Section C ch16 the networking and internet basics notes


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Section C ch16 the networking and internet basics notes

  1. 1. CFSS HKDSE ICT – [Section C] Topic a. The Networking and Internet Basic (Ch. 16 & 17) Page: 1Name:___________________________ Class:____ __( ) HKDSE Information and Communication Technology Section C. Internet and its Application Topic a. The Networking and Internet basics (Book 2 Ch. 16 & 17)Learning Outcomes Remarks• Define and compare Local Area Network (LAN)and Wide Area Network (WAN).• Discuss the common services available in a Services include internal communications,networked environment. conferencing and resources sharing.• Explain the functions of the hardware required for This includes communication links (phone line,a network. coaxial cable, fibre optics, microwave, satellite, etc.), modem (including cable modem), network interface card, network connecting devices (hub, switch and router, etc.).• Compare common methods for Internet access in This includes connections in wireless, leased lineterms of speed, cost, security and availability. and broadband etc.• Understand the need for communications softwareand communication protocols.• Describe how data is transmitted over the Internetand understand concepts of Internet Protocol (IP),Uniform Resource Locator (URL), Domain NameSystem (DNS) and Hypertext Transfer Protocol(HTTP).
  2. 2. CFSS HKDSE ICT – [Section C] Topic a. The Networking and Internet Basic (Ch. 16 & 17) Page: 216.1 Computer NetworksThe Logical Structure of the Internet: a Network of NetworksComputer network is a system of interconnected computers, peripherals and communication devices that canexchange information and share resources. Networking is widely used in government departments,corporations, educational institutions and homes. Internet - the world’s largest computer network connectingbillions of computers together around the world.
  3. 3. CFSS HKDSE ICT – [Section C] Topic a. The Networking and Internet Basic (Ch. 16 & 17) Page: 316.2 Local Area networks (LANs) and Wide Area Networks (WANs)Networks are categorized according to the area they cover.Local area network (LAN)A network that connects computers within a relatively limited area, such as an office, a building or a campus.Wide area network (WAN)A network that spans a wide geographical area, usually across cities, countries or even continents.Comparison between LAN and WAN LAN WANData transfer LANs have a high data transfer rate WANs have a lower data transfer rate asrates: compared to LANsConnection: one LAN can be connected to other LANs LANs over any distance via telephone lines over any distance via telephone lines and and radio waves Computers connected to a radio waves wide-area network are often connected through public networks, such as the telephone system. They can also be connected through leased lines or satellitesSet-up costs: If there is a need to set-up a couple of extra In this case since networks in remote areas devices on the network, it is not very have to be connected hence the set-up costs expensive to do that are higherDefinition: LAN (Local Area Network) is a computer WAN (Wide Area Network) is a computer network covering a small geographic area, network that covers a broad area (e.g., any like a home, office, schools, or group of network whose communications links cross buildings. metropolitan, regional, or national boundaries over a long distanceMaintenance Because it covers a relatively small Maintaining WAN is difficult because of itscosts: geographical area, LAN is easier to wider geographical coverage, and is its maintain at relatively low costs. maintenance costs.Technology: Tend to use certain connectivity WANs tend to use technology like ATM, technologies, primarily Ethernet and Token Frame Relay and X.25 for connectivity over Ring the longer distancesExample: Network in an organization can be a LAN Internet is the best example of a WANGeographical Have a small geographical range and do not Have a large geographical range generallyspread: need any leased telecommunication lines spreading across boundaries and need leased telecommunication linesOwnership: Typically owned, controlled, and managed WANs (like the Internet) are not owned by by a single person or organization any one organization but rather exist under collective or distributed ownership and management over long distances
  4. 4. CFSS HKDSE ICT – [Section C] Topic a. The Networking and Internet Basic (Ch. 16 & 17) Page: 4Local Area Network (LAN)- Consists of networked computers, or workstations, shared peripheral devices, communication devices andlinks.Two popular types of LANs:1. Peer-to-peer (P2P) networks2. Client/server networksPeer-to-peer networkA network of workstations without a serverAll the workstations can communicate directly witheach other.Each computer can access the resources which areshared by all the other peer workstations.Usually have a small number of workstations.Cost of setting up is relatively low.Usually found in small companies and homes.Client/server networkClient workstations are connected to a central server,or a host computer.Clients can access the resources stored on the server.The set-up cost is relatively high.It provides better security controls and networkservices in a large-scale network environment.Ideal for medium or large organizations.Wide Area Network (WAN)Refers to a communication network that spans a large geographical area, across regions or continents.Consists of two or more remote LANs.LANs are connected via different communicationchannels1. Telephone lines2. Leased lines3. Microwave4. Satellites5. Optical fibre cablesThe Internet is the largest WAN in the world.
