Cisco Unified Communications Manager (CUCM) is an IP telephony call-processing solution. It provides distributed, scalable enterprise call processing and IP telephony features for IP phones, Voice over IP (VoIP) gateways, and multimedia applications and devices.
CUCM can be deployed using several different models, as shown in Figure 1-1:
• Single site: In this model, CUCM provides call processing at a single site, with no telephony being implemented over an IP WAN.
• Multisite WAN with centralized call processing: In this case, CUCM is deployed at a central site, and it provides call processing for a number of sites, with VoIP/IP telephony traffic being carried over an IP WAN between sites.