The document discusses network models and layers. It covers the layered architecture of the Internet model and OSI model. The key points are: 1. The Internet and OSI models use a layered approach to break down the complex process of network communication into smaller, well-defined functions. 2. The Internet model has 5 layers - physical, data link, network, transport, and application. The OSI model adds an additional session layer and presentation layer. 3. Each layer only interacts with the layers directly above and below it, performing specific tasks like physical addressing, routing, and providing end-user services.

1. Ch.2 Network Models Lecturer: Tae-Hyong Kim (D132) [email_address]

2. Contents Introduction Layered Tasks Internet Model OSI Model Assignment #1

3. Introduction The process of networking Think about the process of solving a mathematical problem Computer hardware Operating system Problem solving program  Layered architecture (shell, pyramid) How about sending an e-mail?

4. Contents Introduction Layered Tasks Internet Model OSI Model Assignment #1

5. Sender, Receiver, and Carrier Sending a letter  There is a Hierarchy !

6. Contents Introduction Layered Tasks Internet Model Peer-to-peer Processes Functions of Layers OSI Model Assignment #1

7. Internet Layers Today’s layered protocol stack 5-layer model TCP/IP protocol suite model

8. Internet Layers Layers involved in sending message from device A to B

9. Peer-to-Peer Processes Layered architecture concept Physical interaction Logical interaction

10. Interfaces and Organization Organization of the Layers: three subgroups Network support layers: Layers 1, 2, and 3 User support layer: layer 5 Transport layer: layer 4

11. Overall View of the Layers

12. Functions of Layers Physical Layer Data Link Layer Network Layer Transport Layer Application Layer

13. Physical Layer For transmitting individual bits from one node to the next Handles mechanical and electrical specification of the interface and transmission medium

14. Physical Layer Factors Physical characteristics of interfaces and media Representation of bits Data rate (transmission rate) Synchronization of bits

15. Data Link Layer For hop-to-hop (node-to-node) delivery of frames makes the physical layer appear error free to the upper layer (network layer)

16. Data Link Layer Specific responsibilities Framing Physical addressing Flow control Error control Access control

17. Data Link Layer hop-to-hop delivery

18. Data Link Layer Physical Addresses

19. Network Layer For Source-to-destination delivery of packets

20. Network Layer Specific responsibilities Logical addressing Routing

21. Network Layer Source-to-destination delivery

22. Network Layer Logical addresses (IP addresses)

23. Transport layer For process-to-process delivery of a message

24. Transport layer Specific responsibility Port addressing Segmentation and reassembly Connection control Flow control Error control

25. Transport layer Process-to-process delivery

26. Transport layer Port addresses

27. Application Layer For providing services to the user E.g., user interfaces and user support

28. Application Layer Specific services : Human interface services Mail Services File transfer, access Remote log-in Accessing the World Wide Web

29. Summary of Layers

30. Summary of Addresses ex. e-mail address, URL

31. Review Questions 2-1 Match the following to one of five Internet layers Route determination Flow control Interface to transmission media Provides access to the end user

32. Review Questions 2-2 In the following figure, computer A sends a message to computer D via LAN1, router R1, and LAN2. Show the contents of the packets and frames at the network and data link layer for each hop interface.

33. Review Questions 2-3 Suppose a computer sends a frame to another computer on a bus topology LAN. The physical destination address of the frame is corrupted during the transmission. What happens to the frame? How can the sender be informed about the situation? Consider error control feature of data link layer

34. Contents Introduction Layered Tasks Internet Model OSI Model Assignment #1

35. OSI Model Open System Interconnection model (in 1977) cf. ISO : a standard organization Standard : ISO 7498 (in 1984), ITU-T X.200 7-layer model

36. Session Layer Controls the network dialog establishes, maintains, and synchronizes the interaction between communicating systems

37. Session Layer Session The period of time for which two users remain logically connected ex. Session layer dialog

38. Session Layer Specific responsibility : User-oriented connection service Dialog control Synchronization

39. Presentation Layer concerned with the syntax and semantics of the information exchange between two systems

40. Presentation Layer Specific responsibility Code conversion Encryption/Decryption Compression

41. The Internet and OSI Models

42. TCP/IP protocol suite was developed prior to the OSI model. Not match exactly with those in the OSI model Around 1980, everyone was convinced that TCP/IP soon would be replaced by OSI protocols for layer 3-4. However, This did not happen Problem of the OSI model Repeated data exchanging between layers (much overhead) Conceptual and Theoretical model The Internet and OSI Models

43. Integrated Architecture Layered Architecture Cross-Layered Architecture Cross-Layered Architecture?

44. Exercises 17, 18, 19, 20, 23, 24, 25 Explain why for each answer Due Date The next class Assignment #1