[SIPForum-discussion] CSeq count in call scenarios using PRACK andUPDATE Methods

Rajnish Jain rj at pscientific.com
Thu Feb 15 23:28:35 UTC 2007

BYE from UAC will have CSeq: 3
UPDATE from UAC will have CSeq incremented by one from the previous
transaction in the same direction (PRACK in your example).


From: discussion-bounces at sipforum.org
[mailto:discussion-bounces at sipforum.org] On Behalf Of Smitha Harish
Sent: Wednesday, February 14, 2007 4:37 AM
To: discussion at sipforum.org
Subject: [SIPForum-discussion] CSeq count in call scenarios using PRACK
andUPDATE Methods

Hi all,

I have a query on use of reliable Provisional Responses using the PRACK

In the call flow shown below between a UAC and UAS, if CSeq count is 2 in
PRACK from UAC and CSeq is 1 in ACK from UAC, If a BYE gets initiated from
UAC itself, What count shall it hold in its Cseq? 2 (Base on INVITE Cseq
count) or 3(Based on PRACK Cseq count). Kindly clarify?


If an UPDATE is sent by the UAC before a 200 OK response for the INVITE has
been received in order to modify the session parameters in the pending
session, what is the CSeq count? Does it get incremented by 1 at the UAC. If
so does it take PRACK Cseq count as its previous count or INVITE Cseq as its
previous count?Kindly clarify?


Thanks in anticipation,




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