AudioCodes Mediant 1000B User Manual page 529

User's Manual
configured in the Tel-to-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 Tel-
to-IP Routing table, see ''Configuring Tel-to-IP Routing Rules'' on page 511.
Note:
•
Alternative routing based on IP connectivity is applicable only when a proxy server
is not used.
•
You can also enable the Busy Out feature, whereby the device can take specified
actions if all IP destinations of matching routing rules in the Tel-to-IP Routing table
do not respond to connectivity checks. For more information, see the
EnableBusyOut parameter.
•
If the AltRoutingTel2IPEnable parameter is enabled, the Busy Out feature does
not function with the Proxy Set keep-alive mechanism (see Alternative Routing
Based on SIP Responses on page 530). To use the Busy Out feature with the
Proxy Set keep-alive mechanism (for IP Groups), disable the
AltRoutingTel2IPEnable parameter.
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" 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.

No response from a DNS-resolved IP address, where the domain name (FQDN) is
configured for the IP destination. If the device sends the INVITE message to the first
IP address and receives no response, the device makes a user-defined number of
attempts (configured by the HotSwapRtx parameter) to send it again (re-transmit). If
there is still no response after all the attempts, it sends it to the next DNS-resolved IP
address, and so on. For example, if you configure the parameter to "3" and the device
receives no response from the first IP address, it attempts up to three times to send
the INVITE to the first IP address and if unsuccessful, it attempts to send the call to
the next DNS-resolved IP address, and so on.

No response for in-dialog request from a DNS-resolved IP address, where the domain
name is received in the Contact header of an incoming setup or target refresh SIP
message (e.g., 200 OK). If no response is received from the first IP address, the
device tries to send it again for up to a user-defined number of attempts (configured by
the HotSwapRtx parameter). If there is still no response, it attempts to send the SIP
request to the next DNS-resolved IP address, and so on.
The connectivity status of the IP destination is displayed in the 'Status' column of the Tel-
to-IP Routing table per routing rule. If it displays a status other than "ok", 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 527.
The table below shows an example of alternative routing where the device uses an
available alternative routing rule in the Tel-to-IP Routing table to re-route the initial Tel-to-IP
call.
Table 24-6: Alternative Routing based on IP Connectivity Example
Version 7.2
Destination
IP Destination
Phone Prefix
IP Connectivity
Status
529 Mediant 1000B Gateway & E-SBC
24. Routing
Rule Used?