[rtcweb] Issue with new Trickle ICE text

Eric Rescorla <ekr@rtfm.com> Wed, 05 March 2014 09:28 UTC

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From: Eric Rescorla <ekr@rtfm.com>
Date: Wed, 05 Mar 2014 09:27:15 +0000
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Subject: [rtcweb] Issue with new Trickle ICE text
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S 3.4.2 of JSEP now reads:

    JSEP applications typically inform the browser to begin ICE gathering
    via the information supplied to setLocalDescription, as this is where
    the app specifies the number of media streams to gather candidates
    for.  However, to accelerate cases where the browser knows the number
    of media streams to use ahead of time, the application MAY ask the
    browser to gather a pool of potential ICE candidates to help ensure
    rapid media setup.  When setLocalDescription is eventually called,
    and the browser goes to gather the needed ICE candidates, it can
    start by checking if any candidates are available in the pool.

The issue here is that this basically mandates trickle ICE. If the
pool is smaller than the number of independent ICE streams needed,
then there is no way for you to "start gathering" (since this text
says it happens with sLD) and therefore you cannot supply all of the
candidates in the offer.

If that's not the intention to require (and I don't believe we agreed
to this semantic), then this needs to be rewritten.