feat: mdns

content/concepts/discovery-routing/mDNS.md

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+---
+title: "mDNS"
+description: "mDNS uses a multicast system of DNS records over a local network to enable peer discovery."
+weight: 224
+---
+
+## What is mDNS?
+
+mDNS, or multicast Domain Name System, is a way for nodes to use the multicast
+system of DNS records [RFC 6762](https://www.rfc-editor.org/rfc/rfc6762) over a
+local network to discover and communicate with nodes. Nodes broadcast topics
+they're interested in. The discovery, however, is limited to the peers in the
+local network. mDNS is commonly used on home networks to allow devices such as
+computers, printers, and smart TVs to find each other and connect. It uses a
+protocol called multicast to broadcast messages on the network, allowing devices
+to discover each other and exchange information.
+
+## mDNS in libp2p
+
+In libp2p, mDNS is used for peer discovery, allowing peers to find and
+communicate with each other on the same local network without any configuration.
+The basic mDNS node discovery flow begins when a peer starts or detects a
+network change and then sends a query message to all peers. The node adds the
+response it receives from other peers into a local database.
+
+To learn more about
+definitions, specific fields, and peer discovery, [visit the mDNS libp2p
+specification](https://github.com/libp2p/specs/blob/master/discovery/mdns.md).
+<!-- ADD DIAGRAM -->