[SR-Users] Proxying INVITE message without port information in R-URI

[Vikram Ragukumar]

Klaus,

Thanks for your continued help.

> How? Does it change the Contact header?

Yes, the proxy changes the Contact header.

> So the SIP server is the registrar?

Correct.

> The contact usually is the IP address of the client. So, if you the SIP
> server routes based on the contact header, it should send the INVITE
> directly to the client not to the proxy. Somehow this all does not fit
> together.

Clarification : Both clients A and B have the proxy as an outbound 
proxy. Clients register to the SIP server through the proxy. The SIP 
server routes the INVITE (INVITE from A that was proxied to SIP server) 
to the proxy with the R-URI being constructed based on the contents of 
the Contact header (IP only no port info). This is what I meant by 
saying the SIP server routes INVITE based on registered Contact (R-URI 
of INVITE is based on Contact header of client B's REGISTER message).

> It depends on how is the registrar - proxy or the SIP server.
>
> The workaround also depends on the respective buggy behavior of the sip
> server (if there is one at all).
>
> I think it is not possible to further debug this problem without a
> complete trace of the scenario:
>
> ngrep -W byline -t -d any -P "" port 5060

Attached to the email is a sip trace captured at the proxy showing

- Registration of client B
- INVITE messages originated by client A trying to call client B
- The sip trace has been edited to remove "duplicate" messages arising
   from authentication
- Towards the end, the sip trace shows 4 INVITE messages from proxy to
   Client B. However none of these messages reach client B because proxy
   is sending to port 5060, while client B is reachable at Nated port
   55000. This port information is not specified in the R-URI of INVITE
   by SIP server.
- Eventually a timeout will occur (not shown in log for sake of brevity)
- Both clients A,B are behind same NAT (public ip x.x.x.226)

What needs to be done at the proxy to ensure INVITE is forwarded to the 
correct port (55000 in this case) instead of the default port 5060 ?

Once again thanks for your help.

Regards,
Vikram.
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