Re: [MMUSIC] Draft new version: draft-holmberg-mmusic-sdp-dtls-01

Roman Shpount <roman@telurix.com> Mon, 22 June 2015 17:14 UTC

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Date: Mon, 22 Jun 2015 13:14:49 -0400
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From: Roman Shpount <roman@telurix.com>
To: Paul Kyzivat <pkyzivat@alum.mit.edu>
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Cc: "mmusic@ietf.org" <mmusic@ietf.org>, Christer Holmberg <christer.holmberg@ericsson.com>
Subject: Re: [MMUSIC] Draft new version: draft-holmberg-mmusic-sdp-dtls-01
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On Mon, Jun 22, 2015 at 9:24 AM, Paul Kyzivat <pkyzivat@alum.mit.edu> wrote:

> On 6/20/15 11:45 PM, Roman Shpount wrote:
>
>> On Sat, Jun 20, 2015 at 6:05 PM, Christer Holmberg
>> <christer.holmberg@ericsson.com <mailto:christer.holmberg@ericsson.com>>
>> wrote:
>>
>>     > - if the answer has connection:new and the offer didn't have new
>>     >   transport parameters, then the answer must have new ones.
>>
>>     Yes.
>>
>>
>> One thing to keep in mind here, that unless ICE restart was initiated by
>> the offering side (i.e. it had a different ufrag/pwd even if ti
>> specified connection:exisiting), answering side cannot allocate a new
>> transport. Answering side is simply not allowed to respond with a new
>> ufrag/pwd unless new ufrag/pwd was used in the offer. In cases where
>> offer has the same ufrag/pwd, answering side must use
>> connection:existing and issue a new offer to setup new transport and new
>> DTLS association.
>>
>
> What if the answering side *can't* use the existing connection? (E.g.
> because it doesn't know about it.) The conditions that would lead to this
> situation are exotic, but not impossible. (Things that would cause this
> situation would force the end we are here calling the answerer to need to
> issue its own new offer if it hadn't received an offer first.)
>
> I guess a solution for the answerer in this case is to refuse the m-line
> (port zero), and then send a new offer with connection:new.
>

This is exactly what I meant in the last sentence.
_____________
Roman Shpount