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Chapter 3 Cisco CallManager Clusters

Intercluster Communication

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Cisco IP Telephony Network Design Guide

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Clusters for Multisite WAN with Centralized Call Processing

As stated earlier, Cisco CallManagers within a cluster must be interconnected

over a local area network. Cisco CallManager also provides locations-based call

admission control that enables provisioning of small branch and telecommuter

solutions where remote call processing is acceptable. Figure 3-9 illustrates this

model.

Figure 3-9 Locations Based Call Admission Control

In the scheme depicted in Figure 3-9, call processing is maintained only at the

central site, and the devices at the branches are configured as belonging to a

location. For example, branch 1 might have 12 IP phones, each configured to be

in the location Branch 1. Cisco CallManager is then able to track the used and

unused bandwidth per location, and admit or deny WAN calls accordingly.

This scheme has been expanded with Cisco CallManager Release 3.0(5) to allow

centralized call processing for as many as 2500 remote devices. To implement this

type of solution with Cisco CallManager Release 3.0(5), a dedicated

Cisco CallManager cluster is required with a single active Cisco CallManager to

maintain call state and call admission control.

Note In this type of centralized configuration, there is a maximum of 2500

users per cluster, regardless of the number of Cisco CallManagers in

the cluster (1, 2, or 3 for redundancy purposes). In addition, only one

Cisco CallManager in the centralized cluster can be active at a time.

IP WAN

Central

site

Branch 1

Branch 2

Branch 3

Branch n

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Cisco WS-X4604-GWY - VoIP Gateway Dokumentacja Strona 90