38Chapter 4 CS 1000 considerations
Virtual trunk capacity
The SRG supports a number of simultaneous calls depends on the specific codec type used.
SRG50 supports 24 virtual IP trunks that are either H.323 only, SIP only, or a combination of the H.323 and SIP.
In normal mode, the codec selection used is controlled by specific programming of the CS1000. In this case: SRG50 supports up to a maximum of 15 Virtual trunks unless both the intrazone and interzone codecs are configured as Best Quality (G.711) in which case, the maximum number of virtual trunks would be 24.
In local mode, if the WAN has failed, there are no longer any virtual trunks available between the SRG50 and CS1000. However, the SRG50 will continue to convert calls from IP terminals for communication via the PSTN. In this case, if G.711 is used (recommended), the number of simultaneous calls from IP terminals to the PSTN supportable is a maximum of 24.
For more information about virtual trunks for SRG50, see the Main Office Configuration for Survivable Remote Gateway 50
Vacant Number Routing (VNR)
The SRG does not support Vacant Number Routing (VNR). Instead, the SRG uses Call Forward All Calls to emulate VNR for the IP telephones that are in normal mode. Call Forward All Calls is automatically cancelled when the phones revert to local mode.
A single destination code and route (or a group of destination codes and routes) can be configured on the SRG to route all calls not terminated locally by the SRG. These calls are routed over the VoIP trunks. If the VoIP trunks become unavailable, the calls are routed to the proper location using PSTN fallback. This feature is similar to the VNR feature on the Media Gateway 1000B (MG1000B).
Seamless dialing requires that the start digit of the DNs are unique for each system (coordinated dialing plan). If the start digit is the same on both systems, the local users on the SRG must dial a separate destination code before the main office DN.
For details about dialing plan and routing configuration, see Setting up the private VoIP network on page 65.
Bandwidth management
Three levels of bandwidth management are supported by the CS 1000:
•Network Bandwidth Management (NBWM)
•Adaptive Network Bandwidth Management (ADBWM)
•Alternative Call Routing (ACR)
