Re: [rtcweb] BUNDLE with implicit rtcp-mux
Justin Uberti <juberti@google.com> Thu, 20 March 2014 00:21 UTC
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From: Justin Uberti <juberti@google.com>
Date: Wed, 19 Mar 2014 17:21:05 -0700
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To: Magnus Westerlund <magnus.westerlund@ericsson.com>
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Cc: "rtcweb@ietf.org" <rtcweb@ietf.org>
Subject: Re: [rtcweb] BUNDLE with implicit rtcp-mux
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On Mon, Mar 17, 2014 at 6:23 AM, Magnus Westerlund < magnus.westerlund@ericsson.com> wrote: > On 2014-03-14 17:26, Justin Uberti wrote: > > > > > > > > On Fri, Mar 14, 2014 at 1:57 AM, Magnus Westerlund > > <magnus.westerlund@ericsson.com <mailto:magnus.westerlund@ericsson.com>> > > wrote: > > > > Hi, > > (as individual) > > > > Although this discussion really should be on MMUSIC, I am still > > following up here. Anything we come to conclude here really need to > go > > to MMUSIC for confirmation. > > > > Justin, I do agree that it appear unnecessarily of having to include > an > > RTCP transport in an OFFER when the offerer know the answerer is > BUNDLE > > capable. I am fine with that and think the rule needed here is > something > > along the line of the below: > > > > A BUNDLE supporting endpoint MUST implement a=rtcp-mux (that is > already > > required). In any answer by a BUNDLE capable endpoint, it MUST NOT > > change the usage of a=rtcp-mux. If it is present in the offer, it > must > > be confirmed to be used in the answer, and if not present in the > offer, > > it MUST NOT be added in the answer. An BUNDLE capable endpoint is > > RECOMMENDED to use a=rtcp-mux whenever suitable. Cases when it might > not > > be suitable include, lack RTP payload types, or cases when RTCP > traffic > > is needed to be on its own transport flow (5-tuple) to enable QoS or > > other traffic handling functionalities. > > > > The reason for writing the rule like the above, is that then an > endpoint > > can choose when creating an offer to renegotiate the use of > a=rtcp-mux. > > For example due to it running out of available PTs. > > > > Feedback on this proposal? > > > > > > I am not OK with this. It just gets too complicated to deal with all the > > cases, especially if with the provision that rtcp-mux can change during > > the session. > > (still as individual) > > Lets be clear what we are discussing here. I don't think this is lot of > cases. And if you don't want to implement this in your code generating > offer, that is fine. What this describes is that your code handling > reception of offers and generating answers must be able to handle the > lack of a=rtcp-mux in any offer, rather than just the initial one. > > I would question if even that assumption holds considering what happens > if people start implementing session resumption or session mobility > between devices using rehydration style establishment procedures. What > one sides consider an initial offer might not be the state the answering > party is in. Thus, I am worried about cases that are first offer/answer > exchange related. > > To my understanding you will have code to handle the following cases > when offers contains: > > 1) No bundle, no a=rtcp-mux > 2) No bundle, with a=rtcp-mux > 3) Bundle, with a=rtcp-mux > > Considering that you support bundle, and you support usage or not of > a=rtcp-mux. Then I don't see how the code handling the SDP logic for > Bundle, without a=rtcp-mux is that significant. > It is significant because you always know you can rtcp-mux. And you always know you can BUNDLE when rtcp-muxing. But I think trying to BUNDLE a no-rtcp-mux m= line into a rtcp-mux m= line is asking for problems. > > First of all, to be robust, you have to be capable of handling > significant reconfigurations of the Peer Connection session in an Offer. > If someone moves the peer of one peer connection to another device > anything