Chapter 2: Technology Infrastructure: The Internet and the World ...

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Oct 20, 2013 (3 years and 9 months ago)

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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


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

6


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

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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

12

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


Programs apply their routing algorithms to
information they have stored in routing tables


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14

Internet Protocols


Protocol


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

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

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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 (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

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 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


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

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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

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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

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)


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

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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 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

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 802.11b) 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 802.11a


Compatible with 802.11b 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


Internet2


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)


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

46

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)


47

Summary (continued)


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 businesses