Re: [MMUSIC] Bundle offer with different ports - where to expect media?
Justin Uberti <juberti@google.com> Tue, 21 May 2013 22:38 UTC
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From: Justin Uberti <juberti@google.com>
Date: Tue, 21 May 2013 15:37:58 -0700
Message-ID: <CAOJ7v-3HjxmcFoNfUDg_M2wWiUaco=7GBJP8y2czUTaF4JEDbw@mail.gmail.com>
To: Emil Ivov <emcho@jitsi.org>
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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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On Tue, May 21, 2013 at 3:34 PM, Emil Ivov <emcho@jitsi.org> wrote: > Hey Paul, > > On 21.05.13, 20:57, Paul Kyzivat 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. > > Yes, sure. My point was that the party that unbundled the one m= line > can receive it separately. The party that sent the offer can keep > getting it on the same 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. > > No I don't and I suspect you misunderstood me. > > Also in all my comments I kept noting that we shouldn't be allowing the > answer to unbundle a single m= line. In your response to Cullen you > seemed to agree with this so I guess we are in agreement. > > >> 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. > > This makes me wonder: should we even allow for different c= addresses > within a bundle? The reason to use different ports was a compromise, not > a choice based on the necessity to give that option to applications. > While falling back to different port numbers is defendable, I don't see > how we would justify the possibility to fallback to different c= lines. > > > 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? > > The bundle suggestion started out by saying that all ports would be the > same. We then moved to a version where we would use different ports, in > order to prevent some non-bundle endpoints from fainting at the sight of > port reuse. We still agreed that the first one is the bundle port and > the others are there just for fall back. So far so good. > > Now we are discussing the possibility of saying: your bundle port will > be the first one you offer, unless the answerer rejects that m= line, in > which case it could be the port of the second m= line, or the third one ... > > I agree it wouldn't be the end of the world, but to me this doesn't > sound particularly consistent. > Perhaps not the most elegant thing in the world, but it doesn't seem inconsistent to me. I think this is the most practical choice.
- [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)