NetBIOS Name Service (NBNS)
TLDR: The NetBIOS Name Service (NBNS) is a legacy network protocol introduced in 1985 as part of the NetBIOS suite, used primarily for resolving NetBIOS names to IP addresses in early LAN environments. It functions similarly to a DNS for NetBIOS networks, enabling devices to find each other by name instead of relying solely on numeric IP addresses. The service operates over UDP on port 137 and allows NetBIOS clients to announce their services and locate others through name resolution queries. Its use has declined with modern networking standards like DNS, but it remains active in some legacy systems and configurations.
https://en.wikipedia.org/wiki/NetBIOS
The NBNS works by broadcasting queries on the local subnet, where the responding device provides its IP address corresponding to the queried NetBIOS name. Unlike hierarchical systems like DNS, NBNS relies on broadcast-based communication, which can lead to inefficiency and network congestion in larger or segmented networks. However, it is integral to Windows networking environments predating Active Directory and is still supported for backward compatibility. For organizations managing older network setups, NBNS can be a critical service for ensuring interoperability between legacy systems.
https://learn.microsoft.com/en-us/windows-server/networking/netbios-and-wins
Though NBNS is largely deprecated in modern networks, its functionality is often replaced or supplemented by Windows Internet Name Service (WINS), which acts as a centralized NetBIOS name resolution service. The security concerns surrounding NBNS include its susceptibility to spoofing attacks and man-in-the-middle threats, as it lacks the robust security mechanisms of contemporary network protocols. System administrators managing NBNS should consider migrating to modern alternatives like DNS while implementing safeguards to protect the NBNS traffic in existing network environments.
https://www.cisco.com/c/en/us/support/docs/ip/network-basics/13712-wins.html