I`ve attached a drawing of a possible network using 3 x CCM - Sites A-C which are registered against a GK.

From my thinking Zones with the GK are to measure call volume between Zones so Site A=Zone 1, Site B= Zone 2, Site C =Zone 3

However how do I manage the sites off the CCM as in remote sites- Site D & E are remote sites registered to Site C . is the GK is aware of any calls?

Calls between Site D and the main site C is set for 4 calls- 4 x calls are already in use. Now someone in Site A wants to calls someone in Site D. The call request is sent from Site A CCM to the GK and then checked against its zone for Site D the GK shows the zone to be free from that fact it knows about the amount of traffic via itself but we know the link between D and C is full - what happens - does it respond back to the GK as busy and so back to site A ? How far does zone management extend it is only the number of calls it knows about or can it respond from busy states from the CCM?

Would I need something like RSVP ?