The OSI model is a conceptual framework that standardizes networking protocols to facilitate communication over a network, consisting of seven layers: physical, data link, network, transport, session, presentation, and application. Each layer serves specific functions ranging from the physical connection of devices to the management of communication sessions and data formatting. For example, in practical usage, the model can illustrate how an email is sent from one user to another through various layers of processing.

2. What is OSI Model ?
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OSI Model
The OSI Model (Open Systems Interconnection Model) is a
conceptual framework used to understand and standardize how
different networking protocols interact to enable communication
over a network.
Developed by the International
Organization for
Standardization (ISO) in 1984

3. Layers in OSI Model
Physical Layer
Data Link Layer
Network Layer
Transport Layer
Application Layer
Presentation Layer
Session Layer
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4. Layers in OSI Model
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The Physical Layer is the lowest level of the
OSI Model, handling the actual physical
connection between devices.
Physical Layer

5. Functions
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Bit Synchronization
&
Bit Control
Physical Topologies
Transmission Mode

6. Layers in OSI Model
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The Data Link Layer is responsible for the
direct transfer of data between nodes on a
network.
Data Link Layer

7. The Data Link Layer consists of two sublayers:
Logical Link Control
Medium Access Control
Data Link Layer

8. Functions
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Framing
&
Physical Addressing
Error Control
&
Flow Control
Access Control

9. Layers in OSI Model
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The Network Layer is responsible for
transmitting data between hosts that are
located in different networks.
Network Layer

10. Functions
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Routing
Logic Addressing

11. Layers in OSI Model
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The Transport Layer provides essential
services to the Application Layer while relying
on the Network Layer for data delivery.
Transport Layer

12. Types of Services provided by Transport Layer
Connection-Oriented Service
Connectionless
Service
Transport Layer

13. Functions
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Segmentation Reassembly
Service Point
Addressing

14. Layers in OSI Model
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The Session Layer manages the connections
between applications on different devices. It
ensures that communication sessions are
properly established, maintained, and
terminated
Session Layer

15. Functions
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Session
Establishment
Synchronization
Dialog Controller

16. Layers in OSI Model
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The Presentation Layer, also known as the
Translation Layer, is responsible for
transforming data from the Application Layer
into a format suitable for network
transmission.
Presentation
Layer

17. Functions
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Translation Encryption
&
Decryption
Compression

18. Layers in OSI Model
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The Application Layer is the topmost layer of
the OSI model and directly interacts with
network applications.
Application Layer

19. Functions
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Network Virtual
Terminal
File Transfer &
Access Management
Mail Services

20. How data flows in OSI Model ?
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Let’s use an example where
your friend, Alex, writes an
email to his friend, Jamie.

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