Re: [rtcweb] PeerConnection Data Channel

Bernard Aboba <bernard_aboba@hotmail.com> Sat, 03 September 2011 00:11 UTC

Return-Path: <bernard_aboba@hotmail.com>
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 E88FC21F856B for <rtcweb@ietfa.amsl.com>; Fri, 2 Sep 2011 17:11:32 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -102.196
X-Spam-Level:
X-Spam-Status: No, score=-102.196 tagged_above=-999 required=5 tests=[AWL=0.402, BAYES_00=-2.599, HTML_MESSAGE=0.001, USER_IN_WHITELIST=-100]
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 Y7NUUNZE9L4V for <rtcweb@ietfa.amsl.com>; Fri, 2 Sep 2011 17:11:32 -0700 (PDT)
Received: from blu0-omc4-s9.blu0.hotmail.com (blu0-omc4-s9.blu0.hotmail.com [65.55.111.148]) by ietfa.amsl.com (Postfix) with ESMTP id 21B5921F8561 for <rtcweb@ietf.org>; Fri, 2 Sep 2011 17:11:32 -0700 (PDT)
Received: from BLU152-W19 ([65.55.111.136]) by blu0-omc4-s9.blu0.hotmail.com with Microsoft SMTPSVC(6.0.3790.4675); Fri, 2 Sep 2011 17:13:08 -0700
Message-ID: <BLU152-W197013CA571F772294FFF6931B0@phx.gbl>
Content-Type: multipart/alternative; boundary="_ef49723c-b4ff-4505-bf57-a9907e014c0d_"
X-Originating-IP: [64.134.138.94]
From: Bernard Aboba <bernard_aboba@hotmail.com>
To: <randell-ietf@jesup.org>, <public-webrtc@w3.org>
Date: Fri, 2 Sep 2011 17:13:08 -0700
Importance: Normal
In-Reply-To: <4E615505.70508@jesup.org>
References: <CAOJ7v-1xEEA3+AX0hN4kR=9YggX7EW=wr4b67ASjibG_T=m2mQ@mail.gmail.com>, <4E610B78.7000103@skype.net>, <4E615505.70508@jesup.org>
MIME-Version: 1.0
X-OriginalArrivalTime: 03 Sep 2011 00:13:08.0913 (UTC) FILETIME=[42A41210:01CC69CE]
Cc: rtcweb@ietf.org
Subject: Re: [rtcweb] PeerConnection Data Channel
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: Sat, 03 Sep 2011 00:11:33 -0000

> >> Section 5 in the WEBRTC spec 
> >> (http://dev.w3.org/2011/webrtc/editor/webrtc.html) discusses at 
> >> length a mechanism for transmitting and securing datagrams over the 
> >> PeerConnection transport. 
[BA] The objective here appears to be "masking" (e.g. to prevent sending of arbitrary datagrams) rather than providing a full set of security services. 
> > > At both an API and a wire level, this 
> >> mechanism is quite different from the existing mechanisms that are 
> >> used for transmission of audio and video data:> >> - The availability of the data stream is not easily known, whereas 
> >> audio/video can be negotiated and stream existence learned from the 
> >> *Stream methods/callbacks.
[BA] It looked to me that the data channel was negotiated in SDP, no?
> >> - It defines its own encryption mechanism, whereas audio/video will 
> >> use SDES-SRTP, or DTLS-SRTP

[BA] I don't believe that the objective here is to duplicate the security services in SRTP, DTLS, TLS, IPsec or any other comprehensive security framework. It's closer to the "masking" supported by WebSockets.  

> >> - This stream will show up in SDP

[BA] I believe that's what the current spec already says. 
> > Disagree. RTP semantics are inappropriate for sending data. The data 
> > should be sent using one of the two methods for muxing data that were 
> > proposed (one by me, one by cbran).

[BA] Agree that RTP semantics aren't necessarily appropriate for non media-stream data. 
> >> - For encryption, it simply uses the underlying encryption of the 
> >> session, i.e. none, SDES-SRTP, or DTLS-SRTP, as appropriate.

[BA] If the underlying semantics of RTP aren't a good fit, why would that make sense?
> > Absolutely correct. Possibly needs masking for the "none" case 
> > however... need to discuss.

[BA] Right.  That's why it's there, not to provide a generic security framework. 
> 
> Hmmm....  This (blah-SRTP for encrypting the data streams means full 
> un-encrypted RTP headers at a minimum, plus a bunch of those "RTP 
> semantics" you disagreed with above.  Unless I mis-understand how this 
> would work.
[BA] Right.  That's what trying to force RTP security on non-media data isn't appropriate.