Re: [rtcweb] No Plan

Emil Ivov <emcho@jitsi.org> Tue, 04 June 2013 16:12 UTC

Return-Path: <emil@sip-communicator.org>
X-Original-To: rtcweb@ietfa.amsl.com
Delivered-To: rtcweb@ietfa.amsl.com
Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id 40F2321F96F2 for <rtcweb@ietfa.amsl.com>; Tue, 4 Jun 2013 09:12:59 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -1.399
X-Spam-Level:
X-Spam-Status: No, score=-1.399 tagged_above=-999 required=5 tests=[BAYES_00=-2.599, J_CHICKENPOX_14=0.6, J_CHICKENPOX_17=0.6]
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 Qo49AlU9VcSp for <rtcweb@ietfa.amsl.com>; Tue, 4 Jun 2013 09:12:44 -0700 (PDT)
Received: from mail-bk0-x231.google.com (mail-bk0-x231.google.com [IPv6:2a00:1450:4008:c01::231]) by ietfa.amsl.com (Postfix) with ESMTP id 4E1D821F9BA2 for <rtcweb@ietf.org>; Tue, 4 Jun 2013 07:02:28 -0700 (PDT)
Received: by mail-bk0-f49.google.com with SMTP id 6so174821bkj.8 for <rtcweb@ietf.org>; Tue, 04 Jun 2013 07:02:27 -0700 (PDT)
X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20120113; h=message-id:date:from:organization:user-agent:mime-version:to:cc :subject:references:in-reply-to:content-type :content-transfer-encoding:x-gm-message-state; bh=ddKkBxmcHOOBLwj1WWEdl9KYxGgmbmFC4Ciy1Ch+6g0=; b=EC78pDnINRvzlwwAnrpDdcCLRKdG3Ss5M0vX6GdWIV0LMI6IQmhPmxCTP1cvxxHCKz UNGXFzpAASKQk7rVisavBewJnXRA5gHOI4lXVH0jBjgx4Y6E0xUcYXPdikNitHMICr5H Lpwp1zhQHsQ7STmkPxhBgp7b/5sjNpK/xL9E33aSBixNg+7ER8hObHspAT/4Mztp1y5j Kv1l4iUSTgOyClakNZDyBJFHYUQoyJf39UnbpXIIV505QWI8aqzfMzJ+w0Omi79WNFN7 ULcq9H5Vk8axOkLQthdpR8GjAMIjSTPwgJEWXWpEu7d3i23N/HI/iUIwbjTNeGVvhCyg 74wA==
X-Received: by 10.204.172.136 with SMTP id l8mr8070991bkz.49.1370354547461; Tue, 04 Jun 2013 07:02:27 -0700 (PDT)
Received: from camionet.local ([88.128.80.7]) by mx.google.com with ESMTPSA id tl1sm23091853bkb.7.2013.06.04.07.02.19 for <multiple recipients> (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Tue, 04 Jun 2013 07:02:26 -0700 (PDT)
Message-ID: <51ADD8D1.1040306@jitsi.org>
Date: Tue, 04 Jun 2013 15:08:49 +0300
From: Emil Ivov <emcho@jitsi.org>
Organization: Jitsi
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.8; rv:17.0) Gecko/20130509 Thunderbird/17.0.6
MIME-Version: 1.0
To: Jim Barnett <Jim.Barnett@genesyslab.com>
References: <51A65017.4090502@jitsi.org> <7594FB04B1934943A5C02806D1A2204B1C37D144@ESESSMB209.ericsson.se>, <51A9A7E2.7000907@jitsi.org> <7594FB04B1934943A5C02806D1A2204B1C380AA2@ESESSMB209.ericsson.se> <51ACFF31.9090607@alum.mit.edu> <7426877E-42ED-400A-A264-39C692E71308@vidyo.com> <57A15FAF9E58F841B2B1651FFE16D2810437BF@GENSJZMBX02.msg.int.genesyslab.com>
In-Reply-To: <57A15FAF9E58F841B2B1651FFE16D2810437BF@GENSJZMBX02.msg.int.genesyslab.com>
Content-Type: text/plain; charset="ISO-8859-1"; format="flowed"
Content-Transfer-Encoding: 7bit
X-Gm-Message-State: ALoCoQlI0bIkRH8qs16QU1/yvn6i8BihS6PrF/qz5eQTdbkSdc90Mvf9FNjEJdKDufrpb0G6nlq+
Cc: Jonathan Lennox <jonathan@vidyo.com>, "rtcweb@ietf.org" <rtcweb@ietf.org>
Subject: Re: [rtcweb] No Plan
X-BeenThere: rtcweb@ietf.org
X-Mailman-Version: 2.1.12
Precedence: list
List-Id: Real-Time Communication in WEB-browsers working group list <rtcweb.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/rtcweb>, <mailto:rtcweb-request@ietf.org?subject=unsubscribe>
List-Archive: <http://www.ietf.org/mail-archive/web/rtcweb>
List-Post: <mailto:rtcweb@ietf.org>
List-Help: <mailto:rtcweb-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/rtcweb>, <mailto:rtcweb-request@ietf.org?subject=subscribe>
X-List-Received-Date: Tue, 04 Jun 2013 16:12:59 -0000