  5. 5. CFSS HKDSE ICT – [Section C] Topic a. The Networking and Internet Basic (Ch. 16 & 17) Page: 5Example:Jimmy Lam constructs a peer-to-peer network to connect 20 computers of the staff members in the office.(a) Give two advantages of setting up a peer-to-peer network over the client-server network.1. No need to set up specific servers such as FTP server, printer server.2. Each user has the right to control his/her resources sharing.(b) A scanner is to be shared by these 20 computers. Describe, step by step, how to achieve printer sharingamong the computers.1. Install the scanner on one of the computers and make the printer a sharable device2. Install the sharable scanner driver on each of the other 9 computers(c) Give one disadvantage of the scanner sharing method described in (b).If the computer that physically connected to the printer is turned off, other computers in the network will notbe able to use the printer.(d) A company allows its employees to work at home. In the office, computers are connected together toform a local area network, Network A. The employees connect their computers to Network A through thePublic Telephone Network (PTN) to form Network B as follows:(i) What is the hardware device X, which is installed at home?modem(ii) Besides the operating system, what is the necessary software for the home computer to connect toNetwork A?Communication software/ dialup software(iii) Give two disadvantages of Network B over Network A regarding the performance of home connection.1. Network B has lower data transfer rate.2. Network B is less secure.
  6. 6. CFSS HKDSE ICT – [Section C] Topic a. The Networking and Internet Basic (Ch. 16 & 17) Page: 616.3 Network ServicesWhen a computer is connected to a network, it can provide more extensive services.Major services provided by a network are:Service Description RemarkInternal Communication between computes in a Examples: e-mail, instant messaging, filecommunication LAN or a WAN transferHardware LAN: sharing hard disks, printers and Better monitoring and utilizationsharing scanners Saving costs WAN: hard disk storage spaceCentralized data Centralizing data in a network server Keeping information updatedmanagement Better security control Increasing productivity and efficiencySoftware Sharing network licensed software among Lower costsharing computers simultaneously Saving time for installationInternet access Accessing the Internet via a computer Lower cost network Better monitoring and network protectionNetwork Network communication via two-way Video signals must be compressedconferencing audio and video signals Instant and cost savingInformation Backup information on individual For rapid system recoverybackup computers to a server via a networkExample: (b) Mr. Chung redesigns the LAN, as shown belowMr. Chung builds a LAN in a school, as shown and thinks that it is now better. What is thebelow. improvement? Printer Switch Printer Switch(a) How does this LAN benefit the users of thecomputers? Give two examples. 1. Computer A can still use the printer when 1. User of Computer A can use the printer Computer B is off. 2. The Users can share files. (share software/ 2. Occupies less resource of Computer B communication) though Computer A is using the printer.
  7. 7. CFSS HKDSE ICT – [Section C] Topic a. The Networking and Internet Basic (Ch. 16 & 17) Page: 716.4 Connecting to a Computer NetworkQuestion: What hardware do you need in PC to connect to the router? Network Interface Card (NIC)Network Interface Card (NIC) – is an expansionboard for connecting a computer to a network.Each NIC has a unique media access control (MAC)address for identifying the computer on the network. Classification Example Connector BNC and RJ-45 Expansion bus ISA, PCI, PCMCIA and USB Bandwidth 10 Mbps, 100 Mbps and 1,000 MbpsNetwork cablesTwisted-pair cableWidely used in local area networks. Looks similar to a telephone cable and has anRJ-45 on both ends. Winding two conductors together→ eliminate electromagnetic interference Shielded twisted-pair (STP) Unshield twisted-pair (UTP) Has a metal wrapper around each wire to reduce Does not have metal shielding noise and electromagnetic interference Low-cost substitution for the STP cable Maximum data transmission speed of Cat 6 UTP cable is about 1,000 Mbps within 100 m distance limit.
