . . . . . . . . . . . . . . . . . . . 21 6.1. Latency Guidelines . . . . . . . . . . . . . . . . . . . 21
6.1.1. Offer in INVITE . . . . . . . . . . . . . . . . . . . 22 6.1.1. Offer in INVITE . . . . . . . . . . . . . . . . . . . 22
6.1.2. Offer in Response . . . . . . . . . . . . . . . . . . 23 6.1.2. Offer in Response . . . . . . . . . . . . . . . . . . 23
6.2. SIP Option Tags and Media Feature Tags . . . . . . . . . 23 6.2. SIP Option Tags and Media Feature Tags . . . . . . . . . 23
6.3. Interactions with Forking . . . . . . . . . . . . . . . . 24 6.3. Interactions with Forking . . . . . . . . . . . . . . . . 24
6.4. Interactions with Preconditions . . . . . . . . . . . . . 24 6.4. Interactions with Preconditions . . . . . . . . . . . . . 24
6.5. Interactions with Third Party Call Control . . . . . . . 24 6.5. Interactions with Third Party Call Control . . . . . . . 24
7. Relationship with ANAT . . . . . . . . . . . . . . . . . . . 25 7. Relationship with ANAT . . . . . . . . . . . . . . . . . . . 25
8. Setting Ta and RTO for RTP Media Streams . . . . . . . . . . 25 8. Setting Ta and RTO for RTP Media Streams . . . . . . . . . . 25
9. Security Considerations . . . . . . . . . . . . . . . . . . . 25 9. Security Considerations . . . . . . . . . . . . . . . . . . . 25
9.1. Attacks on the Offer/Answer Exchanges . . . . . . . . . . 25 9.1. Attacks on the Offer/Answer Exchanges . . . . . . . . . . 25
9.2. Insider Attacks . . . . . . . . . . . . . . . . . . . . . 26 9.2. Insider Attacks . . . . . . . . . . . . . . . . . . . . . 25
9.2.1. The Voice Hammer Attack . . . . . . . . . . . . . . . 26 9.2.1. The Voice Hammer Attack . . . . . . . . . . . . . . . 26
9.2.2. Interactions with Application Layer Gateways and SIP 26 9.2.2. Interactions with Application Layer Gateways and SIP 26
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 27 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 27
10.1. SDP Attributes . . . . . . . . . . . . . . . . . . . . . 27 10.1. SDP Attributes . . . . . . . . . . . . . . . . . . . . . 27
10.1.1. candidate Attribute . . . . . . . . . . . . . . . . 28 10.1.1. candidate Attribute . . . . . . . . . . . . . . . . 28
10.1.2. remote-candidates Attribute . . . . . . . . . . . . 28 10.1.2. remote-candidates Attribute . . . . . . . . . . . . 28
10.1.3. ice-lite Attribute . . . . . . . . . . . . . . . . . 29 10.1.3. ice-lite Attribute . . . . . . . . . . . . . . . . . 29
10.1.4. ice-mismatch Attribute . . . . . . . . . . . . . . . 29 10.1.4. ice-mismatch Attribute . . . . . . . . . . . . . . . 29
10.1.5. ice-pwd Attribute . . . . . . . . . . . . . . . . . 30 10.1.5. ice-pwd Attribute . . . . . . . . . . . . . . . . . 30
10.1.6. ice-ufrag Attribute . . . . . . . . . . . . . . . . 30 10.1.6. ice-ufrag Attribute . . . . . . . . . . . . . . . . 30
10.1.7. ice-options Attribute . . . . . . . . . . . . . . . 31 10.1.7. ice-options Attribute . . . . . . . . . . . . . . . 31
10.1.8. ice-pacing Attribute . . . . . . . . . . . . . . . . 31 10.1.8. ice-pacing Attribute . . . . . . . . . . . . . . . . 31
10.2. Interactive Connectivity Establishment (ICE) Options 10.2. Interactive Connectivity Establishment (ICE) Options
Registry . . . . . . . . . . . . . . . . . . . . . . . . 32 Registry . . . . . . . . . . . . . . . . . . . . . . . . 32
11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 33 11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 33
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 33 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 33
12.1. Normative References . . . . . . . . . . . . . . . . . . 33 12.1. Normative References . . . . . . . . . . . . . . . . . . 33
12.2. Informative References . . . . . . . . . . . . . . . . . 35 12.2. Informative References . . . . . . . . . . . . . . . . . 35
12.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 36 12.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 36
Appendix A. Examples . . . . . . . . . . . . . . . . . . . . . . 37 Appendix A. Examples . . . . . . . . . . . . . . . . . . . . . . 36
Appendix B. The remote-candidates Attribute . . . . . . . . . . 38 Appendix B. The remote-candidates Attribute . . . . . . . . . . 38
Appendix C. Why Is the Conflict Resolution Mechanism Needed? . . 39 Appendix C. Why Is the Conflict Resolution Mechanism Needed? . . 39
Appendix D. Why Send an Updated Offer? . . . . . . . . . . . . . 40 Appendix D. Why Send an Updated Offer? . . . . . . . . . . . . . 40
Appendix E. Contributors . . . . . . . . . . . . . . . . . . . . 41 Appendix E. Contributors . . . . . . . . . . . . . . . . . . . . 41
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 41 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 41
1. Introduction 1. Introduction
This document describes how Interactive Connectivity Establishment This document describes how Interactive Connectivity Establishment
(ICE) is used with Session Description Protocol (SDP) offer/answer (ICE) is used with Session Description Protocol (SDP) offer/answer
skipping to change at page 5, line 44 skipping to change at page 5, line 44
An ICE lite implementation [ICE-BIS] MUST include an SDP ice-lite An ICE lite implementation [ICE-BIS] MUST include an SDP ice-lite
attribute. A full implementation MUST NOT include that attribute. attribute. A full implementation MUST NOT include that attribute.
