Re: [MMUSIC] Bundle offer with different ports - where to expect media?
Paul Kyzivat <pkyzivat@alum.mit.edu> Tue, 21 May 2013 17:58 UTC
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Date: Tue, 21 May 2013 13:57:44 -0400
From: Paul Kyzivat <pkyzivat@alum.mit.edu>
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To: Emil Ivov <emcho@jitsi.org>
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Cc: mmusic <mmusic@ietf.org>, Christer Holmberg <christer.holmberg@ericsson.com>
Subject: Re: [MMUSIC] Bundle offer with different ports - where to expect media?
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On 5/21/13 4:45 AM, Emil Ivov wrote: > Hey Paul, > > On 20.05.13, 18:09, Paul Kyzivat wrote: >> On 5/20/13 10:51 AM, Emil Ivov wrote: >>> Hey Christer, >>> >>> On 20.05.13, 17:16, Christer Holmberg wrote: >>>> Hi, >>>> >>>>>>> What happens when the offerer knows the answerer has bundle >>>>>>> support, sends all m-lines with the same port, then the >>>>>>> answerer splits the first line away from the bundle? Would the >>>>>>> answerer still send everything to the same port? >>>>>> >>>>>> We discussed this week, >>>>>> >>>>> Yes, sorry, I didn't follow this closely. >>>>> >>>>>> and the outcome (at least my read of it :) was that the answerer >>>>>> is not allowed to split any m- lines away from the bundle in this >>>>>> case. Instead the answerer will have to send a new offer for the >>>>>> split, allowing new ports to be negotiated at both ends. >>>>> >>>>> OK, so shouldn't the same thing happen in the case with different >>>>> ports? >>>> >>>> I suggested that it should never be allowed to split an m- line from >>>> a bundle group in an answer, but others had other opinions. >>> >>> I don't see how we could allow it in one case and disallow it in the >>> other. The only difference between the two cases is how informed the >>> offerer is about the answerers bundle support capabilities and I don't >>> really understand why this would influence the decision to allow >>> splitting bundles one way or the other. >> >> It is a different case because the same port *can't* both be used as the >> bundle port and a port for an unbundled m-line. > > Why not? Obviously the offerer was prepared to demultiplex traffic > there. Why wouldn't it be able to continue doing so even if the answerer > would prefer to receive it separately? The point of wanting the one line unbundled is so that it can be *received* on a different address/port. Perhaps there is a separate device or process that will be supporting that one, that must be reached at its own addr/port. Unless you expect that this would have a common addr/port on the offering side and different addr/ports on the answering side. But we investigated that approach early in the bundle discussions, and gave it up. > Note that I am not defending such an approach. I'd much prefer that > splitting is only allowed when re-offering. > >>>> HOWEVER, it would still not help in the case where the 1st m- line is >>>> rejected. >>> >>> Well, how about looking at it this way: the offerer specifies a bundle >>> port in the first m=line. This also happens to be the port for the first >>> media line but the two are different things and just happen to have the >>> same value for reasons related to syntax and convenience. >>> >>> A bundle supporting answerer should understand this. After receiving the >>> offer that answerer has learned the bundle port number. Rejecting the >>> first m=line in the answer does not change this. >> >> There are many reasons that an answerer may reject an m-line. >> It is *possible* that it is rejecting it because it has a problem with >> the address (c=) for the m-line in the offer. If so, then if you insist >> on using it as the bundle address, even if the m-line is refused, then >> there is no way for the answerer to refuse it. >> >> (*Why* it would have a problem is an open question. Maybe its IPv6 and >> the answerer can't use it, or maybe its an FQDN and it can't be >> resolved. I realize this is unlikely. But making the assumption that the >> address must be acceptable to the answerer is IMO not a good idea.) > > Aha! That's a good point. > > Still, the thing that I don't quite understand is: if the answerer has a > problem with the c= line, how could that problem only apply to the first > m= line and not to the entire bundle? Presumably this would only happen if the c= for were not all the same in the offer. Certainly that is possible. When allocating "ports" for each m-line one might also end up with different addresses. >>> Of course the answer would come with the first m=line having a 0 port >>> but the offerer would then just learn the bundle port number at the >>> first m=line with a non-zero port. >> >> I presume you must have a motivation for wanting