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2. CHAPTER 2 Communications, Networks, the Internet, and the World Wide Web
17. CHAPTER 2 Communications, Networks, the Internet, and the World Wide Web
18. Objectives Define communications
Identify the basic components of a communications system
Describe how and why network computers are used in schools and school districts
Explain how the Internet works
Describe the World Wide Web portion of the Internet
Specify how Web documents are linked to one another
Explain the use of Web browser software
Explain how to use a Web search tool to find information
Identify several types of multimedia products available on the Web
Explain how Internet services such as e-mail, newsgroups, chat rooms, and instant messaging work
Describe how to connect to the Internet and the WWW
19. Communications Networks Communications - refers to the transmission of data and information between two or more computers using a communications channel such as standard telephone lines
Communications network - is a collection of computers and other equipment organized to share data, information, hardware, and software
Communications software - programs that manage the transmissions of data between computers
Communications channel - is the path the data follows as the data is transmitted from the sending equipment to the receiving equipment in a communications system.
20. Communications Networks Continued Transmission media - is the physical materials or other means used to establish a communications channel
Twisted-pair cable - consists of pairs of plastic-coated copper wire twisted together
Other examples (coaxial cable, fiber-optic cable, microwave transmission, communications satellites, and wireless transmissions
21. Communications Networks Continued Digital signals - are individual electric pulses that a computer uses to represent data
Analog signals - continuous electrical wave used for telephone transmission and other devices
Modem - converts analog signals into digital signals
Network interface card (NIC) - connects computers directly to a school or business network without using a modem
22. Types of Networks Local area networks (LAN) - is a communications network that covers a limited geographical area such as a school, an office, a building, or a group of buildings
Wireless LAN (WLAN) - uses no wires, instead it uses wireless media, such as radio waves.
Wide area networks - covers a large geographical region and used regular telephone cables, digital lines, microwaves, wireless systems, satellites, or other combinations of communications channels.
Home networks - if you have multiple computers in your home or home office you can create your own network
23. History of the Internet ARPANET - Advanced Research Projects Agency Network
allow scientists to share information
parts could function even if some of it went down
Established 1969 and by 1984 it had 1,000 hosts
In 1986 NSFnet joined together with ARPANET to serve as the backbone of the Internet
In 1995 NSF turned over responsibilities to major corporations
Internet2 - extremely high speed network that will develop and test advanced Internet technologies for research, teaching, and learning.
24. How the Internet works Step 1. Data is divided into small pieces, called packets.
Step 2. Packets travel over the Internet via routers.
Step 3. At the destination, the packets are reassembled into the original message.
Packet switching
TCP/IP - transmission control protocol/Internet protocol - protocol used to define packet switching
25. ISP vs. OSP vs. WSP Internet service provider (ISP) - allows you to connect to the internet for a fee. (ex. Netzero, ATT)
Online service provider (OSP) - allows you to connect to the internet and also provides other personalized options for a higher fee than an ISP
Wireless service provider (WSP) - allows users to connect to the internet without any wires. (ex. Palm)
26. Ways to Connect to the Internet Dial-up access - you use your computer and a modem to dial in to the internet. (56k)
Cable modem - you use your existing tv cable and a cable modem (20-50 x faster)
Digital subscriber line - you use digital phone lines and dsl card. (25-150 x faster)
27. Internet Backbone Step 1: Request a web page from your home computer
Step 2: Modem converts digital to analog
Step 3: Data travels through telephone lines to local ISP
Step 4: Data may travel through 1 or more routers
Step 5: Regional ISP uses lines, leased from a telephone company, to send data to a national ISP
Step 6: A national ISP routes data across the country to another national ISP
Step 7: Data moves from a national ISP to a local ISP to a server that contains the requested site
Step 8: The server requests the data and sends it back through the internet.
28. Internet Addresses The Internet uses addresses the same way the post office does. Each computer has a specific numeric address.
I.e. 137.49.1.150
Domain name - the text version of a computer address
Domain abbreviations - .com, .edu, .gov, .mil, .net, .org, .k12
Country abbreviations
Au - Australia; CA - Canada; UK - United Kingdom
29. World Wide Web The Web - consists of electronic documents that have built in hyperlinks to other related documents
Hyperlinks - allow users to navigate quickly from one page to another
Web page - electronic document viewed on the Web that can contain audio, video, text, etc.
Web site - a collection of related web pages
Home page - starting point of a web site
URL - uniform resource locator
HTTP - hypertext transfer protocol
30. How a Web Page Works Three types of hyperlinks exist
Target hyperlinks - links within the same page
Relative hyperlinks - link to another document on the same Internet computer (server)
Absolute hyperlinks - link to another document that could be located on a computer across the country
HTML - hypertext mark-up language - the code that defines what a website will look like
31. Web Browser Software A web browser is a program that interprets HTML and displays Web pages and allows links to other pages
Mosaic - developed in 1993 by Marc Andreesen, a student at the University of Illinois
Netscape, Internet Explorer, AOL, Safari
32. Searching for Info. on the Web Search tools - enable users to locate information found at Web sites all over the world
Search engine - a type of search tool that uses keywords
Subject directory - a type of tool that allows the user to navigate the directories and subdirectories
33. Multimedia on the Web Multimedia is the combination of graphics, animation, audio, video, and virtual reality
Graphics - were the first media used to enhance text only sites
Animation - is the appearance of motions created by displaying a series of still images in rapid sequence
Audio - you can listen to prerecorded audio clips and live audio
Video - consists of full motion images that are played back at various speeds
Virtual reality - is the simulation of a real or imagined environment
34. E-mail E-mail (electronic mail) - is the transmission of messages and files via a computer network
E-mail program - allows you to compose, view, send, and receive email
E-mail address - is a combination of a user name and a domain name
35. File Transfer Protocol FTP - is an Internet standard that allows you to exchange files with other computers on the Internet.
Anonymous FTP - anyone can transfer files on this type of site.
36. Information Sharing via the Web Newsgroup - is an online area in which users conduct written discussions about a particular subject
Mailing list - is a group of email addresses given a single name
Chat rooms - is a real-time typed conversation
Instant messaging - is real-time Internet communications service that notifies you when one or more people are online.
Netiquette - is the code of acceptable behavior while on the Internet
37. Interesting Sites http://www.epals.com