  8. 8. CFSS HKDSE ICT – [Section C] Topic a. The Networking and Internet Basic (Ch. 16 & 17) Page: 8Coaxial cable Commonly used for VCR and cable television connections. Has a BNC connector on both ends. Higher ability to retain the strength of a transmitting signal over a long distance than a twisted-pair cable Consists of: a copper wire, a sheath of insulation, a wire mesh that conducts and shields against interference, an outside coating, Strengthened insulation allows coaxial cables to transmit more information than twister-pair cables.Optical fibre cable Advantages: Disadvantages:Made of a bundle of glass Greater signal-carrying capacity Very high costthreads that transmit light Faster data transmission Difficult to installbeams. Reduced susceptibility to interference Require a device for signal Better security for transimission conversion Thinner, ligher and more durable Once installed, it is difficult to change
  9. 9. CFSS HKDSE ICT – [Section C] Topic a. The Networking and Internet Basic (Ch. 16 & 17) Page: 9Example:Which of the following will be assigned by a manufacturer when a network interface card is produced?A. URLB. IP addressC. MAC addressD. Memory addressExample:Which of the following is least sensitive to external interference?A. UTP cableB. Optical fibre cableC. MicrowaveD. STP cableExample:(a) The company is going to subscribe a broadband Internet service. Mr Chung has investigated the existing ISPs in Hong Kong and the results are as follows: ISP A ISP B ISP C Transmission media Optical fibre cables Telephone lines Coaxial cables(i) State two advantages and two disadvantages of optical fibre cables over coaxial cables. Advantages: ● The data transmission speed is higher. ● Optical fibre cables are less susceptible to electromagnetic interference. Disadvantages: ● The cost is higher as special networking devices are required. ● It is much more difficult to set up networks using optical fibre cables. (ii) Regarding ISP C, answer the following questions. (I) State one common connector standard used by coaxial cables. BNC (II) State another kind of signals that are delivered by coaxial cables in household networks. TV signalsExample: Which of the following descriptions about network interface cards (NICs) is correct?A. NICs nowadays use BNC connectors only.B. The minimum bandwidth of an NIC is 1 Gbps.C. Each NIC has a unique IP (Internet Protocol) address.D. The NICs may use USBs as their expansion buses.Example:Arrange the following communication media in descending order of their data transmission rates. (1) Coaxial cable (2) Optical fibre (3) Telephone lineA. (1) > (2) > (3)B. (2) > (1) > (3)C. (2) > (3) > (1)D. (3) > (2) > (1)
  10. 10. CFSS HKDSE ICT – [Section C] Topic a. The Networking and Internet Basic (Ch. 16 & 17) Page: 10Hardware components of networkingNetwork connecting devicesDevice Function / ApplicationHub Connection of computers and servers Central connection point for a network of low data transmission speed. The signals entering a hub are echoed to all other ports, a phenomenon called broadcasting.Switch Connection of computers and servers Central connection point for a network of a high data transmission speed, ranging from 10 Mbps to 1 Gbps. Unlike hub, a switch does not echo signals to all other ports. It keeps a table of the MAC address for each port.Repeater Connection of remote devices Amplifying received signals Removing unwanted noises Sending the amplified signals to the connected deviceBridge Interconnection of LANs Interconnecting two or more LANs of the same typeRouter Interconnection between different types of LANs / between a LAN and the Internet Translating signals from different networks Each router keeps a routing table internally and is able to determine the best path for signalsGateway (not examined) interfaces with another network of different protocolsModem Dial-up modem: Converting between digital signals Setting up a dial-up connection to a and analogue telephone signals network Cable modem: Converting between digital signals Broadband service via cable TV cables and analogue cable TV signals Digital subscriber line (DSL) modem: Filtering DSL Broadband service via telephone cables signals , Converting DSL signals to signals that a computer can process and vice versa.
