Subject: [Sip] Question Caller Preferences 08 draft

From: "George Foti (LMC)" <[email-masked]>
Date: Mon, 31 Mar 2003 11:37:46 -0500

Quoting the 08 draft  section 7.4 (Matching):

Next, the proxy applies the predicates associated with the Accept-Contact header field. For each contact that remains in the target set, the proxy constructs a matching set, Ms. Initially, this set contains all of the Accept-Contact predicates. Each of those predicates is examined. It is matched to the contact predicate using the matching operation of RFC 2533 [2]. If the result is not a match, and the Accept-Contact predicate had its require flag set, the URI corresponding to that contact predicate is discarded from the contact set. If the result is not a match, but the Accept-Contact predicate removed from the target set.

My question relates to the last statement in the above paragraph.
The objective of that step, as I understand it, is to remove from the set all predicates, that don't have an equivalent in the contact.
This step seems to be redundant, as it would not have an impact on the score, since it would not change the score anyway (based on the way the score is calculated)

Is my understanding correct?

My next question relates to the usage of the cancel-directive.
Quoting the Draft :

cancel-directive: This type of directive indicates whether the
             caller would like each proxy server to send a CANCEL
             request downstream ("cancel") in response to a 200 OK from
             the downstream server (which is the normal mode of
             operation, making it somewhat redundant), or whether this
             function should be left to the caller ("no-cancel"). If a
             proxy receives a request with this parameter set to "no-
             cancel", it SHOULD NOT CANCEL any outstanding branches on
             receipt of a 2xx. However, it would still send CANCEL on
             any outstanding branches on receipt of a 6xx.

The strength SHOULD NOT makes it unclear as to how the UAC can decide on what to do, even if the proxy understands caller preferences.

Rgds/gf