Chapter 55 Configuring a VoIP Network

Understanding How a VoIP Network Works

Cisco CallManager

Cisco CallManager is an open and industry-standard call processing system; its software runs on a Windows NT server and sets up and tears down the calls between the phones, integrating traditional PBX functionality with the corporate IP network. Cisco CallManager manages the components of the IP PBX system, the phones, the access gateways, and the resources for such features as call conferencing and media mixing. Each Cisco CallManager manages the devices within its zone and exchanges information with the Cisco CallManager in charge of another zone to make the calls possible across multiple zones. Cisco CallManager can work with the existing PBX systems to route a call over the Public Switched Telephone Network (PSTN).

Note For information on configuring Cisco CallManager to work with the IP devices that are described in this chapter, refer to the Cisco CallManager Administration Guide, the Configuration Notes for Cisco CallManager, and the Cisco CallManager Remote Serviceability Users Guide publications.

Access Gateways

The access gateways allow the IP PBX system to talk to the existing PSTN or PBX systems. The access gateways consist of analog station gateways, analog trunk gateways, digital trunk gateways, and a converged voice gateway.

These sections describe the gateways:

Analog Station Gateway, page 55-5

Analog Trunk Gateway, page 55-6

Digital Trunk Gateway, page 55-6

Converged Voice Gateway, page 55-7

Analog Station Gateway

The Catalyst 6500 series 24-port Foreign Exchange Station (FXS) analog interface module allows the plain old telephone service (POTS) phones and fax machines to connect to the IP PBX network. The analog station gateway behaves like the PSTN side for the POTS equipment. It requires an IP address, is registered with Cisco CallManager in its domain, and is managed by Cisco CallManager.

To configure the analog station interfaces, see the “Configuring VoIP on a Switch” section on page 55-10. The module features are listed in Table 55-1.

Table 55-1 24-Port FXS Analog Interface Module Features

Digital Signal Processing Per Port

G.711 and G.729 voice encoding

Silence suppression; voice activity detection

Comfort noise generation

Ringer, software programmable frequency and cadence, based on country

DTMF1 detection

Signaling, loop start

Catalyst 6500 Series Switch Software Configuration Guide—Release 8.7

 

OL-8978-02

55-5

 

 

 

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Cisco Systems OL-8978-02 manual Cisco CallManager, Access Gateways, Analog Station Gateway, 55-5

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