  11. 11. CFSS HKDSE ICT – [Section C] Topic a. The Networking and Internet Basic (Ch. 16 & 17) Page: 11Example:The following diagram shows a network of four computers, A, B, C and D and two devices, X and Y. A issending data to C.(a) Suppose X is a hub and Y is a switch (i) Can the data also be obtained by B? Explain briefly. (ii) Can the Data also be obtained by D? Explain briefly.(b) Suppose X is a switch and Y is a hub (i) Can the data also be obtained by B? Explain briefly. (ii) Can the Data also be obtained by D? Explain briefly.You are given the task of designing a simple LAN for a multimedia learning centre in your school on thethird floor. The centre has 40 standalone PCs. Each PC is currently running Microsoft Windows 7operating system and some Microsoft Office applications. All others PCs in the school are sharing a 100Mbps broadband Internet service except for this multimedia learning centre.(a) Which type of cable should be used in the LAN? Explain briefly.(b) In addition to the cables, what other two components are needed for the PCs to be connected togetherin the LAN?(c) Draw a diagram to illustrate your design
  12. 12. CFSS HKDSE ICT – [Section C] Topic a. The Networking and Internet Basic (Ch. 16 & 17) Page: 12Radio connectionsSatellite broadband Microwave broadbandCan be used to establish a connection to the Internet in Communicates with the ISP by a microwaveremote areas where wired broadband is not available. signal.Requires a dedicated satellite and a satellite dish on Broadband subscriber and the ISP send andeach end of the connection. receive radio signals directly to each other.Average upload and download speeds are around Consists of a number of access points and50Kbps and 500Kbps respectively. subscriber units.Despite the low transmission speeds, the set-up cost and Access points mounted on top of buildings sincethe monthly charge can be very expensive each subscriber unit must have a line-of-sight to the access point Practical coverage: up to 1.5 km Data transmission speed: up to 100 Mbps May be affected by rainstorms and connection may become unstable or even breaks up.
  13. 13. CFSS HKDSE ICT – [Section C] Topic a. The Networking and Internet Basic (Ch. 16 & 17) Page: 13ExampleMr Lam is the IT manager of a university in London. There are two computer network separately locatedin Building C and Building D which are used by students and staff respectively. The two buildings are 1km apart, as shown in the figure below. Connection across the building (Distance: 1km) Y X . . . Internet X . Y . . Building D Building C (Staff) (Students)(a) (i) What network connecting devices are X and Y? X: ___________________ Y: ___________________ (ii) Suggest a suitable type of network cable for the connection across the buildings and justify you answer. (iii) Instead of using a wired connection, Mr Lam wants to connect two networks by installing microwave dishes on the roofs of the buildings. State two disadvantages of this approach.(b) Mr Lam subscribes to an Internet connection which requires a cable modem to connect the campus network to the Internet. What is the function of the cable modem?
