datagrammen

Datagrammen, or datagrams, are self-contained data packets used in computer networks for independent delivery from a sender to a receiver. Each datagram carries enough information to be routed without relying on prior exchanges, making datagram traffic inherently connectionless. The term is used especially in the context of IP networks and UDP, but the concept extends to any layer that treats messages as independent units.

In an IP network, datagrams are transmitted from source to destination through routers that forward each packet based on its destination address. Each datagram is processed independently; there is no fixed circuit or state maintained for a session across the network. The header includes addressing, length, fragmentation fields, time-to-live, and protocol to indicate the upper-layer payload type. Upper-layer protocols attach their own data, such as UDP port numbers for datagrams in UDP, or indicate that the payload is a complete unit for applications.

Advantages of datagrams include low overhead and simplicity, making them suitable for real-time communications, small queries, and applications that can tolerate some loss. Disadvantages include the lack of delivery guarantees or ordering; potential loss, duplication, and reordering of packets. Fragmentation may complicate reassembly if fragments are dropped or arrive out of order, and many implementations expose these issues to the application layer.

Datagrams are defined within the Internet Protocol suite. The IPv4 datagram is defined in RFC 791; IPv6 in RFC 8200. Datagram-oriented transport in common use includes UDP, defined in RFC 768, which provides a simple, connectionless datagram service.