Re: [MMUSIC] Bundle offer with different ports - where to expect media?

[Martin Thomson <[e-mail]>]

On 28 May 2013 09:16, Martin Thomson <[e-mail]> wrote:
> On 27 May 2013 08:47, Paul Kyzivat <[e-mail]> wrote:
>> no

FWIW, I can live with that.  (Sorry about the earlier empty email.)  I
was simply trying to be aggressively minimalist.

This model requires that each m-line has two independently negotiable
properties:
 - accepted/rejected (signaled using zero port)
 - bundle membership (signaled using a=group)

(and yes, this requires an update to 5888)

Then we need, as you describe, rules for transitioning between states.

Transition between accepted and rejected is always possible in both
offers and answers.

It seems like we are saying that bundle membership can transition in
the following ways:

Any group to no group:
 - In an offer, under all circumstances.
 - In an answer, if the m-line is rejected.
 - In an answer, if unique transport parameters are provided in the offer.

No group to any group:
 - In an offer, under all circumstances.
 - In an answer, never.

Any group to any other group:
 - In an offer, if the m-line was previously rejected.
 - In an answer, if the lines were offered as a bundle and there are
sufficient transport parameters on offer.

Is that the rules you would like to see?  I think that the last option
(splitting) is the only one that I haven't seen anyone else slavering
for.  The model permits it, but I'd rather prohibit features fix it up
later than start with something that ends up too permissive.

For example, it would be possible to split a bundle that had multiple
m-lines and only two sets of transport parameters like the following:

offer:
BUNDLE 1 2 3 4
mid:1  transport A
mid:2  transport A
mid:3  transport A
mid:4  transport B

answer:
BUNDLE 1 2
BUNDLE 4 3

Despite a (possible) preference from the offerer for bundling 1-3
together, 3 has been split off.

I'm sure that we can get the rules right, but I like avoiding these
sorts of little complications.