can happen, and everything can change. > > Secondly, to be able to turn off a=rtcp-mux is one method which can free > up PTs if one run out. The other would be first unbundle the media > types, then to completely unbundle the media sources. The later would be > far worse when it comes to requiring providing ICE candidates and > dealing with new transports. I however think unbundling the media types > is likely to resolve many of the PT shortage situations. > > Just to confirm, you are also against allowing any initial offer request > with bundle but without a=rtcp-mux within that bundle-group? > I am against _any_ offer request with bundle and without a=rtcp-mux (as indicated in the current bundle draft). > > This, I would question, as it prevents anyone from treating the RTCP > packets differently from the RTP packets within one RTP session. I know > that this has been done in some cases, including IMS. > > From a principal point of view I think this should be either be use of > BUNDLE groups results in MUST use a=rtcp-mux with RTP or that any offer > may change the usage of a=rtcp-mux. Anything else depending on initial > offer appears very messy and prone to errors. > > I would appreciate if someone else would provide their input and views > here! > > First on the question if they need to separate the RTP and RTCP at all > within a BUNDLE group? > > Secondly if they see that splitting a bundle group into different groups > if one runs into issue is a sufficient and more preferred method for > dealing with any PT exhaustion issue? > > > Cheers > > Magnus Westerlund > > ---------------------------------------------------------------------- > Services, Media and Network features, Ericsson Research EAB/TXM > ---------------------------------------------------------------------- > Ericsson AB | Phone +46 10 7148287 > Färögatan 6 | Mobile +46 73 0949079 > SE-164 80 Stockholm, Sweden | mailto: magnus.westerlund@ericsson.com > ---------------------------------------------------------------------- > >
- [rtcweb] BUNDLE with implicit rtcp-mux Justin Uberti
- Re: [rtcweb] BUNDLE with implicit rtcp-mux Christer Holmberg
- Re: [rtcweb] BUNDLE with implicit rtcp-mux Magnus Westerlund
- Re: [rtcweb] BUNDLE with implicit rtcp-mux Christer Holmberg
- Re: [rtcweb] BUNDLE with implicit rtcp-mux Magnus Westerlund
- Re: [rtcweb] BUNDLE with implicit rtcp-mux Christer Holmberg
- Re: [rtcweb] BUNDLE with implicit rtcp-mux Magnus Westerlund
- Re: [rtcweb] BUNDLE with implicit rtcp-mux Christer Holmberg
- Re: [rtcweb] BUNDLE with implicit rtcp-mux Bernard Aboba
- Re: [rtcweb] BUNDLE with implicit rtcp-mux Stach, Thomas
- Re: [rtcweb] BUNDLE with implicit rtcp-mux Christer Holmberg
- Re: [rtcweb] BUNDLE with implicit rtcp-mux Justin Uberti
- Re: [rtcweb] BUNDLE with implicit rtcp-mux Magnus Westerlund
- Re: [rtcweb] BUNDLE with implicit rtcp-mux Christer Holmberg
- Re: [rtcweb] BUNDLE with implicit rtcp-mux Magnus Westerlund
- Re: [rtcweb] BUNDLE with implicit rtcp-mux Christer Holmberg
- Re: [rtcweb] BUNDLE with implicit rtcp-mux Justin Uberti
- Re: [rtcweb] BUNDLE with implicit rtcp-mux Paul Kyzivat
- Re: [rtcweb] BUNDLE with implicit rtcp-mux Christer Holmberg
- Re: [rtcweb] BUNDLE with implicit rtcp-mux Christer Holmberg
- Re: [rtcweb] BUNDLE with implicit rtcp-mux Justin Uberti
- Re: [rtcweb] BUNDLE with implicit rtcp-mux Christer Holmberg
- Re: [rtcweb] BUNDLE with implicit rtcp-mux Magnus Westerlund
- Re: [rtcweb] BUNDLE with implicit rtcp-mux Justin Uberti
- Re: [rtcweb] BUNDLE with implicit rtcp-mux Christer Holmberg
- Re: [rtcweb] BUNDLE with implicit rtcp-mux Justin Uberti
- Re: [rtcweb] BUNDLE with implicit rtcp-mux Christer Holmberg
- Re: [rtcweb] BUNDLE with implicit rtcp-mux Justin Uberti
- Re: [rtcweb] BUNDLE with implicit rtcp-mux Christer Holmberg
- Re: [rtcweb] BUNDLE with implicit rtcp-mux Magnus Westerlund
- Re: [rtcweb] BUNDLE with implicit rtcp-mux Justin Uberti
- Re: [rtcweb] BUNDLE with implicit rtcp-mux Magnus Westerlund