IPpaket

IPPaket is the basic unit of data that travels across networks using the Internet Protocol. An IP packet is created when a higher-layer protocol hands data to the IP layer, which encapsulates it in an IP header and a payload. The header carries addressing and control information used to route the packet to its destination, while the payload contains the actual data.

In IPv4, the header contains fields such as version, header length, total length, identification, flags, fragment offset, Time to Live (TTL), protocol, header checksum, source address, destination address, and optional fields. The header length is variable due to options. In IPv6, the header is redesigned with a smaller base header that includes version, traffic class, flow label, payload length, next header, hop limit, and source and destination addresses. Extension headers provide optional functionality and can carry additional information for the processing of the packet.

IP packets are routed independently toward the destination; routers forward packets based on the destination address, while TTL helps prevent routing loops. If a packet is too large for a link, fragmentation can occur, typically at the sender in IPv4. In IPv6, fragmentation is generally handled differently, with Path MTU discovery guiding packet sizes to avoid fragmentation along the route.

IPv4 includes a header checksum; IPv6 does not have a header checksum, and integrity is supported by higher-layer protocols and end-to-end mechanisms. IP provides best-effort delivery: packets may be delivered out of order, duplicated, or lost. Reliability is provided by transport-layer protocols such as TCP, not by IP itself.

IPPaket have been standardized across IPv4 and IPv6 specifications, with IPv4 defined in RFC 791 and IPv6 in RFC 8200.