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

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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

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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

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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