For simplicity reasons, I am going to focus on the IT department, because of the size of the company. In a large enterprise network with a heterogeneous environment, it is uncommon to find PC's running just one type of operating systems. An enterprise network is usually comprised of a client/server structure, and different operating systems can be found on each end. .
On the server side, with servers and mainframes serving the backbone of the network, the servers are usually running UNIX, Windows NT 4.0 and windows 2000 Server OS. Even within the network, there are Cisco switches and routers which are running Cisco IOS as the operating system. The routers and switches are responsible for segmenting the network and to route the network traffic more efficiently. .
The mainframe runs on UNIX and for a long period supported the email system for the company. The email database resided on the mainframe and all the emails and public folders accessed by all users were located on the mainframe. With the explosion of Internet, and the migration of applications to the Internet, the email system was offloaded to NT servers running Windows 2000 server and Exchange 2000. The applications that previously resided on an older mainframe were moved to a newer S390 mainframe, and IBM WebSphere and DB2 were installed to support the applications. .
The older email system Tao was replaced by Exchange 2000. Exchange 2000 is currently implemented on 1U and 2U servers running Microsoft Windows 2000 Server and Advanced Server. The Advanced Sever edition is needed to implement the active/active clustering technology of the Windows 2000 Server operating systems for redundancy and fail-over. Windows 2000 Active Directory replaced Windows NT SAM. The user accounts were moved to the Active Directory of the Windows 2000 server, because of the integration of Exchange 2000 with the Active Directory of Windows 2000.