Connecting to the Internet

Transcription

1 The Internet & The World Wide Web CIT 100 Norm Downey What is the Internet? A global computer network made up of thousands of privately and public owned computers and computer networks. More than one billion computers are directly connected to the Internet. 2 By the way, Internet is a proper name, and as such, it is always capitalized Interoperability Interoperability enables computers that are of different brands and models, and using different operating systems exchange data and even control each other s operation Example: 3 Joe sends an from his Microsoft Windows PC that is processed by a Unix server and read by Jane on her Apple ipad and Jenny on her Android smart phone Internet and the Client/Server Model 4 Client requests some type of service (such as a file or database access) from the server Server fulfills the request and transmits the results to the client over a network 1

2 Client/Server Example You, sitting at your PC in class, type in the web address for the class website into your computers browser. In this case you are the Client. The request you make is processed by a college server (a fast, high capacity computer) sends the page to your PC. 5 The college computer storing/sending the webpage is the Server TCP/IP Transmission Control Protocol (TCP) Divides transmitted data into small packets for transmission, and reassembles data packets upon delivery into a complete message Internet Protocol (IP) Address 6 Numeric address that uniquely identifies each device on a computer network Four sets of numbers (0-255) each separated by a dot Example: Internet Service Providers (ISP) Connecting to the Internet 7 A company that provides access to the Internet For a fee, the Internet Service Provider provides you with a username & password that allows you to connect to the ISP s network 8 2

3 ISP Responsibilities Providing and maintaining connection to the Internet Supporting hardware and software need for connection Protecting network from viruses, hackers and other illegal activities Providing customer service Providing technical support 9 Baseband versus Broadband Baseband Type of data transmission that allows only one signal at a time. Example your telephone land line Broadband A transmission medium that transports high volumes of data at high speeds Data transmission in which a single wire can carry several channels (pathways) of data at one time. Example Cable TV & DSL 10 Baseband versus Broadband 11 Baseband Broadband Bandwidth versus Throughput Bandwidth is the maximum data transfer rate of a communication channel in a specific time period this is a theoretical speed Throughput is the actual amount of data that is transmitted in a specified time period 12 Throughput speed is almost always lower and can never exceed than bandwidth speed 3

4 Bandwidth versus Throughput a real world example (sort of ) Bandwidth 13 in theory you could drive from Monroeville to downtown in 12 minutes, if there was no traffic, you had a fast car and you were allowed to drive over 100 mph Throughput the reality is it takes an hour to go from Monroeville to downtown because of rush hour traffic, the tunnels, speed limits, the limits of your car and driving skill, potholes, etc. Bandwidth is a theoretical maximum speed, throughput is the actual speed Bandwidth Usually expressed in bits per second (bps) The greater the bandwidth, the faster the connection and generally, the more expensive the connection Broadband connections provide greater bandwidth than baseband connections What s a bit? Stay tuned we ll get to that next time. 14 The Last Mile Problem The last mile problem refers to the slowest part of a connection, which is generally local cable or phone lines. Maximum bandwidth is limited by the slowest section of the connectivity chain 15 Types of Internet Connections Dial-up Cable DSL Fiber Optics WiMAX 16 4

5 Dial-Up Connections Slowest, cheapest Internet connection that uses regular phone lines. Dial-up is a Baseband connection 17 Cable (as in Cable TV) High speed, always on Internet connection Uses coaxial cable and a cable modem for a broadband Internet connection Copper coaxial cable provides much greater bandwidth than telephone line Cable s last mile problem is that you share your bandwidth with your neighbors 18 Cable (as in Cable TV) 19 Cable TV Connections 20 How a cable Internet connection looks in your house How a cable Internet connection looks in your neighborhood 5

6 Cable TV Connections Lowest-capacity coaxial cable has far greater capacity than ordinary telephone lines Coaxial cable bandwidth is divided among 3 activities: TV shows downstream to client Upstream data requests Downstream data (web pages, , etc.) Fast Downstream 1 to 50 Mbps rates 21 Digital Subscriber Line (DSL) High-speed, always-on, Internet access 22 Compresses data to improve transmission speed over regular copper telephone lines DSL s last mile problem is that it still uses ordinary phone lines which can be plagued with noise (interference) Supports throughputs of 1 to 6 Mbps Not available everywhere DSL Connection What about Fiber Optics? 23 Central Telephone Switching Station Internet Fiber Optic cable consists of thin strands of glass or plastic that carry data on pulses of light Capable of enormous throughput Fiber optic cable, run directly to your home, virtually eliminates the last mile problem 24 6

7 Other Transmission Media Infrared Wireless using light Limited to line of sight of about 100 feet Bluetooth Named for 10 th century Viking king Limited to 30 feet and 8 devices Uses radio signals not limited to line of sight 25 WiMAX WiMAX Worldwide Interoperability for Microwave Access High speed access over long distances Up to 30 miles for stationary point-to-point 3 to 10 miles for mobile access Not good for mountainous areas What is the World Wide Web? There is a short answer question on the quiz that will ask you to explain the difference between the Internet and the World Wide Web The World Wide Web Billions of specially formatted documents stored on Internet servers and accessed through web browsers These documents are formatted using HTML (Hyper Text Markup Language) HTML supports links to other documents, as well as graphics, audio, and video files Not all Internet servers are part of the World Wide Web 28 7

