Protocol Data Unit

networking

Definition

Protocol Data Unit

Let a protocol stack consist of layers , where layer provides a service to layer via encapsulation.

A protocol data unit (PDU) at layer is the unit of data exchanged between peer layer- entities across the network:

where is the layer- protocol control information and is the service data unit (SDU) received from layer :

Names per Layer

Layer	PDU Name
Application	Message
Transport	Segment (TCP) / Datagram (UDP)
Network	Packet / Datagram
Data link	Frame
Physical	Bit / symbol