[asterisk-bugs] [JIRA] (ASTERISK-21465) wrong routing of ACK request following a 200OK (route header no taken into account)

[sebastien prouvost (JIRA)]

    [ https://issues.asterisk.org/jira/browse/ASTERISK-21465?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=206653#comment-206653 ] 

sebastien prouvost commented on ASTERISK-21465:
-----------------------------------------------

To answer Walter's question above : I use my Asterisk GW as the MGCF function of the IMS (as standardised by 3GPP). In IMS, an incoming initial INVITE is sent to I-CSCF function and subsequent requests sent as part of the dialog established by the initial INVITE (such as the ACK to a 200OK) are sent to the S-CSCF (the I-CSCF do not record route). So in IMS this situation is quite common. No NAT used as I am not at the client interface.  
                
> wrong routing of ACK request following a 200OK (route header no taken into account)
> -----------------------------------------------------------------------------------
>
>                 Key: ASTERISK-21465
>                 URL: https://issues.asterisk.org/jira/browse/ASTERISK-21465
>             Project: Asterisk
>          Issue Type: Bug
>      Security Level: None
>          Components: Channels/chan_sip/General, General
>    Affects Versions: 1.8.8.2, 1.8.15.1
>         Environment: OS : DEBIAN 6.0.5
> DAHDI version 2.6.1 
> LIBPRI version 1.4.12
>            Reporter: sebastien prouvost
>            Assignee: sebastien prouvost
>         Attachments: debug_issue_ack, sip.conf
>
>
> I have an Asterisk GW (PSTN to IP gateway) equiped with digium board. 
> I observe the following behaviors of my Asterisk GW when making a PSTN to IP call: 
> - The GW sends the INVITE request to @IP1 (obtained by DNS query) and receives a 200 OK with a record-route header containing @IP2. 
> - The ACK request sent by the GW contains a route header with @IP2 (according to the record-route header received in the 200 OK) which is correct according the RFC3261. However this ACK request is sent to @IP1 and not to @IP2 which is not correct according to RFC3261 (the asterisk GW must send the ACK request to the first entry of the route header). 
> Here is the extract of RFC3261 which says that a request (in my case the ACK) has to be sent to the first Route header field value in the request, or to the request's Request-URI if there is no Route header field present. In my case I have a route header, therefore the request shall be sent to this route header (and I observe that it is sent to the request-URI). 
> page 41 : 
> "
> 8.1.2 Sending the Request
> The destination for the request is then computed. [...] the procedures are applied to the first Route header field value in the request (if one exists), or to the request's Request-URI if there is no Route header field present.
> "
> This problem is a major non-compatibility issue to the standard SIP protocol which may cause interoperability problems in certain configurations (IMS type for example where the inital INVITE request is routed toward a I-CSCF and the request within a dialog bypass this I-CSCF).
> Regards, Sébastien Prouvost

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