On Nov 21, 2008, at 7:57 AM, Paul Kyzivat wrote:
Dean Willis wrote:
I don't in general
see a need to specify this as part of the extension in general,
but if a
particular package needs a feature tag, let it define one. Keep the
extension simple.
Only standards-track RFCs can define SIP option tags under RFC
3427, and we have no plans to relax this requirement.
But we have a much looser policy for INFO packages; most will not
be standards-track.
So, for those sorts of packages, an info-package option tag is
potentially quite useful.
For that to be useful, each package would need its own option.
Not exactly. If I know you don't support info-packages at all, I can
readily presume you don't support any specific info-package, including
those non-STD-track packages that can't possibly have their own SIP
options tag.
Having discovered via OPTIONS that you support info-packages, I could
then decide to offer the specific package needed in an INVITE. This
can weed out a lot of abortive calls.
Without the info-package tag, I can't use OPTIONS to decide whether or
not you support info-packages, and must probe with a real-live INVITE
(which could make things a bit strange with lots of ring-answer-hangup
calls).
Sure, if every UA supports info-package as a concept this isn't
useful. But in a transitional phase (which is what we have) where a
great many UAs are not supporting it al all, it's better than a call-
and-hangup probe.
While I guess we could define things such that each info-package
registration implied a corresponding option tag registration, then
that would be an end-around of the standards-track requirement for
defining option tags. We really don't want that, or we will have
people defining info-packages they don't intend to use, just to get
an option tag.
I agree heartily.
--
Dean
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