Your application may be running in multiple Microsoft Azure regions (datacenters) in either active-passive or active-active configurations. Active-passive is for disaster recover where passive datacenter becomes active if the active datacenter goes down. And, active-active serves both disaster recovery and load balancing of the traffic.
In this situation, each Windows Azure region (datacenter) has its own in-memory distributed cache cluster. But, you obviously want both caches to be synchronized across Microsoft Azure regions.
NCache provides a WAN replication feature where all the cache updates are asynchronously applied to the other cache and conflicts are also handled automatically. Bridge Topology is that feature in NCache that lets you synchronize and replicate cache across the WAN in Windows Azure.
You can define a one-node or two-node Bridge between both caches and both caches then submit their updates to the bridge for propagation to the other cache. The Bridge also resolves conflicts either on last-update-wins or through a custom conflict resolution handler provided by you, if the same data is updated in both caches.
See more details for this at: WAN Replication with Bridge Topology
Below is a diagram showing how Bridge works in Microsoft Azure.