[MMUSIC] Draft minutes from Vancouver
Colin Perkins <csp@csperkins.org> Sat, 19 November 2005 11:01 UTC
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Subject: [MMUSIC] Draft minutes from Vancouver
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Multiparty Multimedia Session Control (MMUSIC) Working Group Minutes ==================================================================== Reported by Colin Perkins The MMUSIC working group met once at the 64th IETF meeting (Vancouver, November 2005). Topics under discussion included ICE, RTSP, RTSP/ SIP inter-working, and SDP connectivity preconditions, security for early media, identification of QoS mechanisms for preconditions, seamless session mobility, and codec specific parameters. The meeting was chaired by Joerg Ott and Colin Perkins and attended by some 140 participants. ICE draft-ietf-mmusic-ice-06.txt draft-rosenberg-mmusic-ice-tcp-00.txt Jonathan Rosenberg discussed the updated ICE specification starting with a summary of the extensive changes since the previous draft (see slides for details), then moving on to a detailed discussion of the key changes. The specification of how to use TCP alternatives with ICE has been moved into a separate draft. There was some detailed discussion of the new draft, in particular Cullen Jennings asked why it's not possible to run ICE TCP using the same port as the original candidate pair? This in turn led to a discussion of simultaneous open, with Cullen and Flemming Andreasen discussing whether simultaneous open could be made to work in ICE TCP, to facilitate operation through symmetric NATs. It was noted that a BEHAVE compliant NAT will allow simultaneous open without a TURN relay, but this is not allowed in ICE TCP (since some operating systems may have problems with simultaneous open of TCP connections). It was suggested that change ICE TCP from "MUST open from different port" to "MUST open from different port and MAY attempt open from the same port" to resolve this issue. The consensus of the room was that it is appropriate to accept ICE-TCP as an MMUSIC work item. Robert Sparks noted that the new ICE draft has many examples, some of which are rather complex, and suggested splitting them out into a new draft to simplify the base draft. Jonathan wasn't keen on this, seeing benefit in the examples, and they compromised by agreeing to move the complex example to an appendix, replacing it in the main text with a simpler example. The -06 version of ICE solves the race condition noted during the 62nd IETF meeting using a mechanism based on PRACK and UPDATE. There was a heated discussion of this mechanism, with many people complaining that PRACK and UPDATE are complex and difficult to implement, and requesting an alternative ICE formulation which doesn't require them. Others noted that this mechanism was discussed in a previous working group session, and suggested that the complexity argument was overblown. There was no resolution to this discussion in the meeting, and after a review of the issues, an ad-hoc meeting was scheduled to discuss the issues in detail later in the week (notes from the side meeting were sent to the mailing list on 14th November 2005). RTSP draft-ietf-mmusic-rfc2326bis-11.txt draft-ietf-mmusic-rtsp-nat-04.txt Magnus Westerlund reviewed the changes in the latest version of the RTSP specification. The main changes are: changed version number from 1.1 to 2.0; updated the ABNF to conform to RFC 4234 and noted that any "string" in ABNF is case-insensitive; clarified use of the Allow header in SETUP and DESCRIBE methods, use of the Transport header parameter "mode", and use of SET_PARAMETER payloads. The specification is considered largely complete, except that the minimal implementation section needs revising, and there is a need for editorial review and simplification. Anders Klemets asked if the use of the Range header in PAUSE commands is a candidate for simplification, since it's one of the more complex parts of the specification. Magnus replied that this isn't under consideration since its removal would remove the ability to signal "play exactly this segment". The scheduled discussion of how ICE can be used with RTSP did not take place, due to the overrun of the previous ICE discussion. RTSP/SIP inter-working Jonathan Rosenberg briefly discussed RTSP/SIP inter-working, skipping his prepared presentation due to lack of time, and noting that there appears to be interest in this subject, and that he'll put together an initial draft. People who are interested in this work should contact Jonathan to contribute to the proposal. SDP Content Attribute draft-ietf-mmusic-sdp-media-content-00.txt Jani Hautakorpi briefly outlined the concept of the SDP content attribute draft, and noted that the latest draft is now clearly delineated from the work done in other working groups. It also includes pre-defined values of the attribute. Magnus Westerlund suggested that the next version of the draft clarify that the content attribute is declarative in the offer/answer model, not subject to negotiation. Joerg Ott encouraged review, reminding the group that it will take a while to setup the IANA registry to accept further registrations, so it is desirable to ensure the initial list of labels is appropriate and largely complete. SDP Connectivity Precondition draft-ietf-mmusic-connectivity-precon-01.txt Flemming Andreasen discussed the SDP Connectivity Precondition. This completed working group last call without substantive issues, but the authors felt a few changes were warranted, and submitted the -01 draft. Changes in this version include: