Chapter 1: Overview
1-10
The primary function of the border element is to collect, manage, and distribute call routing infor-
mation. A gatekeeper will establish a service relationship with a border element; the gatekeeper pro-
vides its zones capabilities 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 admin-
istrative domains. If a gatekeeper cannot resolve an address, it contacts the border element.
In addition, if you are using more than one Tenor unit, you can configure one of the border elements
for that zone. The
Tenor BX
unit can use two border elements: primary and secondary. These work
together as one entity to provide redundancy and fault tolerance; there are no hierarchal differences.
Call Services
Gatekeepers provide services such as addressing, authorization and authentication of terminals and
gateways, bandwidth management, accounting, billing, and charging. Gatekeepers also provide call-
routing services. Specifically, the
Tenor BX
Gatekeeper provides the functions which follow:
Address Translation.
The gatekeeper translates telephone numbers into IP addresses and vice
versa. It performs Alias Address (phone number) to Transport Address (IP address) translation when
an endpoint requests service. The Gatekeeper uses a translation table to translate an Alias Address
(an address such as an H.323 identifier that a user may not understand) to a transport address. The
translation table is updated using Registration messages.
Autodiscovery.
The gatekeeper is discovered in one of the following ways: An endpoint sends an IP
broadcast called a Gatekeeper Request message (GRQ) message (which includes that correct gate-
keeper name) to discover a Gatekeeper OR the endpoint will discover a gatekeeper by its IP address.
Routing.
The gatekeeper identifies the IP address of endpoints in its administrative domain. The
gatekeeper builds a routing database from information obtained from the border element and also
from gateways and H.323 endpoints.
Border Element
Gatekeeper
Zone
Gatekeeper
Zone
Gatekeeper
Zone
Administrative Domain
Border Element
Gatekeeper
Zone
Gatekeeper
Zone
Gatekeeper
Zone
Administrative Domain
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