mDNS
Multicast DNS: a zero-configuration protocol that resolves .local hostnames on a local network without a central DNS server.
mDNS (Multicast DNS, RFC 6762) lets devices on the same link discover each other by name using the `.local` pseudo-TLD with no central DNS server. A query for `printer.local` is sent to the multicast address 224.0.0.251 (or ff02::fb for IPv6) on port 5353, and any device with that name answers directly. Apple's Bonjour, the Avahi daemon on Linux, and Windows have built-in mDNS support. Combined with DNS-SD (RFC 6763), mDNS powers AirPlay, AirPrint, Chromecast discovery, and IoT pairing flows.