network models

Computer Network Models

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In order to have a data communication between two entities , one end must transmit or send data, while the other end must receive the same without any alteration or modification. To achieve this, we need a systematic approach that enables users to communicate or transmit data in an efficient manner and that approach is called the network model.

Computer network models are blueprints that define how data is transmitted and received over a network. These models provide a common framework for network devices and software to communicate with each other, ensuring that products from different vendors can interoperate. It follows the layered approach to split specific task to perform independently and depends on its adjacent layers only for data exchange.

There are two most famous layered architecture for data communication.

  • OSI Model
  • TCP/IP Model

The OSI Model

The OSI model is a theoretical, seven-layer framework for understanding network communication. It’s used as a reference to describe how data is processed as it moves from one device to another. Each layer has specific functions and communicates with the layers directly above and below it.

The 7 Layers of the OSI Model

  1. Physical Layer (Layer 1): This layer deals with the physical connection between devices. It defines the electrical and physical specifications of the network, such as cables, connectors, and voltage levels. It’s responsible for transmitting raw bit streams (1s and 0s) over a physical medium.
  2. Data Link Layer (Layer 2): This layer provides error-free transmission of data over a physical link. It organizes the raw bits from the physical layer into frames and handles error detection and correction. It also manages access to the network medium.
  3. Network Layer (Layer 3): The network layer is responsible for routing data from one network to another. It uses logical addressing, like IP addresses, to determine the best path for data to travel. Data units at this layer are called packets.
  4. Transport Layer (Layer 4): This layer ensures end-to-end data delivery between hosts. It takes data from the session layer and segments it, adding sequencing and error-checking information. Key protocols at this layer include TCP (Transmission Control Protocol) and UDP (User Datagram Protocol).
  5. Session Layer (Layer 5): This layer establishes, manages, and terminates the communication sessions between two devices. It’s responsible for synchronization and dialogue control, ensuring that the session stays open long enough to transfer all the data.
  6. Presentation Layer (Layer 6): The presentation layer is concerned with the syntax and format of the data. It translates data into a format that the receiving application can understand, handling tasks like encryption, decryption, and data compression.
  7. Application Layer (Layer 7): This is the layer that directly interacts with the user’s software. It provides network services to applications and is where protocols like HTTP (for web Browse), FTP (for file transfers), and SMTP (for email) operate.

The TCP/IP Model

The TCP/IP model is a more practical, four-layer model that is the foundation of the internet. It was developed to be a simpler and more protocol-driven model than the OSI model.

The 4 Layers of the TCP/IP Model

  1. Network Access Layer: This layer combines the functions of the OSI model’s Physical and Data Link layers. It handles the physical transmission of data over the network medium and the hardware addressing (like MAC addresses) needed to communicate on a local network.
  2. Internet Layer: This layer is equivalent to the OSI’s Network layer. It is responsible for routing packets across different networks using IP addresses. The main protocol here is the Internet Protocol (IP).
  3. Transport Layer: This layer provides end-to-end communication and data delivery. It uses protocols like TCP for reliable, connection-oriented data transfer and UDP for faster, connectionless transfer.
  4. Application Layer: This layer combines the functions of the OSI’s Application, Presentation, and Session layers. It provides services directly to user applications through protocols such as HTTP, FTP, and DNS.

Conclusion

Hope you understand the basic concepts of network models and how they are important in data communication. We will discuss OSI Model and TCP/IP separately in details in the next post

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