AudioCodes Media Pack MP-124, User Manual

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Version 6.6 317 MP-11x & MP-124
User's Manual 28. SAS Cascading
28 SAS Cascading
The SAS Cascading feature allows you to increase the number of SAS users above the
maximum supported by the SAS gateway. This is achieved by deploying multiple SAS
gateways in the network. For example, if the SAS gateway supports up to 600 users, but
your enterprise has 1,500 users, you can deploy three SAS gateways to accommodate all
users: the first SAS gateway can service 600 registered users, the second SAS gateway
the next 600 registered users, and the third SAS gateway the rest (i.e., 300 registered
users).
In SAS Cascading, the SAS gateway first attempts to locate the called user in its SAS
registration database. Only if the user is not located, does the SAS gateway send it on to
the next SAS gateway according to the SAS Cascading configuration.
There are two methods for configuring SAS Cascading. This depends on whether the users
can be identified according to their phone extension numbers:

SAS Routing Table: If users can be identified with unique phone extension numbers,
then the SAS Routing table is used to configure SAS Cascading. This SAS Cascading
method routes calls directly to the SAS Gateway (defined by IP address) to which the
called SAS user is registered.
The following is an example of a SAS Cascading deployment of users with unique
phone extension numbers:
•
users registered to the first SAS gateway start with extension number “40”
•
users registered to the second SAS gateway start with extension number “20”
•
users registered to the third SAS gateway start with extension number “30”
The SAS Routing table rules for SAS Cascading are created using the destination
(called) extension number prefix (e.g., “30”) and the destination IP address of the SAS
gateway to which the called user is registered. Such SAS routing rules must be
configured at each SAS gateway to allow routing between the SAS users. The routing
logic for SAS Cascading is similar to SAS routing in Emergency state (see the
flowchart in 'SAS Routing in Emergency State' on page
295 ). For a description on the
SAS Routing table, see 'SAS Routing Based on IP-to-IP Routing Table' on page 308 .
The figure below illustrates an example of a SAS Cascading call flow configured using
the SAS Routing table. In this example, a call is routed from SAS Gateway (A) user to
a user on SAS Gateway (B).
Figure 28-1: SAS Cascading Using SAS Routing Table - Example