SIP User's Manual 284 Document #: LTRT-83310
Mediant 600 & Mediant 1000
alternative destination. For more information on the IP connectivity methods and on
viewing IP connectivity status, see 'IP Destinations Connectivity Feature' on page 282.
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,
unsuccessful Tel-to-IP call routing destination.
Table 18-15: Alternative Routing based on IP Connectivity Example
Destination
Phone Prefix
IP Destination
IP Connectivity
Status
Rule Used?
Main Route
40 10.33.45.68 "No Connectivity" No
Alternative Route #1
40 10.33.45.70 "QoS Low" No
Alternative Route #2
40 10.33.45.72 "ok" Yes
For analog interfaces: The device plays a tone to the Tel endpoint whenever an alternative
route is used. This tone is played for a user-defined time, configured using the
AltRoutingToneDuration parameter.
The steps for configuring alternative Tel-to-IP routing based on IP connectivity is
summarized below.
To configure alternative Tel-to-IP routing based on IP connectivity:
1. Add alternative Tel-to-IP routing rules for specific calls in the Outbound IP Routing
table.
2. Enable alternative routing based on IP connectivity, by setting the
AltRoutingTel2IPEnable parameter to 1.
3. Determine the IP connectivity reason for triggering alternative routing, using the
AltRoutingTel2IPMode parameter:
• Ping or SIP OPTIONS failure
• Poor QoS
• Ping or SIP OPTIONS failure, poor QoS, or unresolved DNS
18.4.6.2 Alternative Routing Based on SIP Responses
You can configure the device to do alternative routing based on the received SIP response.
If the SIP response code reflects an error (i.e., 4xx, 5xx, or 6xx) and you have configured
this specific response code as a trigger for alternative routing, then the device attempts to
re-route the call to an alternative destination.
You can configure up to five SIP response codes for triggering alternative routing. This is
done in the Reasons for Alternative Routing table (AltRouteCauseTel2IP parameter),
explained later in this section.
Typically, the device performs alternative routing when there is no response at all to an
INVITE message after a user-defined number of INVITE re-transmissions, configured using
the SIPMaxRtx parameter. In such a scenario, the device issues itself the SIP response
code 408 "Request Timeout". If this release code is defined in the Reasons for Alternative
Routing table, then alternative routing is done.
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