Multisite Distributed VoIP Deployment

I briefly went over the Multisite Distributed VoIP Deployment section in the SRND Guide. It has very similar attributes and requirements as the centralized model except it is a lot more versatile due to having a call processing cluster at each site. That eliminates the need to depend on the WAN or whatever media of inter-site connectivity for calls as much. I also began reading about the Cisco Intercompany Media Engine which seems to dynamically interconnect different enterprise organization phone numbers and create a network similar to how internet was when it was first created. Instead of just IP services, the network is used to connect Unified Communications within all the Enterprises. There's a lot more to learn about this technology and I may be off a little bit with my understanding of it at this point in time.