OSI Layers


OSI model
Open Systems Interconnection (OSI) model

The Open Systems Interconnection (OSI) model is a conceptual model that characterizes and standardizes the internal workings of computers and communication networks. It was developed in the 1970s by the International Organization for Standardization (ISO) and is still used today.



OSI model history


The Open Systems Interconnection (OSI) model is a conceptual model that characterizes and standardizes the internal workings of a communication system in terms of seven abstraction layers.


Developed in the 1970s, the OSI model was originally designed as a way to standardize the communication process between different types of computer systems.


Since its development, the OSI model has become a widely-used tool for describing and understanding the complex process of communication. Today, the OSI model is used in both academic and industrial settings and is a key component of many communication-related standards.



Seven layers of OSI model


The OSI model has seven layers, each of which corresponds to a specific function in the communication process. The layers are:

  1. Physical layer: The physical layer is responsible for transmitting raw data over a communication channel. It handles the physical aspects of the transmission, such as voltage levels, timing, and error detection.

  2. Data link layer: The data link layer is responsible for formatting data into packets and ensuring that they are properly sequenced and error-free. It also handles the physical addressing of packets, so that they are delivered to the correct destination.

  3. Network layer: The network layer is responsible for routing packets between networks. It determines the best path for packets to take and maintains information about the network topology.

  4. Transport layer: The transport layer is responsible for ensuring the reliable delivery of packets between hosts. It handles the sequencing and reordering of packets, as well as the detection and correction of errors.

  5. Session layer: The session layer establishes and maintains communication sessions between hosts. It manages the exchange of data between the transport and presentation layers.

  6. Presentation layer: The presentation layer converts data from the application layer into a format that can be transmitted over the network. It also performs data compression and decompression.

  7. Application layer: The application layer is responsible for the actual communication between hosts. It provides the interface between the user and the network.


Advantages of OSI Model


The OSI model has a number of advantages over other networking models:

  1. It is layered, which makes it easier to understand and troubleshoot.

  2. It is modular, which makes it easier to update and expand.

  3. It is standards-based, which makes it easier to integrate with other networking technologies.

  4. It is scalable, which makes it suitable for both small and large networks.


Knowing the OSI model can be beneficial for a variety of reasons. For example, understanding the different layers can help you troubleshoot system problems, and it can also help you better understand how different systems work together. Additionally, having a conceptual model like the OSI model can be helpful when designing or implementing a new system, as it can provide a framework for thinking about the system as a whole.



OSI players and cyber security


When viewed from the cybersecurity point of view, the physical layer of the OSI model is responsible for ensuring the physical security of the network infrastructure, while the data link layer is responsible for ensuring the security of data transmissions between devices on the network. The network layer is responsible for routing data packets between devices, and the transport layer is responsible for ensuring the safe and reliable delivery of data packets. The session layer manages the connections between devices, the presentation layer ensures that data is properly formatted for transmission, and the application layer provides the interface for users to access the network.


Cyber security is essential for protecting the confidentiality, integrity, and availability of data. By understanding the OSI model and the functions of each layer, organizations can better protect their electronic information from cyber threats.