User's Manual 27. Routing
Version 6.8 419 Mediant 500L MSBR
These parameters are configured in the Routing General Parameters page, as shown
below:
Figure 27-5: IP QoS Thresholds in Routing General Parameters Page
DNS Resolution: When a host name (FQDN) is used (instead of an IP address) for
the IP destination, it is resolved into an IP address by a DNS server. The device
checks network connectivity and QoS of the resolved IP address. If the DNS host
name is unresolved, the device considers the connectivity of the IP destination as
unavailable.
You can view the connectivity status of IP destinations in the following Web interface
pages:
Outbound IP Routing Table: The connectivity status of the IP destination per routing
rule is displayed in the 'Status' column. For more information, see ''Configuring
Outbound IP Routing'' on page
405.
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
702.
27.5 Alternative Routing for Tel-to-IP Calls
The device supports various alternative Tel-to-IP call routing methods, as described in this
section.
27.5.1 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'' on page 405.
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" 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", the device
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