Its been a long time, and the details are starting to get fuzzy in my
mind. But I'm quite sure Michael is right here. The first registration
with an instance id causes the creation of a permanent gruu, and every
registration with an instance id results in creation of a temp gruu.
This is regardless of whether the registering UA indicates support for
gruu. If it does, then it receives a copy of the gruu in the response.
Thanks,
Paul
Michael Procter wrote:
Christer Holmberg wrote:
Hi,
GRUU is a little more subtle than that. If a UA provides an instance-id
to a GRUU-supporting registrar, then the registrar will create a GRUU
for that UA, whether it indicates support or not.
Then the question is: if I only want to use outbound, is it always ok that the
registrar creates a GRUU for me (no matter whether it returns it or not)?
I raised much the same question last year (March/April time), and I
think the conclusion was that creating the GRUU doesn't cause problems
and should be considered a Good Thing.
Then the text in 5.1, about the Require header is a little confusing. It says
that Require:gruu will NOT require the registrar to even generate a gruu - only
that the registrar is required to support gruu.
OR, does the text refer to the case when the request ONLY contains
Require:gruu, but no instance-id?
"A REGISTER request might contain a Require header field with the
"gruu" option tag; this indicates that the registrar has to
understand this extension in order to process the request. It does
not require the registrar to create GRUUs, however."
I think this is the normal Require processing. Putting 'Require: gruu'
in your REGISTER will ensure that it will only succeed on a GRUU-aware
registrar. It doesn't control or enforce any particular GRUU-related
processing, only that the registrar understands GRUU. This behaviour
(requiring understanding, not invoking) is common for many but not all
SIP options.
Maybe it would be good to clarify, in the outbound spec, that a gruu will be
generated if the registrar supports gruu. Because, at least in 3GPP there has
been some confusion about that, and I believe such clarification would prevent
future interop problems.
I'm certainly in favour of reducing ambiguity, where it exists, but I'm
not sure outbound is the place to talk about GRUUs. How did the
confusion arise? The GRUU spec seems reasonably clear on this point.
Regards,
Michael
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