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Chapter 5Chapter 5

Open Systems Interconnection ModelOpen Systems Interconnection Model

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OSI MODELOSI MODEL

The International Standards Organization (The International Standards Organization (ISOISO) is a ) is a multinational body dedicated to worldwide agreement on multinational body dedicated to worldwide agreement on international standards, established in international standards, established in 19471947. The Open . The Open Systems Interconnection (Systems Interconnection (OSIOSI) model) model isis an ISO standard an ISO standard that covers all aspects of network communications, it was that covers all aspects of network communications, it was first introduced in the late first introduced in the late 1970s1970s. .

Layered ArchitecturePeer-to-Peer ProcessesEncapsulation

Topics discussed in this section:Topics discussed in this section:

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Seven layers of the OSI model

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The interaction between layers in the OSI model

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An exchange using the OSI model

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Physical layer

The physical layer is responsible for movements ofindividual bits from one hop (node) to the next.

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Data link layer

The data link layer is responsible for moving frames from one hop (node) to the next.

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Hop-to-hop delivery

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Network layer

The network layer is responsible for the delivery of individual packets from

the source host to the destination host.

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Source-to-destination delivery

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Transport layer

The transport layer is responsible for the delivery of a message from one process to another.

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Reliable process-to-process delivery of a message

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Session layer

The session layer is responsible for dialog control and synchronization.

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Presentation layer

The presentation layer is responsible for translation, compression, and encryption.

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Application layer

The application layer is responsible for providing services to the user.