Editing Protocol data unit (section)

{{Short description|Unit of information transmitted over a computer network}}
{{Use American English|date = March 2019}}
{{Use mdy dates|date = March 2019}}
{{Refimprove|date=April 2012}}

[[Image:Pdu and sdu.svg|thumb|350px|[[Medium access control]] (MAC) layer protocol data unit (PDU) becomes [[physical layer]] [[service data unit]] (SDU).]]

In [[telecommunications]], a '''protocol data unit''' ('''PDU''') is a single unit of information transmitted among peer entities of a [[computer network]]. It is composed of protocol-specific control information and [[Payload (computing)|user data]]. In the layered architectures of [[communication protocol]] stacks, each layer implements protocols tailored to the specific type or mode of data exchange.

For example, the [[Transmission Control Protocol]] (TCP) implements a connection-oriented transfer mode, and the PDU of this protocol is called a ''segment'', while the [[User Datagram Protocol]] (UDP) uses [[datagram]]s as protocol data units for [[connectionless communication]]. A layer lower in the [[Internet protocol suite]], at the [[Internet layer]], the PDU is called a [[network packet|packet]], irrespective of its payload type.