Given the following topography, what would be the best way to provide call admission control redundancy for H.323 voice gateways? The attached .gif file shows the layout, here are the basic points:
* Hub and spoke design where international sites are spokes with one H.323 gateway per site
* Each international location is a zone.
* Hub is comprised of three symmetrically configured voice gateways (each with one T1 to software defined network, another to local access) .
* Two centralized gatekeeper(s) in hub site serving all international voice sites.
* Gateways and gatekeepers are located in different buildings for diversity, on seperate subnets - within Gigabit Ethernet distance of each other.
* See drawing for more detail.
What would be the most appropriate redundancy configuration, given this detail?