I believe the reason 3261 says this is that without it there's no mechanism
for ensuring registrations are processed in order. With the same Call-ID,
this property comes from the CSeq (as within a dialog).
.. but at the same time, the UA MUST NOT send a new REGISTER while another
one is still in progress. So this out-of-order should only occur for
non-conformant UAs; if a UA were to crash just after sending a REGISTER and
then immediately starts a new one, the second one will generally have a
different Call-ID (and different out-of-order CSeq), so the in order
processing would not be guaranteed.
It does not appear to be a critical issue, the "MUST NOT send new one while
another in progress" is sufficient for in-order processing and the "same
Call-ID" is only extra safety, somewhat redundant.
Would it be recommended to use the same call-ID for *all* registrations if
possible, and perhaps a CSeq number based on a monotonically increasing
clock that survives crashes?
Also from section 10.2:
CSeq: The CSeq value guarantees proper ordering of REGISTER
requests. A UA MUST increment the CSeq value by one for each
REGISTER request with the same Call-ID.
Anders
Paul Kyzivat wrote:
Monica,
I know it specifies this, but it has always been a big mystery to me why.
There is only trivial impact on the UA or registrar if the UA changes the
callid.
If you are asking from the point of view of a UA, I would just say to use
the same one as long as it is convenient. If you are asking from the
point of view of a registrar, I would say that you should not have any
important dependency on this.
Paul
[EMAIL PROTECTED] wrote:
Hi All,
RFC 3261 states that "A UA SHOULD use the same Call-ID for all
registrations during a single boot cycle." And technically a UA is still
within the same boot cycle even when the network connection is lost.
Right?
Hence is it fair to assume that UA should generate the same Call-ID when
UA remains powered on, and got reconnected to network after a network
failure ? (maybe Home gateway or DSL/cable modem or Internet SP
failure). Will be great if anyone can confim if my assumptions are
correct.
RFC 3261, Section 10.2
Call-ID: All registrations from a UAC SHOULD use the same Call-ID header
field value for registrations sent to a particular registrar.
If the same client were to use different Call-ID values, a
registrar could not detect whether a delayed REGISTER request might have
arrived out of order.
RFC 3261, Section 10.2.4
A UA SHOULD use the same Call-ID for all registrations during a single
boot cycle. Registration refreshes SHOULD be sent to the same network
address as the original registration, unless redirected.
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- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
- -
Thanks & Regards
Monica Ingudam (Mail: [EMAIL PROTECTED])
Signal Engineer
AOL Dulles
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