This chapter provided an overview of Cisco IP Communications, including VoIP and how Cisco IP Communications differs from traditional telephone systems, and how you can use VoIP to achieve savings by routing your telephone calls over the IP WAN.
You also learned about CallManager, the heart of Cisco IP Communications, including a short history of how CallManager has evolved and the following components of a Cisco IP Communications network:
Also discussed were the phases that CallManager goes through to set up a call and CallManager's clustering strategy for providing high availability and scalability. Several different deployment models for CallManagers within a cluster were also described, including several methods of deploying clusters to serve both campuses and campuses with remote offices. QoS, including traffic classification, traffic prioritization, and call admissions control (both locations-based and gatekeeper-controlled) by which you can guarantee good voice quality in your network were also discussed.