1. Chapter 1 Introduction 1.1Network and the Internet Network and the InternetNetwork and the Internet 1.1.1 Traditional Needs of Networking Traditional Needs of NetworkingTraditional Needs of Networking 1.1.2 The needs of Home Networks The needs of Home NetworksThe needs of Home Networks 1.1.3 Networking and Economics Networking and EconomicsNetworking and Economics 1.2Network Hardware Components Network Hardware ComponentsNetwork Hardware Components 1.2.1 Servers Servers 1.2.2 Workstations Workstations 1.2.3 Connecting Devices Connecting DevicesConnecting Devices 1.2.4 Networking Medium Networking MediumNetworking Medium

2. Chapter 1 Introduction 1.1 Network and the Internet (1/4) zA network is a set of nodes connected together by a shared medium. yA node can be a computer or a connecting device. xIt is any device with an IP address. xA computer on a network is also called a host. yThe medium may be a cable or radio wave zThe most elementary network yconnects two computers together using a cross-over cable. zThe Internet is a large collection of networks.

3. Chapter 1 Introduction 1.1 Network and the Internet (2/4)

4. Chapter 1 Introduction 1.1 Network and the Internet (3/4) zThe Internet and a home network: ythey use the same protocol xto connect and send information. zTechnologies to connect a network to the Internet: ydial-up access yDSL ycable modems ywireless technologies etc.

5. Chapter 1 Introduction 1.1 Network and the Internet (4/4)

6. Chapter 1 Introduction 1.1.1 Traditional Needs of Networking zNetworking is yto connect computers together for the purpose of xcommunication, and xsharing of resources. yThe resources on a network refer to xdata xhardware xsoftware, and xservices (e.g. Internet access).

7. Chapter 1 Introduction 1.1.1 Traditional Needs of Networking zA. Sharing of Data Sharing of DataSharing of Data zB. Sharing of Hardware Sharing of HardwareSharing of Hardware zC. Sharing of Software Sharing of SoftwareSharing of Software zD. Communication Communication zE. Internet Sharing Internet SharingInternet Sharing

8. Chapter 1 Introduction 1.1.1 Traditional Needs of Networking A. Sharing of Data zOn a network, folders and files in a computer can be shared out yto allow authorised users to access from other computers. zA file server has ya larger storage capacity, and yallows access to files by different users. zAdvantages: yBetter Version Control xUser can always access the most updated version of data which may be modified by different users. xWithout a network, the same file may be stored in several computers -- it is difficult to tell which one is the most updated. yData treated with more intensive care xmore frequent backup, xautomatic file duplication using another hard disk.

9. Chapter 1 Introduction 1.1.1 Traditional Needs of Networking B. Sharing of Hardware

10. Chapter 1 Introduction 1.1.1 Traditional Needs of Networking B. Sharing of Hardware zHardware can be shared out so that it can be accessed by other computers on the network. ye.g. a printer, CD-ROM drive or fax modem, zAdvantage: ysaves the cost in purchasing many hardware yno need to use a particular computer for printing

11. Chapter 1 Introduction 1.1.1 Traditional Needs of Networking C. Sharing of Software zSome software are to work in a networked environment ye.g. the network version of a DBMS xThe DBMS is installed in a computer called database server zSome software vendors provide site licensed software ythe software may be installed xin all the computers in a site, or xsome computers, xdepending on the agreement. ySite license is less expensive than purchasing individual copies for computers xif there are large number of computers in a site

12. Chapter 1 Introduction 1.1.1 Traditional Needs of Networking D. Communications zOn a network, users may communicate with others ye-mails ynotice boards ychat rooms ynewsgroups yvideoconferencing etc. xEach user is identified by the user name. zIf the network is connected to the Internet, communication means yreaching people in another part of the world.

13. Chapter 1 Introduction 1.1.1 Traditional Needs of Networking E. Internet Sharing

14. Chapter 1 Introduction 1.1.1 Traditional Needs of Networking E. Internet Sharing zInternet sharing means ysimultaneous use of one Internet connection by more than one computer within an organisation. yMost ISPs assign one global IP address per subscriber xA router with NAT function allows computers to use the same global IP address zBusiness plans of an ISP yallow Internet sharing yTarget customers xoffices, and xschools.

15. Chapter 1 Introduction 1.1.2 The Needs of Home Networks zA home network is ysimilar to the network of a business, but ycomprises smaller amount of nodes and yless sophisticated software and connecting devices. zWhy setting up a home network? yA. Internet sharing yB. setting up a smart home yC. setting up a home entertainment system.

