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Re: SDP DataChannels

From: Eric Rescorla <ekr@rtfm.com>
Date: Sat, 3 Aug 2013 09:39:15 +0200
Message-ID: <CABcZeBNa4o60Bkvue+j18GDVu3mP_fOGueOsOV3edavi+GV8nA@mail.gmail.com>
To: "piranna@gmail.com" <piranna@gmail.com>
Cc: public-webrtc <public-webrtc@w3.org>
On Sat, Aug 3, 2013 at 9:26 AM, piranna@gmail.com <piranna@gmail.com> wrote:

> Good to know it for reference, seems to be fairly more complicated
> (interesting to see the IP and ports of each one of the DataChannels...
>

Those are the ICE candidates. It's kind of needed to set up the
communications
channel. The only reason you're not seeing them in Chrome is that Chrome
does Trickle ICE and so sends them in a separate message.

-Ekr


> El 03/08/2013 08:12, "Eric Rescorla" <ekr@rtfm.com> escribió:
>
>
>>
>>
>> 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
>> Firefox
>> SDP looks like:
>>
>> v=0
>> o=Mozilla-SIPUA-25.0a1 12613 0 IN IP4 0.0.0.0
>> s=SIP Call
>> t=0 0
>> a=ice-ufrag:9638f069
>> a=ice-pwd:90f72795622bd286d75dde68d9b7e02f
>> a=fingerprint:sha-256
>> 7C:CE:6B:7A:D4:B0:2E:D7:0C:76:07:59:B5:9E:28:5C:14:6C:00:D7:E0:10:C6:CD:25:8B:4B:E8:1D:CC:FC:4F
>> m=application 51189 DTLS/SCTP 5000
>> c=IN IP4 89.246.150.136
>> a=fmtp:5000 protocol=webrtc-datachannel;streams=16
>> a=sendrecv
>> a=candidate:0 1 UDP 2113601791 10.0.1.158 53229 typ host
>> a=candidate:1 1 UDP 1694236671 89.246.150.136 51189 typ srflx raddr
>> 10.0.1.158 rport 53229
>> a=candidate:0 2 UDP 2113601790 10.0.1.158 54571 typ host
>> a=candidate:1 2 UDP 1694236670 89.246.150.136 55176 typ srflx raddr
>> 10.0.1.158 rport 54571
>>
>>
>>
>>
>>
Received on Saturday, 3 August 2013 07:40:22 UTC

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