What is Topology? Types of Topology

 OSI MODEL

The OSI (Open Systems Interconnection) model is a conceptual framework that standardizes the functions of a telecommunication or computing system into seven distinct layers. It was developed by the International Organization for Standardization (ISO) to facilitate interoperability between different network and communication technologies. Each layer of the OSI model performs specific tasks and interacts with the adjacent layers to ensure the smooth transmission of data between devices on a network. The seven layers of the OSI model, from the lowest to the highest, are:

1. Physical Layer:

   ➤ The Physical Layer deals with the physical medium over which data is transmitted, such as cables, wireless signals, or fiber optics.

   ➤ It defines the electrical, mechanical, and functional specifications for the hardware required for transmission and reception of data.

2. Data Link Layer:

   ➤ The Data Link Layer is responsible for the reliable transmission of data between two directly connected devices on the same network segment.

   ➤ It also handles error detection and correction, as well as the flow control to ensure data is delivered without errors or data loss.

3. Network Layer:

   ➤ The Network Layer is involved in the routing of data packets between different networks.

   ➤ It determines the optimal path for data packets to reach their destination and handles addressing and forwarding.

4. Transport Layer:

   ➤ The Transport Layer ensures the reliable delivery of data between end systems (e.g., computers).

   ➤ It is responsible for segmenting data into smaller packets, reassembling them at the destination, and providing error recovery and flow control.

5. Session Layer:

   ➤ The Session Layer establishes, manages, and terminates communication sessions between applications running on different devices.

   ➤ It provides synchronization and checkpoint mechanisms to allow recovery from session failures.

6. Presentation Layer:

   ➤ The Presentation Layer is responsible for data representation and conversion, ensuring that data from the application layer of one system can be understood by the application layer of another system.

   ➤ It handles tasks like data encryption, compression, and character encoding.

7. Application Layer:

   ➤ The Application Layer is the topmost layer and interacts directly with applications and end-users.

   ➤ It provides various network services directly to user applications, such as file transfer, email, web browsing, and remote login.

It's important to note that the OSI model is a theoretical framework, and in practice, many network protocols and technologies do not strictly adhere to its exact layer definitions. The TCP/IP model, for example, is a more commonly used model for the internet and is often compared to the OSI model. Nevertheless, the OSI model remains a valuable reference for understanding how different networking functions relate to each other.