AudioCodes Mediant 4000 SBC User Manual page 501

User's Manual
(regardless of the number of Routing Policies employed). For more information on Routing
Policies, see ''Configuring SBC Routing Policy Rules'' on page 518.
The IP-to-IP Routing table also provides the following features:

Alternative Routing: In addition to the alternative routing/load balancing provided by
the Proxy Set associated with the destination IP Group, the table allows the
configuration of alternative routes whereby if a route fails, the next adjacent (below)
rule in the table that is configured as 'Alt Route Ignore/Consider Inputs' are used. The
alternative routes rules can be set to enforce the input matching criteria or to ignore
any matching criteria. Alternative routing occurs upon one of the following conditions:
•
A request sent by the device is responded with one of the following:
♦
♦
•
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).
Note:
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.

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).

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 on page 523), and then assign it to a routing rule with
'Destination Type' configured to IP Group Set.

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'' on page 265. 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'' on page 518).

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
Version 7.2
SIP response code (i.e., 4xx, 5xx, and 6xx SIP responses) configured in the
Alternative Routing Reasons table (see ''Configuring SIP Response Codes
for Alternative Routing Reasons'' on page 516).
SIP 408 Timeout or no response (after timeout).
If the Proxy Set (see Configuring Proxy Sets on page 363) associated with the
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25. Routing SBC
Mediant 4000 SBC