Least Cost Routing; Overview - AudioCodes Mediant 1000B User Manual

15.4

Least Cost Routing

This section provides a description of the device's least cost routing (LCR) feature and how
to configure it.

15.4.1 Overview

The LCR feature enables the device to choose the outbound IP destination routing rule
based on lowest call cost. This is useful in that it enables service providers to optimize
routing costs for customers. For example, you may wish to define different call costs for
local and international calls, or different call costs for weekends and weekdays (specifying
even the time of call). The device sends the calculated cost of the call to a Syslog server
(as Information messages), thereby enabling billing by third-party vendors.
LCR is implemented by defining Cost Groups and assigning them to routing rules in the
Outbound IP Routing table (Gateway calls) or IP-to-IP Routing table (SBC calls). The
device searches this routing table for matching routing rules, and then selects the rule with
the lowest call cost. If two routing rules have identical costs, then the rule appearing higher
up in the table is used (i.e., first-matched rule). If a selected route is unavailable, the device
selects 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 rules with
Cost Groups. This is determined according to the settings of the Default Cost parameter in
the Routing Rule Groups table.
The Cost Group defines a fixed connection cost (connection cost) and a charge per minute
(minute cost). Cost Groups can also be configured with time segments (time bands), which
define connection cost and minute cost based on specific days of the week and time of day
(e.g., from Saturday through Sunday, between 6:00 and 18:00). If multiple time bands are
configured per Cost Group and a call spans multiple time bands, the call cost is calculated
using only the time band in which the call was initially established.
In addition to Cost Groups, the device can calculate the call cost using an optional, user-
defined average call duration value. The logic in using this option is that a Cost Group may
be cheap if the call duration is short, but due to its high minute cost, may prove very
expensive if the duration is lengthy. Thus, together with Cost Groups, the device can use
this option to determine least cost routing. The device calculates the Cost Group call cost
as follows: Total Call Cost = Connection Cost + (Minute Cost * Average Call Duration).
The below table shows an example of call cost when taking into consideration call duration.
This example shows four defined Cost Groups and the total call cost if the average call
duration is 10 minutes:
Table 15-6: Call Cost Comparison between Cost Groups for different Call Durations
Connection
Cost Group
Cost
A 1
B 0
C 0.3
D 6
If four matching routing rules are located in the routing table and each one is assigned a
different Cost Group as listed in the table above, then the rule assigned Cost Group "D" is
selected. Note that for one minute, Cost Groups "A" and "D" are identical, but due to the
average call duration, Cost Group "D" is cheaper. Therefore, average call duration is an
important factor in determining the cheapest routing role.
Below are a few examples of how you can implement LCR:
User's Manual
Minute Cost
1 Minute
6
10 10
8 8.3
1
226
Mediant 1000B Gateway & SBC
Total Call Cost per Duration
10 Minutes
7
7
Document #: LTRT-27034
61
100
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