Re: [rtcweb] SDP Offer/Answer draft-jennings-rtcweb-signaling - More-coming and final answer (Section 5.2.3)

Cullen Jennings <> Thu, 20 October 2011 00:41 UTC

Return-Path: <>
Received: from localhost (localhost []) by (Postfix) with ESMTP id 2505911E80BF for <>; Wed, 19 Oct 2011 17:41:29 -0700 (PDT)
X-Virus-Scanned: amavisd-new at
X-Spam-Flag: NO
X-Spam-Score: -105.739
X-Spam-Status: No, score=-105.739 tagged_above=-999 required=5 tests=[AWL=0.860, BAYES_00=-2.599, RCVD_IN_DNSWL_MED=-4, USER_IN_WHITELIST=-100]
Received: from ([]) by localhost ( []) (amavisd-new, port 10024) with ESMTP id 4ZqePq1J07IH for <>; Wed, 19 Oct 2011 17:41:28 -0700 (PDT)
Received: from ( []) by (Postfix) with ESMTP id 7256311E80AF for <>; Wed, 19 Oct 2011 17:41:28 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple;;; l=2880; q=dns/txt; s=iport; t=1319071288; x=1320280888; h=subject:mime-version:from:in-reply-to:date:cc: content-transfer-encoding:message-id:references:to; bh=JG6/ZrJkko6rFJ43REpqFyWaPeGuS7Ha4gJUo7oJ9Zs=; b=G9OkppjsnweWXprYiAhflwORzDgL782oufiNp9RKHzPuLrRLj/6t5QnD FTuWggJWqUAOlh2yxgFqS3UsR1ijlEBQaOtELmSStf4TcijKBY6DnQErg QQ5tRvZTtEJ0O+XpqgCz0Cu/TT8bg3rvsrCdgmM5iYbl5Z9UOySosNGwB 4=;
X-IronPort-Anti-Spam-Filtered: true
X-IronPort-AV: E=Sophos;i="4.69,375,1315180800"; d="scan'208";a="9004147"
Received: from ([]) by with ESMTP; 20 Oct 2011 00:41:28 +0000
Received: from [] ( []) by (8.14.3/8.14.3) with ESMTP id p9K0fRJt031352; Thu, 20 Oct 2011 00:41:27 GMT
Mime-Version: 1.0 (Apple Message framework v1251.1)
Content-Type: text/plain; charset="windows-1252"
From: Cullen Jennings <>
In-Reply-To: <>
Date: Wed, 19 Oct 2011 18:41:30 -0600
Content-Transfer-Encoding: quoted-printable
Message-Id: <>
References: <> <>
To: Christer Holmberg <>
X-Mailer: Apple Mail (2.1251.1)
Cc: Jonathan Rosenberg <>, "" <>
Subject: Re: [rtcweb] SDP Offer/Answer draft-jennings-rtcweb-signaling - More-coming and final answer (Section 5.2.3)
X-Mailman-Version: 2.1.12
Precedence: list
List-Id: Real-Time Communication in WEB-browsers working group list <>
List-Unsubscribe: <>, <>
List-Archive: <>
List-Post: <>
List-Help: <>
List-Subscribe: <>, <>
X-List-Received-Date: Thu, 20 Oct 2011 00:41:29 -0000

all good questions and I should clarify in the draft … inline

On Oct 19, 2011, at 7:06 , Christer Holmberg wrote:

> Hi,
> A couple of questions regarding the usage of the more-coming flag:
> Q1. If one sends an ANSWER with the more-coming flag set to 'true', is it allowed to later send *additional* ANSWER(s) with the flag set to 'true' (before sending the final ANSWER)?

> Q2. Are there restrictions when it comes to changing information in a non-final answer and a final answer? Or, can the final answer be completely different from previously sent non-final ANSWERS? In "legacy" O/A there are restrictions.

Any answer has to be a valid answer for the offer but other than that, no restrictions, so the final answer can change everything from an earlier one. 

> Q3. Must the answerer wait for OK for a non-final ANSWER before sending a new ANSWER (non-final or final)?

hmm - not sure :-)  I think the answer to needs to be yes but we should think about this and work through the design choices. 

> Q4. If the answer to Q3 is "no", how does the answerer know to which ANSWER an OK message applies? AFAIK, the seq/sessionId values are identical for all ANSWERs associated with a specific OFFER.
> Q5. The text says, that while the OFFER is "open", ie a final ANSWER has not been sent, the answerer is not allowed to send an OFFER. I assume that also applies to the offerer, ie it is not allowed to send a new OFFER until it has received a final ANSWER - even if it has received one or more non-final ANSWERs. Maybe it's obvious, but I think it would be good to explictily add some text about that (if my assumption is correct, that is :).

yes - agree. 
> Regards,
> Christer
>> -----Original Message-----
>> From: 
>> [] On Behalf Of Cullen Jennings
>> Sent: 15. lokakuuta 2011 6:09
>> To:;
>> Cc: Jonathan Rosenberg
>> Subject: [rtcweb] SDP Offer/Answer draft-jennings-rtcweb-signaling
>> Jonathan and I submitted a new draft on setting up media 
>> based on the SDP Offer/Answer model. The ASCII flows are a 
>> bit hard to read so until I update them, I recommend reading 
>> the PDF version at 
>> Clearly the draft is an early stage but we plan to revise it 
>> before the deadline for the IETF 82. Love to get input - 
>> particularly on if this looks like generally the right 
>> direction to go. 
>> _______________________________________________
>> rtcweb mailing list