NetBIOS Datagram Distribution Service (NBDGM)

NBDGM

NetBIOS Datagram

NBDGM is a message format used by NetBIOS Datagram Distribution Service(NBDD) to exchange information between computers.

Port: 138 UDP  |  RFC: N/A

OSI Layer: 7 (Application Layer)

Cyber Security Stance: Low

Designed by Vivekanand Padala

Protocol Overview

NetBIOS-DGM is a protocol used by the NetBIOS (Network Basic Input/Output System) API for sending and receiving datagrams (messages) between computers on a local area network (LAN).

NBDGM is a connectionless protocol, meaning that there is no need to establish a connection before sending data.

NetBIOS-DGM allows for broadcast-based communication, meaning that a datagram can be sent to all nodes on the network, rather than just a specific destination. This makes it useful for certain types of applications, such as network browsing and service discovery.

NetBIOS-DGM does not provide encryption or authentication, it is vulnerable to security threats such as eavesdropping, spoofing, and denial-of-service (DoS) attacks.

NBDGM workflow

1. A NetBIOS node (i.e., a computer) sends a broadcast message to all other nodes on the network using the NetBIOS-DGM protocol.
2. The message is encapsulated within a NetBIOS datagram and includes the source and destination NetBIOS names.
3. The NetBIOS datagram is sent to the NetBIOS name server, which is responsible for mapping NetBIOS names to IP addresses.
4. The name server determines the IP addresses of all nodes on the network that match the destination NetBIOS name and sends the datagram to those nodes.
5. Each receiving node checks the destination NetBIOS name to see if it matches its own name. If it does, the node processes the datagram. If it doesn't, the node discards the datagram.
6. The node that matches the destination NetBIOS name sends a positive acknowledgment (ACK) back to the sender to confirm receipt of the message.
7. If the sender does not receive an ACK within a certain time frame, it will retransmit the datagram.