3.2.1.5. ICE Extensions 3.2.1.5. ICE Extensions
An agent uses the SDP ice-options attribute to indicate support of An agent uses the SDP ice-options attribute to indicate support of
ICE extensions. ICE extensions.
An agent compliant to this specification MUST include an SDP ice- An agent compliant to this specification MUST include an SDP ice-
options attribute with an "ice2" attribute value. If an agent options attribute with an "ice2" attribute value. If an agent
receives an SDP offer or answer that does not include the attribute receives an SDP offer or answer with ICE attributes but without the
value, the agent assumes that the peer is compliant to [RFC5245]. "ice2" ice-options attribute value, the agent assumes that the peer
is compliant to [RFC5245].
3.2.1.6. Inactive and Disabled Data Streams 3.2.1.6. Inactive and Disabled Data Streams
If an "m=" section is marked as inactive [RFC4566], or has a If an "m=" section is marked as inactive [RFC4566], or has a
bandwidth value of zero [RFC4566], the agent MUST still include ICE bandwidth value of zero [RFC4566], the agent MUST still include ICE
related SDP attributes. related SDP attributes.
If the port value associated with an "m=" section is set to zero If the port value associated with an "m=" section is set to zero
(implying a disabled stream), the agent SHOULD NOT include ICE (implying a disabled stream), the agent SHOULD NOT include ICE
related SDP candidate attributes in that "m=" section, unless an SDP related SDP candidate attributes in that "m=" section, unless an SDP
skipping to change at page 6, line 34 skipping to change at page 6, line 34
b=RS:0 and b=RR:0 SDP attributes, as described in [RFC3556]. b=RS:0 and b=RR:0 SDP attributes, as described in [RFC3556].
3.2.3. Determining Role 3.2.3. Determining Role
The offerer acts as the Initiating agent. The answerer acts as the The offerer acts as the Initiating agent. The answerer acts as the
Responding agent. The ICE roles (controlling and controlled) are Responding agent. The ICE roles (controlling and controlled) are
determined using the procedures in [ICE-BIS]. determined using the procedures in [ICE-BIS].
3.2.4. STUN Considerations 3.2.4. STUN Considerations
Once an agent has provided its local candidates to its peer, within Once an agent has provided its local candidates to its peer in an SDP
an SDP offer or answer, the agent MUST be prepared to receive STUN offer or answer, the agent MUST be prepared to receive STUN
connectivity check Binding requests on those candidates. connectivity check Binding requests on those candidates.
3.2.5. ICE Mismatch 3.2.5. ICE Mismatch
The agent will proceed with the ICE procedures defined in [ICE-BIS] The agent will proceed with the ICE procedures defined in [ICE-BIS]
and this specification if, for each data stream in the SDP it and this specification if, for each data stream in the SDP it
received, the default destination for each component of that data received, the default destination for each component of that data
stream appears in a candidate attribute. For example, in the case of stream appears in a candidate attribute. For example, in the case of
RTP, the IP address and port in the "c=" and "m=" lines, RTP, the IP address and port in the "c=" and "m=" lines,
respectively, appear in a candidate attribute and the value in the respectively, appear in a candidate attribute and the value in the
skipping to change at page 7, line 11 skipping to change at page 7, line 11
normal [RFC3264] procedures, without using any of the ICE mechanisms normal [RFC3264] procedures, without using any of the ICE mechanisms
described in the remainder of this specification with the following described in the remainder of this specification with the following
exceptions: exceptions:
1. The agent MUST follow the rules of section 11 of [ICE-BIS], which 1. The agent MUST follow the rules of section 11 of [ICE-BIS], which
describe keepalive procedures for all agents. describe keepalive procedures for all agents.
