Transcript Internet Tutorial.01.. - Computer and Information Science

Tutorial 1
Introduction to the Internet
and the World Wide Web
History, Structure, and
Getting Connected
Objectives
• Obtain an overview of the information and
tools that are available on the Internet
• Learn what computer networks and
internets are and how they work
• Find out how the Internet and the World
Wide Web began and grew
• Compare different methods for connecting
to the Internet
Internet and World Wide Web:
Amazing Developments
• The Internet is a large collection of computers
all over the world connected to one another.
• One of the most amazing technological
developments of the 20th century.
• The World Wide Web is a subset of computers
on the Internet that has helped make Internet
resources available to people who are not
computer experts.
Internet and World Wide Web:
Amazing Developments
• New Ways to Communicate
– E-mail
– Electronic discussions
– Instant messaging
• Information Resources and Software
– Newspapers & magazines
– Government documents
– Research reports & books
– Software download sites
Internet and World Wide Web:
Amazing Developments
• Doing Business Online
– Electronic storefronts
– Coordinate worldwide operations
– Recruit employees
• Entertainment
– Review restaurants, movies, theater, musical
events and books.
– Interactive games
– Follow sports teams
Antivirus
• Won’t learn till later, but you should have
antivirus software (and firewall) on your
computer.
– Norton
– McAfee
– Etc.
• May be provided by your ISP
Computer Networks
• Network: a collection of connected
computers.
• Network Interface Card (NIC): a card used to
connect a computer to a network of other
computers.
• Server: computer that accepts requests and
shares some or all of its resources with
computers to which it is connected.
Client/Server
Local Area Networks
• Client: computer connected to a server.
• Network Operating System: software that runs
on a server.
• Client/Server Networks: one server computer
sharing its resources with multiple client
computers.
• Local Area Network (LAN): network of
computers located close to each other.
Client/Server LAN
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Client/Server Local Area
Networks
• Node or network node: each computer,
printer, or other device connected to a
network.
• Minicomputer and mainframe
computer: larger, more expensive
computers used by businesses and
organizations to process large amounts of
work.
Connecting Computers
to a Network – Types of Cable
• Twisted Pair: oldest type, used by telephone
companies, usually Category 1.
• Coaxial Cable: 20 times faster than Category 1,
more expensive
• Category 5: carries signals between 10 & 100 times
faster than coaxial cable, easy to install.
• Fiber-optic cable: most expensive, transmits
pulsing beams of light through very thin strands of
glass, fastest transmission rate.
Types of Cable
TWISTED-PAIR
COAXIAL
FIBER-OPTIC
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Wireless Networks
• Becoming more common as costs drop.
• Old buildings -- expensive to install wiring.
• Companies which use laptop computers.
• Schools -- classrooms, libraries, and study
lounges.
• Homes.
Wide Area Networks
• WAN: a network of networks or an
internet.
• Internet: a worldwide collection of
interconnected networks; owners have
voluntarily agreed to share resources and
network connections.
Connectivity: Circuit Switching
• Circuit switching:
– centrally controlled
– single-connection method
– used by most local telephone traffic today
• Vulnerable to destruction of signal control
point or any link in the single path that
carries the signal.
Connectivity: Packet Switching
• Packet-switching: files and messages
broken down into packets and labeled
electronically with codes for their origin and
destination.
• Packets travel from computer to computer
along the network until they reach their
destination.
• Routers determine the best way for a packet
to move towards its destination.
Connectivity: Packet Switching
• Datagram – packet with routing info.
• Packet-switched networks more
reliable:
– rely on multiple routers instead of
central point of control.
– each router can send individual packets
along different paths if parts of the
network are not operating.
Origins of the Internet
• DARPA (Defense Advanced Research
Projects Agency) researchers connected
first computer switches in 1969.
• ARPANET grew over next three years to
include over 20 computers. Grandpa of
Internet.
Open Architecture Philosophy
– Independent networks should not require any
internal changes to be connected to the Internet.
– Packets that do not arrive at their destinations
must be retransmitted from their source network.
– The router computers do not retain information
about the packets they handle.
– No global control will exist over the network.
Open Architecture Philosophy
• Protocol: Rules for formatting, ordering, and
error-checking data sent across a network.
