AudioCodes Mediant 500 E-SBC, User Manual

Page: 408 / 920

User's Manual 408 Document #: LTRT-10437
Mediant 500 E-SBC
24.6.3 Alternative Routing upon ISDN Disconnect
You can configure when the device sends a call to an alternative route if it receives an
ISDN Q.931 Disconnect message with a Progress Indicator (PI) IE from the Tel side for IP-
to-Tel calls. The Disconnect message indicates that the call cannot be established due to,
for example, a busy state on the Tel side. Using the DisconnectCallwithPIifAlt ini file
parameter, you can configure the following modes of operation:

The device does not immediately disconnect the call. Instead, it waits for any
subsequent media from the Tel side (e.g., "this number is currently busy") and
forwards it to the IP side (SIP 183 for early media). Only when it receives a Q.931
Release message, does the device disconnect the call (sends a SIP BYE message to
the IP side). If you have configured an alternative route, the device sends the IP call to
the alternative route.

The device immediately sends the IP call to an alternative route, if you have
configured one. If no alternative route has been configured and the Disconnect
message is received with PI, the device forwards the subsequent early media to the IP
side. The device disconnects the IP call only upon receipt of the subsequent Release
message.