Re: [rtcweb] Summary of Application Developers' opinions of the current WebRTC API and SDP as a control surface

Peter Thatcher <pthatcher@google.com> Thu, 18 July 2013 15:12 UTC

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From: Peter Thatcher <pthatcher@google.com>
Date: Thu, 18 Jul 2013 08:12:04 -0700
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To: "Matthew Kaufman (SKYPE)" <matthew.kaufman@skype.net>
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Subject: Re: [rtcweb] Summary of Application Developers' opinions of the current WebRTC API and SDP as a control surface
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On Wed, Jul 17, 2013 at 2:58 PM, Matthew Kaufman (SKYPE) <
matthew.kaufman@skype.net>; wrote:

> Bernard Aboba:
> >
> > The problem was that we never defined what mangling browsers had to
> > support. Given all the SDP specs that is actually a huge work item.
>
>
> This is exactly what my slides that weren't presented last November
> started to touch upon. It only takes a few minutes with RFC3264 and its
> references to start documenting cases that are clearly "valid SDP
> offer/answer" and yet for which I cannot for the life of me figure out what
> a browser should do if they're presented.
>

I believe I began paying attention to the mailing lists after you sent out
theses slides that you didn't present.  I'm interested in seeing them, and
while I could dig through archives to find them, if convenient, could you
please give me a link to the slides?  Thanks.


>
> Just off the top of my head:
>
> Can I...
> - Change the t= line to be something other than t=0 0?
> - Change the rtpmap associations before calling setLocal?
> - Change a=sendrecv to a=recvonly before calling setLocal?
> - What do you do when you see a=content:sl ?
> - What if someone adds an r= or p= or e=?
> - What is the RFC that describes a=group:BUNDLE (as seen in some browser
> implementations)?
> - Can I remove a=group:BUNDLE (or add it) before calling setLocal?
> - How about removing a=rtcp-mux?
> - Should I do something special at my end if you set
> a=ice-options:google-ice ?
> - If you put a=ssrc lines in there, can I change the ssrc before passing
> it back to setLocal?
> - Can I delete the a=ssrc lines?
> - Is a=rtcp:1 IN IP4 0.0.0.0 valid or not?
> - What about 0.0.0.0 in the o= line?
> - If I get a bunch of a=candidate lines, can I swap them around to change
> the priority before calling setLocal?
> - What if someone claims SAVP instead of SAVPF but gives me rtcp info?
>
> At the *very least* for each and every line that comes from createOffer
> and createAnswer you must be able to answer the following:
> - Can I delete it?
> - Duplicate it?
> - Change it?
> - If not, how are violation handled? (Both when passed to another browser
> at the far end and when these modifications happen before calling setLocal)
>  - And can I add additional valid SDP to what came from createOffer or
> createAnswer and pass it back to setLocal or not?
>
> We appear to be nowhere near a document which explains the answers to
> these questions, certainly not in the W3C WG, and not in any IETF RFC or
> draft I can locate.
>



> Matthew Kaufman
>
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