Re: [rtcweb] Draft agenda for IETF 87

Stefan Håkansson LK <stefan.lk.hakansson@ericsson.com> Sat, 13 July 2013 18:39 UTC

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From: =?iso-8859-1?Q?Stefan_H=E5kansson_LK?= <stefan.lk.hakansson@ericsson.com>
To: Peter Thatcher <pthatcher@google.com>
Thread-Topic: [rtcweb] Draft agenda for IETF 87
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Date: Sat, 13 Jul 2013 18:39:16 +0000
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Cc: "Cullen Jennings \(fluffy\)" <fluffy@cisco.com>, "<rtcweb@ietf.org>" <rtcweb@ietf.org>
Subject: Re: [rtcweb] Draft agenda for IETF 87
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On 7/12/13 7:19 PM, Peter Thatcher wrote:
>
>
>
> On Fri, Jul 12, 2013 at 12:35 AM, Stefan Håkansson LK
> <stefan.lk.hakansson@ericsson.com
> <mailto:stefan.lk.hakansson@ericsson.com>> wrote:
>
>     On 7/11/13 9:38 PM, Martin Thomson wrote:
>      > On 11 July 2013 12:04, Cullen Jennings (fluffy) <fluffy@cisco.com
>     <mailto:fluffy@cisco.com>>
>      > wrote:
>      >> On Jul 11, 2013, at 10:35 AM, Emil Ivov <emcho@jitsi.org
>     <mailto:emcho@jitsi.org>>
>      >>> In you last mail on the subject you mentioned that we will be
>      >>> discussing No Plan in Berlin together with plans A and B. Could
>      >>> we please add this to the agenda?
>      >>
>      >> No. We believe that conversation needs to happen in the W3C WebRTC
>      >> WG. I expect to see a message from W3C chairs on this at some
>      >> point.
>      >
>      > I'm a little nervous about this.  Where does the decision on the
>      > separation of responsibilities (API vs. SDP) get made?
>
>     (I have not been able to confer with any of the other chairs, so this is
>     just my personal opinion):
>
>     To me it seems pretty straightforward to a certain point:
>
>     * The SDP (if we opt to continue using SDP for this purpose) that goes
>     on the signaling wire between the browsers is defined by IETF (and by
>     the rtcweb WG I presume even though MMUSIC seems to have some stake)
>
>     * JS APIs to:
>     ** Apply an SDP (e.g. received on the signaling channel) to the browser
>     ** Hand an SDP generated by the browser over to the application (for
>     transmission over the signaling wire presumably)
>     ** Influencing/modifying the contents of the SDP
>     * All belongs to the W3C WebRTC
>
>
> Would it make sense to change this list to say the following?
>
> * JS APIs to:
> ** Apply a SessionDescription (created by SDP; eg received on the
> signaling channel or built by JS) to the browser
> ** Hand a SessionDescription (serializable to SDP) generated by the
> browser over to the application (for
> transmission over the signaling wire presumably or for immediately
> applying with setLocalDescription for some local effect)
> ** Influencing/modifying the contents of the SessionDescription (and
> thus, SDP, when serialized to SDP)
> * All belongs to the W3C WebRTC

That might well be a better way to put it.

>
>
> My changes highlight a few things:
> 1.  The API (setLocalDescripiton, setRemoteDescription, creatOffer, etc)
> doesn't work with SDP directly.  It works with RTCSessionDescription
> objects.  It just happens to be that currently the only way to interact
> with RTCSessionDescription objects is through SDP.  I think it's worth
> remembering that distinction.
>
> 2.  SDP does not necessarily go over the wire.   It only necessarily
> goes through the API between JS and browser.   I think it's worth
> remembering that distinction.
>
> 3.  Calling setLocalDescription with a new SessionDescription object can
> have purely local effects that don't need to be sent over the wire.  I
> think it's worth remembering those cases.
>
>
>     What seems unclear to me is where we define what modifications to the
>     SDP that are allowed - and when. Even though the ambition is to have
>     APIs that makes SDP mangling an exception, we will still see that
>     happening.
>
>
> I think advanced JS apps are going to use every control knob they can
> get to, whether it's anticipated and well-supported or not.    I think
> there's a good chance that a a popular WebRTC web app will use some SDP
> mangling that wasn't anticipated, but happened to work, but then the
> browser can't remove it because it will break certain websites.  It
> could get even worse if someone writes a popular WebRTC wrapper library
> that uses tricky SDP mangling that is then used by lots of websites.
>   Certain SDP mangling techniques might end up becoming a defacto
> standard API that can't be removed, even if it was originally a bug.  Or
> worse, one browser will have to implement the SDP mangling or even the
> bugs of another, because WebRTC apps have come to rely on them.
>
> In fact, it's already the case that Chrome and Firefox support far
> different SDP manglings.  I don't think any web apps rely on that yet,
> but it's only a matter of time before someone figures out "hey, if I
> mangle the SDP on this browser this way and on that browser that way, I
> can do things I couldn't do otherwise".  Or worse, an advanced web app
> developer says "hey, I can make this work well on browser X via SDP
> mangling, but not on browser Y, so I'll put a 'best used with Browser X'
> icon on my website". Then that someone writes an abstraction on top of
> that, and then maybe shares that with others, and it goes from there.
>
> I think we're in a race with web developers to see if they'll figure out
> SDP mangling before we provide a way to avoid SDP mangling.   Who do you
> think moves faster?

Let's go over to the public-webrtc W3C space and work on this.

>
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>
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>      >
>
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