Re: [MMUSIC] Proposal for what bundle should say about demux

Paul Kyzivat <pkyzivat@alum.mit.edu> Fri, 24 May 2013 14:57 UTC

Return-Path: <pkyzivat@alum.mit.edu>
X-Original-To: mmusic@ietfa.amsl.com
Delivered-To: mmusic@ietfa.amsl.com
Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id 48BF121F93BF for <mmusic@ietfa.amsl.com>; Fri, 24 May 2013 07:57:40 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: 0.526
X-Spam-Level:
X-Spam-Status: No, score=0.526 tagged_above=-999 required=5 tests=[AWL=-0.703, BAYES_00=-2.599, FH_RELAY_NODNS=1.451, HELO_MISMATCH_NET=0.611, RDNS_NONE=0.1, SARE_OBFU_RESULTING=1.666]
Received: from mail.ietf.org ([12.22.58.30]) by localhost (ietfa.amsl.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id wz3dArtnhglg for <mmusic@ietfa.amsl.com>; Fri, 24 May 2013 07:57:34 -0700 (PDT)
Received: from qmta12.westchester.pa.mail.comcast.net (qmta12.westchester.pa.mail.comcast.net [IPv6:2001:558:fe14:44:76:96:59:227]) by ietfa.amsl.com (Postfix) with ESMTP id 1A90621F8EF7 for <mmusic@ietf.org>; Fri, 24 May 2013 07:57:33 -0700 (PDT)
Received: from omta02.westchester.pa.mail.comcast.net ([76.96.62.19]) by qmta12.westchester.pa.mail.comcast.net with comcast id fnPZ1l0020QuhwU5CqxZwK; Fri, 24 May 2013 14:57:33 +0000
Received: from Paul-Kyzivats-MacBook-Pro.local ([50.138.229.164]) by omta02.westchester.pa.mail.comcast.net with comcast id fqxZ1l00Z3ZTu2S3NqxZuR; Fri, 24 May 2013 14:57:33 +0000
Message-ID: <519F7FDC.2070001@alum.mit.edu>
Date: Fri, 24 May 2013 10:57:32 -0400
From: Paul Kyzivat <pkyzivat@alum.mit.edu>
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.7; rv:17.0) Gecko/20130509 Thunderbird/17.0.6
MIME-Version: 1.0
To: Emil Ivov <emcho@jitsi.org>
References: <C5E08FE080ACFD4DAE31E4BDBF944EB11350F3C8@xmb-aln-x02.cisco.com> <519E80E4.6010904@jitsi.org> <519E9131.2080400@alum.mit.edu> <519F1424.8020803@jitsi.org> <CAMvTgcdpz5dh2zxRGu_xu1QdqsdAapgT-zziT5GzyzyodQxYXA@mail.gmail.com> <519F2BD8.8060803@jitsi.org> <CAMvTgcfx1t0d-NEavTxdq=9FEH9Z-wjX2S+HcSimFUgzg5-58g@mail.gmail.com> <519F2F8B.5080004@jitsi.org> <519F7633.1010902@alum.mit.edu> <CAPvvaaKMbee43bWf95iv-FgHZGaC5AWiydpuSh4Tgs122hcTtA@mail.gmail.com>
In-Reply-To: <CAPvvaaKMbee43bWf95iv-FgHZGaC5AWiydpuSh4Tgs122hcTtA@mail.gmail.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=comcast.net; s=q20121106; t=1369407453; bh=7gDBQDerjTbF2Z57/i+/VAOWMVrutwp3IO71OKaeQVQ=; h=Received:Received:Message-ID:Date:From:MIME-Version:To:Subject: Content-Type; b=oBPLbupajWyJ9l++YKuTxY25tq6JofYa1DNJbfkitxRsN7eYDPp/XRwFQbUlch8C3 OgkNgAFh3LeFuGCLeCbuPa0nPCy7iVqRcf+dE0ynoYuArC4lClWCQrRN22fsf0x2cU W5IPsJgU2fpVuECaOWc9qjbX4fnXWuTz4nxfnmxOn9DxRrnPsI7Jc+3rNZBq5SPqxc uDSxkUOMB/wjhiCdx4DXtt6RsKceCAicjW15Fo44r/rVzOtG1+BD9ebi1u4Zl2HWk3 vqL08LcNQjXhJQVmqyuqyyU0DaPVuImlynDaUZBB9IXovVlmX33tofigRP3Jf5ULfN QVZzP9ZlGW6zg==
Cc: mmusic <mmusic@ietf.org>
Subject: Re: [MMUSIC] Proposal for what bundle should say about demux
X-BeenThere: mmusic@ietf.org
X-Mailman-Version: 2.1.12
Precedence: list
List-Id: Multiparty Multimedia Session Control Working Group <mmusic.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/mmusic>, <mailto:mmusic-request@ietf.org?subject=unsubscribe>
List-Archive: <http://www.ietf.org/mail-archive/web/mmusic>
List-Post: <mailto:mmusic@ietf.org>
List-Help: <mailto:mmusic-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/mmusic>, <mailto:mmusic-request@ietf.org?subject=subscribe>
X-List-Received-Date: Fri, 24 May 2013 14:57:40 -0000

On 5/24/13 10:40 AM, Emil Ivov wrote:
> On May 24, 2013 5:16 PM, "Paul Kyzivat" <pkyzivat@alum.mit.edu
> <mailto:pkyzivat@alum.mit.edu>> wrote:
>  >
>  > On 5/24/13 5:14 AM, Emil Ivov wrote:
>  >>
>  >> On 24.05.13, 12:02, Kevin Dempsey wrote:
>  >>>
>  >>> I didn't say anything about changing the PTs.
>  >>
>  >>
>  >> Sorry, I misunderstood.
>  >>
>  >>> The answerer decides what
>  >>> it codecs it will use from the ones listed in the offer. If it doesn't
>  >>> support any other mechanism to allow demux then it must choose codecs
>  >>> that have PTs on only one m-line, or not accept the BUNDLE.
>  >>
>  >>
>  >> Matching packets to m= lines is the concern of the receiving party. So
>  >> is the mechanism that it uses. What you are suggesting is for the
>  >> answerer to basically say: "It seems to me that you won't be able to
>  >> demux these two payloads so I will not send them to you because I know
>  >> better".
>  >>
>  >> In the same time the offerer may be planning on using a demux technique
>  >> that the answerer simply isn't aware of. For example (and this is really
>  >> just to make a point, so please don't assume I am suggesting something
>  >> like this in general) if 101 is mapped to both telephone-event and VP8,
>  >> demuxing can be easily made without any other knowledge of SSRC or
>  >> header extensions.
>  >
>  >
>  > ISTM that after the O/A exchange both sides need to have a common
>  > understanding that their communications will be understandable.
>
> I assume this means you agree that an offerer has to make sure at least
> one of the demuxing mechanisms it supports will be understood by the
> answerer.

No. But the offerer had better ensure that there is some way to answer 
that meets the requirements.

Then it becomes a requirement on the answerer to answer in a way that 
makes the communication unambiguous. If it can't do that while bundling 
then it must remove the bundle, or remove some m-lines from the bundle, 
or reject some of the m-lines in the bundle, so that the resullting 
answer constructs an unambiguous communication.

If the intent is to rely on "magic" then that can be achieved by using 
fewer m-lines in the bundle, in a way that dumps more streams/flows into 
the same m-line. So this is really only an issue for plan A.

	Thanks,
	Paul