Overview#LAN Manager ( Microsoft LAN Manager LANMAN) is an "older" version of NT LAN Manager (NTLM) was a Network Operating System (NOS) available from multiple vendors and developed by Microsoft in cooperation with 3Com Corporation.
LAN Manager was based on the OS/2 Operating System co-developed by IBM and Microsoft and originally used the Server Message Block (SMB) Protocol a top either the NetBIOS Frames protocol (NBF) or a specialized version of the Xerox Network Systems (XNS) protocol. These legacy protocols had been inherited from previous products such as MS-Net for MS-DOS, Xenix-NET for MS-Xenix, and the 3+Share. A version of LAN Manager for Unix-based systems called LAN Manager/X was also available.
In 1990, Microsoft announced LAN Manager 2.0 with a host of improvements, including support for TCP/IP as a transport protocol. The last version LAN Manager, 2.2, which included an MS-OS/2 1.31 base operating system, remained Microsoft's strategic server system until the release of Windows Server NT Advanced Server in 1993.