8 Internet versus World Wide Web Internet 29 Network infrastructure (cables, computers, routers, software, etc.) Used to access computers and exchange data in a variety of formats Uses TCP/IP protocols World Wide Web Billions of specially formatted documents Uses the Internet as its transport mechanism Uses HTTP or HTTPS protocols They are NOT the same thing! Websites Websites and Web pages 30 Location in cyberspace that makes web pages available A collection of related web pages Web pages Specially formatted, linked documents on a website that includes text, graphics, sound, animation or video What s cyberspace? Virtual territory that is accessible only with a computer Web Browsers 31 Software that displays web documents and provides access to linked documents Runs on the client side of the Client/Server Model Includes: Internet Explorer (Microsoft) Firefox (Mozilla Foundation formerly Netscape) Chrome (Google) Safari (by and for Apple Macs) Opera (Opera Software) Web Servers Computers running special server software that Accepts requests for information, Processes requests and Sends requested documents The server side of the Client/Server Model 32 8

9 Hyperlinks Clickable links in webpages that open other web documents Examples: or 33 HTML Web documents are created using HTML (Hypertext Markup Language) 34 HTML is a Markup Language used to define the appearance of Web pages CCAC teaches an HTML class CIT 125 How do you know if a website is secure? Rules for Evaluating Web Pages Look for the lock symbol in Internet Explorer (above). Clicking on the company name in Internet Explorer or Firefox (right) shows security information. 35 Who is the author? Are they an expert? Are the sources cited? Are the authors sources respected? Who pays for the web site? Is the presentation one sided? Is the language objective or argumentative? What is the purpose of the page? Is the page accurate? Is the page up to date? Example:

10 Search Engines A program that searches documents for specified keywords and returns a list of the web documents where the keywords were found Search engines then use those results to display meaningful results Search Engines include: Google Bing Yahoo Dogpile 37 Other Terms to Know 38 URL Uniform Resource Locator Web address Character string that precisely identifies an Internet resources type and location Examples: Cookies Small text files written to your computer s hard drive, generally without users knowledge or consent Used to keep track of user preferences or for compiling information about user s web browsing behavior 40 10

11 Cookies Uploading versus Downloading Cookies allow websites such as Amazon.com to keep track of recent searches and to present lists of related items to hopefully increase their sales Also used to build web Shopping Carts 41 Uploading Transferring files from your computer to another computer on Internet From client to server Downloading Transferring files from another computer to your computer From server to client 42 Wiki Wikis and Blogs From Hawaiian word wiki-wiki meaning fast Web page on which a visitor can post text or images, read and exchange posted information and track changes Blogs Short for web log Allow user to post thoughts and opinions 43 short for electronic mail Allows sending and receiving messages via a computer network including over the Internet address consist of User name (ndowney) At Host (acd.ccac CCAC s Academic server) Domain (.edu top level domain name) Spam unsolicited advertisements 44 11

12 Social Networking Web sites provide Web-based tools for users to share information about themselves with others on the Web, and find, meet, and converse with other members Facebook MySpace LinkedIn 45 Media Sharing Media-sharing web sites provide methods for members to store and share digital media files on the Web YouTube Flickr PhotoBucket 46 Podcasting 47 An audio file that contains a recorded broadcast distributed over the Internet via the World Wide Web Online Safety 48 12

13 Phishing A type of attack where a phisher (a crook) poses as a legitimate business in an or on a website in an attempt to obtain personal information for purposes of identity theft No bank will ever send you an asking for your PIN number Do not click hyperlinks in suspicious s 49 Malware Short for MALicious software Malicious is defined as being characterized by malice; intending to do harm Malware is a class of software designed to damage or infiltrate a computer or network s data without users consent or knowledge Malware CANNOT do physical harm to hardware 50 Types of Malware Spyware Collects your personal information Monitors your web usage Reports information to others for purposes of identity theft 51 Types of Malware Viruses Hidden programming code that damages or destroys infected files Designed to self-replicate Run when file is opened or program is started Spread through sharing infected files often via

14 Types of Malware - Trojans A destructive program that pretends to be a useful application Initially appears to perform a desirable function for the user, but (perhaps in addition to the expected function) steals information or does other harm Derives it s name from the Trojan Horse of Greek Mythology 53 How to Steal Passwords Password guessing Your child or pet s names are not good passwords Shoulder surfing Watch out for lurkers Packet sniffing 54 This involves specialized software to capture unencrypted data moving through a network as data packets How to Steal Passwords Dumpster diving Buy a shredder and use it don t leave sensitive paper in the trash Social engineering Sweet talked into giving up your passwords Super user status 55 Giving password or other sensitive data to people you think you can trust like your teacher or the guy from the Helpdesk Effective Passwords should be Strong & Long 56 Use words that are unrelated to your interests, mix upper and lowercase letters, numbers, and symbols The longer the password the harder to crack Microsoft Password Checker Unique Vary passwords don t use one password for everything Changed regularly Change your passwords at least twice a year 14

15 Protecting Yourself Online 57 Protecting Yourself Online Virus protection Application that runs your computer and searches viruses and other malware Firewall Program designed to control flow between your computer and the Internet Stops malware from Entering your computer or, if it s already in Sending messages out from your computer 58 Protect Yourself Online Parental controls Controls what children can/cannot see & do on Internet and WWW Utilizes database of unacceptable websites Keep Up-to-date Turn on Windows Automatic Updating feature Keep Anti-Virus programs up-to-date Schedule virus scans 59 Protect Yourself Online Be careful what you download and install Be sure the source is reputable When downloading software watch out for Trojans Be careful were you web surf and what you do in public on public networks Avoid being scammed Never give out passwords Don t be so trusting 60 15