[Users] Accounting wrong BYEs

Bogdan-Andrei Iancu bogdan at voice-system.ro
Wed Jul 19 19:03:32 CEST 2006

Hi Klaus,

it does sounds like a realistic scenario.

First of all the UAC may not discover all the branches based on To-tag - 
there might be branches that haven't sent any reply, or replies were 
absorbed by the forking server (ex: 180 after 183 will not be relayed).

Even so, when the BYE is generated, you cannot route it properly to the 
callee set because you do not have a unique routing set for the path. 
Different sets may be returned by each branch; also until the final 
reply the mirroring of RR hdrs is not mandatory. So there is the problem 
how to deliver the BYE to all the branches.

Even so, it suppose that the UAS understands a BYE before 200 OK and is 
able to f proper filtering based on the to tag parameter. Not sure how 
many clients will do this.

again, I do not say is not possible, but I find it highly unrealistic.


Klaus Darilion wrote:

> Bogdan-Andrei Iancu wrote:
>> not sure if this makes sends - how the UAC is aware of the parallel 
>> forking? the fork is transparently done by the proxy and it is the 
>> only one to manage the branches.
> Not sure about this, but what about:
> If it receives several 180/183 with different to-tags, the client has 
> to maintain several dialogs in "early-dialog" state.
> If the UAC sends the BYE in-dialog, it gets routed to the proper UAS, 
> which will response to the INVITE dialog with 487 Request terminated. 
> This should cancel this single branch inside the proxy.

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