Introduction to the Internet
and Web
Introduction
By the turn of the century, information, including access to the Internet,
will be the basis for personal, economic, and political advancement.
The popular name for the Internet is the information superhighway.
Whether you want to find the latest financial news, browse through library
catalogs, exchange information with colleagues, or join in a lively political
debate, the Internet is the tool that will take you beyond telephones, faxes,
and isolated computers to a networked information frontier.
The Internet supplements the traditional tools you use to gather
information, Data Graphics, News and correspond with other people.
What is I N T E R N E T ?
• The largest network of networks in the
world.
What is I N T E R N E T ?
Continue……
• A network of networks, joining many
government,
university
and
private
computers together and providing an
infrastructure for the use of E-mail, bulletin
boards, file archives, hypertext documents,
databases
and
other
computational
resources.
What is I N T E R N E T ?
Continue……
• The vast collection of computer networks
which form and act as a single huge
network for transport of data and messages
across distances which can be anywhere
from the same office to anywhere in the
world.
Brief History of Internet
• ARPA – Advanced Research Project Agency.
• 1969 January 2 – started an experimental
Computer Network.
• Concept – No Server, but equal
importance/participation to every computer in
the Network.
• Even if, one or two node destroyed that will
not affect the Network.
Paul Baran
• Paul Baran developed the
field of packet switching
networks while conducting
research at the historic
RAND organization.
Vinton Cerf
• Father of Internet
• Co-designer of the TCP/IP
networking protocol.
Brief History of Internet
• First named as ARPANET
Continue……
• This is renamed as INTERNET
– TCP/IP (Transmission Control Protocol/Internet
Protocol)
Internet Growth Trends
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1977: 111 hosts on Internet
1981: 213 hosts
1983: 562 hosts
1984: 1,000 hosts
1986: 5,000 hosts
1987: 10,000 hosts
1989: 100,000 hosts
1992: 1,000,000 hosts
2001: 150 – 175 million hosts
2002: over 200 million hosts
By 2010, about 80% of the planet will be on the Internet
Internet Services
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•
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•
•
Electronic Mail (e-mail)
World Wide Web
Telnet
File Transfer Protocol (FTP)
Internet Telephone
Web TV/Radio
Internet Relay Chat
News Groups
How to Connect to Internet
Basic Communication
• Computer Networks interconnects
computers to exchange data and resource
sharing.
• Internet uses some kind of media to connect
computers/networks together.
– Eg:- Telephone line
Basic Communication
• Communication is done by passing
electrical signals across wires.
• Telephone wires are using Analog Signals
for communication.
• Computers are using Digital Signals for
processing.
MODEM
Modulator - Demodulator
• A modem is a device needed for
communication across a dial-up telephone
connection or for long distance
communication across a wire.
• A modem supports two-way
communication because it contains a
modulator for the signal being sent and a
demodulator for the signal being received.
MODEM
Modulator - Demodulator
• When a computer interacts with a modem, it
sends and receives digital data; the modem
encodes the data for transmission.
modem - 1
modem - 2
transmission line
Computer
A
Computer
B
Introduction to Computer Networks
Computer Networks
Computer network
connects two or more
autonomous
computers.
The computers can be
geographically located
anywhere.
Introduction to Computer Networks
Uses of Computer Networks
Resource Sharing
Hardware (computing resources, disks, printers)
Software (application software)
Information Sharing
Easy accessibility from anywhere (files, databases)
Search Capability (WWW)
Communication
Email
Message broadcast
Remote computing
Distributed processing (GRID Computing)
Introduction to Computer Networks
LAN
Network in small geographical Area
(Room, Building or a Campus) is called LAN
• LAN- Local Area Network
– used by schools and businesses
– used to connect around 10-500
computers in a building
– only accessible from within the building
Local Area Network
• A computer communication technology is
classified as a Local Area Network (LAN) if it
provides a way to interconnect multiple
computers across short distances. LANs are
inexpensive, highly reliable, and convenient to
install and manage.
Local Area Network continue…
• A computer needs additional hardware to
connect it to a local area network. The hardware
consists of a circuit board that plugs into the
computer and a cable that attaches the circuit
board to the LAN. Once connected, a computer
uses the network interface to send and receive
data.
Local Area Network continue…
• Because each computer attached to a LAN
contains interface hardware that isolates the
computer from the LAN, the speed of the LAN
does not depend on the speed of the computers
that attach to it. As a result, heterogeneous
computers can communicate across a LAN.
Network Interface Card
• The primary function of a network interface
card (NIC) is to provide a physical link to a
computer network. This connection allows
computers to communicate with servers, as well
as other computers on the network.