  14. 14. CFSS HKDSE ICT – [Section C] Topic a. The Networking and Internet Basic (Ch. 16 & 17) Page: 14Wi-Fi connections [Wireless fidelity (Wi-Fi) ]The network based on the IEEE 802.11 wireless local area network (WLAN) standard. Data is transmittedby radio waves. Any two Wi-Fi-enabled devices can create a wireless connection to communicate with eachother.To transmit data:The sender translates digital data into radio signals and transmits it to the receiverThe receiver then translates the received radio signals back to digital data.STANDARD 802.11a 802.11b 802.11g 802.11nData transmission Up to 54 Mbps Up to 11 Mbps 54 Mbps or above Up to 600 MbpsspeedMaximum signal Indoor: 35m Indoor: 38m Indoor: 38m Indoor: 70mcoverage Outdoor: 120m Outdoor: 140m Outdoor: 140m Outdoor: 250mRadio frequency 5 GHz 2.4 GHz 2.4 GHz 2.4 GHz and/or 5 GHzCost High Lowest Low Very highPopularity Unpopular Very popular Very popular -Without the limitations of cables, it can be connected to a wired LAN by means of an access point.Access Point - A device that allows a wireless device to communicate to other wireless devices by radiofrequencies(Or communicates to a wired network by converting digital signals to radio frequencies and vice versa.)Advantages: Disadvantages:Cost of building up a network is lower. Effective data transfer rate is highly affected by theNetwork structure can be modified if surrounding environment.required. The risk of intrusions is higher.A network can be extended to an outdoor The maximum data transmission speed of a WLAN isarea. significantly lower than that of a wired network. The coverage of a wireless router or access point is limited. The cost of building up a large wireless network can be very high Wireless (IEEE Twisted-pair cable Coaxial cable Optical fibre cable 802.11 standard) Data Maximum rate 100 Mbps to severaltransmission 10 Mbps, 100 Mbps Up to 299 Mbps ranges from 11 Gbps speed Mbps to 600 MbpsTransmission Electrical Electrical Optical Radio waves signal Varied, dependent on Cost Cheap Expensive Most expensive network size
  15. 15. CFSS HKDSE ICT – [Section C] Topic a. The Networking and Internet Basic (Ch. 16 & 17) Page: 15Example:The manager of a shopping centre plans to provide a free Internet connection service for customers.(a) The manager decides that UTP sockets will not be provided to access the Internet. Give two possiblereasons to support the manager’s decision.(b) The manager sets up a wireless network in the shopping centre. The wireless access points are installedas shown below. Assume that the floors and the walls do not affect the signal transmission and the radiusof signal coverage of each of the wireless access points is 35 meters.(i) Suggest a location where the customer may not be able to receive the wireless signal. Explain youranswer.(ii) If a customer walks from access point A to access point B, what will happen to his connection? Explainyour answer(iii) The manager plans to add one more wireless access point to improve the situation in (b)(i). Suggestthe best location for the new device. Explain your answer.(c) What will happen if too many customers try to use the wireless network at the same time? Explain youranswer.Example:When buying a wireless broadband router for a network at home, which of the following considerations isnot necessary?A. The data transfer rate of the broadband connectionB. Security protocolsC. The IP address of the routerD. Coverage of the router
  16. 16. CFSS HKDSE ICT – [Section C] Topic a. The Networking and Internet Basic (Ch. 16 & 17) Page: 1616.5 Methods of Internet AccessInternet service provider (ISP)An ISP is a company that provides Internet access services. It usually offers subscribers a communicationsoftware package for establishing a connection with the ISP server. Includes a username, a password andother necessary information. Data transmission speed or bandwidths vary from 56 Kbps to 1,000 Mbps.Dial-up connectionBasic equipment:1. Dial-up modem2. A telephone lineIntegrated Services Digital Network (ISDN)ISDN works on the same principle as a dial-up connection.Need an ISDN modem connected to a conventional telephone line to establish an ISDN connection to theISP server.Broadband connectionsA much higher data transmission speed than the standard 56 Kbps modemConstant availability without dialing requiredSimultaneous use of data and voice connectionsEquipments required:Digital modem: can send and receive digital data from the ISP through a dedicated transmission cable.Network interface cardMain broadband systems for home users:ADSL SDSL Cable modemIt uses standard telephone lines to It has identical upstream and It connects a computer to a cableconnect with an ADSL modem. downstream data transmission TV network.The system is ‘asymmetric’ speed. It has a designated capacity of 30because the download speed (from The maximum data transmission Mbps, but this has to be shared1.5 to 9 Mbps) is higher than the speed is 24 Mbps. among users at the same location.upload speed (from 16 to 640 They use the whole bandwidth of The data transmission speed isKbps). the communication cable for the normally much lower.Example: Netvigator broadband service and therefore Example: i-Cable the cable cannot be used for the transmission of vocal signals.T-carrier Mainly used by large companies and schools those need a continuous Internet connection.Provides a permanent connection between the network server and the ISP’s server.Allows network users to access the Internet simultaneously.Various types of carriers support different data transmission speeds:Maximum data transmission speed of T-1: 1.54 MbpsMaximum data transmission speed of T-3: 44 Mbps
