When Cisco Unified Border Element is configured to support RSVP-based CAC, at which point

during call setup are the RSVP path and reservation messages sent and received?

A.
The path message is sent immediately after the call setup message is received and the
reservation message is received after H.245 capabilities negotiation is completed.

B.
The reservation message is sent immediately after the call setup message is received and the
path message is received after H.225 call setup messages have been sent.

C.
The path and reservation messages are sent and received after the H.245 capabilities
negotiation is completed.

D.
The path and reservation messages are sent and received immediately after the call setup
message is received.

Explanation:
The H.323 setup is suspended before the destination phone, triggered by the H.225
alerting message, starts ringing. The RSVP reservation is made in both directions because a voice
call requires a two-way speech path and therefore bandwidth in both directions. The terminating
gateway ultimately makes the CAC decision based on whether or not both reservations succeed.
At that point the H.323 state machine continues either with an H.225 Alerting/Connect (the call is
allowed and proceeds), or with an H.225 Reject/Release (call is denied). The RSVP reservation is
in place by the time the destination phone starts ringing and the caller hears ringback.