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S3 Computer Literacy Internet Technology Connecting to the Internet – Hardware Requirement MODEM 56K or Broadband MO dulation and DEM odulation Telephone Line Connecting to the Internet - ISP ISP – Internet Service Provider( 互聯網服務供應商 ) What has ISP done for you?

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S3 computer literacy l.jpg

S3 Computer Literacy

Internet Technology


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Connecting to the Internet – Hardware Requirement

  • MODEM

    • 56K or Broadband

    • MOdulation and DEModulation

    • Telephone Line


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Connecting to the Internet - ISP

  • ISP– Internet Service Provider(互聯網服務供應商)

  • What has ISP done for you?

    • It sends and receives data for you.

    • It provides a connection between you and the other of the Internet.

    • As shown in the animation below, the data is in fact handled by a number of ISP.

Animation for connection to the Internet


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Is ISP running the Internet?

  • No single organization runs the Internet.

  • It is a large network of networks.

  • These networks are linked by high-speed communication channels called backbones.

  • Each Internet computer, called a host, is independent.


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Connecting to the Internet –Type of Access

  • Dial-up Access(撥號上網)

    • It needs

      • a telephone line

      • MODEM

    • User

      • dials a telephone number given by the ISP to connect to the server of the ISP.

      • a user name and password to authenticate the user.

      • User can access hosts on the Internet

    • Data transfer rate maximum of 56Kbps.


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Connecting to the Internet –Type of Access

  • Broadband Access

    • Its speed is measured in Mbps (i.e. Mega bit per second)

    • Unlike dial-up access, it requires a network card / LAN card but no modem required.


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Broadband Access - ADSL

  • ADSL

    • a technology for transmitting digital information at a high bandwidth on existing phone lines to homes and businesses.

    • ISP adopting this technology in HK:

      • Netvigator (網上行)


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Get to the Internet

  • PPPoE

    • Some broadband Internet service providers (ISPs) identify your computer on their networks using Point to Point Protocol over Ethernet (PPPoE). If your ISP requires you to supply a name and password to access the Internet, it most likely uses this protocol (議定 ).


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Broadband Access - ADSL

  • ADSL (Asymmetric Digital Subscriber Line)

    • Asymmetric (不對稱) between download speed is faster.

    • Download Speed – 1.5Mbps to 8Mbps

    • Upload Speed – 16Kbps to 640Kbps

    • Components – Network card, ADSL MODEM, Telephone Line


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Broadband Access –Cable TV Network

  • Cable TV Network

    • A Cable MODEM is used to enables user to connect the PC to a local cable TV line and receive data at about 10Mbps.

    • ISP adopting this technology in HK:

      • iCable (有線寬頻)


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Broadband Access –Cable TV Network

  • Cable TV Network

    • Download and upload speed are the same, but the bandwidth (10Mbps) is shared among users at the same location(e.g. the same building)

    • Hardware used – Network Card, Cable MODEM


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Broadband vs Dial-up Access

  • Faster connection speed – up to 1.5Mbps to 10Mbps.

  • No dialing required.

  • Simultaneous use of data and voice connections

    • ie: unlike dial-up access, user can talk on the phone while surfing the Internet.


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How can we share Internet access in a LAN to a Broadband?

  • A router(路由器) is needed to connect a LAN to the Internet.

  • It will share the broadband access from one Internet account among all users in the LAN.


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Communication Protocol – TCP/IP

  • TCP/IP

    • communication protocol of the Internet

    • set of rules used in message transmission on the Internet.

    • computers need to use the same protocol if they need to communicate



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Advantages of TCP/IP

  • If we send the whole file without breaking it into packets,

    • the whole message then has to be re-sent if the full message fails to reach its destination

    • if it is broken down into packets, then only the packet that fail to be sent are resent.

Packet Animation


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Advantages of TCP/IP

  • Transmission of data is not affected by the failure of any path:

    • there are more than one path. Packets of data can be routed around the problem.

    • the load of the line is evenly distributed.

  • As long as the operating system supports TCP/IP, the computers can communicate through LAN and Internet.

TCP Animation


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IP Address

  • It identifies every host (computer) in any network.

  • When a packet is transmitted over the Internet, it must carry the addresses of the sender and receiver computers so that the routers can choose the best path.


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IP Address – Format

  • The IP address system currently using is called the IPv4 addressing system.


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Question regarding IP Address

  • What is the range of the each set of numbers?

  • As each computer in the Internet has a unique IP address, how many computer can be represented in the Internet?

  • What can we do if the number of IP addresses is not enough?


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Real IP and Virtual IP

  • Imagine if there are not enough IP addresses in a network, what can we do?

  • The solution is to use Virtual IP.


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How Virtual IP works

  • Some of the IP addresses are reserved for private network (ie: LAN). E.g. 10.X.X.X or 192.168.X.X

  • The router will not route these IPs to the Internet, ie: it will route the data sending to these IPs inside the LAN.


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Static IP and Dynamic IP

  • Static IP

    • IP addresses that are fixed every time when the user connect to the Internet.

  • Dynamic IP

    • IP addresses that changes every time the user connect to the Internet.


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Domain Name System (DNS)

  • At the command window, type in the command “ping www.google.com.hk”, what did you find? Why?

  • To connect to a specific computer, we need to know its IP address.

  • Connect to the Yahoo! webpage, we need to know its address, ie: type http://68.142.226.41 in the Internet browser.

  • It is inconvenient to remember the meaningless IP address.


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DNS Server

  • DNS Server responsible for translating the address into the corresponding IP address.

  • Try to get to the nba.com


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Web Server

  • Web Server is a computer that delivers Web pages.

  • A computer can become a web server by installing Web Server Program like Apache and IIS (Internet Information Server)


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Web Browser

  • A software application used to display Web pages.

  • Two most popular browsers are Netscape Navigator and Microsoft Internet Explorer (IE).

  • Plug-in (外掛程式)

    • The browser cannot play all format of audio or video files, so a plug-in program is needed to add support to these types of files.


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Case studies

  • If the hosts (PCs) can communicate well in the LAN but they have difficulties to get to the Internet, what would be the problem?

  • If you are a teacher and you have saved some document in a PC at school. You have checked the IP address of this PC is 10.62.43.55, are you able to get access to this PC at your home, why?

  • Your PC at home cannot access to the web pages, e.g. www.yahoo.com.hk, however, your ISP tells you that your connection to the Internet works fine, what would be the problem?


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