NetBEUI: NetBIOS Extended User Interface

NetBIOS Extended User Interface (NetBEUI) is an extended version of NetBIOS, that lets computers communicate within a local area network. NetBEUI formalizes the frame format that was not specified as part of NetBIOS. NetBEUI protocol may sometimes be called the NetBIOS frame (NBF) protocol.

NetBEUI works at the Transport and Network layers for local area network (LAN). NetBEUI provides data transportation but it is not a routable transport protocol. NetBEUI is a good performance choice for communication within a single LAN. For internetwork routing, its interface must be adapted to other protocols such as Internetwork Packet Exchange (IPX) or TCP/IP. Very often, both NetBEUI and TCP/IP are installed in each computer and the server is set up to use NetBEUI for communication within the LAN and TCP/IP for communication beyond the LAN.

NetBIOS and NetBEUI were developed by IBM for its LAN Manager product and has been adopted by Microsoft for its Windows NT, XP and 2000, LAN Manager, and Windows for Workgroups products. Novell, Hewlett-Packard and DEC use it in comparable products.
Protocol Structure - NetBEUI: NetBIOS Extended User InterfaceNetBEUI frame header:

2	2	1	1	2	2	2 bytes
Length	Deliminator	Command	Data1	Data2	XMIT Cor	RSP Cor
Destination name (16 bytes)
Source name (16 bytes)

• Length - The length of the NETBIOS header.
• Deliminator - A delimiter indicating that subsequent data is destined for the NetBIOS function.
• Command - A specific protocol command that indicates the type of function of the frame.
• Data 1 - One byte of optional data per specific command.
• Data 2 - Two bytes of optional data per specific command.
• Xmit/response correlator - Used to associate received responses with transmitted requests.
• Destination name/num - In non-session frames this field contains the 16-character name.
• Source name/num - In non-session frames this field contains the 16-character source name. In session frames this field contains a 1 byte source session number.

NetBIOS and NetBEUI are IBM protocols.

http://ourworld.compuserve.com/homepages/TimothyDEvans/contents.htm : NetBios, NetBEUI, NBF, SMB, CIFS Networking
http://www.javvin.com/protocol/rfc1001.pdf : PROTOCOL STANDARD FOR A NetBIOS SERVICE ON A TCP/UDP TRANSPORT: CONCEPTS AND METHODS
http://www.javvin.com/protocol/rfc1002.pdf : PROTOCOL STANDARD FOR A NetBIOS SERVICE ON A TCP/UDP TRANSPORT: DETAILED SPECIFICATIONS