2. If the agent is not proceeding with ICE because there were 2. If the agent is not proceeding with ICE because there were
a=candidate attributes, but none that matched the default a=candidate attributes, but none that matched the default
destination of the data stream, the agent MUST include an a=ice- destination of the data stream, the agent MUST include an a=ice-
mismatch attribute in its answer and may omit a=candidate mismatch attribute in its answer and MAY omit a=candidate
attributes for such data streams. See Section 9.2.2 for a attributes for such data streams. See Section 9.2.2 for a
discussion of cases where this can happen. This specification discussion of cases where this can happen. This specification
provides no guidance on how an agent should proceed in such a provides no guidance on how an agent should proceed in such a
failure case. failure case.
3. If the default candidates were relayed candidates learned through 3. If the default candidates were relayed candidates learned through
a TURN server, the agent MUST create permissions in the TURN a TURN server, the agent MUST create permissions in the TURN
server for the IP addresses learned from its peer in the SDP it server for the IP addresses learned from its peer in the SDP it
just received. If this is not done, initial packets in the data just received. If this is not done, initial packets in the data
stream from the peer may be lost. stream from the peer may be lost.
skipping to change at page 8, line 50 skipping to change at page 8, line 50
If the answer does not indicate that the answerer supports ICE, or if If the answer does not indicate that the answerer supports ICE, or if
the offerer detects an ICE mismatch in the answer, the offerer MUST the offerer detects an ICE mismatch in the answer, the offerer MUST
terminate the usage of ICE. The subsequent actions taken by the terminate the usage of ICE. The subsequent actions taken by the
offerer are implementation dependent and are out of the scope of this offerer are implementation dependent and are out of the scope of this
specification. specification.
3.3.4. Concluding ICE 3.3.4. Concluding ICE
Once the state of each check list is Completed, and if the agent is Once the state of each check list is Completed, and if the agent is
the controlling, it nominates a candidate pair [ICE-BIS], it checks the controlling agent, it nominates a candidate pair [ICE-BIS] and
for each data stream whether the nominated pair matches the default checks for each data stream whether the nominated pair matches the
candidate pair. If there are one or more data streams with a match, default candidate pair. If there are one or more data streams with a
the controlling agent MUST generate a subsequent offer match, and the peer did not indicate support for the 'ice2' ice-
option, the controlling agent MUST generate a subsequent offer
(Section 3.4.1), in which the IP address, port and transport in the (Section 3.4.1), in which the IP address, port and transport in the
"c=" and "m=" lines associated with each data stream match the "c=" and "m=" lines associated with each data stream match the
corresponding local information of the nominated pair for that data corresponding local information of the nominated pair for that data
stream. stream.
However, If the support for 'ice2' ice-option is in use, the However, If the support for 'ice2' ice-option is in use, the
nominated candidate is noted and sent in the subsequent offer/answer nominated candidate is noted and sent in the subsequent offer/answer
exchange as the default candidate and no updated offer is needed to exchange as the default candidate and no updated offer is needed to
fix the default candidate. fix the default candidate.
Also as described in [ICE-BIS], once the controlling agent has Also as described in [ICE-BIS], once the controlling agent has
nominated a candidate pair for a data stream, the agent MUST NOT nominated a candidate pair for a data stream, the agent MUST NOT
nominate another pair for that data stream during the lifetime of the nominate another pair for that data stream during the lifetime of the
ICE session. ICE session (i.e. until ICE is restarted).
3.4. Subsequent Offer/Answer Exchanges 3.4. Subsequent Offer/Answer Exchanges
Either agent MAY generate a subsequent offer at any time allowed by Either agent MAY generate a subsequent offer at any time allowed by
[RFC3264]. This section defines rules for construction of subsequent [RFC3264]. This section defines rules for construction of subsequent
offers and answers. offers and answers.
Should a subsequent offer fail, ICE processing continues as if the Should a subsequent offer fail, ICE processing continues as if the
subsequent offer had never been made. subsequent offer had never been made.
skipping to change at page 10, line 32 skipping to change at page 10, line 32
data stream (see Section 3.2.1). This will cause ICE processing to data stream (see Section 3.2.1). This will cause ICE processing to
begin for this data stream. begin for this data stream.