16. Chapter 1 Introduction 1.1.2 The Needs of Home Networks A. Internet Sharing  (As of May 2005, more than 60% of the families in HKSAR have access to the Internet) zVery often, Internet sharing happens in these families. zISP’s Plans for home customers are ylower in price than those business plans ymost ISPs do not agree with Internet sharing by home customers. xHowever, with the growing reality of Internet sharing, many ISPs begin to adjust their policies xcheck your subscriber agreement to see your ISP's policy.

17. Chapter 1 Introduction 1.1.2 The Needs of Home Networks B. Smart Home

18. Chapter 1 Introduction 1.1.2 The Needs of Home Networks B. Smart Home zSmart home yAlso called Home automation system ycombining technologies in networking and controlling home appliances xto enable people to manage their homes from a computer, even remotely zSome of the tasks: y1. Automatic light control y2. Control home appliances remotely y3. Control access to a home y4. Monitor home remotely y5. Enhance home security y6. Others xalert you changes in environment such as temperature, brightness and moisture

19. Chapter 1 Introduction 1.1.2 The Needs of Home Networks C. Home Entertainment System

20. Chapter 1 Introduction 1.1.2 The Needs of Home Networks C. Home Entertainment System zHome Entertainment System yCombines xDVD player, TV tuners of PC xTraditional audio-visual equipment such as TV and Hi-Fi system xNetwork technology yAllows xaudio and video signals, movies and music xto be played from a computer and xdistributed over the network. yExample is xWindows® XP Media Center Edition (MCE)

21. Chapter 1 Introduction 1.1.3 Networking and Economics zAn entire industry has emerged that ydevelops networking technologies and yprovides networking services. zA new platform for people to conduct business ye-commerce zTelecommuting yemployees are working at home, rather than in the office ykept together by xthe company network and xother telecommunication channels. yflexible workplace and time yless traffic congestion ymore quality family time yincreased productivity yless company overhead

22. Chapter 1 Introduction 1.2 1.2 Network Hardware Components zOn a network, hardware include z1.2.1 serversservers z1.2.2 workstationsworkstations z1.2.3 connecting devicesconnecting devices z1.2.4 networking medium.networking medium

23. Chapter 1 Introduction 1.2.1 1.2.1 Servers zA server is a computer that yperforms tasks for other computers ymanages the network xenforcing security xsharing of files xsharing of hardware yA dedicated server is expensive, because xperformance features, and xfault-tolerant features reliable, and robust

24. Chapter 1 Introduction 1.2.1 1.2.1 Servers A. Performance Features z1. Multiple Processors yServers can run using one or more processors. yRequirement: xthe architecture of the motherboard and xthe Operating System (OS). yNote: x2 processors may not double (2x) the overall performance because not all instructions can take the advantage of multiple processors.

25. Chapter 1 Introduction 1.2.1 1.2.1 Servers A. Performance Features

26. Chapter 1 Introduction 1.2.1 1.2.1 Servers A. Performance Features z2. Larger and more reliable RAM yIf RAM is not enough, xswapping is needed and xthe performance suffers yBuffering requires memory xBuffering: look ahead and retrieve data from disks to improve the performance. yECC RAM xError Correcting Code RAM xable to detect errors in two bits, and correct error in one bit xbetter than parity check: detect error in one bit

27. Chapter 1 Introduction 1.2.1 1.2.1 Servers A. Performance Features z3.Bus capabilities yBus: the path between xthe processor, RAM and peripheral devices. yIn a server, large volume of data is moving over the bus. yPeripheral Component Interconnect (PCI) bus x32-bit (33 MHz) xused by traditional PC xmay form a bottleneck in a server with several Network Interface Cards yWider and faster buses are needed xFor example, 64-bit PCI-X bus (133 MHz).

28. Chapter 1 Introduction 1.2.1 1.2.1 Servers A. Performance Features z4.Disk Interface yIDE (Integrated Drive Electronics) xless expensive xmeets the needs in ordinary PCs ySCSI (Small Computer Systems Interface) xhandle simultaneous access to more than one hard disk xmore common in servers

29. Chapter 1 Introduction 1.2.1 1.2.1 Servers B. Fault-tolerant Features zFault-tolerant means that yeven a part fails, the whole system can still operate zFault-tolerant yguarantees the uptime of a network, and yprovides continued data availability. zFault-tolerant requires yredundant components xtake over when there is a failure. y“hot swap” components xcan be replaced without turning off the computer

30. Chapter 1 Introduction 1.2.1 1.2.1 Servers B. Fault-tolerant Features z1. RAID System (Redundant Array of Inexpensive Disks) ya set of hard disks that appear to as a logical disk yfor xfault tolerant and/or ximproving performance. ySome standards xRAID-0, 1, 2, 3, 4, 5 xRAID-10 = RAID-1+ RAID-0 yA. How is speed improved? xdisk heads can work independently yB. How is data loss prevented in case of disk failure? xredundancy

