Subject: [Sip] Treatment of q values on contacts returned in redirects

From: "David R. Oran" <[email-masked]>
Date: Wed, 16 Jul 2003 04:15:54 -0400

The proposal Jonathan made on this is to effectively replace the contact 
that returned the redirect with the contacts in the redirect, and then try 
them in the order of their q values - essentially a depth-first search.

In the SIP meeting, I questioned that this was too restrictive and that 
there was no need to actually mandate that behavior. That is one 
possibility, but not the only one.

As an alternative, what one could do is to go back the the original set of 
registered contacts, eliminate the ones already tried and the one that 
returned the redirect, add the ones in the redirect response and treat them 
as if they were directly registered contacts for the AoR. You throw away 
the results of the current caller-prefs calculation, and rerun it from 
scratch on this set of contacts.

Why is this alternative needed? Imagine a contact which does "Call forward 
no answer" by timing out an alert state and sends back a redirect to some 
random place before the upstream proxy gives up.

What if the callee's policy is to try other of his registered contacts 
first before inviting to a CFNA number returned by a contact?

Sorry for the terseness of this - wanted to get this out right away before 
I forget what the issue is.

Dave.

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