UC Deployment Models

Cisco Unified Communications Manager (CUCM) has the following four deployment models which we will begin discussing in this blog series: • Single Site • Centralized • Distributed • Clustering over the WAN The single site deployment model consists of one geographical location. Every call to other sites is routed over the public switched telephone network (PSTN). This deployment model is frequently used in large organizations that have not rolled out QoS on their wide area network (WAN) links yet. All calls within the site should use the highest quality audio codec possible. Cisco Type B phones (7906, 7970, 79×1, 79×2, 79×5) are capable of using the G.722 audio codec beginning with CUCM 6.0. G.722 uses twice the audio fidelity (16khz) compared to the G.711 audio codec, but both use 64kbps of bandwidth. The DSP hardware of the Cisco IP phone handles the G.722 compression algorithm. The G.722 audio codec is automatically negotiated between two G.722 capable phones beginning with CUCM 6.0. G.722 can be turned off with a Call Manager service parameter. The theoretical maximum number of phones in one CUCM cluster is 30,000 phones. The actual number of phones in one CUCM cluster will be limited by various components including the servers purchased, number of servers, busy hour call attempts (BHCA), Unified Contact Center Express (UCCX), number and type of gateways, etc. The Cisco Call Manager Capacity Tool (CCMCT) is a partner level CCO tool that allows engineers to properly size a CUCM cluster given the various components in the CUCM cluster. The centralized call processing architecture consists of up to 1000 geographical locations (sites) connected over a WAN. In the centralized call processing model, the largest site is normally where the organization decides to physically located the CUCM cluster. Branch locations do not have any local call processing capabilities. There is no requirement in this model for a local PBX or key system at each one of the branch locations. All Skinny Client Control Protocol (SCCP) call signaling is carried over the WAN to the CUCM servers. Each call will require up to 619bps (SIP with signaling encryption). The CUCM 7.x SRND Table 3-12 includes a table with the recommended call control QoS traffic class recommendations based on the number of phones at the remote location. There are a lot of aspects to the centralized call processing deployment model to discuss. We will continue discussing deployment models in the next blog. REFERENCES: CUCM 7.x Solution Reference Network Design (SRND) Guide: http://www.cisco.com/en/US/netsol/ns818/networking_solutions_program_home.html www.cisco.com/go/srnd Cisco Call Manager Capacity Planning Tool (CCMCT): http://www.cisco.com/cgi-bin/CT/CCMCT/ct.cgi (requires CCO login)