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Network Software

Overview

Protocol Hierarchies Design Issues for the Layers Connection-Oriented and ConnectionlessServices

Protocol Hierarchies

-^ protocol

Layer^

n^ on one machine

carries on a

conversation

with

layer^ n

on another machine

The rules and conventions used in this conversation arecollectively known as the layer

n^ protocol

Basically, a protocol is an agreement between thecommunicating parties on how communication is toproceed. As an analogy, when a woman is introduced to a man,she may choose to stick out her hand. He, in turn, maydecide to either shake it or kiss it, depending, forexample, on whether she is an American lawyer at abusiness meeting or a European princess at a formalball. Violating the protocol will make communicationmore difficult, if not impossible.

Protocol Hierarchies - peers A five-layernetwork isillustrated inFig. 1. Theentitiescomprising thecorrespondinglayers ondifferentmachines arecalled^ peers

In other words,it is the peersthatcommunicateusing theprotocol.

Fig. 1. Layers, protocols, and interfaces