Module 3a data communication
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The document introduces the OSI model, a seven-layer architecture for networking. It was developed by ISO in the late 1970s to standardize network communication. Each layer has a specific role, from physical transmission of bits at the lowest layer, to application services at the highest layer. The layers work together to enable communication between applications running on different hosts.
Module 3a data communication
- 1. 2.1 Module-3 Network Models Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
- 2. 2.2 2-1 LAYERED TASKS2-1 LAYERED TASKS We use the concept ofWe use the concept of layerslayers in our daily life. As anin our daily life. As an example, let us consider two friends who communicateexample, let us consider two friends who communicate through postal mail. The process of sending a letter to athrough postal mail. The process of sending a letter to a friend would be complex if there were no servicesfriend would be complex if there were no services available from the post office.available from the post office.
- 3. 2.3 Figure 2.1 Tasks involved in sending a letter
- 4. 2.4 2-2 THE OSI MODEL2-2 THE OSI MODEL Established in 1947, the International StandardsEstablished in 1947, the International Standards Organization (Organization (ISOISO) is a multinational body dedicated to) is a multinational body dedicated to worldwide agreement on international standards. An ISOworldwide agreement on international standards. An ISO standard that covers all aspects of networkstandard that covers all aspects of network communications is the Open Systems Interconnectioncommunications is the Open Systems Interconnection ((OSIOSI) model. It was first introduced in the late 1970s.) model. It was first introduced in the late 1970s.
- 5. 2.5 ISO is the organization. OSI is the model. Note
- 6. 2.6 Figure 2.2 Seven layers of the OSI model
- 7. 2.7 Figure 2.3 The interaction between layers in the OSI model
- 8. 2.8 Figure 2.4 An exchange using the OSI model
- 9. 2.9 2-3 LAYERS IN THE OSI MODEL2-3 LAYERS IN THE OSI MODEL In this section we briefly describe the functions of eachIn this section we briefly describe the functions of each layer in the OSI model.layer in the OSI model. Physical Layer Data Link Layer Network Layer Transport Layer Session Layer Presentation Layer Application Layer Topics discussed in this section:Topics discussed in this section:
- 10. 2.10 Figure 2.5 Physical layer
- 11. 2.11 The physical layer is responsible for movements of individual bits from one hop (node) to the next. Note
- 12. 2.12 Figure 2.6 Data link layer
- 13. 2.13 The data link layer is responsible for moving frames from one hop (node) to the next. Note
- 14. 2.14 Figure 2.7 Hop-to-hop delivery
- 15. 2.15 Figure 2.8 Network layer
- 16. 2.16 The network layer is responsible for the delivery of individual packets from the source host to the destination host. Note
- 17. 2.17 Figure 2.9 Source-to-destination delivery
- 18. 2.18 Figure 2.10 Transport layer
- 19. 2.19 The transport layer is responsible for the delivery of a message from one process to another. Note
- 20. 2.20 Figure 2.11 Reliable process-to-process delivery of a message
- 21. 2.21 Figure 2.12 Session layer
- 22. 2.22 The session layer is responsible for data synchronization. Note
- 23. 2.23 Figure 2.13 Presentation layer
- 24. 2.24 The presentation layer is responsible for translation, compression, and encryption. Note
- 25. 2.25 Figure 2.14 Application layer
- 26. 2.26 The application layer is responsible for providing services to the user. Note
- 27. 2.27 Figure 2.15 Summary of layers