NetBIOS (Network Basic Input Output System) is a program that allows application on different computers to communicate within a LAN (Local Area Network).

It was developed by IBM and SYTEK for pc connectivity.NetBIOS is an interface between the transport and session in OSI layers. NetBIOS is Used in OS/2 and UNIX operating system.It also support TCP/IP.

NetBIOS is the de facto standard today because of its IBM origins. It supports Ethernet, token rings, ARCnet, starLAN.
SERVICES:

A NETBIOS command provides three distinct  services.

Name Service for name registration
· Session Service for connection-oriented communication.
·Datagram distribution service for connectionless  for connectionless communication

NAME SERVICES:The naming services provide the capability to install a LAN adapter card with multiple logical names. This NetBIOS names are 16bytes in length used to designate a “type” similar to the port numbers.
*Add name-register a NetBIOS name
*Add group name-register a NetBIOS group name
*Delete name-un register a NetBIOS name or group name
*Find name-search the names on the network.
SESSION SERVICES:

Session provides a reliable communication services over a network applications can exchange information. The packets are received in order and blocked into usermessages.Duplicated packets are detected and discarded by the session service.
*Call-open a session
*Listen-listen to open a session to a NetBIOS name.
*Hang up-close a session
*Send-send a packet to the computer on other end of the session.
*Send no ACK-send a packet to other end session but it doesn’t require an acknowledgement.
*Receive-wait for a packet to arrive from a send on the other end of the session.
DATAGRAM DISTRIBUTED SERVICES:

Send, Send-Broadcast, Receive, and Receive-Broadcast Datagram. Datagram provides unreliable transmission services with broad cast capabilities. Each Message is sent independently they must be smaller. There is no acknowledgement or tracking of the datagram. It is also responsible for detecting and recovering errors.