Re: [MMUSIC] Bundle offer with different ports - where to expect media?
Emil Ivov <emcho@jitsi.org> Tue, 21 May 2013 12:15 UTC
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Date: Tue, 21 May 2013 15:15:23 +0300
From: Emil Ivov <emcho@jitsi.org>
Organization: Jitsi
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To: Christer Holmberg <christer.holmberg@ericsson.com>
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> <7594FB04B1934943A5C02806D1A2204B1C375336@ESESSMB209.ericsson.se>
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Cc: mmusic <mmusic@ietf.org>, Paul Kyzivat <pkyzivat@alum.mit.edu>
Subject: Re: [MMUSIC] Bundle offer with different ports - where to expect media?
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Hey Christer, On 21.05.13, 14:53, 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? >> >> Note that I am not defending such an approach. I'd much prefer that splitting is only allowed when re-offering. > > Well, it could maybe work - but that means that the endpoint using the same port would have to include the m- line in the bundle group in subsequent offers/answers - otherwise you break the rule of not being allowed to use the same port number in an m- line :) Right. Or now that it at that point it could choose a different port (but again I am not defending this approach). >>>>> 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? > > It could. The reason we're talking about the first m= line is because it has been suggested that should represent the "bundle port". What I meant was the following: Paul expressed a concern that if we were to insist on using the first port from the rejected m= line, this could cause problems in cases where that line was rejected exactly because of that port (or the entire c= address for that line) did not please the answerer. I suppose this was an argument for using the remaining topmost address/port as a bundle address (rather than the one that was rejected). I guess what I don't understand is: what would be the case where an offerer created an offer such that the address in the topmost m=line was problematic for the answerer but the one in the second m= line was different enough so that it wouldn't be and so that it could successfully become the new bundle address. How likely would such a case be? Emil > > Regards, > > Christer > > > >>>>> 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. > > Emil > > -- > https://jitsi.org > -- https://jitsi.org
- [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)