Information Technology Reference
In-Depth Information
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Wildcard (Filter):
Implies a shared reservation and wildcard sender selection
■
Shared Explicit:
Indicates shared reservation and explicit sender selection
gatekeepers
Another method of providing CAC is to use gatekeepers (GK). Gatekeepers provide CAC in H.323 networks (including those
involving CUCM) by subtracting bandwidth from a bandwidth pool when a call is set up and returning the bandwidth to the pool
when the call is disconnected. Gatekeepers use H.225 RAS signaling and are unaware of the network topology. Gatekeeper functions
also include call routing, address translation, and zone management.
Gatekeeper CAC requires the static configuration of (pools of) available bandwidth. When gatekeepers subtract bandwidth from a
configured pool, the amount of bandwidth subtracted is twice that codec bit rate. So, for example, 128 Kbps is subtracted for a (64-
Kbps) G.711 call and 16 Kbps is subtracted for a (8-Kbps) G.729 call.
Gatekeeper CAC is reliant on
zones
. Zones include H.323 devices that have registered with a gatekeeper, and only one active
gatekeeper is allowed in one zone. Devices that are registered with a gatekeeper are said to be in that gatekeeper's local zone. Zones
that are controlled by other (remote) gatekeepers are referred to as
remote zones
. Calls are forwarded between gatekeepers that
control zones.
Gatekeepers can be used to provide CAC in CUCM multisite WAN (hub-and-spoke) distributed call-processing model networks. If a
network does not conform to a hub-and-spoke topology, IP-to-IP gateways can be used to provide call routing and demarcation (and
to allow CAC using RSVP).
The section, “Gatekeeper,” in
Chapter 1,
“Cisco Unified Communications Manager,” contains a sample configuration for an IOS
gatekeeper and descriptions of some basic commands.
Other common IOS commands used to configure gatekeepers not described in
Chapter 1
include the following:
■
zone remote:
Used to statically configure a remote zone on the local gatekeeper. Configuration of this command includes
specifying the name of the remote gatekeeper, the domain of the remote gatekeeper, and the IP address of the remote
gatekeeper.
