HOW TO: NetBIOS (What It Is and How It Works)

NetBIOS provides communications services in local area networks. It is used in Windows as well as Ethernet and Token Ring networks.

Enable NetBIOS over TCPIP via Regedit

In summary, NetBIOS provides communications services on the local network. It uses a software protocol known as NetBIOS Frames (NBF) that enables applications and computers on local networks (LANs) to communicate with network hardware and to transmit data to the entire network.

NetBIOS, which stands for Network Basic Input / Output, is a network industry standard. It was created in 1983 by Sytek and is commonly used with NetBIOS TCP / IP (NBT) protocol. However, it is also used in the Token Ring network, as well as by Microsoft Windows.

Note: NetBIOS and NetBEUI are separate but related technologies. NetBEUI extends NetBIOS's first implementation with additional network capabilities.

How NetBIOS Works With Apps

Software applications on the NetBIOS network find and identify each other by their NetBIOS name. In Windows, the NetBIOS name is separate from the computer name and can be up to 16 characters long.

Applications on other computers access the NetBIOS name via UDP, a simple OSI transport layer protocol for client/server network applications based on Internet Protocol (IP), over port 137 (in NBT).

Registering a NetBIOS name is required by the application but is not supported by Microsoft for IPv6. The last octet is usually the NetBIOS Suffix that describes which services are available.

Windows Internet naming service (WINS) provides name resolution service for NetBIOS.

Two applications initiate a NetBIOS session when a client sends a command to "call" another client (server) via TCP port 139. This is referred to as session mode, in which both parties issue "send" and "receive" instructions for delivering messages in both cases, two-way. The "hang-up" command ended the NetBIOS session.

NetBIOS also supports wireless communication via UDP. Application listening on UDP port 138 to receive NetBIOS datagram. The datagram service can send and receive datagrams and broadcast datagrams.

Here are some name service options allowed to be sent via NetBIOS

1. Add a name to register the NetBIOS name
2. Adding a group name is similar but registering a NetBIOS group name
3. Delete the name is to misuse the NetBIOS name, either name or group
4. Find a name is to find the NetBIOS name on the network

Session services enable these primitives:

1. Call to start the session under the NetBIOS name
2. Listen to see if an attempt can be made to open a session
3. The handle is used to close the session
4. Send will send one packet over the session
5. Sending No Ack is the same as sending but does not require an acknowledgment that it was sent via session
6. Accept waiting for an incoming package

When in datagram mode, these primitives are supported:

1. Send Datagram will send datagram by NetBIOS name
2. Send Datagram Broadcast is to send a datagram to every NetBIOS name registered on the network
3. Receive Datagram waiting for the Send Datagram package
4. Receive Broadcast Datagram awaiting Post Broadcast delivery

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