Introduction to Tandem X.25 Capabilities

Using Identical X.121 Addresses for Load-Sharing
X25AM Implementations
3–6 065307 Tandem Computers Incorporated
Using Identical X.121
Addresses for Ease of
Load-Sharing
A bank in Europe has installed a private packet-switching network to provide
connectivity to its branch network of approximately 360 controllers, each connected to
about 8 workstations via a LAN (Figure 3-3).
The banking application resides on a 4-processor Cyclone system, which is connected
to the bank’s packet-switching network via 12 X25AM lines. Each X25AM line
supports about 30 branch controllers. Each branch controller uses a single SVC, and
all branch controllers use the same calling address (SRCADDR) during call
establishment.
Thus, when an X.25 call arrives from a branch office for the banking application, the
X.25 switches do not need to select a particular Tandem port to use. Instead, they can
use the first available port, which enables the switch to easily load share the traffic
across all the controllers and ports. Also, if a branch controller goes down and some
lines are lost, the traffic from the affected branches can be spread across the rest of the
lines. Configuring all the X25AM subdevices for identical X.121 addresses also
simplifies the bank’s programming of the network routing tables.
The bank uses Tandem OSI/TS class 2 to provide multiplexing. Multiplexing allows
the bank to map functions—such as branch logon, teller logon/logoff, and transaction
types—to specific OSI/TS connections and thereby to specific application code, which
handles the particular function.