THE OSI LAYERS

 THE OSI LAYERS

• Application Layer
• Presentation Layer
• Session Layer
• Transport Layer 
• Network Layer
• Data Link Layer
• Physical Layer

What is the meaning of OSI model? 

- it is The open systems interconnection (OSI) model 

- is a conceptual model created by the International Organization for Standardization which enables diverse communication systems to communicate using standard protocols. In plain English, the OSI provides a standard for different computer systems to be able to communicate with each other.

The OSI Model can be seen as a universal language for computer networking. It is based on the concept of splitting up a communication system into seven abstract layers, each one stacked upon the last.

1. Application Layer

 It ensures an application can effectively communicate with other applications on different computer systems and networks. The application layer is not an application. Instead, it is a component within an application that controls the communication method to other devices. It is an abstraction layer service that masks the rest of the application from the transmission process. The application layer relies on all the layers below it to complete its process. At this stage, the data or the application is presented in a visual form that the user can understand.

2. Presentation Layer

Presentation Layer is the 6th layer in the Open System Interconnection (OSI) model. 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 per 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).

3. Session Layer

provides the mechanism for opening, closing and managing a session between end-user application processes, i.e., a semi-permanent dialogue. Communication sessions consist of requests and responses that occur between applications. Session-layer services are commonly used in application environments that make use of remote procedure calls (RPCs).

4. Transport Layer

The OSI model divides the tasks involved with moving information between networked computers into seven smaller, more manageable task groups. Each of the seven OSI layers is assigned a task or group of tasks. The transport layer's tasks include error correction as well as segmenting and desegmenting data before and after it's transported across the network. This layer is also responsible for flow control and making sure that segmented data is delivered over the network in the correct sequence. Layer 4 (the transport layer) uses the transmission control protocol (TCP) & user data protocol (UDP) to carry out its tasks.

5. Network Layer

Network-to-network connections are what make the Internet possible. The "network layer" is the part of the Internet communications process where these connections occur, by sending packets of data back and forth between different networks. In the 7-layer OSI model (see below), the network layer is layer 3. The Internet Protocol (IP) is one of the main protocols used at this layer, along with several other protocols for routing, testing, and encryption.

6. Data Link Layer

is the second layer of the seven-layer OSI model of computer networking. This layer is the protocol layer that transfers data between nodes on a network segment across the physical layer. The data link layer provides the functional and procedural means to transfer data between network entities and may also provide the means to detect and possibly correct errors that can occur in the physical layer.

7. Physical Layer

The physical layer (also known as layer 1) deals with bit-level transmission between different devices and supports electrical or mechanical interfaces connecting to the physical medium for synchronized communication. This layer plays with most of the network’s physical connections—wireless transmission, cabling, cabling standards and types, connectors and types, network interface cards, and more —as per network requirements.