to go this way. >> Are you thinking this will simplify the implementation? > > No. The implementation is going to be slightly more complicated indeed > because instead of having one bundle demuxing socket and two regular > ones (well ... if rtcp demuxing counts as regular) you would have three > of them. I don't think this would be particularly horrifying in terms of > complexity though. > > Still, I think being consistent about the ports where one could get > multiplexed data is a good thing, and it could help (humans) when > analysing traffic and debugging network issues. Consistency is good. But isn't it just as consistent to say that the first *accepted* m-line defines the bundle addr/port as it is to say that the first offered m-line? Thanks, Paul
- [MMUSIC] Bundle offer with different ports - wher… Christer Holmberg
- Re: [MMUSIC] Bundle offer with different ports - … Emil Ivov
- Re: [MMUSIC] Bundle offer with different ports - … Hutton, Andrew
- Re: [MMUSIC] Bundle offer with different ports - … Emil Ivov
- Re: [MMUSIC] Bundle offer with different ports - … Christer Holmberg
- Re: [MMUSIC] Bundle offer with different ports - … Paul Kyzivat
- Re: [MMUSIC] Bundle offer with different ports - … Emil Ivov
- Re: [MMUSIC] Bundle offer with different ports - … Christer Holmberg
- Re: [MMUSIC] Bundle offer with different ports - … Hutton, Andrew
- Re: [MMUSIC] Bundle offer with different ports - … Emil Ivov
- Re: [MMUSIC] Bundle offer with different ports - … Christer Holmberg
- Re: [MMUSIC] Bundle offer with different ports - … Emil Ivov
- Re: [MMUSIC] Bundle offer with different ports - … Paul Kyzivat
- Re: [MMUSIC] Bundle offer with different ports - … Emil Ivov
- Re: [MMUSIC] Bundle offer with different ports - … Christer Holmberg
- Re: [MMUSIC] Bundle offer with different ports - … Emil Ivov
- Re: [MMUSIC] Bundle offer with different ports - … Cullen Jennings (fluffy)
- Re: [MMUSIC] Bundle offer with different ports - … Paul Kyzivat
- Re: [MMUSIC] Bundle offer with different ports - … Paul Kyzivat
- Re: [MMUSIC] Bundle offer with different ports - … Emil Ivov
- Re: [MMUSIC] Bundle offer with different ports - … Justin Uberti
- Re: [MMUSIC] Bundle offer with different ports - … Justin Uberti
- Re: [MMUSIC] Bundle offer with different ports - … Eric Rescorla
- Re: [MMUSIC] Bundle offer with different ports - … Emil Ivov
- Re: [MMUSIC] Bundle offer with different ports - … Martin Thomson
- Re: [MMUSIC] Bundle offer with different ports - … Justin Uberti
- Re: [MMUSIC] Bundle offer with different ports - … Christer Holmberg
- Re: [MMUSIC] Bundle offer with different ports - … Paul Kyzivat
- Re: [MMUSIC] Bundle offer with different ports - … Kevin Dempsey
- Re: [MMUSIC] Bundle offer with different ports - … Paul Kyzivat
- Re: [MMUSIC] Bundle offer with different ports - … Justin Uberti
- Re: [MMUSIC] Bundle offer with different ports - … Justin Uberti
- Re: [MMUSIC] Bundle offer with different ports - … Paul Kyzivat
- Re: [MMUSIC] Bundle offer with different ports - … Dale R. Worley
- Re: [MMUSIC] Bundle offer with different ports - … Christer Holmberg
- Re: [MMUSIC] Bundle offer with different ports - … Suhas Nandakumar
- Re: [MMUSIC] Bundle offer with different ports - … Christer Holmberg
- Re: [MMUSIC] Bundle offer with different ports - … Emil Ivov
- Re: [MMUSIC] Bundle offer with different ports - … Christer Holmberg
- Re: [MMUSIC] Bundle offer with different ports - … Cullen Jennings (fluffy)
- Re: [MMUSIC] Bundle offer with different ports - … Cullen Jennings (fluffy)
- [MMUSIC] When a bundle offer is forked Paul Kyzivat
- Re: [MMUSIC] When a bundle offer is forked Parthasarathi R
- Re: [MMUSIC] When a bundle offer is forked Paul Kyzivat
- Re: [MMUSIC] Bundle offer with different ports - … Martin Thomson
- Re: [MMUSIC] When a bundle offer is forked Martin Thomson
- Re: [MMUSIC] Bundle offer with different ports - … Paul Kyzivat
- Re: [MMUSIC] When a bundle offer is forked Paul Kyzivat
- Re: [MMUSIC] When a bundle offer is forked Dale R. Worley
- Re: [MMUSIC] Bundle offer with different ports - … Martin Thomson
- Re: [MMUSIC] When a bundle offer is forked Christer Holmberg
- Re: [MMUSIC] When a bundle offer is forked Parthasarathi R
- Re: [MMUSIC] When a bundle offer is forked Christer Holmberg
- Re: [MMUSIC] Bundle offer with different ports - … Paul Kyzivat
- Re: [MMUSIC] When a bundle offer is forked Parthasarathi R
- Re: [MMUSIC] When a bundle offer is forked Christer Holmberg
- Re: [MMUSIC] Bundle offer with different ports - … Martin Thomson
- Re: [MMUSIC] Bundle offer with different ports - … Martin Thomson
- Re: [MMUSIC] Bundle offer with different ports - … Paul Kyzivat
- Re: [MMUSIC] Bundle offer with different ports - … Martin Thomson
- Re: [MMUSIC] When a bundle offer is forked Cullen Jennings (fluffy)