Network Interface Card continue…
• Each NIC has a unique serial number, which is
called a MAC address. Every computer connected
to the network is required to have a unique MAC
address that is stored on the network interface
card. If you are building a home network or
utilizing broadband Web access, your NIC
connects you to the outside world.
Network Interface Card continue…
• Network interface cards are either wired (LAN) or
wireless. Both NICs are generally compatible with
Windows and other popular operating systems.
Most NICs use network drivers, which are
computer programs that allow software
applications to communicate with network
hardware.
Network Interface Card continue…
• The necessary drivers are usually integrated into
the computer system. The drivers usually installs
automatically when the hardware is turned on.
VPN
• Virtual Private Networks (VPNs) are essentially
software applications that use a public network,
such as the Internet, to link computers together.
MAN&WAN
Network in a City is called MAN
(Metropolitan Area Network)
Network spread geographically (Country or
across Globe) is called WAN
(Wide Area Network)
Introduction to Computer Networks
Network Concepts
• Network Hardware
– Servers- powerful computers dedicated
to controlling all of the systems on the
network. All networked computers are
connected to the server in some way
– Printers- One of the reasons networks
were developed was to make a single
printer accessible by many different
computers
– Computers- individual machines that
are connected to the server
– Network Interface Card (NIC)- a device
that is installed into a computer to give
it a terminal that can run a cable to
access the network
Introduction to Computer Networks
Network Software
• Network Operating System
– the system software run on the server
– An operating system (OS) is software that computers
use to run the environment that allows you to access
applications and create files. Without an OS, a
computer is useless.
• Networked Applications
– computer programs located on the network that are
accessed by individual computers
– This makes loading software on individual computers
unnecessary.
OS Logos
Computer Networks
Data Transmission Media
Data Transmission Media
Data Transmission Media
Data Transmission Media
Data Transmission Media
Data Transmission
Packet Switching
• This is the basic communication technology
that Internet uses.
• In Networks multiple devices shares
hardware facilities.
• Arranging for multiple devices to share a
single transmission path lowers cost
because it uses fewer wires and fewer
switching machines.
Packet Switching continue…
• Granting one party exclusive access of a
shared transport path can be impractical
because it can delay all other parties.
• To avoid long delays, network technologies
limit the amount of data that a computer can
transfer on each turn – Packet Switching (1960)
• The unit of data that can be transferred at
one time is called a packet.
SIMPLE SWITCHED NETWORK
2
3
1
5
4
7
3
6
Packet Switching
• Messages are broken up into small packets
• Each packet is transmitted individually .
• Packets may even follow different routes to the
destination.
• At each node the entire packet is received, stored,
and then forwarded (store-and-forward
networks)
• At the destination the packets are reassembled into
the original message.
• Used in the Internet
Packet
packets are split into three parts:
• header - The header contains instructions about the
data carried by the packet.
– Length of packet
– Packet number
– Protocol ( what type of packet is being transmitted:
e-mail, Web page, streaming video)
– Destination address
– Originating address
• payload - actual data of the packet
Packet
• trailer /footer- It contains a couple of bits
that tell the receiving device that it has
reached the end of the packet. It may also
have some type of error checking. The most
common error checking used in packets is
Cyclic Redundancy Check (CRC).
Packet
• Each computer attached to a network is
assigned a unique number called its address.
• A packet contains the address of the
computer that sent it and the address of the
computer to which it is sent.
• Although packet switching technologies
limit the amount of data in a packet, they
allow the sender to transmit any size packet
up to the maximum.
header
A
payload
P
trailer
T
AT
 1
P
time
• header + trailer carry control information for
switching (the source and the final destination
addresses, etc.)
Inside the packet switching router
Packet Switching continue…
• Packet Switching avoids delays.
• To avoid long delays, network technologies
limit the amount of data that a computer can
transfer on each turn – Packet Switching (1960)
• The unit of data that can be transferred at
one time is called a packet.
Packet Switching continue…
• A packet switching system permits multiple
pairs of computers to communicate across a
shared network with minimal delay because
it divides each conversation into small
packets and arranges for the computers that
share a network to take turns sending
packets.
Packet Switching continue…
• Because packet switching systems adapt
instantly as computers become ready to
send data or others finish sending data, each
computer receives a fair share of network
resources at any given time.
Packet Switching continue…
• Like most computer network, the Internet is
a packet switching system. Internet
hardware includes physical wires shared
among multiple users.
• Packet switching allows many
communications to proceed simultaneously,
without requiring an application to wait for
all other communication to complete.
