Computer Networking

1. 广西医科大学 ComputerNetworking 网络课件 双语教学 模拟实验 计算机网络教研室

2. DI 1 2 3 CHAPTER 3 Network Architetures and Standarts The first section Exercises Online lecture

3. 3-7 3-4 3-1 3-13 3-10 A caveat about Standards making org Advs and disadvs of standards Introduction Manufactures Architecture Why have Architecture ISO Reference Model The V.and X.standards 3-11 3-5 3-14 3-2 3-8 3-6 3-3 3-9 3-12 Communication Architecture Definition Architecture Internet Architecture Layered architecture Definition Architecture Chapter 3 Network Architetures and Standarts TCP/IP Architecture www.gxmu.edu.cn

4. Chapter 3 Network Architetures and Standarts OBJECTIVES Explain the difference between architectures and standards. Explain the need for network architecture and standards. Identify a number of communications standards-making org. Describe the OSI model architecture. Describe TCP/IP architecture. Describe the architecture of the Internet. Discuss the ADV and DISADV of layered architecture. www.gxmu.edu.cn

5. Chapter 3 Network Architetures and Standarts 3.1 Introduction Definitions of architectures and standards. The difference among them. The need of them Specific example of them Examine adv & disadv www.gxmu.edu.cn

6. Chapter 3 Network Architetures and Standarts 3.2 DEFINITION OF ARCHITECTURES AND STANDARDS Architecture: is a plan or direction that is oriented toward the needs of the user. Network architecture is a set of principles used as the basic for the design and implementation of a communications network. www.gxmu.edu.cn

7. Chapter 3 Network Architetures and Standarts It includes the organization of functions that must be performed by the network and the description of data formats and procedures. Network architecture=layer + protocols www.gxmu.edu.cn

8. Chapter 3 Network Architetures and Standarts Network architecture features May or may not conform to standards. Don’t provides enough detail how network to be implemented. Provides a set of generic concepts . Most architecture (plan) are designed for the long term use. www.gxmu.edu.cn

9. Hardware & Software Hardware & Software 1 DEVICE A DEVICE B Chapter 3 Network Architetures and Standarts Single Layer Model First Communication Between Computer Devices The communication and application software be intermingled (To mix). The early networks were not flexible. Single specification for all aspects of communication www.gxmu.edu.cn

10. Chapter 3 Network Architetures and Standarts IBM SNA(System Network Architecture) IBM : 1974 by the first computer network architectureIBM’s SNA is a proprietary architecture NOTE:Not SNA(storage area network) Most network architectures developed since use a layered approach. www.gxmu.edu.cn

11. Chapter 3 Network Architetures and Standarts Communication standard The rules that are established to ensure compatibility among similar communications products and services. Communications standards are the flesh on the architectural skeleton. They specify how a particular communications product, service,or interface will operate. V.90 modem www.gxmu.edu.cn

12. Chapter 3 Network Architetures and Standarts 3.3 why have network architectures? 1.Communication system were becoming too complex. 2. wanted to be isolated from the complexities of the network. 3.Wanted to connect different types of devices to the network. 4.Distributed processing and client-server processing became practical. 5.Network needed to be managed. www.gxmu.edu.cn

13. Chapter 3 Network Architetures and Standarts 3.4 TWO VIEWPOINTS ABOUT STANDARDS Background: Communications vendors realized early standards. computer manufacturers were slower to recognize the need for standards. Customers demanded that product was standardization. www.gxmu.edu.cn

14. Chapter 3 Network Architetures and Standarts One People who have a strong networking background see the computer as a tool to enhance a network`s capability. Tend to wait for standards and follow them closely. www.gxmu.edu.cn

15. Chapter 3 Network Architetures and Standarts Figure 3-1 Two different views of the relative roles of networks and computers. Two Those who have a strong computer background tend to focus on what can be done with software or specially designed circuit chips for computers. They forge ahead of the standards-making process www.gxmu.edu.cn

16. Chapter 3 Network Architetures and Standarts Purport While neither viewpoint is wrong ,it leads to differing philosophies. Both are legitimate and have their place. www.gxmu.edu.cn

