Specifications

Chapter 1 Product Overview
Solution
1-4
Catalyst 4224 Access Gateway Switch Software Configuration Guide
OL-2031-02
Figure 1-1 Centralized Call Processing Solution
In the diagram, a Cisco CallManager cluster at a central site uses Simple Client
Control Protocol (SCCP) to control IP phones at two branch offices. In the branch
VoIP network, a Catalyst 4224 acts as an H.323 gateway, interconnecting the
analog devices, the PSTN, and IP WAN. This system uses ISDN Basic Rate
Interface (BRI) as a lifeline to the PSTN.
If the WAN link (or the Cisco CallManager cluster) becomes unavailable,
Survivable Remote Site Telephony (SRST) allows the Catalyst 4224 to keep the
IP phones on the branch networks running. Under these circumstances, the
Catalyst 4224 functions as an H.323 gateway, thereby ensuring uninterrupted
connectivity to the PSTN.
55335
V
B
A
C
VIC/WIC ISDN BU MFT-T1
IP
IP
IP
IP
Catalyst 4224
IP WAN
PSTN
Single T-1 access to
each branch office
12 Channels voice/
12 Channels data