Definition of NetBIOS in Network Encyclopedia.

What is NetBIOS?

NetBIOS stands for Network Basic Input/Output System, is a specification created by IBM and Microsoft that allows distributed applications to access each other’s network services independent of the transport protocol used.


NetBIOS provides network input/output services to support client/server applications on a network. From an architectural viewpoint, the NetBIOS specification defines two things:

  • An interprocess communication (IPC) mechanism or application programming interface (API) that allows applications that are NetBIOS-enabled to communicate remotely over a network and request services from lower levels of the protocol stack. This is the primary and original definition of NetBIOS.
  • A protocol operating at the session and transport layers of the Open Systems Interconnection reference model (7 layers OSI reference model) that enables functions such as session establishment and termination as well as name registration, renewal, and resolution.

NetBIOS has more overhead than other IPC mechanisms. It can take different forms depending on the network protocol on which it is running. The following table lists some common network protocols and the form that NetBIOS takes on each.

NetBIOS Protocol Stacks

Network ProtocolName When Combined with NetBIOS
NetBEUINBF (NetBEUI Frame protocol)
NWLink IPX/SPX-Compatible TransportNWLink NetBIOS

NetBIOS explained

History of NetBIOS

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.[citation needed] 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.

In 1985, Microsoft created a NetBIOS implementation for its MS-Net networking technology. As in the case of IBM’s token ring, the services of Microsoft’s NetBIOS implementation were provided over the IEEE 802.2 Logical Link Control layer by the NBF protocol.[citation needed] Until Microsoft adopted Domain Name System (DNS) resolution of hostnames Microsoft operating systems used NetBIOS to resolve names in Windows client-server networks.

Confusion between NetBIOS and NetBEUI

There still is a relatively 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.

NetBEUI (not NetBIOS)

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).

See also

External References


Articles posted after being checked by editors.

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