ITMA03 Internet And Communications
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ITMA03 Internet And Communications

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ITMA03 Internet And Communications ITMA03 Internet And Communications Document Transcript

  • What You Will Learn . . . How the Internet works Methods for accessing the Internet The Internet and World Wide Web The Internet and the World Wide Web Hypertext Web browsers and Web servers 1 2 What You Will Learn . . . Parts of a URL How to access Web pages Web subject guides and search engines Use operators to improve search results Reliability of information on the Web Most popular Internet services 3 4 The Internet How the Internet Works Interoperability is the ability to communicate with a computer even if it is a different brand or model The Internet is a global, interconnected computer network in which every computer connected to it can exchange data with any other connected computer 5 6 K.Ng Sept08 1
  • Accessing the Internet and Web Accessing the Internet The Internet can be accessed in the following ways: Dial-up access with Point-to-Point Protocol (PPP) Digital Subscriber Line (DSL) You will need: Cable and satellite access A computer with an operating system, such as Windows, ih i h Wi d LAN access MAC OS, or UNIX, that supports Internet protocols Communications equipment such as a modem, ISDN adapter, Internet history or Ethernet card http://www.zakon.org/robert/internet/timeline/ An Internet service provider (ISP) Web browser software such as Internet Explorer or Netscape Navigator 7 8 The Internet and Web: What’s the Difference? The Web Site A Web site is a collection of The Internet is the physical connection of millions of related Web documents that networks are made available to the public The Web uses the Internet for its existence The index page, or home p g , The W b Th Web consists of h i t f hypertext embedded on Web t t b dd d W b page, is the first page of a pages that are hosted on Web sites Web site Web pages are individual Web documents 9 10 Web Browsers and Servers The Hypertext Concept Hypertext is a way of presenting information so that the order in which it’s read is left up to the reader Hyperlinks are underlined or highlighted words that can be used to view another document or Web page Web browsers display a Web document and enable p y Hypermedia refers to a link to multimedia, such as users to link to other Web pages music and movies The first browsers were text-only The Web is a distributed hypermedia system or a Mosaic was the first graphical browser (April 1993) system where the responsibility for creating content Web servers respond to the requests of browsers. is distributed among many people They find and send requested resources back to the browser 11 12 K.Ng Sept08 2
  • Mosaic Web Addresses (URLs) Web addresses are an addressing system that identifies where a Web resource is located The uniform resource locator (URL) is the standard used to identify Web resources The URL consists of: Protocol Server contains Path Resource identifies the domain identifies the specifies the the means name of the location of the filename of the June 1993 Ver.: 0.1a of access Web server document resource Nov 1993 Ver.: 1.0 Oct 1995 Ver.: 2.0 URL http://www.yahoo.com/ help/shop/ shop-01.html 13 14 The Web Browser’s Window Browsing the Web Click to view the various parts of a Web browser’s window. To access a Web page, you can do any of the History Button– List of Program icon– Other Navigation Buttons Animates when following: Standard Web Button– Prints Printer Toolbar– Back & Forward Buttons– sites visited over a Favorites Button– List Opens Media Button– documents Address Bar– downloading Search Button– player of time Contains Navigation buttons RefreshButton– Opens program Button– visited Stop Button– Web pages of Take you to recently period media Contains URL of Click a hyperlink Home engine program bookmarked Returns Updates downloading search (refreshes) the toStops start page E-Mail Button– Opens pagesdefault Web page page Type a URL in the Address box e-mail program Click a button on the Links toolbar Hyperlinks Use the Back and Forward buttons Use a Web site’s navigation aids Status bar– Messages about the browser’s Use the History list operation Use the Favorites or Bookmarks list 15 16 IP Address Domain Names Names are easy to remember than IP addresses Internet Protocol (communications standard) http://hk.yahoo.com = 202.43.220.99 In Windows, “run” → “cmd”→ “nslookup” A unique id no. (just like your postal address) You can own your domain names Typical IP address: 216.27.61.137 For .com, .net, .org, .us…etc. IP is assigned by network administrator e.g. www.networksolution.com You can check your IP (Windows) “run” → “cmd” → “ipconfig” 17 18 K.Ng Sept08 3
