draft-ietf-mmusic-ice-sip-sdp-17.txt   draft-ietf-mmusic-ice-sip-sdp-18.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: September 27, 2018 A. Keranen Expires: October 1, 2018 A. Keranen
Ericsson Ericsson
March 26, 2018 March 30, 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-17 draft-ietf-mmusic-ice-sip-sdp-18
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
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at 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 September 27, 2018. This Internet-Draft will expire on October 1, 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
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If an agent wishes to add a new data stream, it sets the fields in If an agent wishes to add a new data stream, it sets the fields in
the SDP for this data stream as if this was an initial offer for that the SDP for this data stream as if this was an initial offer for that
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.
3.4.1.3. 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, each "m=" section for which
a candidate pair has not yet been nominated, the offer MUST include a candidate pair has not yet been nominated, the offer MUST include
the same set of ICE-related information that the offerer included in the same set of ICE-related information that the offerer included in
the previous offer or answer. The agent MAY include additional the previous offer or answer. The agent MAY include additional
candidates it did not offer previously, but which it has gathered candidates it did not offer previously, but which it has gathered
since the last offer/ answer exchange, including peer reflexive since the last offer/ answer exchange, including peer reflexive
candidates. 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.
3.4.1.4. 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
nominated pair for that data stream. In addition, the offerer only nominated pair for that data stream. In addition, the offerer only
includes SDP candidates representing the local candidates of the includes SDP candidates representing the local candidates of the
nominated candidate pair. The offerer MUST NOT include any other SDP nominated candidate pair. The offerer MUST NOT include any other SDP
candidate attributes in the subsequent offer. candidate attributes in the subsequent offer.
In addition, if the agent is controlling, it MUST include the In addition, if the agent is controlling, it MUST include the
a=remote-candidates attribute for each data stream whose check list a=remote-candidates attribute for each data stream whose check list
is in the completed state. The attribute contains the remote is in the completed state. The attribute contains the remote
candidates corresponding to the nominated pair in the valid list for candidates corresponding to the nominated pair in the valid list for
each component of that data stream. It is needed to avoid a race each component of that data stream. It is needed to avoid a race
condition whereby the controlling agent chooses its pairs, but the condition whereby the controlling agent chooses its pairs, but the
updated offer beats the connectivity checks to the controlled agent, updated offer beats the connectivity checks to the controlled agent,
which doesn't even know these pairs are valid, let alone selected. which doesn't even know these pairs are valid, let alone selected.
See Appendix B for elaboration on this race condition. See Appendix B for elaboration on this race condition.
3.4.1.5. 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, password in a subsequent offer.
Otherwise, it MUST restart ICE. Otherwise, it MUST restart ICE.
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performing off-path QoS reservations, NAT traversal components such performing off-path QoS reservations, NAT traversal components such
as ALGs and Session Border Controllers (SBCs), and diagnostic tools as ALGs and Session Border Controllers (SBCs), and diagnostic tools
that passively monitor the network. For these tools to continue to that passively monitor the network. For these tools to continue to
function without change, the core property of SDP -- that the function without change, the core property of SDP -- that the
existing, pre-ICE definitions of the addresses used for media -- the existing, pre-ICE definitions of the addresses used for media -- the
"m=" and "c=" lines and the rtcp attribute -- must be retained. For "m=" and "c=" lines and the rtcp attribute -- must be retained. For
this reason, an updated offer must be sent. this reason, an updated offer must be sent.
Appendix E. Contributors Appendix E. Contributors
o Christer Holmberg Ericsson Email: christer.holmberg@ericsson.com Following experts have contributed a textual and structural
[9] suggestions for this work
o Roman Shpount TurboBridge rshpount@turbobridge.com [10] 1. Christer Holmberg
o Thomas Stach thomass.stach@gmail.com [11] * Ericsson
* Email: christer.holmberg@ericsson.com [9]
2. Roman Shpount
* TurboBridge
* rshpount@turbobridge.com [10]
3. Thomas Stach
* thomass.stach@gmail.com [11]
Authors' Addresses Authors' Addresses
Marc Petit-Huguenin Marc Petit-Huguenin
Impedance Mismatch Impedance Mismatch
Email: marc@petit-huguenin.org Email: marc@petit-huguenin.org
Suhas Nandakumar Suhas Nandakumar
Cisco Systems Cisco Systems
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