CCNA (third lecture)

Third Lecture
Data Encapsulation 

The OSI Reference Model 

•Open Systems Interconnection

•7-layer

•It divides the network communication process into smaller and simpler components, thus

•aiding component development, design, and troubleshooting.

• It allows multiple-vendor development through standardization of network components.

• It encourages industry standardization by defining what functions occur at each layer of

•the model.

• It allows various types of network hardware and software to communicate.

Upper Layers

Lower Layers

•The OSI reference model has seven layers:

• Application layer (layer 7)

• Presentation layer (layer 6)

• Session layer (layer 5)

• Transport layer (layer 4)

• Network layer (layer 3)

• Data Link layer (layer 2)

• Physical layer (layer 1)

Layer functions

The Application Layer

•interface between the actual application program and the next layer down

•file transfers and email.

The Presentation Layer

•It presents data to the Application layer

•Data translation and code formatting.

•EBCDIC to ASCII translation services

• Data compression and  decompression

•Data encryption, and decryption

The Session Layer

•The Session layer is responsible for setting up, managing, and then tearing down sessions between Presentation layer entities.

•simplex, half duplex, and full duplex.

The Transport Layer

•segments and reassembles data into a data stream.

•connectionless or connection-oriented

•Flow Control

The Network Layer

•Route update packets

•Network addresses

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MAC Addressing 

•Layer 2 Address

•48- Bit

•Hexadecimal

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Author & Editor

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