> -----Original Message-----
> From: Dvir Oren [mailto:[EMAIL PROTECTED]]
> Sent: Tuesday, May 29, 2001 3:27 PM
> To: [EMAIL PROTECTED]
> Subject: [Sip-implementors] CSeq number
>
>
> When should a CSeq be increased?
For each new request sent by a client within a call leg.
>
> If a Client sends a Re-INVITE, which is never received, should the
> next method on the same call be with an increased CSeq?
If the next request is not identical to that failed request, its a new
request, and therefore gets an increased CSeq.
>
> What happens if the Re-INVITE caused an error? The error might have
> been that the message was badly formed, and therefore the server will
> not update the cseq state. If the server will now send a new method,
> it will be with a lower cseq than the state at the client.
Since the next request is not the same as the previous, its a new request,
and therefore gets an increased CSeq.
I think you are concerned about the case where the server sees two
consecutive requests that differ with a CSeq of more than one. This is now
addressed in bis-03:
>From 10.20:
Any request
that is received with a sequence number higher than the highest received so
far (even it is higher by more
than one), SHOULD be accepted.
and from 15.5:
If there was no match to the previous step, the To and From fields are
compared against existing call
leg local and remote addresses. If there is a match, and the CSeq in the
request is higher than the last
CSeq received on that leg, the request is a new transaction for an existing
call leg. It is possible for
the CSeq header to be higher than the previous by more than one. This is not
an error condition, and
a UASSHOULD be prepared to receive and process requests with CSeq values
more than one higher
than the previous received request. A request on an existing call leg with a
lower CSeq MUST be
rejected.
>
> I think there is some ambiguity regarding when to increase the cseq
> number, and what to do with lower (or much higher) numbered messages.
I think the text above spells it out now quite explicitly.
-Jonathan R.
---
Jonathan D. Rosenberg, Ph.D. 72 Eagle Rock Ave.
Chief Scientist First Floor
dynamicsoft East Hanover, NJ 07936
[EMAIL PROTECTED] FAX: (973) 952-5050
http://www.jdrosen.net PHONE: (973) 952-5000
http://www.dynamicsoft.com
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