[SIPForum-discussion] Help needed with SIP routing decision

[Yevgen Krapiva]

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.