Chapter 2 Technology Infrastructure The Internet and the

Chapter 2: Technology Infrastructure: The Internet and the World Wide Web

Objectives In this chapter, you will learn about: • The origin, growth, and current structure of the Internet • How packet-switched networks are combined to form the Internet • How Internet protocols and Internet addressing work • The history and use of markup languages on the Web, including SGML, HTML, and XML • How HTML tags and links work on the World Wide Web • The differences among internets, intranets, and extranets • Options for connecting to the Internet, including cost and bandwidth factors • Internet 2 and the Semantic Web 2

The Internet and the World Wide Web • Computer network – Any technology that allows people to connect computers to each other • The Internet – A large system of interconnected computer networks spanning the globe • World Wide Web – A subset of computers on the Internet 3

History of the Internet • Wikipedia Internet History • Early 1960 s – U. S. Department of Defense funded research to explore creating a worldwide network • In 1969 – Defense Department researchers connected four computers into a network called ARPANET • Throughout the 1970 s and 1980 s – Academic researchers connected to ARPANET and contributed to its technological developments 4

New Uses for the Internet • 1972 – E-mail was born • Mailing list – E-mail address that forwards any message received to any user who has subscribed to the list • Usenet – Started by a group of students and programmers at Duke University and the University of North Carolina 5

Growth of the Internet • In 1991, the NSF: – Eased restrictions on commercial Internet activity – Began implementing plans to privatize the Internet • Network access points (NAPs) – Basis of the new structure of the Internet • Network access providers – Sell Internet access rights directly to larger customers and indirectly to smaller firms and individuals through ISPs 6

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Emergence of the World Wide Web • The Web – Software that runs on computers connected to the Internet • Vannevar Bush speculated that engineers would eventually build a memory extension device (the Memex) • In the 1960 s, Ted Nelson described a similar system called hypertext 8

Emergence of the World Wide Web • Tim Berners-Lee developed code for a hypertext server program • Hypertext server: – Stores files written in the hypertext markup language – Lets other computers connect to it and read files • Hypertext Markup Language (HTML) – Includes a set of codes (or tags) attached to text 9

Packet-Switched Networks • Local area network (LAN) – Network of computers located close together • Wide area networks (WANs) – Networks of computers connected over greater distances • Circuit – Combination of telephone lines and closed switches that connect them to each other 10

Packet-Switched Networks (continued) • Circuit switching – Centrally controlled, single-connection model • Packets – Files and e-mail messages on a packetswitched network are broken down into small pieces, called packets – Travel from computer to computer along the interconnected networks until they reach their destinations 11

Routing Packets • Routing computers – Computers that decide how best to forward packets • Routing algorithms – Rules contained in programs on router computers that determine the best path on which to send packets 12

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Internet Protocols • Protocol – Collection of rules formatting, ordering, and errorchecking data sent across a network • Rules for message handling include: – Independent networks should not require any internal changes to be connected to the network – Packets that do not arrive at their destinations must be retransmitted from their source network – Router computers act as receive-and-forward devices – No global control exists over the network 14

TCP/IP • TCP – Controls disassembly of a message or a file into packets before transmission over the Internet – Controls reassembly of packets into their original formats when they reach their destinations • IP – Specifies addressing details for each packet 15

IP Addressing • Internet Protocol version 4 (IPv 4) – Uses a 32 -bit number to identify computers connected to the Internet • Base 2 (binary) number system – Used by computers to perform internal calculations • Subnetting – Use of reserved private IP addresses within LANs and WANs to provide additional address space 16

IP Addressing (continued) • Private IP addresses – Series of IP numbers not permitted on packets that travel on the Internet • Network Address Translation (NAT) device – Used in subnetting to convert private IP addresses into normal IP addresses • Internet Protocol version 6 (IPv 6) – Protocol that will replace IPv 4 – Uses a 128 -bit number for addresses 17

Domain Names • A domain name is a set of words assigned to a specific IP address • Top-level domain (or TLD) – Rightmost part of a domain name • Internet Corporation for Assigned Names and Numbers (ICANN) – Responsible for managing domain names and coordinating them with IP address registrars 18

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Web Page Request and Delivery Protocols • Web client computers – Run software called Web client software or Web browser software • Web server computers – Run software called Web server software 20

Web Page Request and Delivery Protocols • Hypertext Transfer Protocol (HTTP) – Set of rules for delivering Web page files over the Internet • Uniform Resource Locator (URL) – Combination of the protocol name and domain name – Allows a user to locate a resource (the Web page) on another computer (the Web server) 21

Electronic Mail Protocols • Electronic mail (e-mail) – Must be formatted according to a common set of rules • E-mail server – Computer devoted to handling e-mail • E-mail client software – Used to read and send e-mail – Examples include Microsoft Outlook and Netscape Messenger 22

Electronic Mail Protocols • Simple Mail Transfer Protocol (SMTP) – Specifies the format of a mail message • Post Office Protocol (POP) – POP messages can tell the e-mail server to: • Send mail to a user’s computer and delete it from the e-mail server • Send mail to a user’s computer and not delete it • Simply ask whether new mail has arrived 23

Markup Languages and the Web • Text markup language – Specifies a set of tags that are inserted into text • Standard Generalized Markup Language (SGML) – Older and more complex text markup language than HTML • World Wide Web Consortium (W 3 C) – Not-for-profit group that maintains standards for the Web 24

