NetBIOS Frames (NBF) is a non-routable network- and transport-level data protocol most commonly used as one of the layers of Microsoft Windows networking in the 1990s. NBF or NetBIOS over IEEE 802.2 LLC is used by a number of network operating systems released in the 1990s, such as LAN Manager, LAN Server, Windows for Workgroups, Windows 95 and Windows NT. Other protocols, such as NBT (NetBIOS over TCP/IP), and NBX (NetBIOS-over-IPX/SPX) also implement the NetBIOS/NetBEUI services over other protocol suites.
The NBF protocol is broadly, but incorrectly, referred to as NetBEUI. This originates from the confusion with NetBIOS Extended User Interface, an extension to the NetBIOS API that was originally developed in conjunction with the NBF protocol; both the protocol and the NetBEUI emulator were originally developed to allow NetBIOS programs to run over IBM's new Token Ring network.[1] Microsoft caused this confusion by labelling its NBF protocol implementation NetBEUI. NBF is a protocol and the original NetBEUI was a NetBIOS application programming interface extension.[citation needed]