chapter02
TRANSCRIPT
MIT Nguyễn Hữu PhátKent International College
80 hours
Advanced Diploma of Information Technology
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
E-Commerce: The Second Wave, Fifth Annual Edition 3
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
About Internet2 and the Semantic WebE-Commerce: The Second Wave, Fifth Annual Edition 4
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
E-Commerce: The Second Wave, Fifth Annual Edition 5
Early 1960s› U.S. Department of Defense funded research
to explore creating a worldwide network In1969, Defense Department researchers
› Connected four computers into network called ARPANET
Throughout 1970s and 1980s› Academic researchers connected to
ARPANET and contributed to its technological developments
E-Commerce: The Second Wave, Fifth Annual Edition 6
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 group of students and
programmers at Duke University and the University of North Carolina
E-Commerce: The Second Wave, Fifth Annual Edition 7
In 1991, NSF› Eased restrictions on commercial Internet
activity › Began implementing plans to privatize the
Internet Network access points (NAPs)
› Basis of new structure Internet Network access providers
› Sell Internet access rights directly to larger customers and indirectly to smaller firms and individuals through ISPs
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http://www.internetworldstats.com
E-Commerce: The Second Wave, Fifth Annual Edition 10
The $23.4 billion in annual internet advertising spending exceeded advertising on cable TV for the first time (which was $21.4 billion), and took the No. 3 spot behind national
and local TV ads ($29.8 billion) and newspaper ads ($34.4 billion).
Internet advertising is almost twice as large as broadcast TV advertising was in its 14th year ($13.3 billion) and nearly four times as large as cable TV ($6.5 billion).
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
Tim Berners-Lee› Developed code for
hypertext server program Hypertext server
› Stores files written in hypertext markup language
› Lets other computers connect to it and read files
Hypertext Markup Language (HTML)› Includes set of codes (or
tags) attached to text
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
Circuit switching› Centrally controlled, single-connection model
Packets› Files and e-mail messages on a packet-switched network that are
broken down into small pieces› Travel from computer to computer along the interconnected
networks until they reach their destinations
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 packet
› Programs apply their routing algorithms to information they have stored in routing tables
E-Commerce: The Second Wave, Fifth Annual Edition 18
Protocol› Collection of rules for
formatting, ordering, and error-checking data sent across a network
Rules contributing to success of Internet› 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
TCP› Controls disassembly of a message or a file
into packets before transmission over Internet
› Controls reassembly of packets into their original formats when they reach their destinations
IP › Specifies addressing details for each packet
E-Commerce: The Second Wave, Fifth Annual Edition 20
Internet Protocol version 4/6 (IPv4/6) › 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
E-Commerce: The Second Wave, Fifth Annual Edition 21
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
Sets of words assigned to specific IP addresses
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
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Web client computers› Run software called Web
client software or Web browser software
Web server computer › Runs software called Web
server software Client/server architecture
› Combination of client computers running Web client software and server computers running Web server software
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 user to locate a
resource (the Web page) on another computer (the Web server)
Electronic mail (e-mail)› Must also be formatted
according to common set of rules
E-mail server› Computer devoted to
handling e-mail E-mail client software
› Used to read and send e-mail
› Example: Microsoft Outlook, Netscape Messenger
Simple Mail Transfer Protocol (SMTP)› Specifies format of a mail
message Post Office Protocol (POP)
› POP message can tell the e-mail server to Send mail to user’s computer
and delete it from e-mail server
Send mail to user’s computer and not delete it
Simply ask whether new mail has arrived
› Provides support for Multipurpose Internet Mail Extensions (MIME)
Text markup language› Specifies set of tags that are inserted into text
Standard Generalized Markup Language (SGML)› Older and complex text markup language› A meta language
World Wide Web Consortium (W3C)› Not-for-profit group that maintains standards for the Web
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
Prevalent markup language used to create documents on the Web today
HTML tags› Interpreted by Web browser and used by it
to format the display of the text
HTML Links› Linear hyperlink structure
› Hierarchical hyperlink structureE-Commerce: The Second Wave, Fifth Annual Edition 35
Scripting languages and style sheets› Most common scripting languages JavaScript, JScript, Perl, and VBScript
› Cascading Style Sheets (CSS) Sets of instructions that give Web
developers more control over the format of displayed pages
Style sheet Usually stored in a separate file Referenced using the HTML style tag
E-Commerce: The Second Wave, Fifth Annual Edition 36
Uses paired start and stop tags
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
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E-Commerce: The Second Wave, Fifth Annual Edition 38
Intranet
› Interconnected network that does not extend beyond organization that created it
Extranet
› Intranet extended to include entities outside boundaries of organization
› Connects companies with suppliers, business partners, or other authorized users
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 › A permanent telephone
connection between two points
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 VPN software
› Must be installed on the computers at both ends of the transmission
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 same bandwidth in both directions
Asymmetric connections › Provide different bandwidths
for each direction
POTS, or plain old telephone service› Uses existing telephone
lines and analog modem › Provide bandwidth
between 28 and 56 Kbps Digital Subscriber Line (DSL)
› Connection methods do not use modem
Integrated Services Digital Network (ISDN)› Offers bandwidths
between 128 Kbps and 256 Kbps
Operate at speeds of greater than 200 Kbps
Asymmetric digital subscriber (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
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DS0 (digital signal zero)› Telephone line designed to carry 1 digital signal
T1 line (also called a DS1)› Carries 24 DS0 lines and operates at 1.544 Mbps
Fractional T1› Provides service speeds of 128 Kbps and upward in 128-
Kbps increments T3 service (also called DS3)
› Offers 44.736 Mbps
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
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 potential bandwidth of 11 Mbps and range of about 300 feet
Devices are capable of roamingE-Commerce: The Second Wave, Fifth Annual Edition 47
802.11a protocol › Capable of transmitting data at speeds
up to 54 Mbps 802.11g protocol
› Has 54 Mbps speed of 802.11a › Compatible with 802.11b devices
802.11n› Expected to offer speeds up to 320 Mbps
E-Commerce: The Second Wave, Fifth Annual Edition 48
One version uses system of repeaters to forward radio signal from ISP to customers
Repeaters › Transmitter-receiver devices (transceivers)
Mesh Routing› Directly transmits Wi-Fi packets through
hundreds, or even thousands, of short-range transceivers
Third-generation (3G) cell phones› Combine 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
Internet2
› Experimental test bed for new networking technologies
› Has achieved bandwidths of 10 Gbps and more on parts of its network
› Used by universities to conduct large collaborative research projects
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Semantic Web› Project by Tim Berners-Lee › If successful 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
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)
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Intranets › 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 businessesE-Commerce: The Second Wave, Fifth Annual Edition 54