Subject: [Sipping] methods contact parameter

From: [email-masked]
Date: Tue, 3 Sep 2002 12:10:15 +0300

i have tried to figure out what is the best way to prevent proxies
from proxying requests (such as subscribe and message) to uas that can't
handle them.

it appears that draft-ietf-sip-callerprefs-06.txt defines the methods
contact parameter that the ua can use to list, which methods it
supports.  unfortunately, most uas on the market don't include that
parameter.

the above mentioned i-d also defines an accept-contact header that the
uac can use to specify, which contacts a request should be proxied to.
in order to prevent subscribes and messages from going to sip phones
that don't support them (and that don't include the methods contact
parameter in register), would it be correct proxy behavior to only proxy
a message with

accept-contact: *; methods="method"

to those contacts that actually have explicitly listed the method in the
register message?  if so, then old sip devices that are likely to never
implement the methods contact parameter, would not get useless requests.

-- juha

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