Cisco Cisco IOS Software Release 12.2(15)T Guide Du Développeur

This chapter describes the main functions of a gatekeeper and includes the following sections:

Cisco offers a Voice over IP gatekeeper called the Multimedia Conference Manager, which is an 
H.323-compliant program implemented as part of the Cisco IOS software. The Multimedia Conference 
Manager software can run on Cisco 2500 series, Cisco 2600 series, Cisco 3600 series, and 
Cisco MC3810 Multiservice Access Concentrators.

A zone is defined as the set of H.323 nodes controlled by a single gatekeeper. Gatekeepers co-existing 
on a network can be configured so that they register endpoints from different subnets. 

Endpoints attempt to discover a gatekeeper, and consequently what zone they are members of, using the 
RAS message protocol. The protocol supports a discovery message that can be sent multicast or unicast.

If the message is sent multicast, the endpoint registers nondeterministically with the first gatekeeper to 
respond. Any endpoint on a subnet that is not enabled for the gatekeeper is not accepted as a member of 
that gatekeeper’s zone. If the gatekeeper receives a discovery message from such an endpoint, it sends 
an explicit reject message.

Gatekeepers recognize one of the following types of terminal aliases, or terminal names:

H.323 identifiers (IDs), which are arbitrary, case-sensitive text strings.

E.164 addresses, which are telephone numbers.

E-mail IDs.