3.4.1.2. Procedures for Full Implementations 3.4.1.2. Procedures for Full Implementations
This section describes additional procedures for full This section describes additional procedures for full
implementations, covering existing data streams. implementations, covering existing data streams.
3.4.1.2.1. Before Nomination 3.4.1.2.1. Before Nomination
When an offerer sends a subsequent offer, each "m=" section for which When an offerer sends a subsequent offer; in each "m=" section for
a candidate pair has not yet been nominated, the offer MUST include which a candidate pair has not yet been nominated, the offer MUST
the same set of ICE-related information that the offerer included in include the same set of ICE-related information that the offerer
the previous offer or answer. The agent MAY include additional included in the previous offer or answer. The agent MAY include
candidates it did not offer previously, but which it has gathered additional candidates it did not offer previously, but which it has
since the last offer/ answer exchange, including peer reflexive gathered since the last offer/ answer exchange, including peer
candidates. reflexive candidates.
The agent MAY change the default destination for media. As with The agent MAY change the default destination for media. As with
initial offers, there MUST be a set of candidate attributes in the initial offers, there MUST be a set of candidate attributes in the
offer matching this default destination. offer matching this default destination.
3.4.1.2.2. After Nomination 3.4.1.2.2. After Nomination
Once a candidate pair has been nominated for a data stream, the IP Once a candidate pair has been nominated for a data stream, the IP
address, port and transport in each "c=" and "m=" line associated address, port and transport in each "c=" and "m=" line associated
with that data stream MUST match the data associated with the with that data stream MUST match the data associated with the
skipping to change at page 11, line 23 skipping to change at page 11, line 23
See Appendix B for elaboration on this race condition. See Appendix B for elaboration on this race condition.
3.4.1.3. Procedures for Lite Implementations 3.4.1.3. Procedures for Lite Implementations
If the ICE state is running, a lite implementation MUST include all If the ICE state is running, a lite implementation MUST include all
of its candidates for each component of each data stream in of its candidates for each component of each data stream in
a=candidate attribute in any subsequent offer. The candidates are a=candidate attribute in any subsequent offer. The candidates are
formed identical to the procedures for initial offers. formed identical to the procedures for initial offers.
A lite implementation MUST NOT add additional host candidates or A lite implementation MUST NOT add additional host candidates or
change username fragments, password in a subsequent offer. change username fragments or passwords in a subsequent offer.
Otherwise, it MUST restart ICE. Otherwise, it MUST restart ICE.
If ICE has completed for a data stream and if the agent is If ICE has completed for a data stream and if the agent is
controlled, the default destination for that data stream MUST be set controlled, the default destination for that data stream MUST be set
to the remote candidate of the candidate pair for that component in to the remote candidate of the candidate pair for that component in
the valid list. For a lite implementation, there is always just a the valid list. For a lite implementation, there is always just a
single candidate pair in the valid list for each component of a data single candidate pair in the valid list for each component of a data
stream. Additionally, the agent MUST include a candidate attribute stream. Additionally, the agent MUST include a candidate attribute
for each default destination. for each default destination.
skipping to change at page 12, line 12 skipping to change at page 12, line 12
offer to deal with a race condition between the receipt of the offer, offer to deal with a race condition between the receipt of the offer,
and the receipt of the Binding Response that tells the answerer the and the receipt of the Binding Response that tells the answerer the
candidate that will be selected by ICE. See Appendix B for an candidate that will be selected by ICE. See Appendix B for an
explanation of this race condition. Consequently, processing of an explanation of this race condition. Consequently, processing of an
offer with this attribute depends on the winner of the race. offer with this attribute depends on the winner of the race.
The agent forms a candidate pair for each component of the data The agent forms a candidate pair for each component of the data
stream by: stream by:
o Setting the remote candidate equal to the offerer's default o Setting the remote candidate equal to the offerer's default
destination for that component (e.g., the contents of the "m=" and destination for that component (i.e. the contents of the "m=" and
"c=" lines for RTP, and the a=rtcp attribute for RTCP) "c=" lines for RTP, and the a=rtcp attribute for RTCP)
o Setting the local candidate equal to the transport address for o Setting the local candidate equal to the transport address for
that same component in the a=remote-candidates attribute in the that same component in the a=remote-candidates attribute in the
offer. offer.
The agent then sees if each of these candidate pairs is present in The agent then sees if each of these candidate pairs is present in
the valid list. If a particular pair is not in the valid list, the the valid list. If a particular pair is not in the valid list, the
check has "lost" the race. Call such a pair a "losing pair". check has "lost" the race. Call such a pair a "losing pair".
skipping to change at page 13, line 16 skipping to change at page 13, line 16
that were used in the previous ICE session, but it MUST change the that were used in the previous ICE session, but it MUST change the
SDP ice-pwd and ice-ufrag attribute values. SDP ice-pwd and ice-ufrag attribute values.
