Protocol Hierarchies

• Layers reduce complexity (note similarity to OS design)

• Each layer offers services to higher layers (details are hidden)

• Protocol is an agreement between communicating parties on how communication is to proceed

• Network consists of layers which theoretically communicate with one another (actually no communication between peers occurs)

• Layers pass data and control info to next (and only next) layer until lowest layer (hardware). Communication occurs at physical layer.

• Between adjacent layers is an interface. The interface defines which primitive operations and services the lower layer offers to the upper one. Must design “clean interfaces.”

• A set of layers and protocols is called a network architecture..

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Network software/Protocol Hierarch.