[SIPForum-discussion] Help needed with SIP routing decision

[Tomasz Zieleniewski]

Hi,

This is correct SIP behaviour but it is not compliant with the RFC3261
this acts as specified in RFC 2543. It is called strict routing instead
of loose routing defined in RFC3261.
When UA sends request and route set is not empty and its first URI does
not contain the lr parameter, UA places the first URI from the route set
into the Request-URI.
Because in the ACK there is no lr this is an information to the proxy
that request URI
should contain it's SIP URI and that the next hop is pointed in the
Route header.

Kind regards
- Tomasz Zieleniewski

2009/4/15 Yevgen Krapiva <ykrapiva at gmail.com>:
> Hi.
>
> I'm writing statefull proxy. Statefull proxy behavior section in RFC
> doesn't pay attention to special requests like ACK and BYE.
>
> Here is a ACK I receive in proxy server:
>
> ACK sip:172.20.177.123:5060 SIP/2.0
> Route: <sip:user1 at 172.20.177.70:57211>
> CSeq: 1 ACK
> Via: SIP/2.0/UDP
> 172.20.177.76:5070;branch=z9hG4bK0cb70b0f-1028-de11-9edf-dfde3e6514eb;rport=5070;received=172.20.177.76
> From: "Phone B"
> <sip:user2 at kv-po-ykrapivanb.umc.com.ua>;tag=4647660d-1028-de11-9edf-dfde3e6514eb
> Call-ID: 3e40660d-1028-de11-9edf-dfde3e6514eb at kv-po-krapiva2.umc.com.ua
> To: <sip:user1 at kv-po-ykrapivanb.umc.com.ua>;tag=c066ed41
> Contact: <sip:user2 at 172.20.177.76:5062;transport=udp>
> Allow: INVITE,ACK,OPTIONS,BYE,CANCEL,NOTIFY,REFER,MESSAGE
> Max-Forwards: 70
> Content-Length: 0
>
> Here 172.20.177.123 is proxy's IP, 172.20.177.70 is another peer's IP.
>
> So, this request is for the proxy, and RFC says I should use Location
> Service to determine the next target. Yes, that works, but this ACK
> request also has Route header that points to the same IP as it were
> retrieved from Location Service.
>
> So the question is: Should I check Route header presence before
> contacting Location Service or not ?
>
> I didn't find the statement regarding this issue in RFC. If I've
> missed something, please point.
>
> Thanks.
> _______________________________________________
> This is the SIP Forum discussion mailing list
> TO UNSUBSCRIBE, or edit your delivery options, please visit http://sipforum.org/mailman/listinfo/discussion
> Post to the list at discussion at sipforum.org
>