Unit 1

Lesson 5 - Review of the OSI Model

Primary Functions of OSI Model Layers

The OSI Model Layers Table provides an overview of the primary functions of each layer of the OSI model. It also presents the unit of information and address type where appropriate.

OSI Model Layers

OSI Model Layer

Layer Function

Unit of
Information

Address Type

Application

User functionality

Program

 

Presentation

Character representation
Compression
Security

Characters and words

 

Session

Establishing, conducting, and ending sessions

 

 

Transmitting messages from sending computer process to receiving computer process

Message

Process to process between applications

Transmitting individual packets across a network

Packet

Packet address identifying receiver's network and host location

Transmitting frames containing packet across a link en route to final destination

Frame

NIC (next node in network)

Transmitting bits in the form of signals across physical media

Bit

 

(Click on the Links within the table for more OSI Animations)

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