Osi Model


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Osi Model

  1. 1. – Layered Architecture By: Abid Shahzad Aslam
  2. 2. Lecture–Roadmap <ul><li>Need of a Layered Architecture </li></ul><ul><li>OSI Model </li></ul><ul><ul><li>7 Layers of OSI Model </li></ul></ul><ul><ul><li>Functional Details of OSI Layers </li></ul></ul><ul><ul><ul><li>Physical Layer </li></ul></ul></ul><ul><ul><ul><li>Data Link Layer </li></ul></ul></ul><ul><ul><ul><li>Network Layer </li></ul></ul></ul><ul><ul><ul><li>Transport Layer </li></ul></ul></ul><ul><ul><ul><li>Session Layer </li></ul></ul></ul><ul><ul><ul><li>Presentation Layer </li></ul></ul></ul><ul><ul><ul><li>Application Layer </li></ul></ul></ul>
  3. 3. Layered Architecture <ul><li>Design Philosophy of Layered Architecture </li></ul><ul><ul><li>The complex task of communication is broken into simpler sub-tasks or modules </li></ul></ul><ul><ul><li>Each layer performs a subset of the required communication functions </li></ul></ul><ul><ul><li>Each layer relies on the next lower layer to perform more primitive functions </li></ul></ul><ul><ul><li>Each layer provides services to the next higher layer </li></ul></ul><ul><ul><li>Changes in one layer should not require changes in other layers </li></ul></ul><ul><ul><li>Helps in troubleshooting and identifying the problem </li></ul></ul>
  4. 4. An example Sending a letter
  5. 5. OSI Model <ul><li>To standardize the design of communication </li></ul><ul><li>system, the ISO created the OSI model. </li></ul><ul><li>Open Systems Interconnection </li></ul><ul><li>Developed by the International Organization </li></ul><ul><li>for Standardization (ISO) </li></ul><ul><li>Contains Seven layers </li></ul><ul><li>It describes the functions to be performed at </li></ul><ul><li>each layer </li></ul>
  6. 6. OSI Model <ul><li>ISO Established in 1947 </li></ul><ul><li>ISO standard that covers all aspects of network communications is the Open Systems Interconnection ( OSI ) model. </li></ul><ul><li>First introduced in the late 1970s. </li></ul><ul><li>A layer model </li></ul><ul><li>Each layer performs a subset of the required </li></ul><ul><li>communication functions </li></ul><ul><li>Each layer relies on the next lower layer to </li></ul><ul><li>perform more primitive functions </li></ul><ul><li>Each layer provides services to the next </li></ul><ul><li>higher layer </li></ul><ul><li>Changes in one layer should not require </li></ul><ul><li>changes in other layers </li></ul>
  7. 7. ISO is the organization. OSI is the model. Note
  8. 8. OSI Model Physical Data Link Network Transport Session Presentation Application
  9. 9. Peer-to-Peer Process
  10. 10. An exchange using the OSI model
  11. 11. OSI Model – Physical Layer <ul><li>Physical </li></ul><ul><ul><li>Physical interface between devices </li></ul></ul><ul><ul><li>handles the transmission of bits over a </li></ul></ul><ul><li>communications channel </li></ul><ul><ul><li>Choice of Wired / wireless medium </li></ul></ul><ul><ul><li>Data is converted into signals </li></ul></ul><ul><ul><li>Includes voltage levels, connectors, media choice </li></ul></ul><ul><ul><li>modulation techniques </li></ul></ul><ul><ul><li>EIA/TIA-232, RJ45, NRZ. </li></ul></ul>
  12. 12. Physical Layer
  13. 13. The physical layer is responsible for movements of individual bits from one hop (node) to the next. Note
  14. 14. OSI Model – Data Link Layer <ul><li>• Data Link </li></ul><ul><li>– Transforms data into a frame </li></ul><ul><li>– Means of activating, maintaining and </li></ul><ul><li> deactivating a reliable link </li></ul><ul><li>– Error detection and control </li></ul><ul><li>– Flow Control </li></ul><ul><li>– Higher layers may assume error free </li></ul><ul><li>transmission </li></ul><ul><ul><li>Examples :- Ethernet, Frame Relay, FDDI. </li></ul></ul>
  15. 15. Data Link Layer
  16. 16. The data link layer is responsible for moving frames from one hop (node) to the next. Note
  17. 17. OSI Model – Network Layer <ul><li>Network </li></ul><ul><li>– Transport of information </li></ul><ul><li>– Higher layers do not need to know </li></ul><ul><li>about underlying technology </li></ul><ul><li>– Responsible for creating, maintaining </li></ul><ul><li>and ending network connections </li></ul><ul><li>– Transfers a data packet from node to </li></ul><ul><li>node within the network . </li></ul><ul><li>– Routing </li></ul><ul><li>– Not needed on direct links </li></ul><ul><ul><li>Examples :- IP, IPX, AppleTalk. </li></ul></ul>
  18. 18. Network Layer
  19. 19. The network layer is responsible for the delivery of individual packets from the source host to the destination host. Note
  20. 20. Transport Layer <ul><li>Transport </li></ul><ul><li>– Exchange of data between end </li></ul><ul><li>systems (end to end flow control) </li></ul><ul><li>– Error free </li></ul><ul><li>– In sequence </li></ul><ul><li>– Quality of service </li></ul><ul><li>Layer 4 protocols include TCP (Transmission Control Protocol) and UDP (User Datagram Protocol). </li></ul>
  21. 21. Transport Layer
  22. 22. The transport layer is responsible for the delivery of a message from one process to another. Note
  23. 23. OSI Model – Session Layer <ul><li>Session </li></ul><ul><li>– Control of dialogues between </li></ul><ul><li> applications </li></ul><ul><li>Half Duplex </li></ul><ul><li>Full Duplex </li></ul><ul><li>– Synchronization Points (backup points) </li></ul><ul><li>– Grouping </li></ul><ul><ul><li>Examples :- SQL, ASP(AppleTalk Session Protocol). </li></ul></ul>
  24. 24. The session layer is responsible for dialog control and synchronization. Note
  25. 25. OSI Model – Presentation Layer <ul><li>Presentation </li></ul><ul><li>– Data formats and coding </li></ul><ul><li>– Data compression </li></ul><ul><li>– Encryption </li></ul><ul><ul><li>Examples :- JPEG, MPEG, ASCII, EBCDIC, HTML. </li></ul></ul>
  26. 26. The presentation layer is responsible for translation, compression, and encryption. Note
  27. 27. OSI Model – Application Layer <ul><li>Application </li></ul><ul><li>– Layer where the application using the </li></ul><ul><li>network resides. </li></ul><ul><li>– Common network applications include </li></ul><ul><li>remote login </li></ul><ul><li>file transfer </li></ul><ul><li>e-mail </li></ul><ul><li>web page browsing etc. </li></ul><ul><li>– Means for applications to access OSI environment </li></ul>
  28. 28. The application layer is responsible for providing services to the user. Note
  29. 29. Summary of layers
  30. 30. OSI Layers
  31. 31. OSI Layers
  32. 32. The OSI Environment
  33. 33. The OSI Environment