Re: [MMUSIC] Bundle offer with different ports - where to expect media?
Eric Rescorla <ekr@rtfm.com> Tue, 21 May 2013 22:46 UTC
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References: <7594FB04B1934943A5C02806D1A2204B1C374357@ESESSMB209.ericsson.se> <519A1336.9010001@jitsi.org> <9F33F40F6F2CD847824537F3C4E37DDF1159D127@MCHP04MSX.global-ad.net> <519A229D.7090204@jitsi.org> <7594FB04B1934943A5C02806D1A2204B1C374463@ESESSMB209.ericsson.se> <519A2768.5010904@alum.mit.edu> <CAPvvaa+A=LkYp9A+wENAABwCYaQcD0HVeX4o+O_16iJRPXZfNw@mail.gmail.com> <7594FB04B1934943A5C02806D1A2204B1C3744DC@ESESSMB209.ericsson.se> <CAPvvaaJsPNk1DAJXYoc8aUgZ0ZayV_8q84W=Mm7vwuRRGuwC-g@mail.gmail.com> <7594FB04B1934943A5C02806D1A2204B1C374572@ESESSMB209.ericsson.se> <519A3883.8060006@jitsi.org> <519A3C8F.3040309@alum.mit.edu> <519B343A.30704@jitsi.org> <519BB598.1030909@alum.mit.edu> <CAOJ7v-398_MiXLWjexU0Z0xQju3A-zWuQFkWkJSLPA5UEGAu+g@mail.gmail.com>
From: Eric Rescorla <ekr@rtfm.com>
Date: Tue, 21 May 2013 15:46:03 -0700
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To: Justin Uberti <juberti@google.com>
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Cc: mmusic <mmusic@ietf.org>, Paul Kyzivat <pkyzivat@alum.mit.edu>, Christer Holmberg <christer.holmberg@ericsson.com>
Subject: Re: [MMUSIC] Bundle offer with different ports - where to expect media?
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That sounds good to me. On Tue, May 21, 2013 at 3:38 PM, Justin Uberti <juberti@google.com> wrote: > Lots of discussion here; is this an accurate summary of the discussed > behavior? > > 1) BUNDLE offerers must be able to receive on any port (until they get a > BUNDLE-compatible answer) > 2) Once the answer is received, bundling is activated, and BUNDLEs use > the port of the first non-rejected m= line in the offer > 2a) at this point, the other ports can be discarded > 3) All m= lines offered in a BUNDLE must be present in the answer, unless > they are rejected > 3a) no selective unbundling/BUNDLE splitting is permitted > > > On Tue, May 21, 2013 at 10:57 AM, Paul Kyzivat <pkyzivat@alum.mit.edu>wrote: > >> 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 mailing list >> mmusic@ietf.org >> https://www.ietf.org/mailman/**listinfo/mmusic<https://www.ietf.org/mailman/listinfo/mmusic> >> > > > _______________________________________________ > mmusic mailing list > mmusic@ietf.org > https://www.ietf.org/mailman/listinfo/mmusic > >
- [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)