PDU ( Protocol Data Links or Unité of data of protocol ) is the whole of the information exchanged between levels in the system of layers OSI model.

(NR) - PDU is the unit of data for a layer (number NR). It includes/understands a (N+1) - PDU , and one information of control (NR) - NCV , i.e. the complete whole of the data of the roadbase (N+1) to which one adds nonuseful data to ensure control (checking of error).

Example:

N+1 level: lay down Transport > Message

(N+1) - PDU:

Level NR: lay down network > Paquet

(NR) - PDU

N-1 level: lay down connection > Trame

(N-1) - PDU

See too

• Service Dated Links
• OSI model