NetBIOS is a protocol that was developed by IBM and Sytek back in the late 1980s to facilitate communication between computers within a local area network (LAN). It was mainly designed to enable computers to share resources such as files, printers, and other network devices effectively. NetBIOS allows computers to identify each other on the network, and it also provides a means of accessing network resources through a computer’s user interface.

NetBIOS works by providing an essential name service that maps computer names to the corresponding IP addresses. This name service is known as NetBIOS Name Service (NBNS) and is based on the User Datagram Protocol (UDP). When a computer needs to communicate with another computer on the network, it sends a request to the NBNS, which will then provide the computer’s IP address that matches the requested name. The IP address is then used to establish a direct communication channel between the two computers over the LAN.

Apart from the name service, NetBIOS also provides two other services: the Session Service and the Datagram Service. The Session Service establishes a virtual connection between two computers on the network, allowing them to engage in a dialogue-like conversation. The Datagram Service, on the other hand, enables the transmission of small, single-shot messages between computers without establishing a connection first.

NetBIOS typically uses UDP ports 137 and 138 to communicate over the network. UDP port 137 is utilized by the NBNS to provide name resolution services, while port 138 is used by NetBIOS Datagram Service to send and receive small messages. Both ports are essential for NetBIOS to function properly.

One downside of NetBIOS is that it lacks security features, making it susceptible to attacks such as spoofing and watching. To mitigate these security risks, Microsoft introduced a new protocol called NetBIOS Extended User Interface (NetBEUI) in the early 1990s. NetBEUI is a control protocol that operates at a higher level than TCP/IP and provides enhanced security features such as encryption and authentication.

Despite the introduction of new protocols such as NetBEUI and its successor, Server Message Block (SMB), NetBIOS remains a crucial protocol in LANs today. It’s still used to share resources among computers on the network, especially in small businesses and home networks that don’t require sophisticated network infrastructure.

In conclusion, NetBIOS is an essential protocol that facilitates communication between computers on a local area network. It provides a means of accessing network resources, maps computer names to their corresponding IP addresses, and enables the transmission of messages between computers. Although it lacks robust security features, it’s still used in many small businesses and home networks today