The document presents an overview of the Open Systems Interconnection (OSI) model. It discusses the history and development of the OSI model by international standards organizations in the 1970s and 1980s. The OSI model defines a seven-layer architecture for network communication, with each layer providing services to the layer above and receiving services from the layer below. Each layer has a specific role, such as the physical layer dealing with physical connections, the data link layer handling framing and addressing, and the application layer providing interfaces for users.

2. Presented By: Waqas Ahmad
BS Telecommunication
Su-12-01-003-005
6th semester
Presented To: Mr. Adam Khan
Dept. Computer Science And IT

3. Overview
 Abstract
 OSI HISTORY
 Open Systems Interconnection Model
(OSI Model)
 Component of OSI Model
 Osi Model Arch
 Function of each layer
 Conclusion

4. Abstract
The Open Systems Interconnection model (OSI model) is a product
of the Open Systems Interconnection effort at the International
Organization for Standardization. It is a way of sub-dividing a
communications system into smaller parts called layers. A layer is a
collection of conceptually similar functions that provide services to
the layer above it and receives services from the layer below it. On
each layer an instance provides services to the instances at the layer
above and requests service from the layer below. For example, a layer
that provides error-free communications across a network provides
the path needed by applications above it, while it calls the next lower.

5. OSI HISTORY
In the late 1970s, two projects began independently, with the same goal
 One was administered by the International Organization for Standardization (ISO).
 other was undertaken by the International Telegraph and Telephone Consultative
Committee.
These two international standards bodies each developed a document that defined similar
networking models.
Goal of The project:
 define a unifying standard for the architecture of networking systems

6. OSI HISTORY
In 1983, these two documents were merged to form a standard called The Basic Reference
Model for Open Systems Interconnection. The standard is usually referred to as the Open
Systems Interconnection Reference Model, the OSI Reference Model, or simply the OSI
model.
It was published in 1984 by both the ISO and the renamed CCITT (now called the
Telecommunications Standardization Sector of the International Telecommunication Union or
ITU-T)

7. Open Systems Interconnection Model
(OSI Model)
The Open Systems Interconnection (OSI) Model is a conceptual and logical
layout that defines network communication used by systems open to
interconnection and communication with other systems.
The model is broken into seven layers
i. Physical Layer
ii. Data link
iii. Network layer
iv. Transport layer
v. Session layer
vi. Presentation Layer
vii. Application Layer

8. Component of OSI Model
OSI had two major components
 abstract model of networking, called the Basic Reference Model or seven-layer model,
 set of specific protocols.
The concept of a seven-layer model was provided by the work of Charles Bachman.

9. Osi Model Archi

10. Function of Each Layer(1)
Application Layer:
The Application layer is the first layer of the OSI Model.
The physical layer deals with:
Physical Medium
This layer plays with most of the network’s physical connections:
wireless transmission
 cabling, etc

11. Function of Each Layer(2)
Date Link Layer:
The data link layer is used for the encoding, decoding and logical organization of data bits.
Data packets are framed and addressed by this layer, which has two sublayers.
The data link layer's first sub layer is the media access control (MAC) layer. It is used for
source and destination addresses. The MAC layer allows the data link layer to provide the best
Data
Transmission and manage data flow control.
The data link layer's second sub layer is the logical link control. It manages error checking and
Data flow over a network.

12. Function of Each Layer(3)
Network Layer:
The network layer is the third level of the Osi Model.
 Provides data routing paths for network communication
 Selects and manages the best logical path for data transfer between nodes
This layer contains hardware devices such as,
 Routers
 switches, etc

13. Function of Each Layer(4)
Transport Layer:
Responsible for end-to-end communication over a network
The transport layer is also responsible for the management of error correction
To Transport the Data Addressing is not the responsibility of Transport layer
Services provided by Transport layer
 Reliable
 Unreliable
Issues control by Transport layer
 Segmentation
 Sequencing
 Flow control

14. Function of Each Layer(5)
Session Layer:
Session between Applications
 Establishing
 Managing
 Terminating
To manage the session
Dialog Control
i. Two way Alternative
ii. Two way Simultaneous
Dialog Separation
i. Roll Back
ii. Check Point

15. Function of Each Layer(6)
Presentation Layer:
The presentation layer formats the data to be presented to the application layer.
This layer may translate data from a format used by the application layer into a common
format at the sending station, and then translate the common format to a format known to the
application layer at the receiving station.
The presentation layer provides:
 Data compression
 Data encryption
 Data conversion

16. Function of Each Layer(7)
Application Layer:
Provide an interference
When user communicate wit ha computer hardware
Applications may be:
 Stand alone
 Network application

17. CONCLUSION
The authors tried to explain what exactly an OSI reference model is,
OSI is basically an architecture which only gives us an idea how packets transfer over the
network during any communication. OSI enhancements are done time to time for
developing new technologies.