The Internet and World Wide Web

Objectives Define the concept of a network Describe the components of a network Define Internet Discuss how the Internet works Understand ways to access the Internet Define Domain Name Describe the components of the URL Define World Wide Web (WWW) Describe the components of the WWW

The Internet What is a network? A collection of computers and devices connected together via communications devices and media Modems Cables Telephone lines Satellites Next p. 2.2

What Is a Computer Network? Two or more connected computers Major components in simple network Client computer Server computer Network interfaces (NICs) Connection medium Network operating system Hub or switch connecting multiple computers in a network Routers Device used to route packets of data through different networks, ensuring that data sent gets to the correct address

Components of a Simple Computer Network

Networks in Large Companies Components can include: Hundreds of local area networks (LANs) linked to firmwide corporate network Various powerful servers Web site Corporate intranet, extranet Backend systems Mobile wireless LANs (Wi-Fi networks) Videoconferencing system Telephone network Wireless cell phones

Corporate Network Infrastructure

Key Digital Networking Technologies Client/server computing Distributed computing model Clients linked through network controlled by network server computer Server sets rules of communication for network and provides every client with an address so others can find it on the network Has largely replaced centralized mainframe computing The Internet: Largest implementation of client/server computing

Key Digital Networking Technologies Packet switching Method of slicing digital messages into parcels (packets), sending packets along different communication paths as they become available, and then reassembling packets at destination Previous circuit-switched networks required assembly of complete point-to-point circuit Packet switching more efficient use of network’s communications capacity

Packet-Switched Networks and Packet Communications Data are grouped into small packets, which are transmitted independently over various Communications channels and reassembled at their final destination.

Key Digital Networking Technologies TCP/IP and connectivity Connectivity between computers enabled by protocols Protocols: Rules that govern transmission of information between two points Transmission Control Protocol/Internet Protocol (TCP/IP) Common worldwide standard that is basis for Internet Department of Defense reference model for TCP/IP Four layers Application layer Transport layer Internet layer Network interface layer

TCP/IP Reference Model Application Layer Defines the protocol that applications use to exchange data – FTP, SMTP, HTTP, HTTPS Transport Layer Provides communication session management between host computers. Defines the level of service and status of the connection used when transporting data. TCP Internet Layer Addressing, routing, and packaging data packets called IP diagrams – IP Network Interface Specifies details of how data is physically sent through the network, including how bits are electrically signaled by hardware devices that interface directly with a network medium, such as coaxial cable, optical fiber, or twisted-pair copper wire.

The Transmission Control Protocol/Internet Protocol (TCP/IP) Reference Model

Types of Networks Signals: analog vs. digital Modem: Translates digital signals into analog form Local-area networks (LANs) Campus-area networks (CANs) Peer-to-peer Topologies: star, bus, ring Metropolitan and wide-area networks Wide-area networks (WANs) Metropolitan-area networks (MANs) Spans a city and sometimes major suburs

Network Topologies

Physical Transmission Media Twisted-pair wire (modems) simplest and slowest Coaxial cable Copper wires surrounded by thick insulation Fiber optics and optical networks Dense wavelength division multiplexing (DWDM) Wireless transmission media and devices Microwave Satellites Cellular telephones Transmission speed (hertz, bandwidth)

The Internet What is the Internet? Also called the Net A worldwide collection of networks that links billions of businesses, government agencies, educational institutions, and individuals

The Internet What are some of the services found on the Internet? instant messaging Web file transfer e-mail message board chat

History of the Internet How did the Internet originate? Goal: To allow scientists at different locations to share information and work together on military and scientific projects ARPANET Networking project by Pentagon’s Advanced Research Projects Agency (ARPA) Became functional in September 1969 Goal: To function even if part of the network were disabled or destroyed

History of the Internet What is a host node? University of California at Los Angeles Also called a host Any computer that directly connects to a network Often stores and transfers data and messages Provides network connections for other computers Four original nodes on ARPANET Stanford Research Institute University of California at Santa Barbara University of Utah

History of the Internet What is NSFnet? The National Science Foundation’s network Five supercomputer centers Connected to ARPANET in 1986 The Internet! ARPANET NSFnet

History of the Internet How has this network grown? Today More than 1 Billion users 1984 More than 1,000 host nodes 1969 Four host nodes

From Research Project to Information Infrastructure Growth In The Number Of Internet Hosts

The Web and Commercialization of the Internet Growth Of The World Wide Web

New Structure for the Internet The Internet is organized around four network access points (NAPs). A different company operates each of these NAPs. These companies sell access to the Internet through their NAPs to organizations and businesses.

New Structure for the Internet Network Access Points On The Internet Backbone

May also provide a toll-free number How the Internet Works What is an Internet service provider (ISP)? National ISP Provides local telephone numbers in most major cities and towns nationwide May also provide a toll-free number A business that has a permanent Internet connection Provides temporary connections to individuals and companies for free or for a fee Regional ISP Provides access to the Internet through one or more telephone numbers local to a specific geographic location Next p. 2.5

History of the Internet Who provides the structure for the Internet today? Telephone companies Cable companies Networks from corporations, commercial firms, and other companies Government Satellite companies

Online Service Provider (OSP) Wireless Service Provider How the Internet Works What are other service providers? Online Service Provider (OSP) Supplies Internet access Has many members- only features that offer special content Wireless Service Provider Company that provides wireless Internet access

