Definition
The gatekeeper is the most powerful management tool available for an H.323 multimedia network. As the brain of the H.323 network, this application performs essential control, administrative, and managerial functions required to maintain the integrity of networks in both enterprise and carrier environments.

Overview
As the key industry standard mechanism integrated into the H.323 network, the gatekeeper provides the following functions:

• authentication
• authorization
• accounting
• call control and call routing
• basic telephony services such as directory services and private branch exchange (PBX) functions
• control of H.323 bandwidth usage to provide quality of service (QoS) and protect other critical network applications from H.323 traffic
• total network usage control
• overall system administration and security policies

The goal of this tutorial is to explain to developers, technical solutions builders, systems integrators, and resellers the benefits of integrating a gatekeeper when designing an H.323–based network for Internet protocol (IP)–telephony applications. This tutorial will describe the functionality as well as the practical applications of the gatekeeper from which many organizations have benefited when developing their voice- and video-over–IP solutions.

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