Discuss OSI model layers in Details

Concept of Layers

We use the concept of layers in our daily life. As an example, let us consider two friends who communicate through postal mail. The process of sending a letter to a friend would be complex if there were no services available from the post office.

Example of Layers:

Tasks involved in sending a letter

THE OSI MODEL

Established in 1947, the International Standards Organization (ISO) is a multinational body dedicated to the worldwide agreement on international standards. An ISO standard that covers all aspects of network communications is the Open Systems Interconnection (OSI) model. It was first introduced in the late 1970s. 

• ISO is the organization.

• OSI is the model.

OSI Model Layers

Seven layers of the OSI model

The interaction between layers in the OSI model:

An exchange using the OSI model:

LAYERS IN THE OSI MODEL:

1. Physical Layer
2. Data Link Layer
3. Network Layer
4. Transport Layer
5. Session Layer
6. Presentation Layer
7. Application Layer

Physical layer:

The physical layer is responsible for movements of individual bits from one hop (node) to the next.

Physical Layer Concerned About:

• Physical Characteristics: type of transmission medium
• Bits Representation
• Data Rate: no. of bits sent each second
• Synchronization of Bits
• Line Configuration: P2P, Multi-point
• Physical Topology
• Transmission Model

Data link layer:

The data link layer is responsible for moving frames from one hop (node) to the next.

Data Link Layer Concerned About:

• Framing
• Physical Addressing
• Flow Control
• Error Control
• Access Control

Network layer:

The network layer is responsible for the delivery of individual packets from
the source host to the destination host

Network Layer Concerned About

• Logical Addressing
• Routing

Example of Source-to-destination delivery:

Transport layer:

The transport layer is responsible for the delivery of a message from one process to another.

Transport Layer Concerned About:

• Service Point Addressing
• Segmentation and Reassembly 
• Connection Control
• Flow Control
• Error Control

Reliable process-to-process delivery of a message:

Session layer:

The session layer is responsible for dialog control and synchronization.

Presentation layer:

The presentation layer is responsible for translation, compression, and encryption.

Application layer:

The application layer is responsible for providing services to the user.

Summary of layers