NetBIOS is an OSI Session Layer 5 Protocol and a service that allows applications on computers to communicate with one another over a local area network (LAN). It is a non-routable Protocol and NetBIOS stands for Network Basic Input/Output System. NetBIOS was developed in 1983 by Sytek Inc. as an API for software communication over IBM PC Network LAN technology.
On PC-Network, as an API alone, NetBIOS relied on proprietary Sytek networking protocols for communication over the wire. Despite supporting a maximum of 80 PCs in a LAN, NetBIOS became an industry standard.
In 1985, IBM went forward with the token ring network scheme and a NetBIOS emulator was produced to allow NetBIOS-aware applications from the PC-Network era to work over this new design. This emulator, named NetBIOS Extended User Interface (NetBEUI), expanded the base NetBIOS API with, among other things, the ability to deal with the greater node capacity of token ring.
A new networking protocol, NBF, was simultaneously produced to allow NetBEUI (NetBIOS) to provide its services over token ring – specifically, at the IEEE 802.2 Logical Link Control layer.
Worth noting is the popular confusion between the names NetBIOS and NetBEUI. NetBEUI originated strictly as the moniker for IBM’s enhanced 1985 NetBIOS emulator for token ring. The name NetBEUI should have died there, considering that at the time, the NetBIOS implementations by other companies were known simply as NetBIOS regardless of whether they incorporated the API extensions found in that emulator.
For MS-Net, however, Microsoft elected to name its implementation of the NBF protocol “NetBEUI” – literally naming its implementation of the transport protocol after IBM’s second version of the API. Consequently, even today, Microsoft file and printer sharing over Ethernet continues to be called NetBEUI, with the name NetBIOS commonly used only in reference to file and printer sharing over TCP/IP. In truth, the former is the NetBIOS Frames protocol (NBF), and the latter is NetBIOS over TCP/IP (NBT).