  17. 17. CFSS HKDSE ICT – [Section C] Topic a. The Networking and Internet Basic (Ch. 16 & 17) Page: 17Wireless Internet access - can access the Internet or connect to a computer network instantly almostanywhere with our notebook computer or other mobile devices.Popular wireless connection methods:Wi-Fi hot spots, Wireless Application Protocol (WAP), General Packet Radio Services (GPRS)Comparison of Internet access methods Dial-up Broadband Wi-Fi hot ISDN WAP GPRS connection connection spotData Maximum Maximum 1.5 Mbps – 11 Mbps– 10 Kbps – Maximumtransmission 56 Kbps 128 Kbps 1,000 Mbps 600 Mbps 153 Kbps 115.2 KbpsspeedCost Low Average High Very high Very high Very high ADSL: Area covered by the telephone Area covered Area covered Area covered Area Area covered network by the by the by the Covered by by the mobileAvailability mobile telephone telephone Cable: Area Wi-Fi access phone phone network network covered by points network network the cable TV networkSecurity High Very high High Low Average Average Internet Schools Households Internet access by: Remote Companies Schools Travellers access by: Smart phoneApplication households Large Large PDA users Smart phone PDA Travellers organizations organizations PDA Notebook computerPopularity Minority Minority Majority Moderate Minority Minority16.6 Methods of Internet AccessLatest development for data communicationsA new wireless transmission protocol has been developed, it can transmit data at 2.5 Gbps. The fastest Wi-Ficonnection is available in the market today. However, the security concerns about wireless transmission isstill an unsolved problem .No encryption method is proved to make a wireless network as safe as a wirednetwork. It may take ten more years to complete the migration of all existing 10/100 Mbit computernetworks to Gigabit networks.
  18. 18. CFSS HKDSE ICT – [Section C] Topic a. The Networking and Internet Basic (Ch. 16 & 17) Page: 18Example:A tourist plans to live in a hotel that provides three different Internet connection options in the rooms aswell as in the business centre. The three different options are as follows: Modem Upstream Downstream IP A ADSL 640 kbps 9 Mbps Static IP address B SDSL 30 Mbps 30 Mbps Static IP address C Cable TV 300 kbps 1.5 Mbps dynamic IP address D Dial-up 33 kbps 56 kbps dynamic IP address(a) Are the four options all using broadband connection services? Explain briefly.(b) Describe the meaning of the bandwidth of an Internet connection. How is it measured?(c) What does upstream rate indicate? Why is the upstream rate less than the downstream rate in A, C, Dconnections?(d) Connecting the modems to outside, the hotel has chosen wire X for option A and another type of wireZ for option C. Name X and Z.(e) Which type of connection option do you expect to be used in the business centre of the hotel? Explainbriefly.(f) For Internet connection using ADSL modem, suggest one added-value service that might also beprovided.(g) In what circumstances would you use dial-up modem in Z for Internet connection?(h) Describe one advantage of using a dynamic IP address instead of a static IP address.
  19. 19. CFSS HKDSE ICT – [Section C] Topic a. The Networking and Internet Basic (Ch. 16 & 17) Page: 19Example:A network is set up in ABC School. All computers are connected together by an Ethernet 100BaseTXnetwork. Category 5 unshielded twisted pairs (UTP) cables are used in the network as transmission media.For an Ethernet 100BaseTX network, each UTP cable segment should not be longer than 100 metres.(a) As shown in the figure below, why are the wires in UTP cables twisted?(b) If optical fibres are used instead of UTP cables, should the optical fibres be twisted like the wires in theUTP cables? Explain your answer.(c) The Principal of ABC School plans to connect his computer to the network 150 metres away. State thenumber of UTP cable segments and an additional network device required. Explain your answer anddescribe briefly how these are connected.(d) The teachers in ABC School always use video conferencing to share lessons with other schools overthe Internet. Which of the following types of Internet connection services should be used: modem dial-up,leased line or broadband? Give two reasons to support your answer.Example(a) There is currently a trend of using wireless networks rather than using wired networks. State twoadvantages of using wireless networks.(b) State two disadvantages of current wireless networks