Solutions Fast Track
Understanding Gatekeeper Basics
.. A gatekeeper is a central point of control for an H.323 (voice and video)
network.
.. Gatekeepers usually use E.164 addressing (telephone numbers) for
identifying endpoints and routing calls within a network.
.. Gatekeepers run an H.323/MCM feature set IOS on many common
Cisco routers.
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A Gatekeeper’s Role in Voice and Video Networking
.. Gatekeepers manage one or multiple zones and permit or reject calls
into or out of each zone.
.. Gatekeepers can provide accounting information for calls, such as length
of call, time of call, number called, and so on.
.. Cisco’s Multimedia Conference Manager (MCM) can act as a proxy for
increased security and QoS as well as a gatekeeper.
.. Video gatekeepers can be embedded in the video controller or can be
an MCM.
.. Video gatekeepers interface with gateways for off-network calls, such as
ISDN videoconferences.
.. Gatekeepers monitor (and limit) bandwidth usage to assure existing calls
receive high quality.
A gatekeeper provides much of the intelligence required to operate an efficient
H.323 network.While not technically a requirement of an H.323 network, in
practice the gatekeeper is extremely useful. It provides a single point of control
for a zone—all the devices in its domain. Beyond providing address translation,
admission control, and bandwidth control, the gatekeeper can provide functions
such as accounting, call authorization, and directory services. In addition, gatekeepers
manage devices making voice, video, and collaborative data calls.
The most common Cisco gatekeeper is the Multimedia Conference Manager
(MCM).The MCM runs on a 2600, 3600, or 7200 router platform with the
H.323/MCM IOS feature set.
Gatekeepers typically use E.164 addresses (telephone numbers) to route calls
to the appropriate endpoint, gateway, or gatekeeper (for calls to remote zones).
Small networks can be implemented with a single zone while larger, complex
networks can use many zones.
Using the Hot Standby Router Protocol (HSRP) is an excellent way to provide
gatekeeper redundancy in a network. Gateways can be configured to use
either one of two different gatekeepers to provide redundancy.
Gatekeepers have the ability to not only limit endpoint participation in an
H.323 network, they can control calls based on many factors, such as time of day,
the number being called, or available bandwidth.These qualities make the gatekeeper
an integral part of an H.323 network.