[OpenSER-Devel] [Serdev] Possible bug in the tm module in the presence of packet loss/branches

Bogdan-Andrei Iancu bogdan at voice-system.ro
Tue Mar 11 10:43:48 CET 2008


Hi Maxim,

I followed the discussion on the "sip-implementers" list and they that 
this must be the behaviour (not should and no t default).
The main argument was the total separation between the INVITE and CANCEL 
transaction - and the arrival of the CANCEL transaction should not 
trigger any action (like resetting timer or retransmissions) on the 
INVITE transaction.

Regards,
Bogdan

Maxim Sobolev wrote:
> Klaus Darilion wrote:
>   
>>  From the "sip-implementors" list - looks like Maxim is right.
>>     
>
> Thanks, Klaus! Should this behavior be the default one then?
>
>   
>> regards
>> klaus
>>
>>
>> Robert Sparks schrieb:
>>     
>>> Part of why it does this is to deal with the case that the first
>>> INVITE the proxy sent actually got somewhere, but its response was
>>> lost. The retransmission will stimulate a retransmission of the
>>> response, letting you move forward to sending the CANCEL from the
>>> proxy.
>>>
>>> RjS
>>>
>>> On Mar 7, 2008, at 7:06 AM, Bob Penfield wrote:
>>>
>>>       
>>>> The INVITE transaction must still complete independent of the
>>>> CANCEL. So the proxy would continue to re-transmit the INVITE. If
>>>> the proxy does receive a provisional response, it would then stop 
>>>> retransmissions and send the CANCEL down stream. If timer B fired,
>>>> it would send a 408 response to the INVITE.
>>>>
>>>> Note that the proxy should respond to the CANCEL with 200 OK when
>>>> it receives it since the INVITE transaction is in progress.
>>>>
>>>> cheers, (-:bob
>>>>
>>>> -----Original Message----- From:
>>>> sip-implementors-bounces at lists.cs.columbia.edu 
>>>> [mailto:sip-implementors-bounces at lists.cs.columbia.edu] On Behalf
>>>> Of Klaus Darilion Sent: Friday, March 07, 2008 4:11 AM To:
>>>> Sip-implementors at lists.cs.columbia.edu Subject: [Sip-implementors]
>>>> CANCEL retransmisson question of no provisional response!
>>>>
>>>> Hi!
>>>>
>>>> Could someone help me please with this question.
>>>>
>>>> Scenario: A transaction-stateful proxy forwards the INVITE request.
>>>> The proxy does not receive a provisional response, thus starts 
>>>> retransmissions. Now, the caller CANCELs the call. How is the proxy
>>>>  supposed to handle this? Does the proxy still have to retransmit
>>>> the INVITE or can it stop retransmitting the INVITE?
>>>>
>>>> From logical point of view I would think that the proxy should stop
>>>> the retransmissions, but from Figure 5 in RFC 3261 it looks like
>>>> the only way to come from "Calling" state to "Terminated" state is
>>>> waiting for Timer B fires (as there is no provisional response
>>>> yet).
>>>>
>>>> thanks klaus
>>>>         
>
> Regards,
>   




More information about the Devel mailing list