What is mDNS?
mDNS, or multicast Domain Name System, is a way for nodes to use IP multicast to publish and receive DNS records RFC 6762 within a local network. Nodes broadcast topics they’re interested in. mDNS is commonly used on home networks to allow devices such as computers, printers, and smart TVs to discover each other and connect.
mDNS in libp2p
In libp2p, mDNS is used for peer discovery, allowing peers to find each other on the same local network without any configuration. In the basic mDNS node discovery flow a node broadcasts a request which is consecutively replied to by other nodes within the network with their multiaddresses.
To learn more about definitions, specific fields, and peer discovery, visit the mDNS libp2p specification.