From: Dean Willis <[EMAIL PROTECTED]>
I have yet to figure out how a multiuser UA (including an event
server) is supposed to function if:
1) The To: field does not indicate the user being targeted, which
happens if a UAC-side proxy retargets, as in the case of a speed-dial
service, and
2) The request-URI does not indicate the user being targeted, which
happens in many cases including when the UAS-side proxy does contact-
routing AND the user-part of the contact isn't differentiated per-
user. It also occurs with some load-balancers. That's part of why we
don't specify bulk registration in RFC 3261, but instead recommend
using routing table entries.
This has been a known problem for ages -- a UA should register
different contacts for different AORs, so when a request comes in it
knows which AOR (which "line appearance") the request concerns. I
wrote this in Oct. 2005 (draft-worley-sip-gruu-implement-00), and it
was old information then:
As detailed below, when responding to requests, the UA should use the
GRUU associated with the AOR through which the request was routed to
the UA. In order to ensure that the UA can determine this, it should
register distinct URIs for each AOR it services. (The From header
may contain a different AOR which was routed to one of the UA's AORs,
and so can not be depended on to provide the AOR through which the
request was routed to the UA.)
Guideline: The UA should register distinct URIs for each AOR it
services. (Note that it is not sufficient to generate from each
AOR a contact 'sip:[EMAIL PROTECTED]', since it is common
for a UA to service two AORs with the same user part in different
domains.)
Dale
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