Re: [MMUSIC] Simulcast worries: Fallback in the a=rid language

Martin Thomson <> Wed, 21 October 2015 22:23 UTC

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Date: Wed, 21 Oct 2015 15:23:21 -0700
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From: Martin Thomson <>
To: Peter Thatcher <>
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Subject: Re: [MMUSIC] Simulcast worries: Fallback in the a=rid language
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On 21 October 2015 at 15:05, Peter Thatcher <> wrote:
> But if you have max-goats and max-dogs and max-cats and the answerer
> supports max-dogs but not max-goats or max-cats,  how can it structure it to
> offer all the combinations of what might work and what might not?

Yes, combinatorial explosion ensues.

My view is that we aren't likely to add enough of these extensions
that we will ever reach that explosion point.

And if enough time lapses between introduction of different things,
you can start to make assumptions about things, and do things like
bundle max-dogs and max-cats together.  Sure, the guy who understands
(not supports) only max-dogs falls back to the baseline, but as long
as you have a baseline you don't suffer too badly.

In practice, I think that this will only create a modest amount of
pressure not to extend.  I can't actually think of a downside to that.

BTW, this is a repeat of a similar discussion we had in HTTP.  There,
we settled on having parameters be ignored if not supported.  I don't
think that's feasible in this context because things like limits are