3.4.2.2. Lite Implementation specific procedures 3.4.2.2. Lite Implementation specific procedures
If the received offer contains the remote-candidates attribute for a If the received offer contains the remote-candidates attribute for a
data stream, the agent forms a candidate pair for each component of data stream, the agent forms a candidate pair for each component of
the data stream by: the data stream by:
o Setting the remote candidate equal to the offerer's default o Setting the remote candidate equal to the offerer's default
destination for that component (e.g., the contents of the "m=" and destination for that component (i.e., the contents of the "m=" and
"c=" lines for RTP, and the a=rtcp attribute for RTCP). "c=" lines for RTP, and the a=rtcp attribute for RTCP).
o Setting the local candidate equal to the transport address for o Setting the local candidate equal to the transport address for
that same component in the a=remote-candidates attribute in the that same component in the a=remote-candidates attribute in the
offer. offer.
The state of ICE processing for that data stream is set to Completed. The state of ICE processing for that data stream is set to Completed.
Furthermore, if the agent believed it was controlling, but the offer Furthermore, if the agent believed it was controlling, but the offer
contained the a=remote-candidates attribute, both agents believe they contained the a=remote-candidates attribute, both agents believe they
skipping to change at page 13, line 49 skipping to change at page 13, line 49
it no longer needs to. it no longer needs to.
Besides the potential role change, change in the Valid list, and Besides the potential role change, change in the Valid list, and
state changes, the construction of the answer is performed state changes, the construction of the answer is performed
identically to the construction of an offer. identically to the construction of an offer.
3.4.3. Receiving Answer for a Subsequent Offer 3.4.3. Receiving Answer for a Subsequent Offer
3.4.3.1. Procedures for Full Implementations 3.4.3.1. Procedures for Full Implementations
There may be certain situations where the offerer might receive SDP There may be certain situations where the offerer receives an SDP
answer that lacks ICE candidates although the initial answer did. answer that lacks ICE candidates although the initial answer did.
One example of such an "unexpected" answer might be happen when a One example of such an "unexpected" answer might be happen when an
ICE-unaware B2BUA introduces a media server during call hold using ICE-unaware B2BUA introduces a media server during call hold using
3rd party call-control procedures. Omitting further details how this 3rd party call-control procedures. Omitting further details how this
is done, this could result in an answer being received at the holding is done, this could result in an answer being received at the holding
UA that was constructed by the B2BUA. With the B2BUA being ICE- UA that was constructed by the B2BUA. With the B2BUA being ICE-
unaware, that answer would not include ICE candidates. unaware, that answer would not include ICE candidates.
Receiving an answer without ICE attributes in this situation might be Receiving an answer without ICE attributes in this situation might be
unexpected, but would not necessarily impair the user experience. unexpected, but would not necessarily impair the user experience.
When the offerer receives an answer indicating support for ICE, the When the offerer receives an answer indicating support for ICE, the
skipping to change at page 17, line 45 skipping to change at page 17, line 45
the ones defined by this specification. the ones defined by this specification.
<rel-addr> and <rel-port>: convey transport addresses related to the <rel-addr> and <rel-port>: convey transport addresses related to the
candidate, useful for diagnostics and other purposes. <rel-addr> candidate, useful for diagnostics and other purposes. <rel-addr>
and <rel-port> MUST be present for server reflexive, peer and <rel-port> MUST be present for server reflexive, peer
reflexive, and relayed candidates. If a candidate is server or reflexive, and relayed candidates. If a candidate is server or
peer reflexive, <rel-addr> and <rel-port> are equal to the base peer reflexive, <rel-addr> and <rel-port> are equal to the base
for that server or peer reflexive candidate. If the candidate is for that server or peer reflexive candidate. If the candidate is
relayed, <rel-addr> and <rel-port> are equal to the mapped address relayed, <rel-addr> and <rel-port> are equal to the mapped address
in the Allocate response that provided the client with that in the Allocate response that provided the client with that
relayed candidate (see section Appendix B.3 of [ICE-BIS] for a relayed candidate (see Appendix B.3 of [ICE-BIS] for a discussion
discussion of its purpose). If the candidate is a host candidate, of its purpose). If the candidate is a host candidate, <rel-addr>
<rel-addr> and <rel-port> MUST be omitted. and <rel-port> MUST be omitted.
