AudioCodes E-SBC User Manual page 640

CHAPTER 25 Routing
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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
Destinations Connectivity
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 25-6: Alternative Routing based on IP Connectivity Example
Main Route
Alternative
Route #1
Alternative
Route #2
The following procedure describes how to configure alternative Tel-to-IP routing based on IP
connectivity.
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
on SIP Responses). To use the Busy Out feature with the Proxy Set keep-alive
mechanism (for IP Groups), disable the AltRoutingTel2IPEnable parameter.
Feature.
Destination Phone
Prefix
40
40
40
Mediant 1000 Gateway & E-SBC | User's Manual
IP IP Connectivity
Destination
10.33.45.68 "No Connectivity"
10.33.45.70
10.33.45.72
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Alternative Routing Based
Rule
Status Used?
No
"QoS Low" No
"ok" Yes
IP