[MMUSIC] Some issues with draft-ietf-mmusic-sctp-sdp-02

Paul Kyzivat <pkyzivat@alum.mit.edu> Mon, 03 December 2012 20:29 UTC

Return-Path: <pkyzivat@alum.mit.edu>
X-Original-To: mmusic@ietfa.amsl.com
Delivered-To: mmusic@ietfa.amsl.com
Received: from localhost (localhost []) by ietfa.amsl.com (Postfix) with ESMTP id AC88A21F881F for <mmusic@ietfa.amsl.com>; Mon, 3 Dec 2012 12:29:31 -0800 (PST)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -0.067
X-Spam-Status: No, score=-0.067 tagged_above=-999 required=5 tests=[AWL=-0.230, BAYES_00=-2.599, FH_RELAY_NODNS=1.451, HELO_MISMATCH_NET=0.611, J_CHICKENPOX_111=0.6, RDNS_NONE=0.1]
Received: from mail.ietf.org ([]) by localhost (ietfa.amsl.com []) (amavisd-new, port 10024) with ESMTP id YaxOOx71cx2Z for <mmusic@ietfa.amsl.com>; Mon, 3 Dec 2012 12:29:31 -0800 (PST)
Received: from qmta05.westchester.pa.mail.comcast.net (qmta05.westchester.pa.mail.comcast.net [IPv6:2001:558:fe14:43:76:96:62:48]) by ietfa.amsl.com (Postfix) with ESMTP id 077B321F87EE for <mmusic@ietf.org>; Mon, 3 Dec 2012 12:29:30 -0800 (PST)
Received: from omta13.westchester.pa.mail.comcast.net ([]) by qmta05.westchester.pa.mail.comcast.net with comcast id Wylr1k00317dt5G558VW9a; Mon, 03 Dec 2012 20:29:30 +0000
Received: from Paul-Kyzivats-MacBook-Pro.local ([]) by omta13.westchester.pa.mail.comcast.net with comcast id X8VW1k0013ZTu2S3Z8VWt2; Mon, 03 Dec 2012 20:29:30 +0000
Message-ID: <50BD0BA8.3010901@alum.mit.edu>
Date: Mon, 03 Dec 2012 15:29:28 -0500
From: Paul Kyzivat <pkyzivat@alum.mit.edu>
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.7; rv:17.0) Gecko/17.0 Thunderbird/17.0
MIME-Version: 1.0
To: "Salvatore Loreto (JO/LMF)" <salvatore.loreto@ericsson.com>, Gonzalo Camarillo <Gonzalo.Camarillo@ericsson.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=1354566570; bh=Z2NymZEjiuoSfVzwIXJ0IpN3IHfxJkz2e1HuoE+jBIc=; h=Received:Received:Message-ID:Date:From:MIME-Version:To:Subject: Content-Type; b=pepxWk6oPKb+4rLkFs0im7LnBrFzsyfXYVEaPgb1pggblv3EvCZz0fTSY/FyNYE6T EGS+qnBFiXakHbXYnTeSr4T1w7+dIM0ainR0MCl5PiIlbTW09Xw12JDFJbviyjliYB 5Ce9F21NGSh85t0jaOpvRI+4BxDpDGcOeAAaXclBiCuKq/K8oTZHS8R4vzEa9iiU84 15dDdkZAJb/axlBoibro2rXZCUthHK2+Ev4ZOSwjG7ox6x3tWP2AheQ+A09Z+ABnx8 E4yrXcpIY28/VWHRuBNpujfyr25NHDxQ1W+bEVAj67INWGhLst+teIoE7uDSA4rE4+ ZUrGcAtm0AGeQ==
Cc: IETF MMUSIC WG <mmusic@ietf.org>
Subject: [MMUSIC] Some issues with draft-ietf-mmusic-sctp-sdp-02
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: Mon, 03 Dec 2012 20:29:32 -0000

While commenting on some related discussions I had occasion to look at 
this draft again and I found a few issues:

First, some very specific ones::

Section 4.1 says:

    If the <port> sub-field is 'SCTP' or ...

This is a typo. s/port/proto/

But the major issue is that this draft doesn't explain the semantics of 
the <port> field. The only things I can find that touch on this are:

- section 10.1 refers to "SCTP port 54111" and then shows an m-line
   with: m=application 54111 SCTP 0 1 2
   But this is just an example, not normative text.

- section 4.1 says:

    [OPEN ISSUE 3] do we need also an attribute to specify the SCTP port
    number for the SCTP over DTLS scenario? that can be useful in the
    case where multiple association are running on top of the same DTLS

   This implies that the SCTP port number is *not* what is in the port
   field in this case. Presumably because the UDP port number is in
   that field.

ISTM that there needs to be a clear discussion of all the required port 
numbers for each case, and how they are specified. When there is more 
than one (namely in the SCTP/DTLS and DTLS/SCTP cases), *one* of them 
can be in the m-line and the other one must be somewhere else. And if 
the one that is not in the m-line is optional, then I guess there must 
be a default.