Protocol data unit
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In telecommunications, the term protocol data unit (PDU) has the following meanings:
- Information that is delivered as a unit among peer entities of a network and that may contain control information, address information, or data.
- In layered systems, a unit of data that is specified in a protocol of a given layer and that consists of protocol-control information of the given layer and possibly user data of that layer. For example: Bridge PDU or iSCSI PDU
- Source: from Federal Standard 1037C
PDU's are relevant in relation to one of the first 4 layers of the OSI model as folows :
- The Layer 1 PDU's are the streams
- The Layer 2 PDU's are the frames
- The Layer 3 PDU's are the packets
- The Layer 4 PDU's are the fragments
Given a context pertaining to a specific layer PDU is sometimes used as a synonym for it's representation at that layer.
In telecommunications, the term packet data unit (PDU) has the following meaning:
- The units that are transported in a LIN (Local Interconnect Network) diagnostic frame are called PDU (Packet Data Unit). A PDU used for node configuration is a complete message.
- Source: LIN Diag and Config Spec Revision
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