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Cisco Unified Communications Manager Deployment Models

Chapter Description

In this chapter from Implementing Cisco IP Telephony and Video, Part 1 (CIPTV1) Foundation Learning Guide (CCNP Collaboration Exam 300-070 CIPTV1), 3rd Edition, the author team introduces Cisco Unified Communications Manager (CUCM) and explores different redundancy models.

Multisite Deployment with Distributed Call Processing

The model for a multisite WAN deployment with distributed call processing consists of multiple independent sites, each with its own CUCM cluster.

An IP WAN carries voice traffic between the distributed clusters. CUCM Session Management Edition (SME) cluster or SIP proxy servers can be used to provide intercluster call routing and dial plan aggregation in multisite distributed call-processing deployments. Cisco CUCM Session Management Edition (SME) is the recommended trunk and dial plan aggregation platform in multisite distributed call processing deployments. SME is essentially a CUCM cluster with trunk interfaces only and no IP endpoints. It enables aggregation of multiple unified communications systems, referred to as leaf systems.

Cisco CUCM SME may also be used to connect to the PSTN and third-party unified communications systems such as PBXs and centralized unified communications applications. Figure 2-6 illustrates a distributed multisite deployment.

Figure 2-6

Figure 2-6 Distributed Multisite Deployment

Design Guidelines for Multisite Deployment with Distributed Call Processing Model

The multisite model with distributed call processing has the following design characteristics:

  • A centralized platform for trunk and dial plan aggregation is commonly deployed. This platform is typically a Cisco Unified Communications Session Management Edition (SME) cluster, although an SIP proxy server (for example, Cisco Unified SIP Proxy (CUSP)) could also be used to provide intercluster call routing and dial plan aggregation in multisite distributed call-processing deployments.

  • Centralized services such as centralized PSTN access, centralized voice mail, and centralized conferencing are available. These services can be deployed centrally, thus benefiting from centralized management and economies of scale. Services that need to track end-user status (for example, Cisco IM and Presence) must connect to the CUCM cluster for the users that they serve.

  • The use of high-bandwidth audio (for example, G.711 or G.722) between devices within the same site, but low-bandwidth audio (for example, G.729) between devices in different sites.

  • The use of high-bandwidth video (for example, 1.5 Mbps with 4CIF or 720p, to 2 Mbps with 1080p) between devices in the same site, but low-bandwidth video (for example, 384 kbps with 448p or CIF) between devices at different sites.

  • The use of se a minimum of 1.5 Mbps or greater WAN link speed. Video is not recommended on WAN connections that operate at speeds lower than 1.5 Mbps.

  • Call admission control is achieved through Enhanced Locations CAC or RSVP.

Benefits of Multisite Deployment with Distributed Call Processing Model

The multisite deployment with distributed call-processing model is a superset of both the single-site and multisite WAN with centralized call processing models.

The multisite WAN with distributed call-processing model provides the following benefits:

  • PSTN call cost savings are possible when the IP WAN is used for calls between sites.

  • In this model, you can use the IP WAN to bypass toll charges by routing calls through remote site gateways, closer to the PSTN number that is dialed—that is, TEHO.

  • Maximum utilization of available bandwidth is possible by allowing voice traffic to share the IP WAN with other types of traffic.

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