Cou

rse

ILT

The OSI model

Unit objectives Explain the significance of the OSI

model, label the seven layers of the OSI model, and describe services provided by each layer of the OSI model

Cou

rse

ILT

Topic A

Topic A: Introduction to the OSI model

Cou

rse

ILT

Introducing the OSI model

The OSI model is an international standard, originated to identify a common set of guidelines to facilitate communications between distinct information system components

It provides a mechanism to establish a common set of protocols to support multiple-vendor solutions

The real impact of OSI is the economic benefits derived from a common communications framework

Cou

rse

ILT

Introducing the OSI model

With the OSI model you’ll be able to leverage the available tools and technologies from an end-to-end perspective

The Open Systems Interconnect (OSI) model is an open, seven-layer model

Each layer performs a different function in the exchange of data between different systems

Cou

rse

ILT

The OSI Model

Cou

rse

ILT

Activity A-1

Introducing the OSI model

Cou

rse

ILT

Layers of the OSI model

The different layers of OSI model – OSI Physical layer – OSI Data link layer – OSI Network layer – OSI Transport layer – OSI Session layer – OSI Presentation layer – OSI Application layer

Cou

rse

ILT

OSI Physical layer

The Physical layer governs how data is transmitted across the media

It defines – The mechanical and electrical

characteristics of the cables and connectors that link the network components

– Data encoding – Bit synchronization

Cou

rse

ILT

OSI Data Link layer

The Data Link layer specifies how devices attached to the network gain access to the various computing resources

The two sub layers of this layer– Logical Link Control (LLC) – Media Access Control (MAC)

Cou

rse

ILT

The Data Link layer

Cou

rse

ILT

OSI Network layer

The Network layer is responsible for establishing a unique network address and managing the transport of information packets between different networks

It helps to coordinate the intercommunication activities between different networks

Cou

rse

ILT

OSI Network layer

Cou

rse

ILT

OSI Transport layer

The Transport layer is responsible for the accuracy of the data transmission

This fourth layer provides LAN network operating systems the intelligence to measure traffic performance

Cou

rse

ILT

OSI Transport layer

Cou

rse

ILT

OSI Session layer

The Session layer is responsible for the integrity of the logical connection of the software session

By using this layer two applications on different computers can establish, use, and end a connection called a session

It provides synchronization between user tasks by placing checkpoints in the data stream

Cou

rse

ILT

OSI Session layer

Cou

rse

ILT

OSI Presentation layer

The Presentation layer translates data into an appropriate transmission format

The functions maintained– Terminal emulation – Encryption– Compression

Cou

rse

ILT

OSI Presentation layer

Cou

rse

ILT

OSI Application layer

The Application layer provides a series of definitions that are used to provide network-wide system management functions such as software for file transfers, database access, and electronic mail

Cou

rse

ILT

Activity A-2

Discussing the layers of the OSI model

Cou

rse

ILT

Unit summary

Learned about the significance of the OSI model, labeled the seven layers of the OSI model, and described services provided by each layer of the OSI model