Open Systems Adaptor (OSA)

In the 1990s IBM introduced TCP/IP and the Open Systems Adaptor (OSA) hardware feature which allows the mainframe to be directly connected to a Local Area Network (LAN).

TCP/IP has become the dominant telecommunications vehicle in terms of communication with the outside world, although IBM's VTAM (Virtual Telecommunications Access Method) has been retained for compatibility reasons as not all traditional online applications support native TCP/IP.

A companies LAN is likely to be connected to a Wide Area Network (WAN) and access to the WEB on users PCs is an indicator of this. It is ackowledged that a firewall will exist to protect critical applications and data.