Newer high-speed technologies How the Internet Works How can you connect to the Internet? Dial-up access Home or small business Computer, modem, regular telephone line Dial into an ISP or OSP High speed connection Employees Computers part of a local area network (LAN) Connect to service provider through a high-speed connection line leased from local telephone company Newer high-speed technologies Home and small business Digital subscriber line (DSL) – provides high-speed Internet connections over regular copper telephone line Cable modem- provides high-speed Internet connections through cable television network

first part identifies network last part identifies specific computer How the Internet Works What is an Internet protocol (IP) address? Number that uniquely identifies each computer or device connected to the Internet Four groups of numbers, each separated by a period Number in each group is between 0 and 255 IP address 199.95.72.10 first part identifies network last part identifies specific computer

Tim Berners-Lee Created the World Wide Web Director of the World Wide Web Consortium (W3C) at MIT

How the Internet Works What is a domain name? IP address 199.95.72.10 Text version of an IP address Components are separated by periods Each domain name represents one or more IP addresses IP address 199.95.72.10 www.scsite.com Domain name

How the Internet Works What is a top-level domain (TLD) abbreviation? Identifies the type of organization associated with the domain Sometimes called dot com when TLD is com TLD Abbreviation Type of Domain Com Commercial organizations, businesses, and companies Edu Educational institutions Gov Government agencies Mil Military organizations Net Network provider Org Non-profit organizations

The World Wide Web What is a Uniform Resource Locator (URL)? Unique address for a Web page Browser retrieves a Web page by using the URL Also called a Web address Type the URL into the address text box on the browser and press the Enter key to display a Web page http://www.nationalgeographic.com/travel/index.html address text box

The World Wide Web What are the parts of a URL? protocol domain name path http://www.nationalgeographic.com/travel/index.html Click to view Web Link then click URLs

History of the Internet Who controls the Internet? The Internet is a public, cooperative, and independent network No single entity controls or owns the Internet Several organizations advise and define standards World Wide Web Consortium (W3C) Oversees research and sets standards and guidelines Internet2 (I2) Internet-related research and development project Develops and tests advanced Internet technologies

How the Internet Works What systems control domain names? Internet Corporation for Assigned Names and Numbers (ICANN) Group that assigns and controls TLDs Domain name system (DNS) System on the Internet that stores the domain names and their corresponding IP addresses DNS server Translates the domain name into its associated IP address

The World Wide Web What is the World Wide Web (WWW)? Also known as the Web A worldwide collection of electronic documents Each document on the Web is called a Web page Can contain text, graphics, sound, and video Can contain built-in connections to other documents A Web site is a collection of related Web pages

The World Wide Web What is a Web browser? Also called a browser Software program that allows you to access and view Web pages Two popular browsers for personal computers Netscape Internet Explorer Next p. 2.9 Fig. 2-6

Can take from a few seconds to several minutes The World Wide Web What is downloading? The process of receiving information, such as a Web page, onto your computer from a server on the Internet Can take from a few seconds to several minutes You can speed up the display of pages by turning off the graphics and displaying only text in most Web browsers

The World Wide Web What is a hyperlink? Also called a link Built-in connection to another related Web page or part of a Web page Allows you to obtain information in a nonlinear way

The World Wide Web How can you identify a link? Link can be a word, phrase, or image Text links usually are underlined or in a color different from the rest of the document A graphical link may change its appearance when you point to it The shape of the pointer on the screen changes to a small hand with a pointing index finger when you position it on a link or point to the link Click the link to activate it

The World Wide Web How do you navigate a variety of links? pointer Some links display a different color when you point to them. Click the link to display its associated Web site or Web page. pointer Some links are underlined. Click the link to display the associated Web site or Web page. pointer Some links are graphical images. Click the link to display its associated Web site or Web page.

The World Wide Web What is surfing the Web? Links can point to an item on the same Web page, a different Web page at the same Web site, or a separate Web page at a different Web site in another city or country The activity of jumping from one Web page to another is surfing

The World Wide Web What is a search engine? A software program you can use to find Web sites, Web pages and Internet files Spider A program that reads pages on Web sites in order to find Web pages that contain the search text Also called a crawler or bot Search text A word or phrase entered in the search engine’s text box Also called keywords

The World Wide Web What is a hit? Any Web page name that lists as the result of a search The fewer ‘hits’ the better Point of searching the web is to narrow your search

The World Wide Web What is a directory? An organized set of topics Used by a search engine to aid in locating Web sites Each major topic has related subtopics

business/marketing Web page informational Web page The World Wide Web What are the six basic types of Web pages? advocacy Web page business/marketing Web page informational Web page portal Web page personal Web page news Web page

The World Wide Web What is an advocacy Web page? Contains content that describes a cause, opinion, or idea Purpose is to convince the reader of the validity of the cause, opinion, or idea

The World Wide Web What is a business/marketing Web page? Contains content that promotes or sells products or services Often allows you to purchase products or services online

The World Wide Web What is an informational Web page? Contains factual information Many U.S. government sites provide information

The World Wide Web What is a news Web page? Contains newsworthy material Stories and articles relating to current events, life, money, sports, and the weather

The World Wide Web What is a personal Web page? A Web page maintained by a private individual who normally is not associated with any organization Reasons: job hunting and sharing life experience with the world

The World Wide Web What is a portal Web page Often called a portal Offers a variety of Internet services from a single, convenient location

The World Wide Web What services are often found on a portal? search engine e-mail sports and weather stock quotes newsgroups or message boards local , national, and worldwide news instant messaging reference tools maps free personal Web pages chat rooms shopping malls and auctions calendars p. 2.17

newsgroup or message board The World Wide Web What is a Web community? A Web site that joins a specific group of people with similar interests or relationships Usually offer special services to facilitate communication among members newsgroup or message board e-mail online photo albums chat room