Jawaharlal Nehru Technological University Hyderabad B.Tech IV COMPUTER NETWORKS Previous Question Paper (September - 2020 - R16)

The ISO OSI (Open Systems Interconnection) reference model is a conceptual framework that standardizes the functions of a telecommunication or computing system into seven distinct layers to ensure interoperability between diverse communication systems. Each layer provides specific services to the layer above it while hiding the implementation details.

1. Physical Layer: Responsible for the transmission and reception of raw bit streams over a physical medium. It defines mechanical, electrical, and procedural specifications for interfaces, including voltage levels, timing, and cable characteristics.
2. Data Link Layer: Provides reliable node-to-node data transfer. It is responsible for framing, physical addressing (MAC addresses), error detection, and flow control. It is often divided into the Media Access Control (MAC) and Logical Link Control (LLC) sublayers.
3. Network Layer: Manages logical addressing and routing of packets across multiple networks. It determines the best path for data transmission and handles congestion control and packet forwarding.
4. Transport Layer: Ensures end-to-end communication and data integrity. It handles segmentation, reassembly, and error recovery. Common protocols include TCP (connection-oriented) and UDP (connectionless).
5. Session Layer: Establishes, manages, and terminates sessions between applications. It provides mechanisms for dialogue control, synchronization, and checkpointing of data streams.
6. Presentation Layer: Acts as a data translator. It handles data formatting, encryption, decryption, and compression to ensure that information sent from the application layer of one system is readable by the application layer of another.
7. Application Layer: The topmost layer that provides network services directly to end-user applications. It includes protocols like HTTP, FTP, SMTP, and DNS that facilitate user interaction with the network.