Re: [Sip] Sent 18x with 'require:100rel' but no PRACK recieved

<> Fri, 19 August 2011 10:16 UTC

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Date: Fri, 19 Aug 2011 15:42:42 +0530
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Thread-Topic: [Sip] Sent 18x with 'require:100rel' but no PRACK recieved
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Subject: Re: [Sip] Sent 18x with 'require:100rel' but no PRACK recieved
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Hi ,


First of all , please use "sip-implementers
(" forum for the answer of this query. 


As per SIP RFC3262, you must reject the call in SIP side with 5xx (
provided you had SDP in reliable 18x ). You can reject ISUP side with a
RELEASE message.


But if you want to relax your software compliance a bit here , you can
do that,  but remember your early media negotiation may be in trouble.
If you are sure that on ISUP side the call is answered ( ANM is received
) you can proceed for sending 200 to SIP side.





From: [] On Behalf Of
Sent: Friday, August 19, 2011 8:48 AM
To: sip
Subject: [Sip] Sent 18x with 'require:100rel' but no PRACK recieved




  I'm facing a ISUP - SIP interworking issue recently.  


 I receive INVITE from remote SIP server and send IAM to ISUP side, ISUP
reply ACM/CPG and then I send 18x with 100rel out, but I did not receive
any PRACK from remote SIP server, and I re-send 18x to them. During this
period, ISUP side send ANM to me. 


 If connect the call, but my end haven't receive PRACK yet, it become a
unreliable call.

 If disconnect the call, I should not base on ANM to release a call.

 If continue 18x re-transmission untill time-out, it will have charging
issue. Because ISUP side start billing base on ANM already, but my SIP
side haven't start charging because not answer.