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Re: SDP DataChannels

From: Eric Rescorla <ekr@rtfm.com>
Date: Sat, 3 Aug 2013 08:11:32 +0200
Message-ID: <CABcZeBNHVvcmbaD0NiTr3Ohmq0Y4O9s=QXUXiENc1F1vwwCN1Q@mail.gmail.com>
To: "piranna@gmail.com" <piranna@gmail.com>
Cc: public-webrtc <public-webrtc@w3.org>
On Sat, Aug 3, 2013 at 1:29 AM, piranna@gmail.com <piranna@gmail.com> wrote:

> I've just been able to generate an offer only with DataChannels (seems
> the fact that audio m-lines where added on Chrome due a bug on the
> mediaConstraints, and that was the reason why SDP strings were so
> long) and I've been able to dump the generated SDP, being now more
> confident that SDP is not the best format at least for this use case
> (only DataChannels). Could be any body explain me why there are so
> much (almost) duplicated lines? What are the essential ones? What are
> just the essential bits of data required to create this DataChannels?

It's probably better to look at the SDP from Firefox because Chrome doesn't
currently implement the  data channel specification. Here is what the
SDP looks like:

o=Mozilla-SIPUA-25.0a1 12613 0 IN IP4
s=SIP Call
t=0 0
m=application 51189 DTLS/SCTP 5000
c=IN IP4
a=fmtp:5000 protocol=webrtc-datachannel;streams=16
a=candidate:0 1 UDP 2113601791 53229 typ host
a=candidate:1 1 UDP 1694236671 51189 typ srflx raddr rport 53229
a=candidate:0 2 UDP 2113601790 54571 typ host
a=candidate:1 2 UDP 1694236670 55176 typ srflx raddr rport 54571
Received on Saturday, 3 August 2013 06:12:39 UTC

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