[OpenSIPS-Users] dialog and CANCEL

Bogdan-Andrei Iancu bogdan at opensips.org
Wed Apr 6 16:35:25 CEST 2011

Hi Denis,

On 03/21/2011 01:55 PM, Denis Putyato wrote:
> Hello
> There is such scheme of call
> One gateway –
> Opensips –
> Another gateway –
> Calls from to through
> I use CDR_flag for accounting
> As you can see in testlog file, trying cancel initial request 
> by sending CANCEL, this CANCEL Opensips forwarding to but from 
> Opensips receives 200 OK on INVITE. Because of this there is 
> no CANCEL of the dialog on Opensips and after 1800 sec (see 
> “default_timeout”) I have a CDR record in Opensips with duration of 
> 1800 sec.
> The question. Why does Opensips forward 200 OK from to 
> when initial request was cancelled, and why Opensips makes accounting 
> dialog when initial request was cancelled?
RFC3261 says a proxy must forward all 2xx replies (disregarding the 
transaction state), just to solve the possible race between CANCEL and 
2xx -> such race must be handled by end point and not by proxy.

So, it your case, if caller sent a CANCEL but still receives a 200 
(callee picked up before actually receiving the CANCEL from caller), the 
caller must sent a BYE and the callee should send a negative reply to 

So, it is a bug in the caller device.


Bogdan-Andrei Iancu
OpenSIPS eBootcamp - 2nd of May 2011
OpenSIPS solutions and "know-how"

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