Chapter 3 ______________________________________________________  Functional Description
VAISALA_______________________________________________________________________ 29
CDU Software Components
The CDU includes the following software components (minimum level): 
- Operating system: Windows® Server 2008 (Windows® Server 2003 
in upgrades)
- Device drivers for serial communications adapter
- AviMet system programs (Processes and applications) 
- AviMet configuration files (INI files) 
- TCP/IP Protocol network software 
To ensure maximum system reliability, an AviMet system can also be 
duplicated. A duplicated system contains two CDUs. For more information 
on duplicated systems, see section Duplicated System on page 20. 
UPS
The Uninterrupted Power Supply (UPS) is crucial for ensuring high system 
availability. Customers can also use their own arrangements for ensuring 
uninterrupted power supply. 
LAN
The communication between the applications is based on the TCP/IP 
protocol. In systems that include several workstations, the workstations are 
connected to each other by a local area network (LAN). 
Serial/LAN Adapter
The serial/LAN adapter communicates with the sensors using serial line 
protocols and then converts these messages to LAN (TCP/IP protocol).
CAUTION
A missing or defective UPS arrangement can result in data loss and 
incorrect operation of the system.
CAUTION
Congested LANs, or LANs with excessive downtime can result in data 
loss and incorrect operation of the AviMet system. Vaisala recommends 
a load of less than 10 % of the network bandwidth and an availability of 
at least 99.9 %.