17. Chapter 3 Network Architetures and Standarts 3.5 STANDS AND STANDS-MAKING ORGANIZATIONS Because of the recognized need for common international standards, there is a great deal of cooperation among communications standards making organizations. Data communication standards are more complicated than Voice communication standards. Early standards were mostly electrical in nature. The standards-setting process is slow. Writing standards is difficult work. www.gxmu.edu.cn

18. Chapter 3 Network Architetures and Standarts ITU (The International Telecommunication Union) 1865 in the U S was established in Paris, 1947 as part of the United Nations, members from 188 countries, headquartered in Geneva, Switzerland. The most important telecommunications standards-setting organization in the world is the ITU . ITU-T has created two sets of standards for the electrical connection of terminals to communications networks. www.gxmu.edu.cn

19. Chapter 3 Network Architetures and Standarts ISO:International Standards Organization Don’t confuse the OSI with ISO and IOS,. ISO :means the international organization for standardization. IOS :(internet operation system) is used in CISCO system’s routers and switches.  www.gxmu.edu.cn

20. Chapter 3 Network Architetures and Standarts Figure of the organizations involved in setting telecommunications standards or in passing input to the standards-setting bodies. The American National Standards Institute (ANSI) is not involved in setting communications standards. The official TCP/IP model is now maintained by the IETF. All communications standards are developed by one organization, the ISO.F www.gxmu.edu.cn

21. Chapter 3 Network Architetures and Standarts 3.6Ｖ.STANDARD X.STANDARD The ITU-T has created two sets of standards for the electrical connection of terminals to communications networks. They are called the V. and X. standards www.gxmu.edu.cn

22. Chapter 3 Network Architetures and Standarts V.standards : define the connection of digital equipment to the PSTN`s analog lines V.32, V.33, V.42 standard for the use of telephone transmission of data made a clear statement . X.standards: Define the connection of digital equipment to digital lines. E.G X.25, X.400, X.500 www.gxmu.edu.cn

23. Chapter 3 Network Architetures and Standarts 3.7 ADVANTAGES AND DISADVANTAGES OF STANDARDS Adv Standards allow products from multiple vendors to be connected to one another and to communicate. www.gxmu.edu.cn

24. Chapter 3 Network Architetures and Standarts disadvance The standards-setting process is slow. Standards tend to freeze technology. Multiple conflicting standards. The standards-setting process can occur quickly(Writing standards is relatively easy )， when an architecture is in place.F www.gxmu.edu.cn

25. Chapter 3 Network Architetures and Standarts 3.8 COMMUNICATIONS ARCHITECTURES ISO and ITU-T developed OSI reference model in 1978. OSI-RM: Open Systems Interconnection reference model. The standards development process took so long that the osi model never came into widespread use. It is the standard reference point by which data communications networks are described www.gxmu.edu.cn

26. Chapter 3 Network Architetures and Standarts 3.9 THE ISO`S OSI REFERENCE MODEL 3.9.1 Objective Provide a basis for interconnecting dissimilar systems for the purpose of information exchange. Define communications rules. www.gxmu.edu.cn

27. Chapter 3 Network Architetures and Standarts OSI and most network architecture use a layered approach. A layer in the OSI RM represents a component of the total process of communicating. Each one layer requests services from the layer below it. N layer Provide services to N+1 layer The same network, any two-system must have the same level. The actual physical communication completed  only in the bottom layer. www.gxmu.edu.cn

28. Chapter 3 Network Architetures and Standarts Why layering? 1) Layering forces the modularization of function . Dealing with complex systems. The output of laying definition process is standards. eases maintenance, updating of system. One layer can be changed without affecting other layers Different implementations can be substituted relatively Transparently。 www.gxmu.edu.cn

29. 前置处理机 中央主机 前置处理机CCP 中央主机 前置处理机 中央主机 Chapter 3 Network Architetures and Standarts Layer Layer requires reasonably sophisticated software and hardware at each end of the connection. www.gxmu.edu.cn

30. The philosopher-translator-Secretary architecture. Chapter 3 Network Architetures and Standarts www.gxmu.edu.cn

31. CN scientists Chapter 3 Network Architetures and Standarts Example:Scientific exchange layered Scientific opinion JP scientists protocol English JP Translate CN Translate protocol Letters CNTelegrafisten JPTelegrafisten protocol Telegraph code Telex machine Telex machine protocol www.gxmu.edu.cn

