H.323

H.323
H.323 is considered a peer-to-peer protocol, although H.323 is not a single protocol.
Rather, it is a suite of protocols. The necessary gateway configuration is relatively complex,
because you need to define the dial plan and route patterns directly on the gateway.
Examples of H.323-capable devices are the Cisco VG224 Analog Phone Gateway and the
Cisco 2600XM Series, Cisco 2800 Series, 3700 Series, and 3800 Series routers.
The H.323 protocol is responsible for all the signaling between a Cisco UCM cluster and
an H.323 gateway. The ISDN protocols, Q.921 and Q.931, are used only on the Integrated
Services Digital Network (ISDN) link to the PSTN, as illustrated in Figure 1-2.
Chapter 1: Introducing Voice over IP Networks 13
PSTN
H.323
V
Q.921
Q.931
Figure 1-2 H.323 Signaling