NetBIOS (Network Basic Input/Output System) is a legacy networking protocol used primarily in Microsoft Windows-based networks for communication between computers on a local area network (LAN). It provides services related to the session layer of the OSI model, enabling applications to communicate over the network.
Here are key aspects of NetBIOS:
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Name Resolution: NetBIOS provides a name resolution service that maps NetBIOS names to IP addresses. This allows computers on the network to identify and communicate with each other using friendly names rather than IP addresses.
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Session Establishment: NetBIOS facilitates the establishment and management of sessions between computers on the network. It enables applications to establish connections, exchange data, and terminate sessions when communication is complete.
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Datagram Services: NetBIOS supports both connection-oriented (session) and connectionless (datagram) modes of communication. Datagram services allow for the transmission of data between computers without the need to establish a session.
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NetBIOS over TCP/IP (NBT): NetBIOS was originally designed to work over NetBEUI (NetBIOS Extended User Interface), a non-routable protocol. However, with the adoption of TCP/IP as the standard networking protocol, NetBIOS functionality was adapted to work over TCP/IP using a protocol known as NetBIOS over TCP/IP (NBT).
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Ports: NetBIOS uses ports 137 (NetBIOS Name Service), 138 (NetBIOS Datagram Service), and 139 (NetBIOS Session Service) for communication. These ports are used by NetBIOS-enabled applications and services to facilitate various aspects of network communication.
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Limitations: NetBIOS has several limitations, including a lack of built-in security features, limited scalability, and reliance on broadcast messages for name resolution, which can lead to network congestion and performance issues in large networks.
While NetBIOS was widely used in the past, its functionality has been largely supplanted by newer networking protocols such as SMB (Server Message Block) for file sharing and Active Directory for directory services in modern Windows-based networks. However, NetBIOS remains in use in some legacy environments and may still be encountered in certain network configurations.
