Protocol Layering

Ethernet Protocol

• details of the Frame
• network Access policy
• Frame error handling procedures

IP

• IP Addressing
• Datagram format
• Concept of Connectionless delivery

Protocols

• specify how data is represented when being transferred from one machine to another
• specify the procedure for transfer
• specify the error detection and handling procedures
• specify Acknowledgement procedures
• help us to understand communication without knowing details of underlying hardware

Complexity of Protocols

A protocol must take into account all possible contingencies like

• Hardware failure
• Network Congestion
• Packet delay or loss
• Data Corruption
• Data duplication or Sequencing errors

Concept of Layering

Standard specify

• the Functionality of each layer
• the Interfacing of layers

Path of a message on Internet

Realistic View of Software Organisation

Every Layers - a Multiplexer and a Demultiplexer

Principle of Layering

Layer N at the destination receives exactly the same object sent by the layer N at the source

At higher layers,

end-to-end application

At lower layers,

applies to a single machine transfer.

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