What is NETBIOS – Network Basic Input Output System?
It is an interface between transport and session layer of the OSI model. The name NETBIOS refers to network extension of the facilities that have historically been provided by the Input/output system (BIOS) included in read-only memory in every IBM compatible computer.
NETBIOS effectively extend the local IO capabilities of a personal computer, operating system to a networking environment. It defines an API for requesting transport layer for communication services and protocol that describe how those services are provided
NETBIOS has become a defacto transport layer standard for personal computers, LAN communication and NETBIOS services are provided by a wide variety of different networking software sub system
Services of NETBIOS
General or NETBIOS status
These are used to request and return status information for a particular network name and to terminate a trace that originated at a local or remote system
NETBIOS name services
Add, add group, delete and find, the naming services provide the capability to install a LAN adapter card with multiple logical names thus a remote adapter can be referred to by a logical such as xyz, abcrd etc
NETBIOS Session Services
Session services provide reliable data transfer by establishing a session between two names over which data can be transmitted. A given network user can be involved in multiple session. When a session is established, it is assigned a one octet session identifier to differentiate the different session a user might have active. Messages that are send are acknowledge by the receiving station, if an expected acknowledgement is not received the sender retransmit the message
NETBIOS Datagram services
Whereby one has sent, sent broadcast, receive and receive broadcast, datagram services allows a user to send messages without fast establishing a session. Messages can be sent to other network users by specifying individual names or group names or by broadcasting messages to all users. The datagram service does not use acknowledgement and this should be consider a reliable services