Re: [MMUSIC] BUNDLE and ZERO PORT VALUE

[Paul Kyzivat <[e-mail]>]

Christer,

I think what you suggest should work.

An implication is that you can't signal how you would like to bundle a 
hypothetical m-line (currently with port zero) were it to subsequently 
be offered with a non-zero port. I think that is ok.

My take has always been that the mechanism of signaling a 
rejected/unused m-line with a zero port was intended to imply that none 
of the accompanying media section lines need to be valid, and ones that 
otherwise might have been required are not required in this case. That 
is necessary so that an answerer can successfully refuse an offered 
m-line that it doesn't understand, and so can't construct a consistent 
answer. So the recipient must be very tolerant about what it receives in 
this case. That means it isn't appropriate to specify *anything* about 
what goes into the media section of a rejected m-line.

	Thanks,
	Paul


On 5/2/13 8:55 AM, Christer Holmberg wrote:
> Hi,
>
> One of the open issues is the usage of m- lines with port value zero
> within a BUNDLE group.
>
> As Paul has indicated, RFC 5888 does not currently allow it.
>
> One suggestion has been to update RFC 5888. But, before we go down that
> path, I think we need to see whether NOT allowing zero port m- lines in
> BUNDLE groups would work.
>
> So, how would it impact BUNDLE?
>
> Zero port value in answer:
>
> If an m- line in the offer contains a non-zero port value, but the
> associated m- line in the answer contains a zero port value (read: the
> answerer rejected the offered media associated with the m- line), the
> number of m- lines associated with the BUNDLE group would differ in the
> offer and answer.
>
> As the media is rejected, no matter whether it would be part of a BUNDLE
> group or not, I can’t think of any issues.
>
> Zero port value in offer:
>
> If an m- line in the offer contains a zero port value, the associated m-
> line in the answer MUST also contain a zero port value.
>
> If the m- line has previously been part of a BUNDLE group, with a
> non-zero port value, it means that the number of m- lines in the BUNDLE
> group will be reduced. But, again, as the media is rejected, no matter
> whether it would be part of a BUNDLE group or not, I can’t think of any
> issues.
>
> Then, if one later wants assign a non-zero value to the m- line, and
> insert it into a BUNDLE group, the number of m- lines in the BUNDLE
> group would increase. I don’t see any issues as such with that. One
> question, however, is whether the answerer is allowed to accept the m-
> line, but reject it being part of a BUNDLE group. But, let’s discuss
> that in a separate thread.
>
> SUGGESTION:
>
> My suggestion is that we do NOT allow m- lines with zero port value in a
> BUNDLE group. Please indicate whether you are aware of restrictions, or
> problems, that this would bring, and we will document those.
>
> Regards,
>
> Christer
>
>
>
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