Hey Jim,

On 04.06.13, 01:16, Jim Barnett wrote:
> Just checking if I understand No Plan:  since the bundling is added via JS APIs, and not SDP,

I am not sure where you got this. No Plan does depend on the browser to 
provide support for BUNDLE and to generate the SDP accordingly.

Emil

> then if the app looks at
> The localDescription and remoteDescription attributes of the PeerConnection, it won't be able to tell if sources are bundled or not (since localDescription and remoteDescription are defined to contain SDP)
>
> - Jim
> -----Original Message-----
> From: rtcweb-bounces@ietf.org [mailto:rtcweb-bounces@ietf.org] On Behalf Of Jonathan Lennox
> Sent: Monday, June 03, 2013 6:03 PM
> To: Paul Kyzivat
> Cc: rtcweb@ietf.org
> Subject: Re: [rtcweb] No Plan
>
>
> On Jun 3, 2013, at 4:40 PM, Paul Kyzivat <pkyzivat@alum.mit.edu> wrote:
>
>> +1
>>
>> The more we dig into this the more it looks like Plan B.
>>
>> 	Thanks,
>> 	Paul
>
> I think No Plan and Plan B are largely isomorphic in a WebRTC context.  The primary difference is that rather than using a=ssrc and a=receive-ssrc (and whatever other Plan B attributes would be needed) to control sources within an m-line, instead direct Javascript APIs are used for the same semantics. It's up to the application to communicate the relevant information end-to-end, in parallel to however it communicates the SDP blob.
>
> As I see it, the primary advantages of No Plan, then, are that:
>
> a) It allows "implicit" signaling of sources -- where that's sufficient -- by just sending RTP traffic.  This prevents problems related to the timing and synchronization between signaling and media.  (Note that Plan B probably actually needs this as well, for legacy interop.)
>
> b) It carves a Comment 22 corner out of the SDP-based APIs, thus decoupling source signaling from SDP offer/answer.  This is for a scenario where there aren't any issues of legacy compatibility, and there isn't any (or at least much) existing IETF standardization -- as best I can recall, legacy compatibility and existing standardization were the primary motivations for using SDP as the WebRTC API.
>
> Other than that, I think the two proposals are pretty similar for WebRTC, and it would probably be a Simple Matter of Programming to translate between the two (though you have to worry about the O/A state on the Plan B side).
>
> In particular, if you have disaggregated media, you need multiple m-lines of the same type.  The No Plan document's suggestion that you offer only one m-line of a given media type is guidance on how to avoid interop failures on initial offers to legacy devices, I think, not an essential aspect of the proposal.
>
>
> In a SIP context, No Plan requires defining a separate signaling channel for this source information, in scenarios where something beyond implicit signaling is needed.  As Emil has stated, I think that something like the SIP/XCon conference package, or something like the CLUE channel, would be the obvious places to start.
>
> I think SIP, even more than RTCWeb, is where you'd want something lighter-weight and better-designed than SDP offer/answer to signal source changes.
>
>> On 6/1/13 7:05 AM, Christer Holmberg wrote:
>>>
>>> Hi,
>>>
>>>>> The draft says:
>>>>>
>>>>>        "For the sake of interoperability this specification strongly advises
>>>>>        against the use of multiple m= lines for a single media type."
>>>>
>>>> This should probably be clarified. The above referred mostly to a
>>>> browser's expectations and default offers. Multiple m= lines can
>>>> confuse a number of existing legacy endpoints which is why they
>>>> should be avoided when initiating a session that could reach a
>>>> similar device (and by default this should be assumed for any session).
>>>>
>>>> If applications *know* that they need to have multiple m= lines of a
>>>> given type they can request this the same way they could do it with Plan B:
