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

Paul Kyzivat <pkyzivat@alum.mit.edu> Fri, 24 May 2013 14:16 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 342E521F8F43 for <mmusic@ietfa.amsl.com>; Fri, 24 May 2013 07:16:25 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -0.306
X-Spam-Level:
X-Spam-Status: No, score=-0.306 tagged_above=-999 required=5 tests=[AWL=0.131, BAYES_00=-2.599, FH_RELAY_NODNS=1.451, HELO_MISMATCH_NET=0.611, RDNS_NONE=0.1]
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 H61iGFjNU9sj for <mmusic@ietfa.amsl.com>; Fri, 24 May 2013 07:16:20 -0700 (PDT)
Received: from qmta15.westchester.pa.mail.comcast.net (qmta15.westchester.pa.mail.comcast.net [IPv6:2001:558:fe14:44:76:96:59:228]) by ietfa.amsl.com (Postfix) with ESMTP id B1B2121F8F20 for <mmusic@ietf.org>; Fri, 24 May 2013 07:16:20 -0700 (PDT)
Received: from omta02.westchester.pa.mail.comcast.net ([76.96.62.19]) by qmta15.westchester.pa.mail.comcast.net with comcast id fnMQ1l0060QuhwU5FqGLgH; Fri, 24 May 2013 14:16:20 +0000
Received: from Paul-Kyzivats-MacBook-Pro.local ([50.138.229.164]) by omta02.westchester.pa.mail.comcast.net with comcast id fqGK1l01T3ZTu2S3NqGLF2; Fri, 24 May 2013 14:16:20 +0000
Message-ID: <519F7633.1010902@alum.mit.edu>
Date: Fri, 24 May 2013 10:16:19 -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>
In-Reply-To: <519F2F8B.5080004@jitsi.org>
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=1369404980; bh=nN7JlXQu8TBe+IDUb//Ld/Et+9YKMSHsaRI9Q73WKvM=; h=Received:Received:Message-ID:Date:From:MIME-Version:To:Subject: Content-Type; b=VWD+/3TdJpu7IqWJL/FWDR0jFBsIduvXgMbtBm9RNFbGKsOnM69epn1BfE4Bkhr1J diseZlRRD79I4R1cs9r4hGtuU0VRRuHwLAqIJhjligR9vbGZNpeDZdL3cCz+UBscCu dAOe7JiEEF2Jc8eFoJlZxYZ3E4QFT2sOv119qu0sgqlj+AGqxYJE14XSh5H2YQu3AC GZLYTSFNHgYdkPY9pOiCSFlycu+LiAFKJmXHN5neKeSLr9XRKqeRXNCoxoj2Ua0PCx A7I6cqBYwwhwz64VycsYseromSj8QURDoPMCCfUdYcmKBRai2Yh7lCPP/CpuyjJxOW IqJfqp5KdZKGA==
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 14:16:25 -0000

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.

If the combination of the offer and answer aren't sufficient for each 
side to encode what it sends in a way that it knows can be demuxed 
according in accord with the O/A, then that offer should be incorrect.

IMO injecting "magic" into this isn't helpful.

	Thanks,
	Paul

> Cheers,
> Emil
>
>
>>
>>
>> On 24 May 2013 09:59, Emil Ivov <emcho@jitsi.org
>> <mailto:emcho@jitsi.org>> wrote:
>>
>>      On 24.05.13, 11:40, Kevin Dempsey wrote:
>>      > Isn't the onus on the answerer to ensure the demux is possible,
>>      since it
>>      > is accepting the bundle. Therefore if it doesn't support signalling
>>      > SSRCs or an offerred 'fancy-RFC m-line matching' method, it must only
>>      > send PTs that are tied to a single m-line.
>>
>>      PTs are defined by the offerer. The answerer cannot change them for the
>>      offerer-bound direction (even if it could request different values for
>>      the packets that it, the answerer, is going to receive).
>>
>>      Emil
>>
>>
>>      >
>>      >
>>      > On 24 May 2013 08:17, Emil Ivov <emcho@jitsi.org
>>      <mailto:emcho@jitsi.org>
>>      > <mailto:emcho@jitsi.org <mailto:emcho@jitsi.org>>> wrote:
>>      >
>>      >     On 24.05.13, 00:59, Paul Kyzivat wrote:
>>      >     > IMO the "before the O/A completes" issues are separate from
>>      the "after
>>      >     > the O/A completes" issues. I'm still not convinced that the
>>      >     "before the
>>      >     > O/A completes" issues are important. (We have reliable 183
>>      >     responses to
>>      >     > deal with it.) But I'm ok with Cullen using PT to solve that
>>      >     problem if
>>      >     > he thinks he needs to.
>>      >
>>      >     I wasn't referring to "before the O/A completes" situations.
>>      If your
>>      >     peer does not support fancy-RFC m-line matching nor does it
>>      provide
>>      >     SSRCs, you have to be able to fall back to PT demuxing.
>>      >
>>      >     Therefore, all your offers have to accommodate for that
>>      possibility
>>      >     unless you know that the offer is going to someone who also
>>      supports
>>      >     other mechanisms.
>>      >
>>      >     Emil
>>      >
>>      >     --
>>      >     https://jitsi.org
>>      >     _______________________________________________
>>      >     mmusic mailing list
>>      >     mmusic@ietf.org <mailto:mmusic@ietf.org>
>>      <mailto:mmusic@ietf.org <mailto:mmusic@ietf.org>>
>>      >     https://www.ietf.org/mailman/listinfo/mmusic
>>      >
>>      >
>>
>>      --
>>      https://jitsi.org
>>
>>
>