Understanding the NetBIOS protocol
Network Basic Input/Output System (NetBIOS) is a set of protocols developed in the early 1980s for LAN communications, in order to provide services for the session layer (fifth layer in the OSI model). A few years later, it was adopted by Microsoft for their networking over LAN, and then it was migrated for working over TCP/IP (NetBIOS over TCP/IP—NBT), which is discussed in RFC 1001 and 1002.
In today's networks, NetBIOS provides three services:
- Name service (port
137) for name registration and name to IP address resolution. Also referred to as NetBIOS-NS. - Datagram distribution service (port
138) for service announcements by clients and servers. Also referred to as NetBIOS-DGM. - Session service (port
139) for session negotiation between hosts. This is used for accessing files, opening directories, and so on. Also referred to as NetBIOS-SSN.
NBNS is the service that registers and translates names to IP addresses. Registration happens when a client registers its...
