unicasts

Unicast is a form of one-to-one communication in which a single sender transmits data to a single, specified receiver. In IP networks, a unicast address designates one particular interface, and each packet includes the destination address for that endpoint. Routers forward unicast packets along a chosen path based on routing tables, delivering the packet to that single recipient.

Unicast is distinct from multicast and broadcast. Multicast delivers data to a defined group, with replication occurring in the network to reach multiple receivers; broadcast sends to all devices on a local network segment. Because unicast requires separate transmissions for each recipient, it does not inherently scale to large groups as efficiently as multicast, where appropriate.

Most Internet traffic is unicast. Examples include web pages, email, file transfers, and many real-time communications such as voice over IP when using unicast streams. Unicast supports bidirectional communication, with responses sent from the destination back to the source over a separate unicast path.

Addressing and routing for unicast are central to IP networks; routing protocols maintain per-destination routes, and individual traffic can be optimized by end-to-end transport protocols (for example TCP provides reliability, while UDP offers best-effort delivery). In IPv6, unicast addresses include global, link-local, and unique local forms, used to identify interfaces for direct communication.