The OSI reference model defines a standard framework for how information is communicated between computers. It consists of 7 layers, with each layer defining a set of rules or protocols for how data is formatted and transmitted between devices. The physical layer deals with physical connections and transmission of raw bits. Higher layers deal with networking, routing, sessions, data translation and presentation for applications. Gateways allow communication between systems that use different protocols by translating between protocol layers. The OSI model provides interoperability standards for network communication.

1. OSI Reference Model

2. Why to learn OSI reference Model?
The answer is too simple that It tells us
that how communication takes place
between computers on internet but how??

3. Nowadays, When we talk about
communication of computer we got to
know a term communication protocols.
What are they??
Set of rules which defines the rules
followed by all involved in the process of
communication but what are they
actually??

4. What if someone is using some other
rules/Protocols?
If it is necessary to communicate with
computers following totally different
protocols then we have to connect a device
called Gateway between such systems.
Gateways are computers loaded with special
software, which do the job of translation
work from one protocol to other so that
communication between heterogeneous
systems may take place.

5. The Seven-layer Architecture of the OSI model

6. PHYSICAL LAYER
TRANSMISSION MEDIUM
From Data link Layer To Data link Layer

7. • Physical layer is the bottom layer of OSI
model
• It is responsible for the actual physical
connection between the devices. Such
physical connection may be made by using
twisted pair cable, fiber-optic, coaxial cable or
wireless communication.
• Physical layer is concerned with transmitting
raw bits over a communication channel.

8. Function of Physical layer
• Transforming bits into signals
• Bit Synchronization
• Provides physical characteristics of interfaces
and medium
• Bit rate control
• Line configuration
• Transmission mode
• Physical topologies
• Multiplexing
• Circuit switching

9. DATA LINK LAYER

10. Functions of Data link layer
• Framing
• Physical Addressing
• Flow control
• Error control
• Access Control
• Feedback

11. Network Layer

12. Functions of Network layer
• Logical Addressing
• Routing

13. Transport Layer
• Transport layer provides two types of services
• Connection oriented
• Connectionless

14. Session Layer

15. Function of Transport layer
• Segmentation of message into packet and
reassembly of packets into message
• Connection management
• Service point addressing
• Flow control
• Error control

16. Function of Session layer
• Establishment, maintaining and ending a
session
• Dialog control
• Dialog separation or Synchronization

17. Presentation Layer
• Different computers may use different coding
schemes for data transmission. For example
some computers may send the most
significant bit of a byte first and least
significant bit last and in some other
computers it may be other way round, the
sequence may be different at byte level also.
The job of the presentation layer is to do the
job of code translation and present the data
in the format used at the destination
computer.

18. Functions of presentation
layer
• Data Presentation or Translation
• Data Encryption
• Data compression

19. Application Layer
• This is the layer with which users have direct
interface. At the transmitting computer the
message originates at this layer and at the
destination computer the message is finally
received by this layer and presented to the
user in desired format. The data packets at
the application layer are known as messages

20. Functions of Application Layer
• Network Virtual Terminal
• File transfer, access and management (FTAM)
• Mail services
• Directory services

21. THANKS
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