Chapter 1: Overview
H.323 Gatekeeper Services
Gatekeeper
A Gatekeeper in an H.323 network provides call control services and other services to H.323 endpoints (i.e., gateways, terminals, and MCUs). The Tenor CMS has a
The Gatekeeper performs IP call routing functions, such as call control signaling and call authorization for Gateways, IP phones, and H.323 terminals. The Gatekeeper communicates with other Gatekeepers through a Border Element. When using a group of Tenor CMS units, you can assign one unit as the Gatekeeper for the network. We recommend you configure each CMS as its own gatekeeper.
Tenor CMS supports gatekeeper to gatekeeper communication using LRQ (Location Request) messaging scheme.
Zone Management
A zone is a group of H.323 defined endpoints controlled by a Gatekeeper. Endpoints can be gateways (i.e., Tenor CMS), terminals, and/or multipoint conferencing units (MCUs). Endpoints establish control channels with a gatekeeper for registration, admission, security, and call routing information about the endpoint is sent to the gatekeeper, including: IP address, unit type (gateway, terminal, or MCU) and routing information (such as phone numbers, number patterns, etc.).
A collection of zones is an administrative domain. An administrative domain provides call routing services for its zones through gatekeeper to gatekeeper messages or gatekeeper to border element messages (see Border Element” for more information).
Call Registration
H.323 endpoints in the same zone register with the designated gatekeeper. When registration is complete and a call is originated, the call request is sent to the gatekeeper. The call request provides the Gatekeeper with the dialed number and requests the routing information. The gatekeeper confirms the dialed number and supplies the endpoint with the destination IP address. For example, a Tenor CMS’s gatekeeper will act as the gate- keeper for that zone and all of the other endpoints will register with it.
Border Element
The Tenor CMS’s gatekeeper uses a border element to gain access to the routing database of the administrative domain for the purpose of call completion or any other services that involve communications with other end- points out of the administrative domain. The border element functionality is built into the Tenor CMS unit, along with the gateway and gatekeeper.
The primary function of the border element is to collect, manage, and distribute call routing information. A gatekeeper will establish a service relationship with a border element; the gatekeeper provides its zones capa- bilities and the border element shares call routing capabilities of other zones in the administrative domain. Through the border element, gatekeepers from multiple zones will be able to communicate.
A border element also establishes relationships with other border elements to route between administrative domains. If a gatekeeper cannot resolve an address, it contacts the border element.
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