CHAPTER34 Routing SBC
Mediant 1000 Gateway & E-SBC | User's Manual
● The DNS resolution includes IP addresses that the device has yet to try (for the current
call).
Messages are re-routed with the same SIP Call-ID and CSeq header fields (increased by 1).
If the Proxy Set (see Configuring Proxy Sets) associated with the destination of the call
is configured with multiple IP addresses, the device first attempts to route the call to
one of these IP addresses, starting with the first listed address. Only when the call
cannot be routed to any of the Proxy Set’s IP addresses does the device search the IP-
to-IP Routing table for an alternative routing rule for the call.
■ Load Balancing: You can implement load balancing of calls, belonging to the same source,
between a set of destination IP Groups known as an IP Group Set. The IP Group Set can
include up to five IP Groups (Server-type and/or Gateway-type only) and the chosen IP Group
depends on the configured load-balancing policy (e.g., Round Robin). To configure the feature,
you need to first configure an IP Group Set (see Configuring IP Group Sets), and then assign it
to a routing rule with 'Destination Type' configured to IP Group Set.
■ Re-routing SIP Requests: This table enables you to configure "re-routing" rules of requests
(e.g., INVITEs) that the device sends upon receipt of SIP 3xx responses or REFER
messages. These rules are configured for destinations that do not support receipt of 3xx or
REFER and where the device handles the requests locally (instead of forwarding the 3xx or
REFER to the destination).
■ Least Cost Routing (LCR): If the LCR feature is enabled, the device searches the routing
table for matching routing rules and then selects the one with the lowest call cost. The call cost
of the routing rule is done by assigning it a Cost Group. To configure Cost Groups, see Least
Cost Routing. If two routing rules have identical costs, then the rule appearing higher up in the
table (i.e., first-matched rule) is used. If a selected route is unavailable, the device uses the
next least-cost routing rule. However, even if a matched rule is not assigned a Cost Group, the
device can select it as the preferred route over other matched routing rules that are assigned
Cost Groups, according to the default LCR settings configured for the assigned Routing Policy
(see Configuring SBC Routing Policy Rules).
■ Call Forking: The IP-to-IP Routing table can be configured to route an incoming IP call to
multiple destinations (call forking). The incoming call can be routed to multiple destinations of
any type such as an IP Group or IP address. The device forks the call by sending simultaneous
INVITE messages to all the specified destinations. It handles the multiple SIP dialogs until one
of the calls is answered and then terminates the other SIP dialogs.
Call forking is configured by creating a Forking group. A Forking group consists of a main
routing rule ('Alternative Route Options' set to Route Row) whose 'Group Policy' is set to
Forking, and one or more associated routing rules ('Alternative Route Options' set to Group
Member Ignore Inputs or Group Member Consider Inputs). The group members must be
configured in contiguous table rows to the main routing rule. If an incoming call matches the
input characteristics of the main routing rule, the device routes the call to its destination and all
those of the group members.
An alternative routing rule can also be configured for the Forking group. The alternative route is
used if the call fails for the Forking group (i.e., main route and all its group members). The
alternative routing rule must be configured in the table row immediately below the last member
of the Forking group. The 'Alternative Route Options' of this alternative route must be set to Alt
Route Ignore Inputs or Alt Route Consider Inputs. The alternative route can also be
configured with its own forking group members, where if the device uses the alternative route,
the call is also sent to its group members. In this case, instead of setting the alternative route's
'Group Policy' to None, you must set it to Forking. The group members of the alternative route
must be configured in the rows immediately below it.
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