Specifications

Chapter 5 Dial Plan Architecture and Configuration
Cisco CallManager Dial Plan Architecture
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Cisco IP Telephony Network Design Guide
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Note IP phones are not the only devices that can be accessed in this
manner. Other devices that register with Cisco CallManager and
maintain a directory number can include Cisco IP SoftPhones,
analog phones, and fax machines attached to gateways that use
MGCP or the Skinny Gateway Protocol.
Configuring Cisco CallManager to handle external calls requires the use of a
route pattern. In most cases, the route pattern is used for directing calls out to a
PSTN gateway, but it is also used in the case of an IP WAN call to a remote
Cisco CallManager. The Cisco CallManager Release 3.0 dial plan architecture is
a three-tiered decision tree that allows multiple routes for a given dialed number,
as well as digit manipulation based on the network requirements. Digit
manipulation is the task of adding or subtracting digits from the original dialed
number to accommodate user dialing habits or gateway needs. You can also
configure capabilities such as trunk groups for gateway redundancy and a form of
least-cost routing.
As an example of alternate route selection, the path to a given dialed number
typically takes the IP WAN as the first choice and the PSTN as the second choice
if the IP WAN is down or has insufficient resources. The dial plan criteria for
using an alternate route could be based on an indication by the call admission
control mechanism that insufficient trunks are available on a gateway, meaning
that the IP WAN cannot accept the call.
Figure 5-2 illustrates the Cisco CallManager Release 3.0 dial plan architecture
that supports alternate route selection. The elements in this architecture are
described in the subsections that follow.