In some cases, e.g., for privacy reasons, an agent may not want to In some cases, e.g., for privacy reasons, an agent may not want to
reveal the related address and port. In this case the address reveal the related address and port. In this case the address
MUST be set to "0.0.0.0" (for IPv4 candidates) or "::" (for IPv6 MUST be set to "0.0.0.0" (for IPv4 candidates) or "::" (for IPv6
candidates) and the port to zero. candidates) and the port to zero.
The candidate attribute can itself be extended. The grammar allows The candidate attribute can itself be extended. The grammar allows
for new name/value pairs to be added at the end of the attribute. for new name/value pairs to be added at the end of the attribute.
Such extensions MUST be made through IETF Review or IESG Approval Such extensions MUST be made through IETF Review or IESG Approval
[RFC5226] and the assignments MUST contain the specific extension and [RFC5226] and the assignments MUST contain the specific extension and
a reference to the document defining the usage of the extension a reference to the document defining the usage of the extension
An implementation MUST ignore any name/value pairs it doesn't An implementation MUST ignore any name/value pairs it doesn't
understand. understand.
Example: SDP line for UDP server reflexive candidate attribute for the RTP component Example: SDP line for UDP server reflexive candidate attribute for the RTP component
a=candidate:2 1 UDP 1694498815 192.0.2.3 45664 typ a=candidate:2 1 UDP 1694498815 192.0.2.3 45664 typ srflx raddr 10.0.1.1 rport 8998
srflx raddr 10.0.1.1 rport 8998
4.2. "remote-candidates" Attribute 4.2. "remote-candidates" Attribute
The syntax of the "remote-candidates" attribute is defined using The syntax of the "remote-candidates" attribute is defined using
Augmented BNF as defined in [RFC5234]. The remote-candidates Augmented BNF as defined in [RFC5234]. The remote-candidates
attribute is a media-level attribute only. attribute is a media-level attribute only.
remote-candidate-att = "remote-candidates:" remote-candidate remote-candidate-att = "remote-candidates:" remote-candidate
0*(SP remote-candidate) 0*(SP remote-candidate)
remote-candidate = component-ID SP connection-address SP port remote-candidate = component-ID SP connection-address SP port
skipping to change at page 19, line 28 skipping to change at page 19, line 26
session-level or media-level. When present in both, the value in the session-level or media-level. When present in both, the value in the
media-level takes precedence. Thus, the value at the session-level media-level takes precedence. Thus, the value at the session-level
is effectively a default that applies to all data streams, unless is effectively a default that applies to all data streams, unless
overridden by a media-level value. Whether present at the session or overridden by a media-level value. Whether present at the session or
media-level, there MUST be an ice-pwd and ice-ufrag attribute for media-level, there MUST be an ice-pwd and ice-ufrag attribute for
each data stream. If two data streams have identical ice-ufrag's, each data stream. If two data streams have identical ice-ufrag's,
they MUST have identical ice-pwd's. they MUST have identical ice-pwd's.
The ice-ufrag and ice-pwd attributes MUST be chosen randomly at the The ice-ufrag and ice-pwd attributes MUST be chosen randomly at the
beginning of a session (the same applies when ICE is restarting for beginning of a session (the same applies when ICE is restarting for
an agent.). an agent).
The ice-ufrag attribute MUST contain at least 24 bits of randomness, The ice-ufrag attribute MUST contain at least 24 bits of randomness,
and the ice-pwd attribute MUST contain at least 128 bits of and the ice-pwd attribute MUST contain at least 128 bits of
randomness. This means that the ice-ufrag attribute will be at least randomness. This means that the ice-ufrag attribute will be at least
4 characters long, and the ice-pwd at least 22 characters long, since 4 characters long, and the ice-pwd at least 22 characters long, since
the grammar for these attributes allows for 6 bits of information per the grammar for these attributes allows for 6 bits of information per
character. The attributes MAY be longer than 4 and 22 characters, character. The attributes MAY be longer than 4 and 22 characters,
respectively, of course, up to 256 characters. The upper limit respectively, of course, up to 256 characters. The upper limit
allows for buffer sizing in implementations. Its large upper limit allows for buffer sizing in implementations. Its large upper limit
allows for increased amounts of randomness to be added over time. allows for increased amounts of randomness to be added over time.
skipping to change at page 20, line 28 skipping to change at page 20, line 22
The same rule applies for ice-pacing attribute values lower than The same rule applies for ice-pacing attribute values lower than
50ms. This mandates that, if an agent includes the ice-pacing 50ms. This mandates that, if an agent includes the ice-pacing
attribute, its value MUST be greater than 50ms or else a value of attribute, its value MUST be greater than 50ms or else a value of
50ms is considered by default for that agent. 50ms is considered by default for that agent.
