Alternative Routing For Tel-To-Ip Calls; Alternative Routing Based On Ip Connectivity - AudioCodes Mediant 500 E-SBC User Manual


IP Connectivity: This page displays a more informative connectivity status of the IP
destinations used in Tel-to-IP routing rules in the Outbound IP Routing table. For
viewing this page, see ''Viewing IP Connectivity'' on page 627.
24.5

Alternative Routing for Tel-to-IP Calls

The device supports various alternative Tel-to-IP call routing methods, as described in this
section.

24.5.1 Alternative Routing Based on IP Connectivity

You can configure the device to route Tel-to-IP calls to an alternative IP destination when
the connectivity state of an IP destination is unavailable. The alternative routing rules are
configured in the Outbound IP Routing table. These rules must be configured anywhere
below the "main" routing rule and with identical matching characteristics (e.g., destination
prefix number) to the "main" routing rule. The device uses the first alternative route that is
available. For more information on configuring alternative Tel-to-IP routing rules in the
Outbound IP Routing table, see ''Configuring Outbound IP Routing Table'' on page 385.
Note: Alternative routing based on IP connectivity is applicable only when a proxy
server is not used.
The device searches for an alternative routing rule (IP destination) when any of the
following connectivity states are detected with the IP destination of the "main" Tel-to-IP
routing rule:

No response received from SIP OPTIONS messages. This depends on the chosen
method for checking IP connectivity.

Poor QoS according to the configured thresholds for packet loss and delay.

Unresolved DNS, if the configured IP destination is a domain name (or FQDN). If the
domain name is resolved into two IP addresses, the timeout for INVITE re-
transmissions can be configured using the HotSwapRtx parameter. For example, if
you set this parameter to 3, the device attempts up to three times to route the call to
the first IP address and if unsuccessful, it attempts up to three times to re-route it to
the second resolved IP address.
The connectivity status of the IP destination is displayed in the 'Status' column of the
Outbound IP Routing table per routing rule. If it displays a status other than "ok", then the
device considers the IP destination as unavailable and attempts to re-route the call to an
alternative destination. For more information on the IP connectivity methods and on
viewing IP connectivity status, see ''IP Destinations Connectivity Feature'' on page 399.
The table below shows an example of alternative routing where the device uses an
available alternative routing rule in the Outbound IP Routing table to re-route the initial Tel-
to-IP call.
Table 24-4: Alternative Routing based on IP Connectivity Example
Main Route
Alternative Route #1
Alternative Route #2
User's Manual
Destination
IP Destination
Phone Prefix
40 10.33.45.68
40 10.33.45.70
40 10.33.45.72
400
Mediant 500 E-SBC
IP Connectivity
Status
"No Connectivity"
"QoS Low"
"ok"
Document #: LTRT-10437
Rule Used?
No
No
Yes