This chapter explained how Cisco CallManager servers replace many PBX functions in an IP telephony environment. For redundancy and scalability, we grouped CCM servers into clusters. We determined how many CCM servers were needed for a cluster, based on the number of supported IP phones and redundancy requirements.
Features available on Cisco IP Phones rival, and, in many cases, surpass, present-day PBX features; and this chapter explored the operation of many of the more popular IP phone features. Features available on various Cisco IP Phone models were also reviewed.
Cisco CallManager version 4.0 introduced support for video calls and enhanced security. This chapter discussed the VT Advantage product used for video calls and explored how CCM servers secure our voice transmissions through identity, integrity, and privacy mechanisms.
Finally, we discussed how a small- to medium-sized office could leverage the features offered by the CME and the CUE products. The CME feature allows an IOS router to support up to 240 IP phones, as opposed to supporting these IP phones with CCM servers. The CUE feature offers voice mail and autoattendant features within an IOS router.