Also the larger of the ice-pacing attribute values between the offer Also the larger of the ice-pacing attribute values between the offer
and the answer (determined either by the one provided in the ice- and the answer (determined either by the one provided in the ice-
pacing attribute or by picking the default value) MUST be considered pacing attribute or by picking the default value) MUST be considered
for a given ICE session. for a given ICE session.
The mux category [I-D.ietf-mmusic-sdp-mux-attributes] for the 'ice-
pacing' attribute is 'TRANSPORT'.
Example shows ice-pacing value of 5 ms: Example shows ice-pacing value of 5 ms:
a=ice-pacing:5 a=ice-pacing:5
4.6. "ice-options" Attribute 4.6. "ice-options" Attribute
The "ice-options" attribute is a session- and media-level attribute. The "ice-options" attribute is a session- and media-level attribute.
It contains a series of tokens that identify the options supported by It contains a series of tokens that identify the options supported by
the agent. Its grammar is: the agent. Its grammar is:
ice-options = "ice-options:" ice-option-tag ice-options = "ice-options:" ice-option-tag
0*(SP ice-option-tag) 0*(SP ice-option-tag)
ice-option-tag = 1*ice-char ice-option-tag = 1*ice-char
The existence of an ice-option in an offer indicates that a certain The existence of an ice-option in an offer indicates that a certain
extension is supported by the agent and is willing to use it, if the extension is supported by the agent and is willing to use it, if the
peer agent also includes the same extension in the answer. There peer agent also includes the same extension in the answer. There
might be further extension specific negotiations needed between the might be further extension specific negotiation needed between the
agents that determine how the extensions gets used in a given agents that determine how the extensions gets used in a given
session. The details of the negotiation procedures, if present, MUST session. The details of the negotiation procedures, if present, MUST
be defined by the specification defining the extension (see be defined by the specification defining the extension (see
Section 10.2). Section 10.2).
Example shows 'rtp+ecn' ice-option SDP line from <<RFC6679>>: Example shows 'rtp+ecn' ice-option SDP line from <<RFC6679>>:
a=ice-options:rtp+ecn a=ice-options:rtp+ecn
5. Keepalives 5. Keepalives
skipping to change at page 26, line 34 skipping to change at page 26, line 27
will first perform connectivity checks to the target of media before will first perform connectivity checks to the target of media before
sending media there. If this target is a third-party host, the sending media there. If this target is a third-party host, the
checks will not succeed, and media is never sent. checks will not succeed, and media is never sent.
Unfortunately, ICE doesn't help if it's not used, in which case an Unfortunately, ICE doesn't help if it's not used, in which case an
attacker could simply send the offer without the ICE parameters. attacker could simply send the offer without the ICE parameters.
However, in environments where the set of clients is known, and is However, in environments where the set of clients is known, and is
limited to ones that support ICE, the server can reject any offers or limited to ones that support ICE, the server can reject any offers or
answers that don't indicate ICE support. answers that don't indicate ICE support.
User Agents that are not willing to receive non-ICE answers MUST SIP User Agents (UA) [RFC3261] that are not willing to receive non-
include an "ice" Option Tag in the Require Header Field in their ICE answers MUST include an "ice" Option Tag in the SIP Require
offer. Clients that rejects non-ICE offers SHOULD use a 421 response Header Field in their offer. UAs that rejects non-ICE offers SHOULD
code, together with an Option Tag "ice" in the Require Header Field use a 421 response code, together with an Option Tag "ice" in the
in the response. Require Header Field in the response.
9.2.2. Interactions with Application Layer Gateways and SIP 9.2.2. Interactions with Application Layer Gateways and SIP
Application Layer Gateways (ALGs) are functions present in a Network Application Layer Gateways (ALGs) are functions present in a Network
Address Translation (NAT) device that inspect the contents of packets Address Translation (NAT) device that inspect the contents of packets
and modify them, in order to facilitate NAT traversal for application and modify them, in order to facilitate NAT traversal for application
protocols. Session Border Controllers (SBCs) are close cousins of protocols. Session Border Controllers (SBCs) are close cousins of
ALGs, but are less transparent since they actually exist as ALGs, but are less transparent since they actually exist as
application-layer SIP intermediaries. ICE has interactions with SBCs application-layer SIP intermediaries. ICE has interactions with SBCs
and ALGs. and ALGs.
skipping to change at page 33, line 20 skipping to change at page 33, line 20
Some of the text in this document was taken from [RFC6336], authored Some of the text in this document was taken from [RFC6336], authored
by Magnus Westerlund and Colin Perkins. by Magnus Westerlund and Colin Perkins.
