[MMUSIC] A corner-case: Rejection/change of bundle tag, bundle-only, and trickle ICE

Byron Campen <docfaraday@gmail.com> Fri, 24 February 2017 17:17 UTC

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To: mmusic WG <mmusic@ietf.org>
From: Byron Campen <docfaraday@gmail.com>
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Date: Fri, 24 Feb 2017 11:16:59 -0600
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Subject: [MMUSIC] A corner-case: Rejection/change of bundle tag, bundle-only, and trickle ICE
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     Let's say we have an offer like the following (very pruned down, 
for clarity). Note that it is using trickle ICE, and no candidates have 
been gathered yet.

a=group:BUNDLE 1 2 3

m=audio 9 ...

a=mid:1

...

m=video 9 ...

a=mid:2

...

m=application 0 ...

a=mid:3

a=bundle-only

...


I see a couple of questions here about what transport (if any) mid 3 uses:

* What happens if the answerer rejects mid 1? (2 seems reasonable?)

* What happens if the answerer moves mid 1 out of the bundle? (2 seems 
reasonable?)

* What happens if the answerer rejects both mid 1 and 2? (Uh oh...)

* What happens for combinations of rejecting mids, and moving them out 
of the bundle? (Oh fun...)

     From the signaling alone, it is not always clear to the offerer 
which mid the answerer has chosen to use for transport stuff, so saying 
the answerer chooses arbitrarily doesn't quite solve the problem. I 
suppose the offerer could wait for the first trickle candidate, and use 
the mid specified there (provided it is valid, which I'm not sure has 
been adequately specified...).

Best regards,

Byron Campen