Data packet
In data processing, a data packet or simply “packet” is generally one of the names for self-contained data units that a transmitter (e.g. a digital measuring probe) or a sending process sends to a receiver (e.g. a measuring station via a RS-232 cable connection).
In contrast to a data stream , such a data packet has a well-defined length and shape, so it can be checked for completeness and usability. The OSI layer model hardly makes sense for such packages, since 4 of 7 OSI layers (presentation layer, session layer, transport layer and network layer) are irrelevant here and are not implemented .
This expression is also used in computer networks : A data packet is one of the names for the data units that are sent in a computer network or telecommunications network. This primarily includes the data units on layer 3 of the OSI model ; however, the term is often not used entirely correctly for the protocol data units of the other layers.
Most of the data packets consist of the information to be sent. It also contains important addressing and management information - in IP -based networks, for example, the source and destination IP addresses in order to deliver the packet to the correct computer. Such information is often entered in the so-called header . A network connection usually transmits multiple data packets that are not necessarily the same route the same physical network routed to.
Usually the term datagram is used synonymously with data packet . Occasionally, however, they are also distinguished from one another. A datagram is often viewed as a data packet, the additional information of which contains, among other things, the sender and recipient address, but also order number and error correction key, while a data packet is generally considered to be any data unit that is transmitted over networks based on packet switching . In contrast to the protocol data unit and service data unit , the term data packet is not precisely defined.
In the case of serial transmission in particular, a telegram is also used instead of a data packet .