Chapter 4. Meet the "Brain" of the Voice over IP Network
What You Will Learn
After reading this chapter, you should be able to
Do you remember the scene from 2001: A Space Odyssey where Dave Bowman is attempting to deactivate the HAL 9000 computer? A very concerned HAL says, "Just what do you think you're doing Dave?" If our private branch exchanges (PBXs) could speak, I imagine they might say something similar when we begin unpacking our Cisco CallManager (CCM) servers, because Cisco CallManager serves as a PBX replacement in an IP telephony environment.
This chapter explores CallManager's role in the Voice over IP (VoIP) network and how groups of CallManager servers work together. You then get to apply this knowledge in a design scenario. We also discuss CallManager features. For example, perhaps we don't want users sitting in the lobby to be able to place long-distance calls. CallManager's partitions and calling search spaces allow us to dictate which IP phones can call which phone numbers. New CallManager features include video and security, allowing us to see the person we're talking with and transmit our voice packets securely protected from would-be eavesdroppers.
Cisco IP Phones offer a variety of styles and features, and this chapter helps you become a better comparison shopper of these phones. Cisco CallManager also comes in an Express version, which runs on a Cisco router, as opposed to a server. This chapter explains how not only CallManager features but also voice mail features and auto attendant features are optionally serviced from a router.