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Re: [Sip] INFO Framework: Tags
On Nov 24, 2008, at 10:33 AM, Bob Penfield wrote:
The thing that makes me most uncomfortable with an option tag for
info-packages is that it is expanding the scope of an option tag
from a single well-defined extension/feature to a whole class of
features that are not necessarily related. I see it as being
analogous to defining an option tag for event-packages that could be
used to fail calls because the UAS does not support SUBSCRIBE/NOTIFY.
We have one; SUBSCRIBE. If it doesn't show in the Supported methods,
don't send a SUBSCRIBE.
Unfortunately, INFO method support is not enough, as there are
prepackage INFO implementations in the wild. So we have three cases to
differentiate: No INFO, Old INFO, and new INFO packages.
The other thing that is bothersome is that one day, the calls are
failing for your mystery application, the next day they succeed
because the UAS was upgraded to support SOME info-package, but not
your mystery feature and you will have to terminate successful calls
because of it.
But now you can look at the info package negotiation and figure out
that it does not support the mystery-package, and tell what other
packages it does support (and write the application to adapt to the
available packages).
I think we should change the section about OPTIONS to require the
UAS to include its supported info-packages in the response if the
request had a Recv-Info header. That way you could probe the far end
if you really require your info-package to be there.
While that makes perfect sense, it is inconsistent with the use of
OPTIONS tags in RFC 3261. I'd like to change that part of 3261
someday . . .
--
Dean
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