32. Chapter 3 Network Architetures and Standarts Network Architecture Layered principle Basic concept  ： Entity：Can send or receive any information of hardware / software process Peer layer：Two different systems the same level 。 Interface：Interaction between the two neighboring layer SERVE：for the upper classes a capacity to provide services through the interface Protocol：Communication both in communication must comply with the rules. www.gxmu.edu.cn

33. SYSB SYSA SYSB SYSA entity Peer layer Pn+1 N+1 N+1 server Pn N N peer entity Pn-1 N-1 N-1 P3 3 3 P2 Physical communication line 2 2 P1 1 1 Physical communication line Chapter 3 Network Architetures and Standarts Layered network Architecture interfact The way that the interaction between the layers actually takes place is that each one requests services from the layer above it. www.gxmu.edu.cn

34. Chapter 3 Network Architetures and Standarts Services The way that the interaction between the layers actually takes place is that each one requests services from the layer above it. Each layer provides services to the next higher layer www.gxmu.edu.cn

35. Chapter 3 Network Architetures and Standarts Service Primitives www.gxmu.edu.cn

36. Chapter 3 Network Architetures and Standarts Relations among Service Primitives 服务用户 （N+1） 服务提供者 （N） 服务提供者 （N） 服务用户 （N+1） 系统A 系统B Request PDU Indication 需证实 Response Confirm 无需证实 Request Indication www.gxmu.edu.cn

37. Chapter 3 Network Architetures and Standarts 电话系统工作示例 www.gxmu.edu.cn

38. Chapter 3 Network Architetures and Standarts Services, interface protocols and functions Protocols can provide a service for upper layer . Protocols is “level”， But Services is “Vertical ”， Service is adopted by the lower layer of interface. Functions is the internal activities 。 www.gxmu.edu.cn

39. Services to Protocols Relationship The relationship between a service and a protocol. Chapter 3 Network Architetures and Standarts www.gxmu.edu.cn

40. Chapter 3 Network Architetures and Standarts Layers of the ISO’s OSI reference model. A layer in the OSI model represents a compon- ent of the total process of communicating. T The layers of the OSI model on each node communicate with each other. www.gxmu.edu.cn

41. Chapter 3 Network Architetures and Standarts Actual communication passes down through the layers on the sending node and then up through the layers on the receiving node. www.gxmu.edu.cn

42. Chapter 3 Network Architetures and Standarts X.25 The first three layers of the OSI model have been standardized, and together are called the X.25 standard for data transmission. www.gxmu.edu.cn

43. Chapter 3 Network Architetures and Standarts GOSIP government open system Interconnetion Protocol. a subset of the OSI model that vendors must support if they want to sell network services or equipment to the U.S. government. GOSIP is neither a new architecture nor a New standard.It is a more precise specification of what parts of the OSI model the government will use. www.gxmu.edu.cn

44. Chapter 3 Network Architetures and Standarts 3.9.2The Function Of Each Layer LAYER 1 THE PHYSICAL LINK LAYER It specifies the electrical characteristics between the communications line and the terminal or computer . Cabling Interconnect methods (topology / devices) Data encoding (bits to waves) Electrical properties www.gxmu.edu.cn

45. Chapter 3 Network Architetures and Standarts Typical equipment What are the Physical Layer components on my computer? www.gxmu.edu.cn

46. Chapter 3 Network Architetures and Standarts Physical Layer This is the only layer at which actual bits pass. The only layer that is implemented strictly in hardware. The only layer that actually communicates across the transmission line to the other node. Layer1 only knows about a strem of bits. Data transmission unit is bits.  Transmission media does not belong to the physical layer.  www.gxmu.edu.cn

47. Chapter 3 Network Architetures and Standarts www.gxmu.edu.cn

48. Chapter 3 Network Architetures and Standarts LAYER2 THE DATA LINK LAYER Function Framing（成帧） Line discipline Flow control Error control www.gxmu.edu.cn

49. Chapter 3 Network Architetures and Standarts Data link layer It is responsible for establishing a link between two points on a network and ensuring that data are successfully transferred between the two points . Divide the data into smaller units for transmission.（FRAME） Detecting transmission errors and correcting errors. www.gxmu.edu.cn

50. Chapter 3 Network Architetures and Standarts www.gxmu.edu.cn