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Standard Generalized Markup Language • Offers a system of marking up documents that is independent of any software application • Nonproprietary and platform independent • Offers user-defined tags • Costly to set up and maintain 26

Hypertext Markup Language (HTML) • Prevalent markup language used to create documents on the Web today • HTML tags are interpreted by a Web browser and are used by it to format the display of the text • HTML links can be structured as: – Linear hyperlink structures – Hierarchical hyperlink structures 27

Hypertext Markup Language (HTML)) • The most common scripting languages include Java. Script, JScript, Perl, and VBScript • Cascading Style Sheets (CSS) are sets of instructions that give Web developers more control over the format of displayed pages – Style sheet is: • Usually stored in a separate file • Referenced using the HTML style tag 28

Extensible Markup Language (XML) • XML uses paired start and stop tags • It includes data management capabilities that HTML cannot provide • Differences between XML and HTML: – XML is not a markup language with defined tags – XML tags do not specify how text appears on a Web page 29

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Intranets and Extranets • Intranet – Interconnected network that does not extend beyond the organization that created it • Extranet – Intranet extended to include entities outside the boundaries of an organization – Connects companies with suppliers, business partners, or other authorized users 31

Public and Private Networks • Public network – Any computer network or telecommunications network available to the public • Private network – A private, leased-line connection between two companies that physically connects their intranets • Leased line – Permanent telephone connection between two points 32

Virtual Private Network (VPN) • VPN – An extranet that uses public networks and their protocols • IP tunneling – Effectively creates a private passageway through the public Internet • Encapsulation – Process used by VPN software 33

Internet Connection Options • Bandwidth – Amount of data that can travel through a communication line per unit of time • Net bandwidth – Actual speed that information travels • Symmetric connections – Provide the same bandwidth in both directions • Asymmetric connections – Provide different bandwidths for each direction 34

Voice-Grade Telephone Connections • POTS, or plain old telephone service – Uses existing telephone lines and an analog modem – Provides bandwidth between 28 and 56 Kbps • Digital Subscriber Line (DSL) – Connection methods that do not use a modem • Integrated Services Digital Network (ISDN) – Bandwidths between 128 Kbps and 256 Kbps 35

Broadband Connections • Broadband connections operate at speeds of greater than 200 Kbps • Asymmetric digital subscriber line (ADSL) – Transmission bandwidth is from 100 to 640 Kbps upstream and from 1. 5 to 9 Mbps downstream • Cable modems – Provide transmission speeds between 300 Kbps and 1 Mbps • DSL – Private line with no competing traffic 36

Leased-Line Connections • DS 0 (digital signal zero) – Telephone line designed to carry one digital signal • T 1 line (also called a DS 1) – Carries 24 DS 0 lines and operates at 1. 544 Mbps • Fractional T 1 – Provides service speeds of 128 Kbps and upward in 128 -Kbps increments • T 3 service (also called DS 3) – Offers 44. 736 Mbps 37

Wireless Connections • Bluetooth – Designed for personal use over short distances – Low-bandwidth technology, with speeds of up to 722 Kbps – Networks are called personal area networks (PANs) or piconets – Consumes very little power – Devices can discover each other and exchange information automatically 38

Wireless Ethernet (Wi-Fi) • Wireless Ethernet (Wi-Fi or 802. 11 b) is the most common wireless connection technology for use on LANs • Wireless access point (WAP) – Device that transmits network packets between Wi-Fi-equipped computers and other devices • Has a potential bandwidth of 11 Mbps and a range of about 300 feet 39

Wireless Ethernet (Wi-Fi) (continued) • 802. 11 a protocol – Capable of transmitting data at speeds up to 54 Mbps • 802. 11 g protocol – Has 54 Mbps speed of 802. 11 a – Compatible with 802. 11 b devices • 802. 11 n – Expected to offer speeds up to 320 Mbps 40

Fixed-Point Wireless • One version of fixed-point wireless uses a system of repeaters to forward a radio signal from an ISP to customers • Repeaters – Transmitter-receiver devices (transceivers) • Mesh routing – Directly transmits Wi-Fi packets through hundreds, or even thousands, of short-range transceivers 41

Cellular Telephone Networks • Third-generation (3 G) cell phones – Combine the latest technologies available today • Short message service (SMS) – Protocol used to send and receive short text messages • Mobile commerce (m-commerce) – Describes the kinds of resources people might want to access using wireless devices 42

Internet 2 and the Semantic Web • Internet 2 – Experimental test bed for new networking technologies – Includes bandwidths of 10 Gbps and more on parts of its network – Used by universities to conduct large collaborative research projects 43

Internet 2 and the Semantic Web (continued) • Semantic Web – Project by Tim Berners-Lee – If successful, it would result in words on Web pages being tagged (using XML) with their meanings • Resource description framework (RDF) – Set of standards for XML syntax • Ontology – Set of standards that defines relationships among RDF standards and specific XML tags 44

Summary • TCP/IP – Protocol suite used to create and transport information packets across the Internet • POP, SMTP, and IMAP – Protocols that help manage e-mail • Languages derived from SGML – Hypertext Markup Language (HTML) – Extensible Markup Language (XML) 45

Summary (continued) • Intranets – Private internal networks • Extranet – Used when companies want to collaborate with suppliers, partners, or customers • Internet 2 – Experimental network built by a consortium of research universities and businesses 46