Re: [rtcweb] BUNDLE with implicit rtcp-mux
Magnus Westerlund <magnus.westerlund@ericsson.com> Mon, 10 March 2014 14:28 UTC
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Date: Mon, 10 Mar 2014 15:27:53 +0100
From: Magnus Westerlund <magnus.westerlund@ericsson.com>
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To: Christer Holmberg <christer.holmberg@ericsson.com>, Justin Uberti <juberti@google.com>, "rtcweb@ietf.org" <rtcweb@ietf.org>, Eric Rescorla <ekr@rtfm.com>
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Archived-At: http://mailarchive.ietf.org/arch/msg/rtcweb/6CeR9bM0Ct7r1NEmm32CM8Qh3kM
Subject: Re: [rtcweb] BUNDLE with implicit rtcp-mux
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On 2014-03-10 15:13, Christer Holmberg wrote: > Hi, > >>> Before I comment on your proposal, let's take a few steps back >>> (maybe it can even solve your issue). >>> >>> BUNDLE currently mandates the usage of both the SDP rtcp-mux and >>> rtcp attributes. I remember we had discussions about that, but I >>> don't remember the justification at the moment. But, I wonder >>> whether that text is from before we made a decision that, unless >>> both endpoints support BUNDLE, no endpoint will use a single >>> address:port. >>> >>> >>> >>> So, the question is: do we really need the SDP rtcp attribute? >> >> I think it is a question of how you want the fallback to work. In >> the case of bundle only lines, a non bundle supporting peer will >> reject them, thus no issues with what is written around RTCP-mux >> and a=rtcp in those m= blocks. However, the first one if you want >> that to support fallback that makes sense then you will need both >> a=rtcp-mux and an a=rtcp (with a different port) to handle that >> with optimal backwards compatibility. >> >> Regarding the motivation for a=rtcp-mux and a=rtcp, I think it is >> reasonably straight forward. We want a=rtcp-mux to minimize port >> usage, i.e. ports=1. Not supporting a=rtcp-mux with bundle that >> would mean two ports (RTP and RTCP) for the bundle group. To get >> the backwards compatibility the usage of a=rtcp would be required. > > Keep in mind that the offerer must always be prepared that the > answerer does not support the rtcp-mux attribute (or the rtcp > attribute). Yes, that was what I meant with fallback in the above text. What you do in case the peer doesn't support bundle. > > So, at least my understanding is: no matter whether BUNDLE is used or > not, if the answer does not contain a rtcp-mux (e.g. in case of > fallback) attribute, the offerer must use the default "rtp+1" port. I have a tendency to agree, which means that the first m= block in a bunde-only group will be required to contain a=rtcp and if RTCP mux is desired also that attribute. I think a=rtcp could be skipped for a bound-only m= block due to the requirement on supporting a=rtcp-mux if you do bundle. 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