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

2. 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
Internet2 and the Semantic Web

3. 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

4. History of the Internet
Wikipedia Internet History
Early 1960s
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 1970s and 1980s
Academic researchers connected to ARPANET and contributed to its technological developments

5. New Uses for the Internet
1972
was born
Mailing list
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

6. Growth of the Internet In 1991, the NSF: Network access points (NAPs)
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

8. 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 1960s, Ted Nelson described a similar system called hypertext

9. 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

10. 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

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

12. Routing Packets Routing computers Routing algorithms
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
Programs apply their routing algorithms to information they have stored in routing tables

14. Internet Protocols Protocol Rules for message handling include:
Collection of rules for formatting, ordering, and error-checking 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

15. 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

16. IP Addressing Internet Protocol version 4 (IPv4)
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

17. 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 (IPv6)
Protocol that will replace IPv4
Uses a 128-bit number for addresses

18. 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

20. 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
The web uses a thin-client/server architecture
Combination of client computers running Web client software and server computers running Web server software

21. 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)

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

23. Electronic Mail Protocols
Simple Mail Transfer Protocol (SMTP)
Specifies the format of a mail message
Post Office Protocol (POP)
POP messages can tell the server to:
Send mail to a user’s computer and delete it from the server
Send mail to a user’s computer and not delete it
Simply ask whether new mail has arrived
POP provides support for Multipurpose Internet Mail Extensions (MIME)

24. 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
A meta language
World Wide Web Consortium (W3C)
Not-for-profit group that maintains standards for the Web

26. 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

27. 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

28. Hypertext Markup Language (HTML))
The most common scripting languages include JavaScript, 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

29. 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

31. Intranets and Extranets
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

32. 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

33. Virtual Private Network (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

35. 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

36. 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

37. 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

38. Leased-Line Connections
DS0 (digital signal zero)
Telephone line designed to carry one digital signal
T1 line (also called a DS1)
Carries 24 DS0 lines and operates at Mbps
Fractional T1
Provides service speeds of 128 Kbps and upward in 128-Kbps increments
T3 service (also called DS3)
Offers Mbps

39. 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

40. Wireless Ethernet (Wi-Fi)
Wireless Ethernet (Wi-Fi or 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
Devices are capable of roaming

41. Wireless Ethernet (Wi-Fi) (continued)
802.11a protocol
Capable of transmitting data at speeds up to 54 Mbps
802.11g protocol
Has 54 Mbps speed of a
Compatible with b devices
802.11n
Expected to offer speeds up to 320 Mbps

42. 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

43. Cellular Telephone Networks
Third-generation (3G) 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

44. Internet2 and the Semantic Web
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

45. Internet2 and the Semantic Web (continued)
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

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

47. Summary (continued) Intranets Extranet Internet2
Private internal networks
Extranet
Used when companies want to collaborate with suppliers, partners, or customers
Internet2
Experimental network built by a consortium of research universities and businesses