DNS Name Server Identifier (NSID): Definition, Use Cases, and Limitations

The DNS Name Server Identifier (NSID) is a non-standard extension to the DNS protocol that allows a DNS server to identify itself using a unique identifier. This identifier can be used to differentiate between multiple instances of the same DNS server or to provide additional information about the server. NSID is typically used in conjunction with DNS Query Name Minimization (QNAME minimization) to improve privacy and security by reducing the amount of information that is disclosed in DNS queries. However, NSID is not widely supported by DNS servers and clients, so its use is limited.