Subject: [SIP] REGISTER Method questions.

From: "m. ranganathan" <[email-masked]>
Date: Thu, 07 Sep 2000 16:42:18 -0400

Hello!

At the risk of asking simple questions that have been asked and answered
in the past,  I would be grateful if somebody could help me understand a
few things  about the REGISTER  request.

1. The RFC states that Registrations with the same Call-ID must have
increasing CSeq header values, however the server does not reject out of
order requests. I am confused about the purpose of the CSeq value in
that case. Is there an implication here that the headers must have
montonically increasing  (but not necessarily sequentially increasing )
values?

2. If a new registration for a given SIP URI supersedes an existing
registration for the same URI,  do the contact headers  in the new
request replace the existing ones?  (i.e. are the old contact headers
implicitly discarded or do they have to be explicitly discarded with
another register request containing the contact header and a 0 expires
time?)

3. What "action value" is being referred to in the statement "All
current registrations must share the same action value"

Thank you in advance for your replies.

Ranga.

--
M.Ranganathan
NIST Advanced Networking Technologies Group,
100 Bureau Drive, Stop 8920, Gaithersburg, MD 20899.
Tel: 301 975 3664 Fax: 301 590 0934

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From: Hisham Khartabil <[email-masked]>
Date: Fri, 08 Sep 2000 08:51:40 +0300

> montonically increasing  (but not necessarily sequentially increasing )

This is for the scenario where an older request arrives at the server later
than a newer one.

> another register request containing the contact header and a 0 expires

no, you don't discard the older ones, you just add the new ones to the
list.  Contacts are removed when they expire according to the Expires header
upon registration or with a REGISTER request with expires 0.

> current registrations must share the same action value"

Action indicates whether the client wishes that the server proxy or redirect
future requests intended for the client.  So, you can't have one contact
with action=proxy and another with action=redirect.

Regards,
Hisham