Data Encapsulation, Protocol Data Units (PDUs) and Service Data Units (SDUs) Data Encapsulation, Protocol Data Units (PDUs) and Service Data Units (SDUs)(Page 1 of 3) Protocols are what describe the rules that control horizontal communication, that is, conversations between processes that run at corresponding layers within the OSI Reference Model.
At every layer (except layer one) these communications ultimately take the form of some sort of message that is sent between corresponding software elements on two or more devices. Since these messages are the mechanism for communicating information between protocols, they are most generally called protocol data units (PDUs). OSI Model. OSI model. Model with 7 layers to describe communications systems The Open Systems Interconnection model (OSI model) is a conceptual model that characterizes and standardizes the communication functions of a telecommunication or computing system without regard to its underlying internal structure and technology.
Its goal is the interoperability of diverse communication systems with standard protocols. The model partitions a communication system into abstraction layers. The original version of the model defined seven layers. A layer serves the layer above it and is served by the layer below it.