Many thanks to Christer Holmberg for providing text suggestions in Many thanks to Christer Holmberg for providing text suggestions in
Section 4 that aligns with [ICE-BIS] Section 4 that aligns with [ICE-BIS]
Thanks to Thomas Stach for text help, Roman Shpount for suggesting Thanks to Thomas Stach for text help, Roman Shpount for suggesting
RTCP candidate handling and Simon Perreault for advising on IPV6 RTCP candidate handling and Simon Perreault for advising on IPV6
address selection when candidate-address includes FQDN. address selection when candidate-address includes FQDN.
Many thanks to Flemming Andreasen for shepherd review feedback.
Thanks to following experts for their reviews and constructive Thanks to following experts for their reviews and constructive
feedback: Christer Holmberg, Adam Roach and the MMUSIC WG. feedback: Christer Holmberg, Adam Roach and the MMUSIC WG.
12. References 12. References
12.1. Normative References 12.1. Normative References
[I-D.ietf-mmusic-sdp-mux-attributes]
Nandakumar, S., "A Framework for SDP Attributes when
Multiplexing", draft-ietf-mmusic-sdp-mux-attributes-17
(work in progress), February 2018,
<http://www.rfc-editor.org/info/rfc7656>.
[ICE-BIS] Keranen, A. and J. Rosenberg, "Interactive Connectivity [ICE-BIS] Keranen, A. and J. Rosenberg, "Interactive Connectivity
Establishment (ICE): A Protocol for Network Address Establishment (ICE): A Protocol for Network Address
Translator (NAT) Traversal for Offer/Answer Protocols", Translator (NAT) Traversal for Offer/Answer Protocols",
draft-ietf-ice-rfc5245bis-00 (work in progress), March draft-ietf-ice-rfc5245bis-00 (work in progress), March
2015. 2015.
[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,
<http://www.rfc-editor.org/info/rfc2119>. <http://www.rfc-editor.org/info/rfc2119>.
skipping to change at page 35, line 41 skipping to change at page 35, line 36
[RFC6679] Westerlund, M., Johansson, I., Perkins, C., O'Hanlon, P., [RFC6679] Westerlund, M., Johansson, I., Perkins, C., O'Hanlon, P.,
and K. Carlberg, "Explicit Congestion Notification (ECN) and K. Carlberg, "Explicit Congestion Notification (ECN)
for RTP over UDP", RFC 6679, DOI 10.17487/RFC6679, August for RTP over UDP", RFC 6679, DOI 10.17487/RFC6679, August
2012, <http://www.rfc-editor.org/info/rfc6679>. 2012, <http://www.rfc-editor.org/info/rfc6679>.
[RFC6724] Thaler, D., Draves, R., Matsumoto, A., and T. Chown, [RFC6724] Thaler, D., Draves, R., Matsumoto, A., and T. Chown,
"Default Address Selection for Internet Protocol Version 6 "Default Address Selection for Internet Protocol Version 6
(IPv6)", RFC 6724, September 2012, (IPv6)", RFC 6724, September 2012,
<http://www.rfc-editor.org/info/rfc6724>. <http://www.rfc-editor.org/info/rfc6724>.
[RFC7656] Lennox, J., Gross, K., Nandakumar, S., Salgueiro, G., and
B. Burman, Ed., "A Taxonomy of Semantics and Mechanisms
for Real-Time Transport Protocol (RTP) Sources", RFC 7656,
DOI 10.17487/RFC7656, November 2015,
<http://www.rfc-editor.org/info/rfc7656>.
12.2. Informative References 12.2. Informative References
[RFC3725] Rosenberg, J., Peterson, J., Schulzrinne, H., and G. [RFC3725] Rosenberg, J., Peterson, J., Schulzrinne, H., and G.
Camarillo, "Best Current Practices for Third Party Call Camarillo, "Best Current Practices for Third Party Call
Control (3pcc) in the Session Initiation Protocol (SIP)", Control (3pcc) in the Session Initiation Protocol (SIP)",
BCP 85, RFC 3725, DOI 10.17487/RFC3725, April 2004, BCP 85, RFC 3725, DOI 10.17487/RFC3725, April 2004,
<http://www.rfc-editor.org/info/rfc3725>. <http://www.rfc-editor.org/info/rfc3725>.
[RFC3960] Camarillo, G. and H. Schulzrinne, "Early Media and Ringing [RFC3960] Camarillo, G. and H. Schulzrinne, "Early Media and Ringing
Tone Generation in the Session Initiation Protocol (SIP)", Tone Generation in the Session Initiation Protocol (SIP)",
 End of changes. 27 change blocks. 
56 lines changed or deleted 44 lines changed or added

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