COMPUTER NETWORKS

[Audio] COMPUTER NETWORKS UNIT – I OSI MODEL PREPARED BY G.GEERTHIGA,AP/AD.

[Audio] OSI NETWORK ARCHITECTURE(OSI MODEL) The OSI (Open Systems Interconnection)Model is a framework that standardizes how different network protocals interact in seven layers. Each layer has specific responsibilities in ensuring communication across a network..

[Audio] OSI LAYERS. OSI LAYERS. 7 6 5 4 3 2 Application Layer Presentation Layer session Layer Transport Layer Network Layer Data Link Layer Physical Layer Human-computer interaction layer, where applications can access the network services Ensures That data iS in a usable format and iS where data encryption occurs Maintains connections and is responsible for controlling ports and sessions Transmits data using transmission protocols including TCP and UDP Decides which physical path the data will take Defines the format of data on The network Transmits raw bit stream over the physical medium.

[Audio] FUNCTION : Physical Layer: First layer is the physical layer, which deals with the physical aspects (such as cables, connectors, and signaling) of transmitting data between two devices. This layer define transmission mode also whether it is simplex, half duplex or full duplex. It define topology configuration. Data Link Layer: The second layer is the data link layer, which is responsible for establishing and maintaining communication between two devices on the same network. Data link layer is responsible for moving frames from one hope to next hope. Network Layer: The third layer is the network layer, which handles the routing of data between networks. Network layer is responsible for the delivery of individual packet from source to destination. OSI LAYERS.

[Audio] Transport Layer: The fourth layer is the transport layer, which ensures reliable transmission of data between two devices. Transport layer is responsible for process to process delivery. A process is an application program running on a host. Session Layer: The fifth layer is the session layer it is also known as network dialog controller, which establishes and manages sessions between applications. Presentation Layer: The sixth layer is the presentation layer, which deals with the syntax and semantics of the data being transmitted. Application Layer: Seventh layer is the application layer, which provides services to applications for network communication..

[Audio] How Data Flows Through the OSI Model? The OSI Model (Open Systems Interconnection) is like a roadmap for how data travels from one device to another over a network. Here each layer handling a specific job..

[Audio] Physical Layer: Sends raw data (like bits, which are 1s and 0s) through cables or wireless signals. Data Link Layer: Packages the raw data into chunks called frames and checks for any errors. Network Layer: Finds the best route for the data to travel and adds addresses (like IP addresses) so it knows where to go. Transport Layer: Breaks the data into smaller pieces (called segments) and ensures everything arrives correctly and in order. Session Layer: Manages the conversation between two devices, making sure they stay connected during the data exchange. Presentation Layer: Translates the data into a format that the receiving device can understand, like converting text or images. Application Layer: This is where the user interacts with the data through apps like web browsers, email, or games..

[Audio] Helps understand how networks work It breaks communication into clear steps (layers), making networking easier to learn and understand. Makes troubleshooting easier If something goes wrong, you can find which layer has the problem instead of guessing blindly. Allows different technologies to work together Devices from different companies can communicate because they follow the same layered rules. Guides network design and development Engineers use it to build, upgrade, and improve networks in an organized way. Why Does The OSI Model Matter?.

[Audio] Here are some of the key uses of the OSI model: Facilitates Communication: The OSI model defines a clear and standardized set of protocols for communication between different devices on a network. This ensures that devices from different manufacturers can communicate with each other seamlessly. Helps in Network Design: The OSI model helps network designers and administrators to understand how different protocols and technologies work together to provide network communication. This understanding is essential when designing new networks or upgrading existing ones. Simplifies Troubleshooting: If there is a problem in the network, the OSI model helps isolate the problem to a specific layer. This makes it easier for network administrators to troubleshoot and fix the issue quickly. Encourages Interoperability: The OSI model promotes interoperability between different devices and software from different vendors. This means that devices can work together regardless of their origin. Provides a Common Language: The OSI model provides a common language and framework for network communication. This helps network administrators and engineers to communicate effectively about network issues and solutions. What is an OSI Model Used for?.

[Audio] Key Issues of the OSI Model Here are some of the key issues of the OSI model: Too Complex: The OSI model has seven layers, which can make it difficult for some people to understand. This complexity can make it hard for network administrators to troubleshoot issues, as it can be challenging to determine which layer is causing the problem. Not Always Practical: The OSI model is a theoretical model that is not always practical in real-world network communication. In practice, some layers may be combined or omitted altogether. Not Widely Adopted: While the OSI model is widely used as a reference model, it is not always used in practice. Instead, many networks use a simplified model, such as the TCP/IP model. Limited Scope: The OSI model is focused solely on network communication and does not cover other aspects of computer systems, such as storage or processing. Limited Flexibility: The OSI model is a fixed model that does not allow for much flexibility in terms of adapting to new technologies or protocols..

[Audio] In the early days of computer networking (1960s-1970s), different companies made their own systems that couldn’t easily talk to each other. This made sharing information across networks very difficult. As the internet and networking grew, people needed a common set of rules so that devices from different companies (like IBM, Apple, or others) could communicate. The International Organization for Standardization (ISO) saw this problem and wanted to create a universal way to connect systems worldwide. In 1984, the OSI Model was developed by ISO. It was designed to standardize the way data is transmitted between devices. The model broke the communication process into 7 layers, making it easier to understand and fix problems in networks. History of the OSI Model.

[Audio] Characteristics of the OSI Model It is the conceptual model that enables the diverse communication systems to communicate using the network. It was developed by the ISO (International Organization for Standardization) in 1984. It acts as an architecture for inter-computer communications. It is divided into 7 layers and each layer performs a particular task. Each layer is independent of the other and can perform its operations independently..

[Audio] CONCLUSION The OSI Model provides a clear framework for understanding how data communication works. It simplifies network design, learning, and troubleshooting by dividing tasks into layers. It ensures standardization and compatibility between different networking technologies. Overall, it helps in building efficient, reliable, and secure networks..