• New set of protocols developed in 1970 by
Vincent Cerf and Robert Kahn:
– Transmission Control Protocol
– Internet Protocol
– (TCP/IP)
Open Architecture Philosophy
• TCP: rules used by computers on a network to
establish and break connections.
• IP: rules for routing of individual data packets.
• TCP/IP used today in LANs and on the Internet.
• Vincent Cerf considered to be the father of the
Internet by many.
Birth of E-Mail:
A New Use for Networks
• Ray Tomlinson, an ARPANET researcher, wrote
a program that could send and receive
messages over the network in 1972.
• E-mail was born and rapidly became widely
used in the computer research community.
• ARPANET continued to develop faster and more
effective network technologies.
• Began sending packets by satellite in 1976.
More New Uses for
Networks Emerge
• File Transfer Protocol (FTP) - transfer files
between computers.
• Telnet - users log in to their computer accounts
from remote sites.
• Mailing lists (LISTSERV), information posting
areas (Usenet), and adventure games among
new applications appearing on the ARPANET.
Commercial Interest Increases
• National Science Foundation (NSF) prohibited
commercial network traffic on its networks.
• Larger firms built TCP/IP-based WANs that used
leased telephone lines to connect field offices to
corporate headquarters.
• NSF permitted commercial access. Initially there
was resentment but business invested much
money, speed increased and costs fell.
Commercial Interest Increases
• Intranet: LANs or WANs that use TCP/IP
protocol but do not connect to sites outside the
firm.
• Extranet: an intranet that allows selected
outside parties to connect.
• ARPANET grew from 4 computers in 1969 to
over 300,000 by 1990.
Growth of the Internet
• Formal definition of
Internet was adopted in
1995 by the Federal
Networking Council
(FNC).
From Research Project to
Information Infrastructure
Growth in number of Internet hosts
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Growth of the Internet
• Number of hosts connected to Internet includes
only computers directly connected to the
Internet.
• Internet traffic now carries more files that contain
graphics, sound, and video, so Internet files
have become larger.
New Structure for the Internet
• Organized around four network access points
(NAPs), operated by four different telecommunications companies.
• The four companies and their successors sell
access to the Internet through their NAPs to
organizations and businesses.
• The NSFnet still exists for government and
research use.
New Structure for the Internet
• More than 180 million connected host computers
and more than 700 million worldwide Internet
users.
• TCP/IP numbering system that identifies users
on the Internet is running short of numbers.
– IP version 4 provides a maximum of about 4 billion
addresses.
– IP version 6 approved in 1997 by the IETF allows
existing users to continue accessing the Internet while
new system is being implemented.
New Structure for the Internet
• The Internet has become one of the most
amazing technological and social
accomplishments of the century.
• Computers linked to this interconnected network
are located in almost every country of the world.
• Billions of dollars change hands every year over
the Internet.
World Wide Web
• World Wide Web: a way of thinking about
information storage and retrieval. Can view
multimedia documents (text, graphics, audio,
and video.
• Web: software that runs on some of the
computers connected to each other through the
Internet.
• In 1990, Tim Berners-Lee of CERN developed
the World Wide Web.
• HTTP: Protocol that transfers Web pages.
Hypertext
• Hypertext Markup Language (HTML): a
language that includes a set of codes (or tags)
attached to text.
• Hypertext Server: a computer that stores files
written in HTML; other computers connect to it
and read files.
• Hypertext Link (hyperlink): points to another
location in the same or another HTML
document.
Hypertext
• Web Browser: software that lets users
read HTML documents and move from
one HTML document to another through
hypertext link tags in each file.
• HTML is a subset of Standard Generalized
Markup Language (SGML) which has
been used for many years to manage
large document-filing systems.
GUI
• GUI (graphical user interface): a way of
presenting program output using pictures,
icons, and other graphical elements.
• e.g. CoreFTP vs. command line
• Much easier to learn and use
• Point and click
Hypertext and Graphical User
Interfaces Come to the Internet
• Mosaic: first GUI
program to read HTML
and use HTML
documents’ hyperlinks
to navigate from page
to page on computers
anywhere on the
Internet.
Commercialization
of the Internet
• Businesses quickly recognized profit-making
potential offered by a world-wide network of
easy-to-use computers.
• The Netscape Navigator Web browser was an
instant success.
• Internet Explorer Web browser entered the
market soon after Netscape’s success became
apparent.
