SIP
Like the H.323 protocol, the SIP is a peer-to-peer protocol. The configuration necessary
for the gateway is relatively complex because the dial plan and route patterns need to be
defined directly on the gateway. Examples of SIP-capable devices are the Cisco 2800
Series and 3800 Series routers.
The SIP protocol is responsible for all the signaling between a Cisco UCM cluster and a
gateway. The ISDN protocols, Q.921 and Q.931, are used only on an ISDN link to the
PSTN, as illustrated in Figure 1-4.
14 Authorized Self-Study Guide: Cisco Voice over IP (CVOICE)
PSTN
SIP
V
Q.921
Q.931
Figure 1-4 SIP Signaling