31. Chapter 1 Introduction 1.2.1 1.2.1 Servers B. Fault-tolerant Features

32. Chapter 1 Introduction 1.2.1 1.2.1 Servers B. Fault-tolerant Features z2. UPS (Uninterruptible Power Supply) yconnected between xthe mains power supply, and xthe computer. yincludes xa battery, and xcharging circuit yAdvantages: xData availability the server is still accessible when power fails xPreventing data loss alerts user to save data in files xAvoiding hardware damage power fluctuation can reduce life-expectancy of electrical devices

33. Chapter 1 Introduction 1.2.1 1.2.1 Servers B. Fault-tolerant Features z3. Backup Server ytakes over services when needed by xinstalled with the services in duplicate xholding an updated copy of the important information e.g. the user account database yneeds not be exactly the same as the working server yExamples “backup domain controllers” BDC

34. Chapter 1 Introduction 1.2.2 1.2.2 Workstations zA workstation is a computer that yallows users to make access to the resources on the network yalso called clients on a client/server network ymay be connected to network using xcables, or xradio waves ycan be converted from a standalone PC xby installing Network Interface Card (NIC), and networking software.

35. Chapter 1 Introduction 1.2.2 1.2.2 Workstations A. Network Interface Card (NIC) (1/4) zNetwork Interface Card (NIC) yAlso called network adapter yis required in all computers xincluding servers and workstations yconsists of circuitry that prepares/receives data yseveral types: xEthernet NIC 10Base-2, 10Base-T, 100Base-T and 1000Base-T, 10Base-F, 10GBase-LR etc. different data transmission rates and for different cables xToken Ring NIC xwireless NIC

36. Chapter 1 Introduction 1.2.2 1.2.2 Workstations A. Network Interface Card (NIC) (2/4)

37. Chapter 1 Introduction 1.2.2 1.2.2 Workstations A. Network Interface Card (NIC) (3/4) zMAC address (Medium Access Control) yunique identifier of NIC ysix-byte (48-bit) code yburnt permanently xin the ROM of the NIC C:\>IPCONFIG /ALL... Description........ : VIA Rhine II Fast Ethernet Adapter Physical Address...... : 00-30-18-52-68-2E....

38. Chapter 1 Introduction 1.2.2 1.2.2 Workstations A. Network Interface Card (NIC) (4/4) yThe first 3 bytes identify the manufacturer xe.g. 00-11-11 (16) represents Intel® Corporation.

39. Chapter 1 Introduction 1.2.2 1.2.2 Workstations B. Networking Software (1/4)

40. Chapter 1 Introduction 1.2.2 1.2.2 Workstations B. Networking Software (2/4) zOperating systems (OS) forms the major difference between xa workstation, and a server zServers are installed with yNetwork Operating System (NOS) xmanages the network, and xentertains requests from clients zWorkstations are installed with yDesktop OS + networking software for xcommunicating with other computers, and xsending and receiving data over the network ydrivers for the NIC, and programs for protocols

41. Chapter 1 Introduction 1.2.2 1.2.2 Workstations B. Networking Software (3/4) zWorkstations may use OS from different vendors ye.g. a Windows 2003 network allows Macintosh PC as well as Windows PC to connect zThe networking software for workstations ymay be available from the NOS of the server yor from the desktop OS itself Type of computerOperating System ServerNetwork Operating System ClientDesktop OS with networking software

42. Chapter 1 Introduction 1.2.2 1.2.2 Workstations B. Networking Software (4/4)

43. Chapter 1 Introduction 1.2.3 1.2.3 Connecting Devices zA connecting device ymoves data from one network cable to another ydirects traffic xwithin a network, or xacross multiple networks. yinclude xrepeaters xhubs xbridges xswitches, and xrouters.

44. Chapter 1 Introduction 1.2.3 1.2.3 Connecting Devices A. Repeater zAttenuation ysignal travelling along a cable would become weaker and weaker zEffective transmission length yguarantees signal transmission over the given distance xbeyond which the signals may become too weak to be detected. ye.g. 100 m for Cat-5 UTP zA repeater yamplifies signals yare electrically powered ydoes not understand the signals ycannot help direct traffic ycannot join dissimilar networks xe.g. Ethernet network and Token Ring network are dissimilar

45. Chapter 1 Introduction 1.2.3 1.2.3 Connecting Devices B.Hubs zA hub yalso called cable concentrator ycommon connection for cables xEach cable connects the NIC of a computer to a port of the hub yconsist of multiple ports ycan be used as a repeater zBroadcasting yA hub broadcasts xbecause it echoes incoming signals to all ports yA hub-based network would easily get overloaded

46. Chapter 1 Introduction 1.2.3 1.2.3 Connecting Devices C.Bridge zA bridge yis not dumb because yit can confine the traffic within each segment xby examining the data xagainst a forwarding table that records the MAC addresses of all nodes xand forward data to the correct segment ycan divide a larger network into smaller segments xto improve efficiency yconnects two dissimilar networks xe.g. Token Ring and Ethernet

