Cisco WS-X4604-GWY - VoIP Gateway Especificaciones descargar pdf (Pagina 149)

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Cisco IP Telephony Network Design Guide

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Chapter 6 Multisite WAN with Distributed Call Processing

Dial Plan Considerations

As shown in Figure 6-9, the route list contains two route groups, SJ-IPWAN and

PHL-PSTN, listed in order of priority. The SJ-IPWAN route group is listed first

(highest priority) and points to the San Jose Cisco CallManager. The digit

manipulation specified in route pattern SJ-IPWAN discards the access code (52).

This ensures that, when the call is sent across the IP WAN, five digits are delivered

to the remote Cisco CallManager because that is what it requires for its internal

dial length. The H.323 device associated with the remote Cisco CallManager must

be configured to be gatekeeper controlled to ensure that the gatekeeper is

consulted before attempting the call across the IP WAN.

If the call is rejected by the gatekeeper, the route list uses the next route group,

PHL-PSTN. This route group is configured to prepend 1408 to the dialed number

to ensure that the call transparently reaches the other end.

Using the Gatekeeper to Route Calls

The example in Figure 6-9 illustrates one strategy for implementing a dial plan

that uses a specific route pattern to select the IP WAN as the preferred path for

calls between sites. Cisco CallManager Release 3.0(5) and later provides a second

strategy that uses the gatekeeper to perform address resolution on calls between

sites, thus simplifying the dial plans at the individual sites.

Prior to Cisco CallManager Release 3.0(5), each Cisco CallManager had to

dial plan. For example, a network with 10 Cisco Callmanager sites required 10x9

or 90 gatekeeper registrations. In addition, each Cisco CallManager had to have

an intercluster trunk and at least one route pattern to each of the other

Cisco CallManagers (nine intercluster trunks and at least nine route patterns for

this example). Cisco CallManager Release 3.0(5) has simplified and enhanced the

gatekeeper registration process and has added a new Anonymous Device gateway.

The gatekeeper registration process has been enhanced in many areas. First, each

Cisco CallManager cluster now registers only once with the gatekeeper. This

allows up to 100 Cisco CallManager clusters to register with a single gatekeeper.

In addition, the registration process now supports lightweight registration, which

reduces the processing overhead on the gatekeeper. Finally, each

Cisco CallManager sends its E.164 address in the Admission Request (ARQ)

message, and the gatekeeper returns the IP addresses of all the other

Cisco CallManagers in the Admission Confirm (ACF) message. Thus, the call

admission transaction with the gatekeeper achieves two results: call admission

control, as previously, and E.164 address resolution.

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Cisco WS-X4604-GWY - VoIP Gateway Especificaciones Pagina 149