The document discusses the layered architecture model known as the Open Systems Interconnection (OSI) model. The OSI model contains seven layers that each perform a specific communication function and rely on the layer below. It describes the functions of each layer, including the physical, data link, network, transport, session, presentation, and application layers. The layered design philosophy breaks communication tasks into simpler sub-tasks at each independent layer to standardize network communication.

1. – Layered Architecture By: Abid Shahzad Aslam

2. Lecture–Roadmap Need of a Layered Architecture OSI Model 7 Layers of OSI Model Functional Details of OSI Layers Physical Layer Data Link Layer Network Layer Transport Layer Session Layer Presentation Layer Application Layer

3. Layered Architecture Design Philosophy of Layered Architecture The complex task of communication is broken into simpler sub-tasks or modules Each layer performs a subset of the required communication functions Each layer relies on the next lower layer to perform more primitive functions Each layer provides services to the next higher layer Changes in one layer should not require changes in other layers Helps in troubleshooting and identifying the problem

4. An example Sending a letter

5. OSI Model To standardize the design of communication system, the ISO created the OSI model. Open Systems Interconnection Developed by the International Organization for Standardization (ISO) Contains Seven layers It describes the functions to be performed at each layer

6. OSI Model ISO Established in 1947 ISO standard that covers all aspects of network communications is the Open Systems Interconnection ( OSI ) model. First introduced in the late 1970s. A layer model Each layer performs a subset of the required communication functions Each layer relies on the next lower layer to perform more primitive functions Each layer provides services to the next higher layer Changes in one layer should not require changes in other layers

7. ISO is the organization. OSI is the model. Note

8. OSI Model Physical Data Link Network Transport Session Presentation Application

9. Peer-to-Peer Process

10. An exchange using the OSI model

11. OSI Model – Physical Layer Physical Physical interface between devices handles the transmission of bits over a communications channel Choice of Wired / wireless medium Data is converted into signals Includes voltage levels, connectors, media choice modulation techniques EIA/TIA-232, RJ45, NRZ.

12. Physical Layer

13. The physical layer is responsible for movements of individual bits from one hop (node) to the next. Note

14. OSI Model – Data Link Layer • Data Link – Transforms data into a frame – Means of activating, maintaining and deactivating a reliable link – Error detection and control – Flow Control – Higher layers may assume error free transmission Examples :- Ethernet, Frame Relay, FDDI.

15. Data Link Layer

16. The data link layer is responsible for moving frames from one hop (node) to the next. Note

17. OSI Model – Network Layer Network – Transport of information – Higher layers do not need to know about underlying technology – Responsible for creating, maintaining and ending network connections – Transfers a data packet from node to node within the network . – Routing – Not needed on direct links Examples :- IP, IPX, AppleTalk.

18. Network Layer

19. The network layer is responsible for the delivery of individual packets from the source host to the destination host. Note

20. Transport Layer Transport – Exchange of data between end systems (end to end flow control) – Error free – In sequence – Quality of service Layer 4 protocols include TCP (Transmission Control Protocol) and UDP (User Datagram Protocol).

21. Transport Layer

22. The transport layer is responsible for the delivery of a message from one process to another. Note

23. OSI Model – Session Layer Session – Control of dialogues between applications Half Duplex Full Duplex – Synchronization Points (backup points) – Grouping Examples :- SQL, ASP(AppleTalk Session Protocol).

24. The session layer is responsible for dialog control and synchronization. Note

25. OSI Model – Presentation Layer Presentation – Data formats and coding – Data compression – Encryption Examples :- JPEG, MPEG, ASCII, EBCDIC, HTML.

26. The presentation layer is responsible for translation, compression, and encryption. Note

27. OSI Model – Application Layer Application – Layer where the application using the network resides. – Common network applications include remote login file transfer e-mail web page browsing etc. – Means for applications to access OSI environment

28. The application layer is responsible for providing services to the user. Note

29. Summary of layers

30. OSI Layers

31. OSI Layers

32. The OSI Environment

33. The OSI Environment