the recommended baseline method of connectivity checks for datagram transport was changed from RTP No-op to ICE; procedures associated with using ICE to verify connectivity were clarified; and it was clarified that the semantics of the connectivity preconditions do not include verification of the peer identify. This draft will be updated to match future changes in ICE, and is intended to progress in tandem with ICE (on which there is now a normative dependency). Early Media for SDP Security Descriptions draft-wing-mmusic-sdes-early-media-00.txt Dan Wing and Rob Raymond discussed early media and security descriptions for SDP. The issue here is that early media can't be secured until the SDP answer arrives, and this can potentially cause clipping. A possible solution is to use security preconditions, but this adds additional call setup time and is complex to implement, therefore this draft proposes to include a key for the called party to use in the initial SDP offer. This doesn't require PRACK of preconditions, and so is simpler to implement. There are some open issues regarding use of MKI, early media forking, and retargeting. Dave Oran repeated a comment from the ICE discussion that PRACK will be needed eventually, and that implementers need to accept its complexity. He also agreed that this is the logical solution, should one not wish to implement PRACK. There was discussion regarding the usefulness of secure early media, with the general consensus that it was useful. There was no consensus on this particular proposal however: an approach going forward would be to consider the requirements and constraints, and how they are addressed by existing mechanisms, before completing the details of this proposal. QoS Mechanism Identification in SDP draft-polk-mmusic-qos-mechanism-identification-00.txt Gonzalo Camarillo discussed a new draft that proposes ways to indicate which QoS mechanism is to be used for media streams. This can be used with the QoS precondition and the SDP offer/answer model, for example, to negotiate either RSVP or NSIS. Gonzalo posed two questions: is there a need to agree on something else in addition to the mechanism to use (e.g. parameters for the mechanism), and if so should the draft discuss how to agree those parameters? Flemming Andreasen asked how things like within-network RSVP proxies interact with this sort of mechanism? Jonathan Rosenberg asked where the fallback to a different QoS scheme was handled? E.g. if one wishes to try NSIS then fallback to RSVP when not available, is that handled by the QoS layer or does it need to be signalled in SDP? These questions led to further requirements discussion, rather than consideration of the details of the draft. There was no clear consensus to accept this as an MMUSIC work item. The chairs noted that there was general interest in the concept though, and suggested that draft be further revised as an individual draft with more requirements discussion, and we can revisit the decision to accept this as a work item at next meeting. Requirements for IPsec Negotiation in the SIP Framework draft-saito-mmusic-ipsec-negotiation-req-01.txt Makoto Saito discussed requirements for IPsec negotiation in the SIP framework. This draft discusses why one might want to use SDP offer/ answer with sdescriptions/mikey to negotiate IPsec parameters, which can be applied to secure the media streams. Colin Perkins noted that IPsec can be used to secure arbitrary sessions, not just multiparty multimedia sessions, and wondered if SDP offer/answer is an appropriate base for such negotiation, or if this is outside the scope of MMUSIC? Others, including Jon Peterson, considered this in scope, since it requires extensions to sdescriptons. Jon Peterson and Joerg Ott noted, however, that there is no obvious community interest in the work, and as a result it seems premature to consider it as an MMUSIC work item. SDP Extensions for Seamless Session Mobility draft-mingqiang-mmusic-session-mobility-attribute-01.txt Xu Mingqiang discussed requirements for seamless session mobility, aiming to transfer a streaming media session between devices without disruption to the playout. Compared to the version discussed at the previous meeting, this draft contains a more detailed requirements discussion, without presupposing a particular solution. Magnus Westerlund and Colin Perkins noted that the draft still confuses several problems that should be treated separately, for example moving sessions between users and synchronised playout. Further clarification of requirements is needed, treating problems individually, rather than with a systems focus. Codec Specific Parameter in SDP draft-xu-mmusic-sdp-codec-param-00 Peili Xu discussed adding general codec parameters to SDP. There are two requirements here: 1) a per-codec equivalent to "a=ptime:", rather than a media level parameter as currently defined; and 2) codec level transport addresses, to divert certain payload formats away from the addresses on the c= and m= lines, for example to insert a transcoder. Magnus Westerlund noted that the second requirement can be solved using a separate signalled session incorporating the transcoder. Joerg Ott and Colin Perkins agreed, suggesting both requirements might be solved using existing protocols and mechanisms. Further clarification of requirements and the degree to which existing mechanisms apply is needed before this draft can proceed. - + - _______________________________________________ mmusic mailing list mmusic@ietf.org https://www1.ietf.org/mailman/listinfo/mmusic
- [MMUSIC] Draft minutes from Vancouver Colin Perkins