New subject: [Serusers] Re: [Serdev] Problem with Via Branch/Strange Looping Problem with ACK's

1 May 2005

For reference:
The "Cisco_7960" traces exhibit strict_routing, and shows the SER
looping problem

The "Ambit_vg20" traces show the proper (RFC3261, Reference #1 at the
bottom of the email) behaviour and works perfectly.

*SER_SIP_PROXY*:15061 is SER
*SER_SIP_PROXY*:5080 is Asterisk
Both SER and Asterisk are on the same server

*SIP_UAC* is the client device

There are two traces for each session, one taken from the external
interface (ETH0) and one from loopback (LO)

In the "Cisco_7960" traces, the Cisco 7960 responds to the session
initiating "200 OK" with an ACK that seems to follow Strict Routing
behaviour.

The issue is that the ACK does NOT match the loose_route() statement in
the SER config and eventually hits a t_relay, however the RURI is that
of the SER proxy itself so it routes to itself over and over again.

What i expect is that it should hit loose_route() (or perhaps
strict_route() ), which should replace the RURI with the information in
the "Route:" header which would allow it to be properly routed to its
destination.

This same problem seems to happen with BYE messages as well (same
situation and results)

-----------------------

Reference #1:

Section 12.1.2 of RFC3261 states:
--
The route set MUST be set to the list of URIs in the Record-Route
   header field from the response, taken in reverse order and preserving
   all URI parameters.  If no Record-Route header field is present in
   the response, the route set MUST be set to the empty set.  This route
   set, even if empty, overrides any pre-existing route set for future
   requests in this dialog.  The remote target MUST be set to the URI
   from the Contact header field of the response.
--