Copyright © 2008 Pearson Education, Inc. Publishing as Pearson Addison-WesleyFluency with Information TechnologyThird Editionby Lawrence SnyderChapter 3:Making the Connection: The Basics of Networking3-21-2Copyright © 2008 Pearson Education, Inc. Publishing as Pearson Addison-WesleyNetworked Computers Change Our Lives• The Information Age has brought profound changes– Nowhere is remote– People are interconnected– Social relationships are changing– English is becoming a universal language– Freedom of speech and assembly have expanded3-31-3Copyright © 2008 Pearson Education, Inc. Publishing as Pearson Addison-WesleyNowhere Is Remote• Internet is a complete information resource no matter where you are– Some differences remain because older sources are not yet all online• Homes are not remote from work– Information workers can telecommute and live long distances from their offices3-41-4Copyright © 2008 Pearson Education, Inc. Publishing as Pearson Addison-WesleyPeople Are More Interconnected• Family and friends stay in closer, more frequent contact via Internet than via telephone or "snail mail"• WWW lets us meet people passively– People with similar interests find each other through search engines– Associations can form rapidly3-51-5Copyright © 2008 Pearson Education, Inc. Publishing as Pearson Addison-WesleySocial Interactions Are Changing• Time spent online displaces other in-person social activities (displacement effect)• The effects are complicated (pros/cons)• The Internet is changing social interactions, but we don't fully understand how3-61-6Copyright © 2008 Pearson Education, Inc. Publishing as Pearson Addison-WesleyEnglish Is Becoming a Universal Language• Influence of American pop culture since World War II• Dominance of science and technology in English-speaking countries• Much software is available only in English• Most web pages are in English3-71-7Copyright © 2008 Pearson Education, Inc. Publishing as Pearson Addison-WesleyFreedom of Speech and of Assembly Have Expanded• Internet use is unmediated– No editorial oversight or significant restrictions– Wikis• Allows for political and artistic expression• Blogs record personal thoughts for public viewing• Like-minded people can communicate, even on private topics3-81-8Copyright © 2008 Pearson Education, Inc. Publishing as Pearson Addison-WesleyCommunication Types• General Communication– Synchronous: sender and receiver are active at the same time• e.g., telephone call, instant messaging (IM)– Asynchronous: sending and receiving occur at different times• e.g., e-mail– Broadcast communication (or multicast): single sender and many receivers– Point-to-point communication: single sender and single receiver3-91-9Copyright © 2008 Pearson Education, Inc. Publishing as Pearson Addison-Wesley3-101-10Copyright © 2008 Pearson Education, Inc. Publishing as Pearson Addison-WesleyThe Internet's Communication Properties• Internet provides a general communication "fabric" linking all computers connected to it– Can be applied in many ways:• Point-to-point asynchronous– E-mail is alternative to standard mail• Point-to-point synchronous– IM is alternative to telephone• Multicasting– Chat rooms are alternatives to magazines• Broadcasting– Web pages are alternatives to radio and television3-111-11Copyright © 2008 Pearson Education, Inc. Publishing as Pearson Addison-WesleyThe Client/Server Structure• Server is the computer that stores the web page– Web server, file server, mail server• Client is the computer that accesses the web page• When you click link, your computer enters client/server relationship with web server• Once the page is sent to you, the client/server relationship ends• Server can form many brief relationships so it can serve many clients at the same time3-121-12Copyright © 2008 Pearson Education, Inc. Publishing as Pearson Addison-Wesley3-131-13Copyright © 2008 Pearson Education, Inc. Publishing as Pearson Addison-WesleyThe Medium of the Message• The Name Game of Computer Addresses– IP addresses: Each computer connected to the Internet is given a unique numerical address• For example: 128.95.1.207– Hostnames: Human-readable symbolic names, based on domain hierarchy• Easier to read and remember• For example: spiff.cs.washington.edu3-141-14Copyright © 2008 Pearson Education, Inc. Publishing as Pearson Addison-Wesley3-151-15Copyright © 2008 Pearson Education, Inc. Publishing as Pearson Addison-Wesley3-161-16Copyright © 2008 Pearson Education, Inc. Publishing as Pearson Addison-Wesley3-171-17Copyright © 2008 Pearson Education, Inc. Publishing as Pearson Addison-WesleyDNS Servers• The Domain Name System (DNS) translates the human-readable hostnames into IP addresses• Internet host knows the IP address of its nearest DNS server, a computer that keeps a list of host/domain names and corresponding IP addresses• When you use a hostname to send information, your computer asks the DNS server to look up the IP address• If the DNS server doesn't know the IP address, it asks a Root name server, which keeps the master list of name-to-address relationships3-181-18Copyright © 2008 Pearson Education, Inc. Publishing as Pearson Addison-Wesley3-191-19Copyright © 2008 Pearson Education, Inc. Publishing as Pearson Addison-WesleyTop-level Domains• Domain is a related group of networked computers• Top-level domains appear in the last part of domain name:.edu educational institutions.org organizations.net networks.mil military.gov government agenciesMnemonic two-letter country designators such as .ca (Canada)3-201-20Copyright © 2008 Pearson Education, Inc. Publishing as Pearson Addison-WesleyFollowing Protocol• A protocol describes how the information is actually sent• TCP/IP (Transmission Control Protocol/Internet Protocol)– Information is broken into a sequence of small fixed-size units called IP packets– Each packet has space for the unit of data, the source and destination IP addresses, and a sequence number– The packets are sent over the Internet one at a time using whatever route is available– Because each packet can take a different route, congestion and service interruptions do not delay transmissions3-211-21Copyright © 2008 Pearson Education, Inc. Publishing as Pearson Addison-Wesley3-221-22Copyright © 2008 Pearson Education, Inc. Publishing as Pearson Addison-Wesley3-231-23Copyright