1、S3 Computer LiteracyInternet Technology.Connecting to the Internet Hardware RequirementMODEM56K or BroadbandMOdulation and DEModulationTelephone Line.Connecting to the Internet - ISPISP Internet Service Provider(互聯(lián)網(wǎng)服務(wù)供應(yīng)商)What has ISP done for you? It sends and receives data for you. It provides a co

2、nnection 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.Is ISP running the Internet?No single organization runs the Internet.It is a large network of networks. These networks are linke

3、d by high-speed communication channels called backbones. Each Internet computer, called a host, is independent. .Connecting to the Internet Type of AccessDial-up Access(撥號上網(wǎng))It needsa telephone lineMODEMUserdials a telephone number given by the ISP to connect to the server of the ISP.a user name and

4、 password to authenticate the user.User can access hosts on the InternetData transfer rate maximum of 56Kbps.Connecting to the Internet Type of AccessBroadband AccessIts 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 requ

5、ired.Broadband Access - ADSLADSLa 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(wǎng)上行).Get to the InternetPPPoESome broadband Internet service providers (ISPs) identify your computer on

6、 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 ).Broadband Access - ADSLADSL (Asymmetric Digital Subscriber Line)Asymmetric (不對稱) between download speed is faste

7、r.Download Speed 1.5Mbps to 8MbpsUpload Speed 16Kbps to 640KbpsComponents Network card, ADSL MODEM, Telephone Line.Broadband Access Cable TV NetworkCable TV NetworkA 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 tech

8、nology in HK:iCable (有線寬頻).Broadband Access Cable TV NetworkCable TV NetworkDownload 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.Broadband vs Dial-up AccessFaster connection speed

9、 up to 1.5Mbps to 10Mbps.No dialing required.Simultaneous use of data and voice connectionsie: unlike dial-up access, user can talk on the phone while surfing the Internet.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

10、the broadband access from one Internet account among all users in the LAN.Communication Protocol TCP/IPTCP/IPcommunication protocol of the Internetset of rules used in message transmission on the Iputers need to use the same protocol if they need to communicate.TCP and IP.Advantages of TCP/IPIf we s

11、end 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 destinationif it is broken down into packets, then only the packet that fail to be sent are resent.Packet Animation.Advantages of TCP/IPTransmission of data is not affe

12、cted 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.IP AddressIt identifies ever

13、y 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.IP Address FormatThe IP address system currently using is called the IPv4 addressing system.Question regardin

14、g IP AddressWhat 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?.Real IP and Virtual IPImagine if there are not enough IP addresses in a

15、network, what can we do?The solution is to use Virtual IP.How Virtual IP worksSome of the IP addresses are reserved for private network (ie: LAN). E.g. 10.X.X.X or 192.168.X.XThe router will not route these IPs to the Internet, ie: it will route the data sending to these IPs inside the LAN.Static IP

16、 and Dynamic IPStatic IPIP addresses that are fixed every time when the user connect to the Internet.Dynamic IPIP addresses that changes every time the user connect to the Internet.Domain Name System (DNS)At the command window, type in the command “ping google.hk, what did you find? Why?To connect t

17、o a specific computer, we need to know its IP address.Connect to the Yahoo! webpage, we need to know its address, ie: type 1 in the Internet browser.It is inconvenient to remember the meaningless IP address.DNS ServerDNS Server responsible for translating the address into the correspondi

18、ng IP address.Try to get to the nba.Web ServerWeb 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).Web BrowserA 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 cann