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OSI Reference Model

 

Communication Standards in Computer Networks: OSI Reference Model

Computer networks are the cornerstone of communication and data exchange in today's digital world. To understand and standardise the complexity of these networks, the OSI (Open Systems Interconnection) reference model is considered a milestone in the field of computer networking. Developed by the International Standards Organisation (ISO) in the late 1970s, this model organises and standardises network communication by dividing it into seven different layers.

Basic Functions of the Model

The OSI model allows us to understand the functioning of computer networks and offers the possibility to analyse these networks by breaking them down. Among its main functions are the following:

  • It defines and enables the communication of network components. This determines how data transfer between different devices takes place.
  • It determines how data is transferred from the sending device to the receiving device. This includes how data packets are created, sent and received.
  • It facilitates communication between different hardware and software. This enables different types of devices and operating systems to work harmoniously.
  • It enables different operating systems to communicate harmoniously. This enables communication between devices with various operating systems.

Layers and Descriptions of the Model

The OSI reference model divides network communication into seven layers. Each layer fulfils a specific function and enables data transmission by communicating with the layers above and below it. These layers make network communication easier to understand and standardise. The layers are as follows:

  1. Physical Layer: Handles electrical signals, cables and physical connections in data transmission. It is responsible for physically sending and receiving data. For example, this layer includes physical connections such as Ethernet cable.
  2. Data Link Layer: Provides secure data communication over physical lines and performs error correction. It also converts data packets into a specific format called a frame. Protocols such as Ethernet and Wi-Fi are available at this layer.
  3. Network Layer: It is responsible for routing data packets between source and destination and identifies devices with IP addresses. This layer is the data routes packets on different networks and provides communication between devices on the internet. Protocols such as IP and ICMP are found in this layer.
  4. Transport Layer: It regulates the data flow, ensures its integrity and performs error control. This layer provides end-to-end communication and carries it by dividing it into parts called data segments. Protocols such as TCP and UDP are found at this layer.
  5. Session Layer: It provides the establishment, management and termination of a session between two devices. The session layer ensures synchronisation during data exchange. This layer determines the beginning and end of the data flow.
  6. Presentation Layer: Provides inter-format conversions of data and performs compression functions. The presentation layer determines how data is displayed, encoded and compressed. This layer includes data compression formats such as JPEG and MPEG.
  7. Application Layer: This is the layer where users interact with network applications. Protocols and applications reside here, such as web browsers, e-mail clients, and file transfer protocols. This layer is the top layer with which users interact directly.

Each layer performs a specific function and communicates with the layers above and below it, enabling data transmission. This modular structure facilitates the development, testing and maintenance of network protocols. The OSI reference model provides a basic conceptual framework for understanding and managing the complexity of computer networks.

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