A data packet is in the data processing in general, one of the indications for self-contained data units (eg, a digital sensor ) or a sending process to a receiver ( eg a monitoring station via an RS232 cable connection ), a transmitter (see: Frame ( Communications Engineering ) ). Such a data packet - in contrast to a data stream - has a well-defined length and shape, it can therefore be checked for completeness and usability. The OSI reference model is hardly useful for such packages since 4 of 7 OSI layers ( presentation layer, session layer, transport layer and the network layer) are irrelevant here and not be implemented.
In computer networks, this term is used, a data packet is there one of the names for the data items that are shipped to a computer network or telecommunications network. These include primarily the data units at layer 3 of the OSI model, the term is also often used not entirely correct for the Protocol Data Units of the other layers.
The majority of data packets consists of the information to be mailed. It also contains important addressing and management information - in IP -based networks, for example, the source and destination IP addresses, to deliver the packet to the correct computer. Such information is often recorded in the so-called header. A network connection typically carries more data packets that are routed over the same path is not necessarily the same physical network.
Normally the term datagram is used synonymously with data packet. Occasionally, however, they are distinguished from each other. Thus, a datagram is often regarded as a data packet, the additional information includes, among other things, the sender and recipient address, as well as order number and error correction key while a data packet is generally regarded as each unit of data that is transmitted over networks that are based on packet switching. Unlike Protocol Data Unit and Service Data Unit, the term packet is not well defined.
Especially with serial transfer is spoken instead of a data packet by a telegram.