Hi Mahesh , 
This may be possible if the UAS receiving the ACK , does not understand it
or cannot correlate it to the dialog created 
by the INVITE/200 OK exchange , Hences it just retransmits the 200 OK. 
This can happen multiple reasons , does the number portion of Cseq in ACK
match the number portion of the INVITE request ? 
Generation of the ACK should match the in dialog request creation rules
specified in section 12.2.1.1 in 3261 plus the number portion in the CSeq of
ACK should be same as that of the INVITE .... 
Regards ,
Sayan




-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] Behalf Of mahesh
akarapu
Sent: Tuesday, November 30, 2004 10:48 AM
To: [EMAIL PROTECTED]
Subject: [Sip-implementors] 200 OK after recieving ACK


Hi all,
I have a doubt regarding how ACK requests are handled.
I am trying to establish a SIP session. The following is the scenario.
 A------------B
INV--------->
 <----------100
 <----------180
 <----------200
ACK--------->
Till this point, it is OK.But after this there are repeated 200Ok from B
as below.
 <----------200
ACK--------->
 <----------200
ACK--------->

I guess according to the RFC 3261, once ACK is received, the UA should
stop sending the 200 OK.Could someone please tell me if this a possible
scenario, that is under what circumstances 200 OK is sent after
recieving ACK. I could not get the answer for this from the RFC.

Could someone answer this.

thanks
Mahesh



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