OSI MODEL LAYERS
According to the Open Systems Interconnection (OSI) concept, computer systems may communicate with one another through a network at seven different levels. It was the first consensus model for network communications, and all significant computer and telecommunications companies embraced it at the start of the 1980s.
Instead of using the more complicated OSI model, the current Internet is based on the more straightforward TCP/IP paradigm. On the other hand, the OSI 7-layer model is still widely utilised since it aids in both seeing and comprehending how networks operate as well as in isolating and diagnosing networking issues.
Major computer and telecommunications company representatives introduced OSI in 1983, and ISO recognised it as a global standard in 1984.
(7) APPLICATION LAYER
👉The OSI model's highest level, the application layer, communicates with an application program. The OSI layer closest to the end-user is the application layer.
👉 Enables users to interface with other software program.
👉To implement a communication component, the application layer communicates with software applications. The application program's interpretation of data is always outside the scope of the OSI model.
👉 Example of the application layer : file transfer, email, remote login, or other program.
(6) PRESENTATION LAYER
syntactic layer is another name for this layer.
👉 Assists you with data compression and encryption.
👉 Converts data into a format that the application can understand.
👉 Formats and encrypts data that needs to be transmitted across all networks.
(5) SESSION LAYER
👉 In charge of computer-to-computer communication. It aids in the establishment of connections between the local and remote applications, as well as their termination.
👉 Requests the establishment of a logical connection based on the needs of the end user. All crucial log-on or password validation is handled by this layer.
👉 Provides features such as duplex or half-duplex dialogue discipline. It's typically used in remote procedure call-based application setups.
(4) TRANSPORT LAYER
👉 Data is transported from a process on a source system to a process on a target computer via the transport layer, which is built on top of the network layer. It can be hosted on a single or multiple networks and ensures quality of service.
👉 Determines how much data to deliver where and at what rate. The application layer sends messages to this layer, which it builds upon. It helps to deliver error-free and sequential data units.
👉 Flow control, error control, and segmentation or de-segmentation are all transport layer functions that can be used to manage the reliability of a network.
(3) NETWORK LAYER
👉 Provides the functional and procedural means for transmitting variable-length data sequences between nodes connected in "different networks"
👉 At the network layer, message reliability is not guaranteed.
👉 Routing protocols, multicast group management, and network- layer address assignment are network layer- management protocols.
(2) DATA LINK LAYER
👉 Responsible for correcting errors that may occur on the physical layer. At this layer, you can specify the protocol for establishing and terminating connections between two network devices.
👉 It is an IP address understandable layer that helps define logical addressing so that each endpoint can be addressed and should be recognized.
👉 Helps implement packet routing throughout a network. It helps you determine the best possible path that will allow you to transfer data from one location to another.
There are two types of sublayers in the data link layer:
👉The Media Access Control (MAC) layer is responsible for determining how devices on the network access the information carriers and transmit data.
👉This layer is responsible for identifying and encapsulating network layer protocols, allowing fault isolation. The data link layer also provides a way to send data across multiple interconnected networks.
(1) PHYSICAL LAYER
👉 Helps define the electrical and physical specifications of the data connection.
👉 Establish the relationship between the device and the physical transmission medium.
👉 Does not handle protocols or other higher layer elements.
👉Examples of physical layer hardware : network adapters, Ethernet, repeaters and network hubs.
