Re: [splices] Using Two Separate Devices to Start a Conversation proposal

Alan Johnston <alan.b.johnston@gmail.com> Mon, 06 June 2011 19:36 UTC

Return-Path: <alan.b.johnston@gmail.com>
X-Original-To: splices@ietfa.amsl.com
Delivered-To: splices@ietfa.amsl.com
Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id ADA551F0C4C for <splices@ietfa.amsl.com>; Mon, 6 Jun 2011 12:36:07 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -102.203
X-Spam-Level:
X-Spam-Status: No, score=-102.203 tagged_above=-999 required=5 tests=[BAYES_00=-2.599, MIME_QP_LONG_LINE=1.396, RCVD_IN_DNSWL_LOW=-1, USER_IN_WHITELIST=-100]
Received: from mail.ietf.org ([64.170.98.30]) by localhost (ietfa.amsl.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id df+Zxu0enQyO for <splices@ietfa.amsl.com>; Mon, 6 Jun 2011 12:36:07 -0700 (PDT)
Received: from mail-iw0-f172.google.com (mail-iw0-f172.google.com [209.85.214.172]) by ietfa.amsl.com (Postfix) with ESMTP id 275771F0C44 for <splices@ietf.org>; Mon, 6 Jun 2011 12:36:07 -0700 (PDT)
Received: by iwn39 with SMTP id 39so5049759iwn.31 for <splices@ietf.org>; Mon, 06 Jun 2011 12:36:04 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:references:in-reply-to:mime-version :content-type:message-id:content-transfer-encoding:cc:x-mailer:from :subject:date:to; bh=BfRWJM/PvzWq8N5GC8KzgjVj8A7hfrv8MhxuJhpLYvE=; b=svtaonc7RLObWVAZDTfXCL/VSGTsFZ2RKjzRlUYlnj+BSBVyhUVr6Rch7srrS9X17M tmAv9DTw/A18YxLoHNUPBCFaZipH7qoWliLQT2KBjBGLf+PGC9CN9mNxehJK/fkngZw6 9Py3zH0WwSI46Eu0acDj1hAOyBMzEe3gl5RmI=
DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=references:in-reply-to:mime-version:content-type:message-id :content-transfer-encoding:cc:x-mailer:from:subject:date:to; b=g5ySO9+1Po9S/EYIuwIGKMK+gOkYoQBqXAJr5ZE+RutkEQ8gTXTszoE4ltbi+Tt+xB L4yhKu76BUFhwwCQnwPXUNaUnWv5MzbFEReXed6O/EtgfAPsoNwMN5o183PUTH6DM1OY BcnlUaeUpP5+Kre0qJ+wdUw7o79WAWKZI+2h0=
Received: by 10.42.134.129 with SMTP id l1mr8329929ict.73.1307388963941; Mon, 06 Jun 2011 12:36:03 -0700 (PDT)
Received: from [10.18.181.3] (mobile-166-137-140-220.mycingular.net [166.137.140.220]) by mx.google.com with ESMTPS id s2sm2944662icw.17.2011.06.06.12.36.01 (version=TLSv1/SSLv3 cipher=OTHER); Mon, 06 Jun 2011 12:36:03 -0700 (PDT)
References: <AcwcBjEKPHRsQSI9R9CEF7Om5nHptA==> <6369CB70BFD88942B9705AC1E639A33822CCE270F5@DC-US1MBEX4.global.avaya.com> <BANLkTin+7fnDjmsfZVWKsmt631B7toRYVw@mail.gmail.com> <CD5674C3CD99574EBA7432465FC13C1B222907E9A1@DC-US1MBEX4.global.avaya.com>
In-Reply-To: <CD5674C3CD99574EBA7432465FC13C1B222907E9A1@DC-US1MBEX4.global.avaya.com>
Mime-Version: 1.0 (iPhone Mail 8J2)
Content-Type: text/plain; charset=us-ascii
Message-Id: <1C6C5AB3-6085-4CCA-9F1D-8BA5D98ED651@gmail.com>
Content-Transfer-Encoding: quoted-printable
X-Mailer: iPhone Mail (8J2)
From: Alan Johnston <alan.b.johnston@gmail.com>
Date: Mon, 6 Jun 2011 14:35:56 -0500
To: "Worley, Dale R (Dale)" <dworley@avaya.com>
Cc: "splices@ietf.org" <splices@ietf.org>
Subject: Re: [splices] Using Two Separate Devices to Start a Conversation proposal
X-BeenThere: splices@ietf.org
X-Mailman-Version: 2.1.12
Precedence: list
List-Id: "Loosely-coupled SIP Devices \(splices\) working group discussion list" <splices.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/splices>, <mailto:splices-request@ietf.org?subject=unsubscribe>
List-Archive: <http://www.ietf.org/mail-archive/web/splices>
List-Post: <mailto:splices@ietf.org>
List-Help: <mailto:splices-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/splices>, <mailto:splices-request@ietf.org?subject=subscribe>
X-List-Received-Date: Mon, 06 Jun 2011 19:36:07 -0000

If I understand correctly, there will be two separate RTP streams, two m= lines?

If this is the case, then two separate NAT traversal mechanisms will be used (i.e. ICE rubs twice or two relays used). As far as ZRTP or other media path keying protocols, each session will be keyed separately. With ZRTP the endpoint will see two different ZIDs.  This does unfortunately mean two Diffie Hellman calculations. 

Since these are separate sessions, each will have an RTCP session as well, and these may need NAT traversal as well.

So this will work, but things like logging and quality reporting will be quite complicated. 

- Alan -



On Jun 6, 2011, at 2:07 PM, "Worley, Dale R (Dale)" <dworley@avaya.com>; wrote:

> ________________________________________
> From: splices-bounces@ietf.org [splices-bounces@ietf.org] On Behalf Of Peter Musgrave [musgravepj@gmail.com]
> 
> I have concerns about this approach. Fundamentally the RTP stream is not symmetric (in the sense of RFC4961). This has consequences for NAT traversal, general interoperability and media path security schemes like ZRTP.
> _______________________________________________
> 
> I have to agree and disagree...  As Rifaat diagrammed it, the call should work, as it uses already-defined SIP facilities.  Indeed, it's rather clever, I'd never thought of joining a sendonly dialog with a recvonly dialog.  There are some limitations, in that we depend on the far-end UA to execute the join in the way we want.
> 
> The problems you raise, those of asymmetric RTP, already exist -- One can make a sendonly audio call, or a recvonly audio call.  We need to ensure that NAT traversal and ZRTP work correctly when  media stream is set up to be one-way.
> 
> Dale
> 
> _______________________________________________
> splices mailing list
> splices@ietf.org
> https://www.ietf.org/mailman/listinfo/splices