Growth of the World Wide Web
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Connection Options
• NAPs (network access points) offer connections
to large organizations and businesses.
• Those businesses provide Internet access to
other business and individuals as ISPs.
• Internet service providers (ISPs) provide
customers with software to connect to the ISP,
browse the Web, send and receive e-mail
messages, and perform other Internet-related
functions.
Hierarchy of Internet Service
Providers
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Connection Bandwidth
• Bandwidth: amount of data that can travel
through a communications circuit in one second.
• Bandwidth depends on the type of connection
ISP has to the Internet and the kind of
connection you have to the ISP.
• Available bandwidth for any type network
connection between two points is limited to
narrowest bandwidth that exists in any part of
the network.
Connection Bandwidth
• Bandwidth measured in bits per second (bps).
• When you extend your network beyond a local
area, the speed of the connection depends on
type of connection used.
• POTS (or plain old telephone service) is one
way to connect computers or networks over
longer distances. 28-56 kbps
Connection Bandwidth
• Digital Subscriber Line (DSL): higher grade of
service offered by some telephone companies.
• Integrated Services Digital Network (ISDN):
first technology developed using a DSL protocol;
offers bandwidths up to 256 Kbps.
• Asymmetric Digital Subscriber Line (ADSL):
offers transmission speeds ranging from 16 Kbps
to 9 Mbps.
• T1 or T3 connections: often used by businesses
and large organizations; much more expensive
than POTS or ISDN connections.
Connection Bandwidth
• Cable connection: increasingly available in the
U.S.; can deliver up to 10 Mbps to an individual
user.
• Satellite connection: appealing to users in
remote areas; can download at a bandwidth of
approximately 400 Kbps.
• Fixed-point wireless connections: offered by
some companies
– technology similar to wireless LANs
– limited and more expensive.
Internet2
• Internet 2: operated by group of
research universities and the NSF; has
backbone bandwidths greater than 10
Gbps.
• Develop new technologies that will be
rapidly deployed to expand the
Internet.
http://www.internet2.edu/about/
• Internet2 is a consortium being led by 207 universities
working in partnership with industry and government to
develop and deploy advanced network applications and
technologies, accelerating the creation of tomorrow's
Internet. Internet2 is recreating the partnership among
academia, industry and government that fostered
today´s Internet in its infancy.
• The primary goals of Internet2 are to:
– Create a leading edge network capability for the national
research community
– Enable revolutionary Internet applications
– Ensure the rapid transfer of new network services and
applications to the broader Internet community.
Connecting Through Your
School or Employer
• Many universities and employers offer Internet
access to their students, faculty members, and
employees.
• Most schools and employers have an acceptable
use policy (AUP) that specifies the conditions under
which you can use their Internet connections.
– possibly least expensive option
– should carefully consider if limitations placed on
use of the Internet are greater than the benefits
Connecting Through an
Internet Service Provider
• Reliable connectivity at a reasonable price.
• Terms of AUPs usually less restrictive.
• Offer modem connections to individuals and
higher speed connections to businesses. May
also offer DSL connections to individual and
business customers.
• Quality of service may deteriorate significantly
over time if ISP adds many new customers
without expanding bandwidth.
Connecting Through a
DSL Provider
• Connections increasingly available in the U.S.
and a few other countries.
• Significantly faster connection that dial-up
service.
• Speeds and subscription rates similar to cable
modems.
• Sometimes long delays in installation and repair
services.
Connecting Through Your
Cable Television Company
• Cable modem converts digital signals into
radio-frequency analog signals similar to
television transmission signals.
• Signals travel over the same lines that carry
cable television signals.
• Cable connection is up to 170 times faster than
a telephone line connection.
• Cable connection is not available in all areas.
Connecting by Satellite
• Satellite Internet connections may be only option
available in rural areas.
• Speeds and monthly fees similar to those of
cable and DSL providers.
• Installation fee usually considerably higher
because the dish must be installed and aimed at
the satellite.
Summary
• The Internet and the Web began in the military and
research communities.
• The Internet and the Web have become an important
worldwide infrastructure.
• The Internet and the Web support many resources
through one of the most powerful communication
tools the world has ever known.
• There are a number of options for connecting your
computer and the computers of businesses and
other organizations to the Internet.