Describing A Fallback Network - Nortel BCM50 Configuration Manual

374 Chapter 43 VoIP trunk gateways
On any IP gateway for which you want to allow fallback based on network quality, you need to
ensure that QoS monitor is enabled.
Warning: QoS monitor must be turned on at both endpoints. To enable the QoS Monitor
select Configuration > Resources > Telephony Resources > IP Trunks > Routing
Table panel.

Describing a fallback network

Figure 114 shows how a fallback network would be set up between two sites.
Figure 114 PSTN fallback diagram
BCM50 A
Public or Private
PSTN line
In a network configured for PSTN fallback, there are two connections between a BCM and a
remote system.
• One connection is a VoIP trunk connection through the IP network.
• The fallback line is a PSTN line, which can be the public lines or a dedicated T1, BRI, PRI or
analog line, to the other system.
When a user dials the destination code, the system checks first to see if the connection between the
two systems can support an appropriate level of QoS (if enabled). If it can, the call proceeds as
normal over the VoIP trunk. If the minimum acceptable level of QoS is not met, the call is routed
over the second route, through the PSTN line.
In many cases, this involves configuring the system to add and/or absorb digits.
For detailed information about inserting and absorbing digits, see
NN40020-603 NN40020-603
IP network
PSTN
Public or Private
PSTN line
BCM50 B
"Dialing plans" on page 217.