PDU in OSI model

PDU in OSI model




In telecommunication the term protocol data unit (PDU) has the following meaning.


In a OSI layered model, a unit of data which is specified in a protocol of a given layer and which consists of protocol-control information and possibly user data Of that layer.

The PDU for each layer of the OSI model is listed below.

  1. Physical layer — raw bits (Is or Os) transmitted physically via the hardware
  2. Data Link layer — a frame (or series of bits)
  3. Network layer — a packet that contains the source and destination address
  4. Transport layer — a segment that includes a TCP header and data
  5. Session layer — the data passed to the network connection
  6. Presentation layer — the data formatted for presentation
  7. Application layer — the data received or transmitted by a software application
As you can see, the protocol data unit changes between the seven different layers. The resulting information that is transferred from the application layer to the physical layer (and vice versa) is not altered, but the data undergoes a transformation in the process. The PDU defines the state of the data as it moves from one layer to the next.


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