10.1 The Historical Development of the Internet and WWW

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10.1 The Historical Development of
the Internet and WWW
 Internet
 A worldwide network which connects
millions of small computer networks all over
the world
 Estimated Internet users worldwide: over a
billion
Country
Internet users
(million)
Country
Internet users
(million)
UK
35.8
Hong Kong
4.9
USA
203
South Korea
31.6
China
103
Singapore
2.1
Japan
78.1
India
39.2
10.1 The Historical Development of
the Internet and WWW
 The ARPANET
 ARPA: Advanced Research Projects Agency
 In 1969, four universities in the USA
connected their computers by telephone
lines to create a network called ARPANET
Stanford
Research
Institute
University
of Utah
ARPANET
UCSB
UCLA
10.1 The Historical Development of
the Internet and WWW
 The Growth of the Internet
 National Science Foundation Network
(NSFNET)
Establish in 1985
A general-purpose research network
Enabled the connection of regional
networks
 Most universities connected to the
ARPANET eventually moved to NSFNET
 The global network system was known as
the Internet
10.1 The Historical Development of
the Internet and WWW
 The Growth of the Internet
 NSFNET served as the high-speed
communication backbone for the Internet
until 1995
 Hosts
Responsible for providing services and
network connections for other
computers
By 2004, there were over 900 million
hosts connected to the Internet
10.1 The Historical Development of
the Internet and WWW
 The World Wide Web
 A collection of hypertext documents called
web pages
 Stored on servers connected to the Internet
<html>
<head>
<title>My webpage</title>
<html>
</head>
<head>
<body>
<title>My webpage</title>
<html>
<p>Hello world!</p>
</head>
<head>
<p>This is my first webpage!</p>
<body>
<title>My webpage</title>
</body>
<p>Hello world!</p>
</head> </html>
<p>This is my first webpage!</p>
<body>
</body>
<p>Hello world!</p>
</html>
<p>This is my first webpage!</p>
</body>
</html>
Stored
Hypertext
document
Server
Connected
to the
Internet
10.1 The Historical Development of
the Internet and WWW
 The World Wide Web
 Web page
An electronic document written in
hypertext format
The hypertext can be interpreted and
displayed by a web browser
<html>
<head>
<title>My webpage</title>
</head>
<body>
<p>Hello world!</p>
<p>This is my first
webpage!</p>
</body>
</html>
HTML text
Displayed
in a
browser
10.1 The Historical Development of
the Internet and WWW
 The World Wide Web
 WWW included text-only pages at first
 Mosaic was the first web browser that
could support audio, video clips, forms,
bookmarks and history files.
Mosaic – the
first web
browser that
supports
multimedia
10.1 The Historical Development of
the Internet and WWW
 The World Wide Web
 WWW included text-only pages at first
 Mosaic was the first web browser that
could support audio, video clips, forms,
bookmarks and history files.
Mosaic – the
first web
browser that
supports
multimedia
10.2 Making Connections
 How to make a connection
 To make a connection, a person needs to
register an account with an Internet
service provider
set up the necessary computer
equipment
install the appropriate software
establish a connection
10.2 Making Connections
 Internet Service Provider
 A company that provides Internet access
service
 Usually offers subscribers a communication
software package for establishing
connection with the ISP server
 Users are provided with a user name, a
password and all the necessary information
 Users can log on to the Internet via modem
 Bandwidths vary from 56 Kbps to
1000Mbps
10.2 Making Connections
 Dial-up Access Connection
 To connect to the Internet using dial-up
access, a person needs
A dial-up modem
A telephone line
 Modem
Converts digital signals into analogue
signals and vice versa
can be installed internally or externally
Maximum transmission speed of a dialup modem is 56 Kbps
10.2 Making Connections
 Dial-up Access Connection
 Internal modem
A modem expansion
card to be placed on
a motherboard
10.2 Making Connections
 Dial-up Access Connection
 External modem
External modem a single device that
can connect to the
connection port of
the computer
10.2 Making Connections
 Dial-up Access Connection
 Software for Internet access
A web browser – for viewing web pages
An email program – for receiving and
sending e-mails
Communication software - for establishing
connection with ISP
10.2 Making Connections
 Integrated Services Digital Network
(ISDN)
 Works on the same principle as dial-up
access
 To establish ISDN connection, one needs
An ISDN modem
A telephone line
 Data Transmission
Transmission speed: 128 Kbps
Data is transmitted along ISDN line as
digital (not analogue) signals
Transmission in digital form is more stable
10.2 Making Connections
 Broadband Connections
 Features
Transmission speed
 1.5 Mbps - 1000Mbps
 Much higher than standard 56Kbps modem
 High speed enables continuous transmission
of video, audio and 3-D animation
Constant availability with no dialing
required
Simultaneous use of data and voice
connections
10.2 Making Connections
 Broadband Connections
 To make a broadband connection, a person
needs
A digital modem
 Can send and receive digital data from the ISP
through a dedicated transmission cable
A network interface card
Network interface
card (nic)
10.2 Making Connections
 Broadband Connections
 Two main broadband systems for domestic
users
Broadband
system
Description
ADSL

Uses standard telephone line
 ‘asymmetric’: download speed (1.5-9
Mbps) >> upload speed (16-640Kbps)
 Example service provider: Netvigator
Cable modem

