Re: [MMUSIC] Merging ICE aggressive and regular nomination (was Re: [tram] Comment on draft-williams-peer-redirect-01: might it not converge?)

Martin Thomson <martin.thomson@gmail.com> Wed, 30 July 2014 22:01 UTC

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Date: Wed, 30 Jul 2014 15:01:29 -0700
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From: Martin Thomson <martin.thomson@gmail.com>
To: Emil Ivov <emcho@jitsi.org>
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Cc: Jonathan Lennox <jonathan@vidyo.com>, mmusic <mmusic@ietf.org>
Subject: Re: [MMUSIC] Merging ICE aggressive and regular nomination (was Re: [tram] Comment on draft-williams-peer-redirect-01: might it not converge?)
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On 30 July 2014 14:48, Emil Ivov <emcho@jitsi.org> wrote:
> When it's RTP you don't care where you get it from as long as you do. If
> it's a DTLS client halo then what do you do exactly?
>
> Can the controlling agent simply respond on a different valid pair than the
> one on which it received it? (This is what Chrome currently does but its
> frowned upon by the DTLS/SRTP draft which binds the context to a specific
> address:port). Does the controlled agent need to resend it on the new pair
> after it gets the USE-CANDIDATE?

RFC 5764 says this:
   A single DTLS-SRTP session only protects data carried over
   a single UDP source and destination port pair.

But I'll postulate that this is only because the alternative (a
shifting substrate) was not yet conceived.  There is nothing in (D)TLS
that requires anything of the underlying transport protocol,
intentionally.  (c.f., tcpinc wg)

Firefox code seems to be OK (at least superficially) with the idea
that packets can arrive from anywhere.  However, I can see why some
implementations might get sad if things shift around.