Subject: [Sipping] draft-ietf-sipping-media-policy-dataset: Rejecting a media stream

From: "Worley, Dale R (Dale)" <[email-masked]>
Date: Fri, 10 Dec 2010 15:45:37 -0500

In draft-ietf-sipping-media-policy-dataset-10 there is no explicit way to indicate that a stream has been rejected (which is needed to correspond to an m= line in SDP where the port number is 0).  Implicitly, this can be done by setting the port number in the <local-host-port> or <remote-host-port> to 0.  But that is pretty ugly.  I propose that we introduce an attribute of the <stream> element to indicate that a stream has been rejected/disabled:

    <stream enabled="no">

The default value of "enabled" would be "yes".

This resolves the problem of how a policy server would modify a <session-info> to make it conform to a policy if one of the <stream>s contradicted the policy:  The policy server would put enabled="no" onto the <stream>.

For consistency, a policy server could effectively reject a proposed session by rejecting all of the streams within it.  This would be slightly different than rejecting the session as a whole by returning an empty session-info document, <session-info/>.  This distinction corresponds to the difference between an SDP offer/answer negotiation failing, and the negotiation succeeding but the answer rejecting all the m= lines in the SDP.

Dale