Connects a computer to a cable TV
network
 Designated capacity (30 Mbps) shared
among users
 Data transfer rate: 1.5 Mbps
 Example service provider: i-Cable
10.2 Making Connections
 T-carrier
 Provides a permanent connection between
the network server and the ISP’s server
 Allows network users to access the Internet
simultaneously
 Different carriers support different data
transmission speed
T-1
Maximum
data transfer
speed: 1.54
Mbps
T-3
Maximum
data transfer
speed: 44
Mbps
10.2 Making Connections
 Wireless Connections
 Two ways to obtain Internet access for
mobile devices such as mobile phones, PDAs
and handheld computers
Wireless Application Protocol (WAP)
General Packet Radio Services (GPRS)
 WAP
A communication protocol for
communication between handheld
wireless devices
Maximum data transfer rate: 10 Kbps –
153 Kbps
10.2 Making Connections
 Wireless Connections
 GPRS
A technology designed for mobile phones
Maximum data transfer rate: 115.2 Kbps
Provides a constant connection
Connection requires GPRS network card
10.2 Making Connections
 Wireless Connections
 GPRS
A technology designed for mobile phones
Maximum data transfer rate: 115.2 Kbps
Provides a constant connection
Connection requires GPRS network card
10.3 Introduction to TCP/IP
 Transmission Control Protocol/
Internet Protocol (TCP/IP)
 The communication protocol suite of the
Internet
 TCP
Divides the message into packets
Verifies the correct delivery of packets
from node to node
Triggers retransmission until a packet is
correctly and completely received
Reassembles the received packets into
original message on recipient side
10.3 Introduction to TCP/IP
 Transmission Control Protocol/
Internet Protocol (TCP/IP)
 IP
Adds destination address to every packet
Routes the packet to the destination
through network server
10.3 Introduction to TCP/IP
 Transmission Control Protocol/
Internet Protocol (TCP/IP)
How a message is transmitted using TCP/IP
10.3 Introduction to TCP/IP
 Transmission Control Protocol/
Internet Protocol (TCP/IP)
How a message is transmitted using TCP/IP
10.4 IP Address
 IP Address
 Uniquely identifies every computer on a
network
 A computer connected to the Internet must
use the IP address issued by the InterNIC
(Internet Network Information Centre)
InterNIC’s
homepage –
www.internic.net
10.4 IP Address
 IP Address
 Structure of IP address
32-bit numeric address
Expressed as four denary numbers
separated by periods
Example: 203.129.88.118 is the IP address
of the Hong Kong Observatory web site
IP address expressed in 32-bit
binary number
Equivalent IP
address in
decimal
representation
10000000 00110100 00110000 00000000
128.52.48.0
11000000 00001001 00000110 00100101
192.9.6.37
10.4 IP Address
 The Classes of Ipv4 Address
 Each IP address consists of two parts
 Network address
 Identifies a particular network
 Host address
 Identifies a device in the network
Number
of hosts
owned
Network
Size
0
16,777,214
Huge
B
10
65534
Large
C
110
254
Medium
to small
Clas
s
Class
number
A
Partition of IP address
10.4 IP Address
 The Classes of Ipv4 Address
 Internet Protocol Version 6 (Ipv6)
New address system
Accommodates more IP addresses
Meets the current growth of the Internet
IPv4 and IPv6
10.4 IP Address
 The Classes of Ipv4 Address
 Internet Protocol Version 6 (IPv6)
New address system
Accommodates more IP addresses
Meets the current growth of the Internet
IPv4 and IPv6
10.5 Domain Names and Domain
Name Servers
 Domain Names
 Associate an easy to remember name to an
IP address
 Official terminology: Fully Qualified Domain
Name (FQDN)
Domain name
IP Address
Corresponds to
www.redcross.org
www.google.com
162.6.217.197
Corresponds to
66.249.89.99
10.5 Domain Names and Domain
Name Servers
 Domain Names
 Structure
Each domain name consist of two or
more groups of characters separated by
periods
Each group identifies the top-level domain
(TLD), second level domain or the host
name
10.5 Domain Names and Domain
Name Servers
 Domain Names
10.5 Domain Names and Domain
Name Servers
 Domain Names
 Common TLDs
Countrycode TLD
Country
au
Australia
Educational institutes
cn
China
gov
Government (US)
de
Germany
org
General organizations
fr
France
mil
Military (US)
uk
United
Kingdom
net
Network provider
jp
Japan
TLD
Type of organization
com
Commercial
organizations
edu
10.5 Domain Names and Domain
Name Servers
 Domain Names
 Non-US domain names use country-code
TLD based on the country which the server
is in
 Network Solutions
A company which ensures no duplication
of domain name
10.5 Domain Names and Domain
Name Servers
 URL
 Full name: uniform resource locator
 Refers to a particular web page or a file
residing on a web site
Format of URL
http://www.books.com/storybooks/harry-potter.htm
protocol
domain name
folder name
file name
10.5 Domain Names and Domain
Name Servers
 Domain Name Servers (DNS)
 Translate domain names to IP addresses
 The translation process is called name
resolution
 Enable users to access a registered domain
by its domain name instead of its IP address
 Process
DNS receives a domain name
Searches for the associated IP address
If no datum available, asks other DNS on
the Internet
Process continues until IP address is
found
10.5 Domain Names and Domain
Name Servers
 Domain Name Servers (DNS)
http://www.google.com
Output IP
address
Domain name
http://66.249.89.99
IP address
Case I:
relevant
data in its
database
DNS
Input domain
name
Case II: no
relevant data
in its
database
DNS
Relevant
data found
Ask other DNS
10.5 Domain Names and Domain
Name Servers
 Domain Name Servers (DNS)
http://www.google.com
Output IP
address
Domain name
http://66.249.89.99
IP address
Case I:
relevant
data in its
database
DNS
Input domain
name
Case II: no
relevant data
in its
database
DNS
Relevant
data found
Ask other DNS