[OpenSIPS-Users] Opensips should reply "SIP/2.0 200 canceling" to CANCEL after forwarding ? or wait after reply
bogdan at voice-system.ro
Mon Jun 21 18:09:53 CEST 2010
I doubt opensips generates a 487 Request terminated for an INVITE when
the CANCEL is passing through - the 497 is end to end, not hop by hop
(as the CANCEL), So, the 487 is generated by callee and opensips simply
relays it back.
Julien Chavanton wrote:
> Hi, regarding handling of CANCEL request,
> Please correct me if I am wrong,
> I have glare condition on how Opensips handled Cancel requests.
> The problem is taht Opensips respond "487 Request terminated" strait
> after forwarding the CANCEL but it does not know if the targe UA will
> accept it.
> I think it should wait after the target UA to reply before, as this
> can create out of sync situation if there is a problem with the target.
> in this senario the "200 OK" is received at the same time as the
> CANCEL is sent, in this case the target UA as the right to ignore the
> CANCEL because it as generated a final response.
> UA -----> CANCEL ------------------------> osips
> UA <------ SIP/2.0 200 canceling --------> osips
> osips <--- 200 OK <-- UA
> osips ---> CANCEL --> UA
> UA <---- SIP/2.0 487 Request Terminated -> osips
20 - 24 September 2010, Frankfurt, Germany
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