  • Uploading and Downloading Emerging Technologies Downloading – document or Ways to share information on the Internet file is transferred from Wiki – open-content encyclopedia another computer to your Weblog (blog) – Internet journal or diary computer Moblog (mobile blog) - content posted from a portable Uploading – files transferred p g phone or PDA from your computer to another computer 19 20 Finding Information on the Web Using Search Engines Ways to find information on To use a search engine, you: the Web: Choose a search engine (MSN, Lycos, Alta-Vista, Yahoo, Browse or surf the Web – This etc) involves linking from one Web Type in one or more words describing your topic page to another, and so forth oa o e ,a d o Search the Web – This method The search engine checks its database of Web pages involves using search engines to that contain the words typed locate Web pages with the The results are sent to your computer information you’re looking for Clicking on the link takes you to that page Subject guides – Web pages are grouped under headings 21 22 Using Search Techniques Using Search Techniques The following tables show the results of using and not using search operators Using Search Operators Learning a few search techniques can increase the Words Entered Possible Results – Web accuracy of Web searches No Search Operators pages containing Searches using search operators will improve search Words Entered Possible Results – Web pages +Fire+station Fire station performance containing +Fire+station* Fire station Fire stations Fire Most h i h following M search engines use the f ll i search h station +Fire-station* Fire Fire station operators: Fire station “Fire station” Fire station Inclusion/exclusion operators Fire and station Fire station Wild cards Fire Phrases Fire or station station Fire station Boolean operators Fire not station Fire 23 24 K.Ng Sept08 4
  • Rules for Evaluating Web Pages Using the Web for Schoolwork 1. Author – Who is the author? Use authoritative online sources 2. Sources – Where does the information come from? Use your library to find articles and books 3. Server – Who provides the server for the page? Cite online and offline references 4. Objectivity – Is the information objective or one- sided? 5. Style – Is the language objective or argumentative? 6. Purpose – What is the purpose of the page? 7. Accuracy – Is the information accurate? 8. Currency – Is the page up-to-date? 25 26 E-Mail: Staying in Touch E-Mail Addresses myname@someserver.com Users name@name of the server that the user is on E-mail is short for electronic mail It’s the most popular of the Internet services Messages are sent and received in a few seconds Attachments such as photos, music files, and any document may be sent with the message 27 28 Instant Messaging: E-Mailing Made Faster Spam: Can It Be Stopped? Spam – unsolicited e-mail advertising With Spam the recipient pays the postage To avoid spam Avoid posting your e-mail address Instant messaging systems let a user know when a friend or Use spam protectors business associate is online Don’t reply to spam It provides a means of communicating through real-time, text-based conversations 29 30 K.Ng Sept08 5
  • IRC: Text Chatting in Real Time File Transfer Protocol (FTP) Your Computer FTP Server DOWNLOAD UPLOAD FTP is a part of the Internet that enables client computers to transfer files Transferring files from an FTP site to the client is known as Internet relay chat consists of real-time, text-based downloading conversations Transferring files from the client to an FTP site is known as Chat groups are divided into channels that cover a uploading specific topic Clients may store files on an FTP site’s server 31 32 Usenet Standard Newsgroup Subcategories Usenet is the part of the comp computer applications, databases, multimedia Internet which enables users to participate in discussions misc activism, books, business, health and newsgroups sci chemistry, archeology, math Usenet newsgroups are soc human rights, world cultures organized into hierarchies (categories) and subcategories talk Euthanasia, gun control, religion Subcategories include news Usenet announcements Standard, Alt, Biz, and Local rec sports, gardening, bicycles newsgroups 33 34 Summary Listservs: Electronic Mail Lists • The Internet is the network of networks A listserv is an automatic • The Internet is accessed by way of an ISP list server • World Wide Web is a global system with Mail is sent to everyone billions of hypertext document on the list when e-mail is • Related information is linked using hypertext g yp generated. • A Web browser is a program that displays Web It is similar to a pages newsgroup or a forum • URL consists of a protocol, a server, a path, and a resource name • Search engines enable you to search huge databases of Web documents 35 36 K.Ng Sept08 6
  • Summary (continued) • You can improve search results using operators • You should always evaluate information you receive from the Web • Popular Internet services Wired and Wireless Communication • E-mail • Instant messaging • Internet Relay Chat • File Transfer Protocol • Discussion groups • Listservs 37 38 What You Will Learn . . . What You Will Learn . . . The definition of bandwidth Multiplexing and digital telephony and their impact The bandwidth needs of a typical user on line usage How modems change digital signals into analog Examples of how digitization and convergence are Transmission media and methods blurring the boundaries between popular communication devices i i d i Limitations of public switched telephone network (PTSN) for sending and receiving data Various wired and wireless applications 39 40 Connectivity Moving Data: Bandwidth and Modems Communications – sending and receiving messages Communications channels – paths through which messages are passed Signals can be: Analog – data is in continuous waveforms g the ability to link various media and devices Digital – data is in discontinuous pulses (0’s & 1’s) digital analog 41 42 K.Ng Sept08 7
