Introduction
Key Features
How This Application Works
Communication between Cisco EGW 2200 and Cisco CallManager
Component List

Introduction

Successfully transitioning enterprise networks from TDM-based to IP-based telephony requires a level of signaling and feature interworking between both networks. Leveraging its signaling interworking capabilities, the Cisco EGW 2200 provides support for Cisco CallManager deployments requiring feature and signaling interworking with DPNSS PBXs. Coupled with E1 interfaces and signaling backhaul provided on Cisco 2600, 3600, and 3700 class access routers, the Cisco EGW 2200 allows Cisco CallManager to be inserted into existing DPNSS networks with enough feature availability and scalability to facilitate a graceful migration to IP telephony.

Multiple Cisco CallManager clusters are supported.

You can combine this application with the the Cisco Unity voice messaging and Tandem Signaling and Toll Bypass applications. Optionally, you can include connection to the Public Switched Telephone Network (PSTN) through a PRI ISDN trunk.

Note: The illustration shows the use of a gatekeeper and the registration, admission, and status protocol for the H.323 interface between Cisco EGW 2200 and Cisco CallManager. The gatekeeper is optional; small networks can use H.323 direct mode without a gatekeeper.

Figure 1. Application example: Interwork DPNSS PBXs with Cisco CallManager

For more information on a component in the illustration, point to it. To go to a detailed description, click on it. Click a connector line for information on the interfaces and connections between components.

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Key Features

Key features of this application include:

• Tightly coupled integration with Cisco CallManager through CTI client interfaces
• Simplified installation, provisioning, and management of key components on the Cisco EGW 2200 using Cisco’s network appliance model
• Administration using browser-accessible applications with an Intuitive graphical user interface
• Conformance with best practices recommended for PBX to IP migration

How This Application Works

A Cisco CallManager cluster serves as an IP PBX. (A cluster is a set of Cisco CallManagers sharing a single database.) The Cisco EGW 2200 provides the signaling, call control, and DPNSS interworking that allow DPNSS calling features to operate transparently across DPNSS and Cisco CallManager networks. One Cisco EGW 2200 (a single or active/standby configuration for fault tolerance) is required for the Cisco CallManager cluster. Multiple Cisco CallManager clusters are supported.w

A voice-enabled access router serves as the gateway (DPNSS media gateway) between the TDM and IP-based PBX networks. The media gateway is physically connected through one or more of its E1 or T1 interfaces to the DPNSS PBX. The media gateway interfaces with the IP network through one (or two, for redundancy) of its Ethernet ports. The media gateway performs two functions in the network: packetizing voice for transmission across the IP network and backhauling the DPNSS call control signaling over IP to the Cisco EGW 2200. If desired, multiple media gateways can be used for improved fault tolerance.

Gatekeeper or direct mode: You can set up your Cisco EGW network to operate with or without an H.323 gatekeeper (gatekeeper mode or direct mode). A gatekeeper is not required for the Cisco EGW, but is advisable if you need to make effective use of network functions such as call admission and bandwidth control for large installations. The gatekeeper provides a means for Cisco EGW to loadshare traffic across the Cisco CallManager hosts, and allows Cisco CallManager to loadshare traffic across H.323 interfaces in a fault-tolerant Cisco EGW configuration.

With a gatekeeper, the Cisco CallManager and Cisco EGW 2200 H.323 signaling interface (HSI) register with the gatekeeper at startup. When a new call is set up, the Cisco CallManager and Cisco EGW 2200 query the gatekeeper to get the IP addresses of an available Cisco EGW 2200 or Cisco CallManager, respectively. Without a gatekeeper, the H.323 component in the Cisco EGW system routes the call directly to the primary Cisco CallManager IP address and port specified in Cisco EGW Administration. Specifying a second IP address and port allows communication in the event that a Cisco CallManager failure within part of a cluster
prevents communication using the first address.

The Cisco EGW 2200 can optionally serve as an entry or exit point to the PSTN through ISDN PRI trunks terminated on any of the supported Cisco AS5000-series media gateways (PRI gateway).

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Communication between Cisco EGW 2200 and Cisco CallManager

The Cisco EGW 2200 communicates with the Cisco CallManager using the following interfaces, each providing a part of the required functionality:

• H.323 signaling support: This can be provided through an optional H.225 gatekeeper-controlled trunk or through direct mode without a gatekeeper. The gatekeeper is recommended for large networks where call admission and bandwidth control are desired.
• The Cisco AVVID XML (AXL) Simple Object Access Protocol (SOAP) interface performs lookups in the Cisco CallManager configuration database for device names and call forwarding information, allowing the Cisco EGW 2200 to identify and monitor individual end-user lines.
• The Cisco CallManager CTI (Computer Telephony Integration) Manager interface is the messaging interface used over TCP/IP.
• The eXtensible Markup Language (XML) interface is used for sending visual notifications (including soft keys) of events such as Call Back when Free to IP phones with XML support.

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Components List

This application uses the following components. See the Component Chart for hardware and software specifications and see component details for links to overviews and detailed requirements and recommendations for each component.

• Cisco EGW 2200, in either a single or dual (active/standby) configuration
• One or more Cisco CallManager clusters with a minimum of one node
• At least one Cisco DPNSS media gateway
• Optionally, a Cisco H.323 gatekeeper, in either a single or redundant configuration
• Cisco XML-enabled IP phones

Component Details

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