The document summarizes the OSI model, which is a conceptual framework that characterizes computing functions into 7 layers. It describes that the upper layers deal with application issues and are implemented in software, while the lower layers deal with data transport and are implemented in both hardware and software. It then provides details on the functions of each individual layer, including the application, presentation, session, transport, network, data-link, and physical layers.

1. OSI Model
Submitted By:
Name : Md.Al-amin Hossen
ID : 1925102523
Batch : 51st
Semester : Summer-21
Program : B.Sc. In CSE

2. Submitted to:
Pranab Bandhu Nath
Lecturer , Dept. of CSE
City University

3. OSI Model:-
The OSI Model is a conceptual framework used to describe the functions of a networking system.
The OSI model characterizes computing functions into a universal set of rules and requirements
in order to support interoperability between different products and software.
• The OSI model is divided into two layers: upper layers and lower layers.
• The upper layer of the OSI model mainly deals with the application related issues,
and they are implemented only in the software. The application layer is closest to
the end user. Both the end user and the application layer interact with the
software applications. An upper layer refers to the layer just above another layer.
• The lower layer of the OSI model deals with the data transport issues. The data link
layer and the physical layer are implemented in hardware and software. The
physical layer is the lowest layer of the OSI model and is closest to the physical
medium. The physical layer is mainly responsible for placing the information on
the physical medium.
• (https://www.javatpoint.com/osi-model)

4. Characteristics of OSI Model

5. Function of The OSI Layers

6. Application Layer
An application layer is an abstraction layer that specifies the shared
communications protocols and interface methods used by hosts in a
communications network. An application layer abstraction is specified in
both the Internet Protocol Suite (TCP/IP) and the OSI model.

7. Presentation Layer
This layer is also known as Translation layer, as this layer serves as a data
translator for the network. The data which this layer receives from the
Application Layer is extracted and manipulated here as pert the required
format to transmit over the network. The main responsibility of this layer is to
provide or define the data format and encryption. The presentation layer is
also called as Syntax layer since it is responsible for maintaining the proper
syntax of the data which it either receives or transmits to other layer(s).

8. Session Layer
This layer allows users on different machines to establish active
communications sessions between them. It is responsible for establishing,
maintaining, synchronizing, terminating sessions between end-user
applications.

9. Transport Layer
In computer networking, the transport layer is a conceptual division of
methods in the layered architecture of protocols in the network stack in the
Internet protocol suite and the OSI model. The protocols of this layer provide
host-to-host communication services for applications.

10. Network Layer
Anything that has to do with inter-network connections takes place at the
network layer. This includes setting up the routes for data packets to take,
checking to see if a server in another network is up and running, and
addressing and receiving IP packets from other networks. This last process
is perhaps the most important, as the vast majority of Internet traffic is
sent over IP.

11. Data-Link Layer
• The main responsibility of the Data Link Layer is to transfer the datagram
across an individual link.
• The Data link layer protocol defines the format of the packet exchanged
across the nodes as well as the actions such as Error detection,
retransmission, flow control, and random access.
• The Data Link Layer protocols are Ethernet, token ring, FDDI and PPP.

12. Physical Layer
It is responsible for the actual physical connection between the devices. The
physical layer contains information in the form of bits. It is responsible for
transmitting individual bits from one node to the next.