Mohammed,
Strict Router is the one that follows route processing rules as
described in RFC 2543. And with reference to your question below,
The route set at UAC consists of
<sip:proxy1>,<sip:proxy2>,<sip:proxy3;lr>,<sip:proxy4;lr>
As the first entry in the route set does not contain the lr parameter,
it implements strict routing. Since the UAC sees proxy 1 as strict
router
UAC places the first URI in the route set in the Request URI. That's how
a Strict Routing Element expects a request to be received ( with its own
URI in the Request-URI and the next location to visit in the first Route
Header field value) .And then places the remote target URI as the last
entry in the Record-Route header.
So the request appears as
METHOD sip:proxy1
Route: <sip:proxy2>, <sip:proxy3;lr>,<sip:proxy4;lr>,<sip:[EMAIL PROTECTED]>
The request arriving at proxy3 would look like
METHOD sip:proxy2
Route: <sip:proxy3;lr>,<sip:proxy4;lr>,<sip:[EMAIL PROTECTED]>
Proxy 2 is also a strict router, so it forwards the request to proxy 3
METHOD sip:proxy3
Route: <sip:proxy4;lr>,<sip:[EMAIL PROTECTED]>
Proxy 3 sees that Request-URI is the value it placed in the Record-Route
Header field. So before further processing it rewrites the request to
METHOD <sip:[EMAIL PROTECTED]>
Route: <sip:proxy4;lr>
I hope this makes you clear....
Thanks,
Bharat
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of
Mohammad Farooq
Sent: Tuesday, April 01, 2008 11:56 AM
To: [email protected]
Subject: [Sip-implementors] Please provide explanation on strict-routing
In RFC 3261, section 12.2.1.1 it gives example of strict routing. It
explains that uac has route set:
<sip:proxy1>, <sip:proxy2>,
<sip:proxy3;lr>,<sip:proxy4>,<sip:[EMAIL PROTECTED]>
Since uac see the proxy1 is strict route it create the following
request:
METHOD sip:proxy1
Route: <sip:proxy2>, <sip:proxy3;lr>,<sip:proxy4>,<sip:[EMAIL PROTECTED]>
My question is if uac try to send this request the sip stack will send
this request to proxy2. Because the first entry in the Route header is
proxy2 and we know Route header has presidence over requestURI. I would
appreciate if someone can educate me. Thanks.
M. Farooq
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