Re: [MMUSIC] UP: Can a partial offer be a full offer?

[Paul Kyzivat <[e-mail]>]

On 8/21/13 10:33 AM, Hadriel Kaplan wrote:
>
> On Aug 21, 2013, at 9:34 AM, Paul Kyzivat <[e-mail]> wrote:
>
>>> Maybe we should use media level o- lines for POFs/PANs....
>>
>> I don't know how you could do that in a backward compatible way.
>
> Backward compatible to what?  There's no POFs/PANs thing today.  You don't even need to use SDP syntax if you don't want to, or you could use some diff-style format of SDP lines, or use what look and act exactly like SDP lines but aren't technically "SDP" to avoid any legacy RFC rules.

Maybe we are thinking of this differently, but my thinking is that 
consistency with a full SDP must be maintained. If you start off with an 
O/A, then some POFs/PANs, eventually you may need to do another O/A. And 
at that point there needs to be consistency.

I think that means that POFs/PANs always contain a subset of a full SDP, 
and act as deltas, implicitly updating a full SDP. That means everything 
in the POFs/PANs needs to be valid SDP. And when that stuff is used in a 
full O/A, there need to be rules for how those are reconciled.

So, to introduce a media level o-line, it would need to be defined for 
SDP too.

It might be possible to arrange so that it won't be seen by an endpoint 
that doesn't support POFs/PANs, but that will take some care, and is 
likely to be fragile.

	Thanks,
	Paul