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
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