47. Chapter 1 Introduction 1.2.3 1.2.3 Connecting Devices C.Bridge

48. Chapter 1 Introduction 1.2.3 1.2.3 Connecting Devices D.Switches zA switch yis a cable concentrator xjoins the network cables together ydoes not echo signals to all other ports, because it xexamines data against a table of the MAC address of each port xforwards data to the correct port similar to a bridge. yproduces less “collisions” yallows several pairs of nodes to transmit at the same time yallows full-duplex zConclusion: yswitch-based networks are faster than hub- based

49. Chapter 1 Introduction 1.2.3 1.2.3 Connecting Devices E.Routers zA router yconnects two or more networks together yroutes data between networks ykeeps a routing table yis able to determine the best path for signals xNote: a router port is either connected to a network, or another router. yis a vital equipment for a LAN to connect to the Internet xcalled SOHO router, broadband router or residential gateway

50. Chapter 1 Introduction 1.2.4 1.2.4 Networking Medium zNetworking media are classified into ytangible xexists in the form of a physical cable, e.g. coaxial cable, twisted pair and fiber optic yintangible xuses in wireless technology e.g. radio waves zNote: yData is always transmitted in the form of physical signals xknown as carrier. xe.g. electronic or optical signals in cables; xradio waves in wireless technology

51. Chapter 1 Introduction 1.2.4 1.2.4 Networking Medium A.Coaxial Cable (1/2) zA coaxial cable yconsists of xa central copper wire (core) xan insulating layer xa wire mesh used as shielding xan outer plastic jacket yneeds a BNC connector yhas effective transmission length up to 500 m yis mainly used in bus network xe.g. old Ethernet networks (10Base-2 and 10Base-5) yis used in cable TV network xfor broadband Internet accesses.

52. Chapter 1 Introduction 1.2.4 1.2.4 Networking Medium A.Coaxial Cable (1/2) zShielding yis done by wire mesh ystops xexternal electromagnetic interference (EMI) due to other electric currents xthe cable from interfering neighbouring cables to eliminate cross-talk zAdvantages of shielding: yincrease effective transmission length yincrease rate of transmission

53. Chapter 1 Introduction 1.2.4 1.2.4 Networking Medium B.Twisted Pair Cable zA twisted pair cable yconsists of copper wires twisted in pairs zWhy use twists? yTo cancel the magnetic fields due to xboth wires yResult: xcables do not produce EMI xeliminate cross-talk

54. Chapter 1 Introduction 1.2.4 1.2.4 Networking Medium B.Twisted Pair Cable z1.UTP (Unshielded Twisted Pair) Cables ycan be placed side by side without affecting each other yBut, susceptible to external EMI xbecause unshielded yare lower price than STP. yseveral grades : Cat-3, Cat-5, Cat-7 etc. xCat-5 the most popular maximum effective transmission length: 100 m consists of 4 pairs of wires used in –Ethernet, ATM and Token Ring networks. speed: 100 Mbps, 1 Gbps (1000 Mbps)

55. Chapter 1 Introduction 1.2.4 1.2.4 Networking Medium B.Twisted Pair Cable z2.STP (Shielded Twisted Pair) cables yare able to xresist external EMI xeliminate cross-talk between two cables yare xmore expensive, but xhigher speed xlonger effective transmission length yare best used in “noisy” environment xe.g. near a transformer station.

56. Chapter 1 Introduction 1.2.4 1.2.4 Networking Medium C.Powerline zPowerline communication (PLC) yuses powerline as networking medium yhas two types xindoor, and xoutdoor. zIndoor PLC yfor setting up local area network zOutdoor PLC yBroadband over Power Lines (BPL) yAdvantage: xinfrastructure is already available yMajor problem: xinterfere with radio transmission, because power cable is unshielded and untwisted

57. Chapter 1 Introduction 1.2.4 1.2.4 Networking Medium D.Fiber-optic Cable zFiber-optic cables yuse glass to carry light signals xinstead of electrical signals yare used as network backbone xto provide high speed connection xup to 10 Gbps ycannot be intercepted easily because xthey do not emit electromagnetic waves (radio waves) xSo, very secure yhave little attenuation xcan span miles of distance xoften used across floors in a building or between buildings. yare expensive xcostly to install and maintain.

58. Chapter 1 Introduction 1.2.4 1.2.4 Networking Medium E.Radio waves zRadio waves yare used in wireless technology yrequire xwireless NIC in computers, and xan access point for common connection yAdvantages: xinexpensive xflexible xeasy to install yDisadvantages: xslow in transmission xradio signals can be intercepted easily.