>>>>
>>>>     If the application wishes, it can request that a given
>>>>     media source be placed onto a separate m= line, by setting a new
>>>>     .content property on the desired MediaStreamTrack; the values for the
>>>>     .content property are those defined for the a=content attribute in
>>>>     [RFC4796].
>>>>
>>>> I'll make sure this is part of the next version.
>>>>
>>>> Does this make sense?
>>>
>>> I have nothing against a general recommendation to, for a given media type, have as few m- lines as possible.
>>>
>>> But, I do think the draft need to point out that it is not always possible, e.g. because:
>>>
>>> 1) m- lines have different characteristics (normally indicated using
>>> SDP attributes) that does not "fit" all content for the given media
>>> type;
>>> 2) different protocols are used for different m- lines, even if the
>>> media type is the same; or
>>> 3) the remote endpoint only supports a single (or, another given number) of sources per m- line.
>>>
>>> Etc.
>>>
>>> Regards,
>>>
>>> Christer
>>>
>>>
>>>
>>>
>>>
>>>> My understanding is that the usage of multiple m= lines for a single
>>>> media type would not affect the mechanism as such, but I just want
>>>> to verify that :)
>>>>
>>>> Also, there ARE "legacy" implementations that use multiple m= lines for a single media type (e.g. video enabled devices using two video m= lines: one for camera content, and one for slides).
>>>>
>>>> So, while I definitely think that legacy interoperability shall be taken into consideration, I would not like to make such strong statements. In my opinion (the draft also talks about it), the usage of multiple simultaneous SSRCs per m- line is a much bigger issue when it comes to legacy interoperability.
>>>>
>>>> Also, in CLUE we have been working on signaling scenarios with multiple m= lines per media type.
>>>>
>>>>
>>>> Regards,
>>>>
>>>> Christer
>>>>
>>>>
>>>>
>>>> -----Original Message-----
>>>> From: rtcweb-bounces@ietf.org [mailto:rtcweb-bounces@ietf.org] On
>>>> Behalf Of Emil Ivov
>>>> Sent: 29. toukokuuta 2013 22:00
>>>> To: rtcweb@ietf.org
>>>> Subject: [rtcweb] No Plan
>>>>
>>>> Hey all,
>>>>
>>>> Based on many of the discussions that we've had here, as well as many others that we've had offlist, it seemed like a good idea to investigate a negotiation alternative that relies on SDP and Offer/Answer just a little bit less.
>>>>
>>>> The following "no plan" draft attempts to present one such approach:
>>>>
>>>> http://tools.ietf.org/html/draft-ivov-rtcweb-noplan
>>>>
>>>> The draft relies on conventional use of SDP O/A but leaves the intricacies of multi-source scenarios to application-specific signalling, with potentially a little help from RTP.
>>>>
>>>> Hopefully, proponents of Plans A and B would find that the interoperability requirements that concerned them can still be met with "no plan". Of course they would have to be addressed by application-specific signalling and/or signalling gateways.
>>>>
>>>> Comments are welcome!
>>>>
>>>> Cheers,
>>>> Emil
>>>>
>>>> --
>>>> https://jitsi.org
>>>> _______________________________________________
>>>> rtcweb mailing list
>>>> rtcweb@ietf.org
>>>> https://www.ietf.org/mailman/listinfo/rtcweb
>>>> .
>>>>
>>>
>>> --
>>> https://jitsi.org
>>> _______________________________________________
>>> rtcweb mailing list
>>> rtcweb@ietf.org
>>> https://www.ietf.org/mailman/listinfo/rtcweb
>>>
>>
>> _______________________________________________
>> rtcweb mailing list
>> rtcweb@ietf.org
>> https://www.ietf.org/mailman/listinfo/rtcweb
>>
>
> --
> Jonathan Lennox
> jonathan@vidyo.com
>
>
> _______________________________________________
> rtcweb mailing list
> rtcweb@ietf.org
> https://www.ietf.org/mailman/listinfo/rtcweb
>
> _______________________________________________
> rtcweb mailing list
> rtcweb@ietf.org
> https://www.ietf.org/mailman/listinfo/rtcweb
>

-- 
https://jitsi.org