Packet Switching continue…
• As a consequence, whenever a user
transfers data across the Internet, network
software on the sending machine divides the
data into packets, and network software on
the receiving machine must reassemble the
packets to produce the data.
• All data is transferred across the Internet in
packets. Packets from many machines
traverse the Internet at the same time.
•
•
http://www.pbs.org/opb/nerds2.0.1/geek_glossary/packet_switching_flash.html
http://www.webopedia.com/TERM/P/packet_switching.html
Example
C
out of order
D
B
in order
E
A
Delays in datagram networks
Delays in datagram networks
host 1
node 1
node 2
host 2
transmission time
Waiting Time
Total Delay
Waiting Time
time
Advantages
• Line efficiency
– Single node to node link can be shared by many packets
over time
• Packets are accepted even when network is busy
– Delivery may slow down
• Priorities can be used
Disadvantages
– Excessive congestion: packet delay and high loss
– Packet header overhead
– Provides no transparency to a user
ISPs and Network Connections
• Internet Service Providers(ISPs) and Fees.
– A company that provides Internet Access and Services is
known as an ISP.
• ISP charges for its services.
– A charge for using the Internet.
– A charge for a physical connection to the Internet
• Types of Billing.
– Flat rate per month – independent of the number of
minutes a customer uses the service, but charges more for
transfers large volume of data.
– Charges for the connection, for dedicated connection.
– More for connections capable of transferring larger
volume of data.
Addresses on the Web:IP Addressing
• Each computer on the internet does have a
unique identification number, called an IP
(Internet Protocol) address.
• The IP addressing system currently in use on
the Internet uses a four-part number.
• Each part of the address is a number ranging
from 0 to 255, and each part is separated from
the previous part by period,
• For example, 106.29.242.17
IP Addressing
• The combination of the four IP address parts
provides 4.2 billion possible addresses (256 x
256 x 256 x 256).
• Members of various Internet task forces are
working to develop an alternate addressing
system that will accommodate the projected
growth.
• However, all of their working solutions require
extensive hardware and software changes
throughout the Internet.
Domain Name Addressing
• Most web browsers do not use the IP address to locate
Web sites and individual pages.
• They use domain name addressing.
• A domain name is a unique name associated with a
specific IP address by a program that runs on an
Internet host computer.
• The program, which coordinates the IP addresses and
domain names for all computers attached to it, is called
DNS (Domain Name System ) software.
• The host computer that runs this software is called a
domain name server.
Domain Name Addressing
• Domain names can include any number of parts separated by
periods, however most domain names currently in use have only
three or four parts.
• Domain names follow hierarchical model that you can follow
from top to bottom if you read the name from the right to the
left.
• For example, the domain name gsb.uchicago.edu is the computer
connected to the Internet at the Graduate School of Business
(gsb), which is an academic unit of the University of Chicago
(uchicago), which is an educational institution (edu).
• No other computer on the Internet has the same domain name.
Uniform Resource Locators
• The IP address and the domain name each identify a particular
computer on the Internet.
• However, they do not indicate where a Web page’s HTML
document resides on that computer.
• To identify a Web pages exact location, Web browsers rely on
Uniform Resource Locator (URL).
• URL is a four-part addressing scheme that tells the Web
browser:
 What transfer protocol to use for transporting the file
 The domain name of the computer on which the file resides
 The pathname of the folder or directory on the computer on
which the file resides
 The name of the file
Structure of a Uniform Resource Locators
pathname
protocol
http://www.chicagosymphony.org/civicconcerts/index.htm
Domain name
http => Hypertext Transfer Protocol
filename
HTTP
• The transfer protocol is the set of rules that the
computers use to move files from one computer to
another on the Internet.
• The most common transfer protocol used on the
Internet is the Hypertext Transfer Protocol
(HTTP).
• Two other protocols that you can use on the
Internet are the File Transfer Protocol (FTP) and
the Telnet Protocol
How to find information on the Web?
• A number of search tools have been developed and
available to you on certain Web sites that provide
search services to help you find information.
• Examples:
 Yahoo
 www.yahoo.com
 Excite
 www.excite.com
 Lycos
 www.lycos.com
 AltaVista
 www.alta-vista.com
 MSN WebSearch  www.search.msn.com
How to find information on the Web?
• You can find information by two basic means.
• Search by Topic and Search by keywords.
• Some search services offer both methods, others only
one.
• Yahoo offers both.
 Search by Topic
You can navigate through topic lists
 Search by keywords
You can navigate by entering a keyword or phase into
a search text box.