  • Moving Data: Bandwidth and Modems Moving Data: Bandwidth and Modems Bandwidth – the amount of data that can be Modems transmitted through a given communications channel Transmit data over telephone lines Analog measured in cycles per second (Hz) Modulation – converts digital (from computer) to analog to Digital measured in bits per second (bps) cross telephone lines Broadband – any transmission medium that transports Demodulation – converts analog (phone lines) to digital for computer t high volumes of data at high speeds 43 44 Wireless Transmission Media Wireless Transmission Media: Twisted Pair Wireless transmission media refers to the methods of carrying data through the air or space using Twisted Pair – two infrared, radio, or microwave signals insulated wires twisted around each other – used for telephone p wires 45 46 Wireless Transmission Media: Coaxial Cable Wireless Transmission Media: Fiber Optic Coaxial Cable – center copper wire surrounded by insulation, surrounding a layer of braded wire Fiber-optic cable – thin strands of glass that carry data by light pulses 47 48 K.Ng Sept08 8
  • Wireless Transmission Media: Infrared Wireless Transmission Media: Radio Radio is a wireless transmission medium that carries Infrared is a wireless transmission medium that data via radio frequency signals carries data via light beams Wireless LANs in a home or business are one type of radio Transmitter and receiver must be in line of sight technology An IrDa port is needed to use infrared with a computer Radio signals can be long range (between cities or regions) and short range (within a building) Radio signals are susceptible to noise and electrical interference 49 50 Wireless Transmission Media: Bluetooth Wireless Transmission Media: Microwaves Short-range radio Microwaves are high- transmission technology frequency radio waves Devices identify each other by Much of long-distance identification number telephone service is carried by Connection is confirmed microwaves i before it is made final Microwaves travel in a straight Does not require a line of sight line Microwave relay stations are built about 30 miles apart 51 52 Wireless Transmission Media: Satellites Wired Communication via the PSTN The public switched telephone network (PSTN) is Satellites are microwave relay stations suspended in the world telephone system space It is used for data as well as voice communications They are positioned in geosynchronous orbits Twisted-pair wire and fiber-optic cable provide the connections for the system Satellites use microwave signals to transmit data to Home and business phones are connected to subscriber p and from earth-based microwave relay stations df th b d i l t ti loop carriers (SLCs) The area serviced by SLCs is called the local loop 53 54 K.Ng Sept08 9
  • Multiplexing Last Mile Technologies The “last mile” refers to the phone lines that connect homes and businesses to the local loop Multiplexing technology enables simultaneous multi- The inability of users to access the high-speed fiber-optic use of transmission lines cable creates a bottleneck of data called the last mile Copper wire allows up to 24 simultaneous calls per wire problem Fiber-optic cable permits up to 43,384 calls per strand 55 56 Convergence: Is it a Phone or a Last Mile Technologies Computer? Digital telephony technologies that use twisted-pair wire are referred to as last mile technologies Digitization – transformation of data into digital ISDN form DSL Convergence – merging of disparate objects or ideas Cable Modems into e i t new combinations bi ti Leased lines SONET MMDS 57 58 Cellular Telephones Risk of Using Cell Phones???? Cellular telephones enable calls to be placed through a wireless telecommunications system Frequency (Hertz, Hz) Cellular phones use radio or infrared signals Power (Watt, W) Cells are limited geographic transmission areas A mobile telephone switching office (MTSO) monitors the signal strength of cellular phones 59 60 K.Ng Sept08 10
  • Personal Communication Service (PCS) Web-Enabled Devices Personal Communication Service (PCS) A Web-enabled device is any device that can display refers to digital cellular telephone service and respond to HTML or XML technologies PDAs, cell phones, and tablet PCs are Web-enabled Digital cellular phones offer: devices Noise-free N i f sound d Improved coverage Protection from eavesdropping and phone fraud Voice recognition High-speed Internet access 61 62 Wired and Wireless Applications Wired and Wireless Applications Internet telephone – using the Internet for real-time Videoconferencing – using sound and video voice communications technologies to meet with others 63 64 Facsimile (Fax) Transmission Satellite Radio, GPS Satellite radio - broadcasts are transmitted through a satellite GPS – global positioning systems 27 earth orbiting satellites g Navigation systems Fax transmission is the means of sending an image of a document over telephone lines Fax modems support fax as well as data protocols 65 66 K.Ng Sept08 11
  • Text, Picture, and Video Messaging Summary • Bandwidth is the data transfer capacity of a Text messaging – sending text communication channel communications over a cell phone • A modem is used to send digital data over a phone line Picture messaging – using • Physical and wireless media are used to y camera phones to send pictures h t d i t to other cell phones communicate with technology • The public switched telephone network (PSTN) is mostly digital 67 68 Summary • Multiplexing is the transmission of more than one communication on a single line • Digitization is the transformation of data into digital form • Internet telephony and faxing can be p y g accomplished through the Internet 69 K.Ng Sept08 12