[Users] Locally generated single-hop ACKs with Route headers

Augustin, Andrew (external) Andrew.Augustin at external.t-mobile.de
Wed Jul 26 13:25:32 CEST 2006


Hi Klaus, Thanks for your response. In answer to your question: yes, the INVITE does contain a Route header. 

Further info on the problem: 

There are 3 proxies between A and B parties. 

The INVITE message is routed from A-Party through Proxy-1, through Proxy-2 before finally reaching B-Party. The Route header first appears in the INVITE message sent by Proxy-1 and is removed at Proxy-2. 

There is an errored response message to this INVITE (e.g. 'Busy' or 'Request Terminated'). The errored response is acknowledged with a one-hop locally generated ACK at each point between B and A. 

I expected the ACK at Proxy-2 to take the same one-hop route as the original INVITE at Proxy-2, i.e. the ACK sent by Proxy-2 will contain routing data based on routing data from the INVITE previously sent by Proxy-2. 

What actually occurs is that the Route header in the ACK sent by Proxy-2 is a duplicate of the Route header of the INVITE that Proxy-2 has RECEIVED from Proxy-1 and NOT that of the INVITE message it had previously sent. 

Are you aware of this problem and any resolution and/or workarounds? 

We would like to remove this unwanted Route header from the ACK. How is it possible to do this (i.e. which routing block?)? 

The known issue described in the previous email (below) appears to prevent us from removing this header from the ACK. Are you or anyone else in the OpenSER community aware of any fix or resolution to this problem? 

Best regards,
Andrew Augustin

-----Ursprüngliche Nachricht-----
Von: Klaus Darilion [mailto:klaus.mailinglists at pernau.at] 
Gesendet: Dienstag, 25. Juli 2006 18:15
An: Augustin, Andrew (external)
Cc: users at openser.org
Betreff: Re: [Users] Locally generated single-hop ACKs with Route headers

I wonder why there are route headers in the ACK - they are only 
necessary if the INVITE also hed route headers (RFC3261,


Augustin, Andrew (external) wrote:
> Hello,
> I am using OpenSER v1.0.1
> I am currently testing with proxies running OpenSER.
> I have a problem with ACK messages generated and routed for scenarios
> where an inititiated call session fails to establish between A and B 
> parties e.g. Unsuccessful No Answer, Unsuccessful Busy. The ACK 
> messages are single hop locally generated responses to the sip error 
> message e.g. '487 Request Terminated', '486 Busy'.
> The behaviour I observe is that Route headers are 'remembered' from 
> the initiating INVITE message and inserted into the ACK messages
> automatically generated by OpenSER.
> This extra Route header causes problems with routing and the 
> generation unwanted messages (error message resends) in addition to 
> expeceted scenario call-flow. It is also visible at the B-Party.
> I would like to either prevent the creation of, or remove this Route
> header. I have tried to remove this header using the OpenSER available 
> methods, but this has failed.
> I have noticed that the known issue described in the document: SIP
> Express Router v0.8.8 - Developer's Guide under section: 9.6.4 Known 
> Issues appears to describe this problem.
>         "local ACK/CANCELs copy'n'pastes Route and ignores deleted 
> Routes"
> Has this issue been resolved? If so, from what version of OpenSER?
> If it has not been resolved, is there a way to resolve or workaround
> this problem?
> Best regards,
> Andrew Augustin
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