A packet is a compact unit or bundle. In everyday language it denotes a small package or sachet used for goods such as sugar, seeds, cigarettes or condiments. In transport and postal history a packet referred to a regular mail or freight conveyance (often a packet ship or packet boat) that carried parcels and passengers on scheduled runs. In computing and telecommunications, a packet is a formatted unit of digital data routed between network points.

Packet structure and role in networking

In networking, packets are basic carriers of information. A packet typically combines a header and a payload: the header holds control information (addresses, sequence numbers, protocol identifiers, integrity checks) and the payload carries the user data. Networks break large messages into packets to improve reliability and efficiency; routers forward packets independently and packets may follow different paths to the destination.

  • Common header elements: source and destination addresses, protocol type, length, error-detection codes.
  • Types and behaviors: datagrams (connectionless), segments (TCP-level), frames (link-level).

Packet switching—where independent packets share transmission resources—is the dominant model for modern digital networks, contrasting with circuit switching which reserves a dedicated path. Packet-based systems handle congestion, retransmission, fragmentation and reassembly when packets exceed link size limits (MTU).

History, etymology and other senses

The word packet comes from a European term for a small parcel and was adopted into English to mean small bundled goods and scheduled carrying services. From there it became applied figuratively to discrete units of information as telecommunication and computing developed in the 20th century.

Packets are important both technically and culturally: they enable the Internet’s scalability and resilience, underpin data services (web, email, streaming) and have everyday physical analogues in retail and postal systems. Distinctions to note: a packet is not always identical to a frame or segment—those terms describe units at specific layers of network architecture—and packet loss, duplication and delay are key performance concerns in networks.