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

Paul Kyzivat <pkyzivat@alum.mit.edu> Mon, 22 June 2015 13:24 UTC

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Date: Mon, 22 Jun 2015 09:24:13 -0400
From: Paul Kyzivat <pkyzivat@alum.mit.edu>
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To: Roman Shpount <roman@telurix.com>, Christer Holmberg <christer.holmberg@ericsson.com>
References: <7594FB04B1934943A5C02806D1A2204B1D8F4457@ESESSMB209.ericsson.se> <5585A71F.4080808@alum.mit.edu> <7594FB04B1934943A5C02806D1A2204B1D8F4863@ESESSMB209.ericsson.se> <CAD5OKxuUKq3VHoENvU+hWg3CoK3MB_zbS7Vg-3nWdDUOfmxP+Q@mail.gmail.com>
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Subject: Re: [MMUSIC] Draft new version: draft-holmberg-mmusic-sdp-dtls-01
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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.

	Thanks,
	Paul