The CallManager Platform
CallManager is probably the most integral part of Cisco’s IP telephony solution.
It provides the rest of the IP telephony architecture with a central point for call
processing, connection services, signaling, and registration for IP telephone handsets,
analog and digital gateways, and legacy telephony devices such as PBX systems.
Communication with IP telephony devices is enabled by the use of several
IP telephony protocols such as Skinny Station Protocol (SSP), H.323, Media
Gateway Control Protocol (MGCP), and Simplified Message Desk Interface
(SMDI).These protocols will be discussed in more detail later in the chapter.
CallManager offers an open programming interface utilizing the Telephony
Application Programming Interface (TAPI) and the Java Telephony Application
Programming Interface (JTAPI). By utilizing industry standard protocols, Cisco
has opened the door for several other software vendors to further augment the IP
telephony product offering. Some of these applications will be discussed later in
this chapter as well as in Chapter 7.
Current releases of the CallManager platform allow a single CallManager
server to support up to 2500 IP telephone/5000 IP telephony devices per individual
server. An IP device can be any of the following:
IP telephone
Analog or digital gateway
IP SoftPhone
Digital signal processor (DSP)
CallManager has gone through two major revisions.The first revision of the
CallManager Platform was the 2.x release of the platform.This revision has been
discontinued, and CallManager 3.x is the current standard, which we will discuss
in the sections to follow.