A Brief History of the Internet
Internet: The early years …
The Proliferation of LANs
 Engineers have devised many LAN technologies
 LAN performance determines cost; high
performance LANs are more expensive
 A particular LAN technology may only work with
specific computers
Internet: The early years …
The Proliferation of LANs
Star topology
Internet: The early years …
The Proliferation of LANs
Ring topology
Internet: The early years …
The Proliferation of LANs
Bus topology
Internet: The early years …
The Proliferation of LANs
Ethernet sharing
Internet: The early years …
The Proliferation of LANs
 A LAN technology is chosen for its speed,
ease of use, and the availability of
interfaces for specific computers. Most
large organization use many LAN
technologies
Internet: The early years …
LANs are incompatible
 Various LAN technologies are completely
incompatible.
Accounting Dept.
Shipping Dept.
Internet: The early years …
LANs are incompatible
Simply
connecting
the
 Various LAN technologies
are completely
cables cannot
incompatible.
make them
work together
Accounting Dept.
Shipping Dept.
Internet: The early years …
Wide Area Technologies Exist
A wide area network
technology (WAN) differs
from a set of disjoint
transmission lines because
the WAN includes an
additional special purpose
computer at each side that
connects to the
transmission lines and
keeps communication
independent of the
computers that use the
WAN
Internet: The early years …
Wide Area Technologies Exist
Internet: The early years …
 Few WANs, Many LANs
 WANs and LANs are Incompatible
 Many LAN and WAN technologies exist, and most
are incompatible with each other. One cannot
produce a usable, large network merely by
interconnecting the wires from two different
networks.
Internet: The early years …
 The Desirability of A Single Network …
Internet: The early years …
 The Internet Emerges …
 ARPANET …
 Advanced Research Project Agency (ARPA)
funded research projects to research new
approaches to connecting LANs and WANs.
 A prototype system that researchers built
became known as an internetwork – Internet.
Internet: The early years …
 The Internet Emerges …
Diagrams of two nodes on the ARPANET
IMP - Interface Message Processors
Internet: The early years …
 The Internet Emerges …
Internet: The early years …
 The Internet Emerges …
Internet: The early years …
 Internet Software
 Computer software forms an important part
of the technology that makes it possible to
interconnect networks
Internet: The early years …
 The Name is TCP/IP
 Two pieces of Internet software stand out
as particularly important and innovative
 Internet Protocol – software provide basic
communication
 Transmission Control Protocol – Provide reliable
communication
Internet: The early years …
 An Open System
 The Internet project aspired to produce an
open system that permitted computers
from all vendors to communicate.
Internet: The early years …
 Summary …
 The Internet began as a research project funded by ARPA.
Researchers studied ways to connect computers that used
various kinds of networks. The name Internet refers to
both the project and the prototype network system that
researchers built.
 TCP/IP is the software necessary to make the Internet
works. The software hides the detail of the underlying
hardware and provides the illusion of a seamless system.
 The Internet is an open system.
Internet: Incredible Growth
 1981 – The Internet connects about 100
computers at research sites and universities
 20 years later – 60,000,000
Year
1983
1984
1985
1986
1987
1988
1989
1990
#computers
562
1,024
1,961
2,308
5,089
28,174
80,000
290,000
Year
1991
1992
1993
1994
1995
1996
#computers
500,000
727,000
1,200,000
2,217,000
4,852,000
9,472,000
Internet: Incredible Growth
Internet: Incredible Growth
By 1999; a
computer was
added to the
Internet every
second.
Internet: Incredible Growth
By 2006; more
than 10 computers
were added to the
Internet every
second.
Internet: Incredible Growth
 Factors contribute to its growth …
 Advances in computer science research – the
introduction of UNIX operating system
 UNIX meets TCP/IP – enables connection of LANs to
the Internet
 US Military Chose the Internet – The military funded
and adopted the Internet, technologies were
developed at civilian sites
Internet: Incredible Growth
 Factors contribute to its growth …
 National Science Foundation (NSF) Takes a Leading
Role – connect universities to the Internet
 NSF decided that to keep the US competitive, it
needed to extend network access to every science
and engineering researcher.
 The NSFNET
Internet: Incredible Growth
 Factors contribute to its growth …
 The NSFNET Backbone
Internet: Incredible Growth
 Factors contribute to its growth …
 The ANS Backbone – IBM, MERIT, and MCI formed a
nonprofit company, Advanced Networks and
Services (ANS)
 ANS owned the transmission lines and computers
that comprised the network – ARPANET and NSFNET
were funded by government
 First step toward commercialization and
privatization of the Internet
The Global Internet
 Internet starts from the USA …expanded to
the globe
 Electronic mail connection – use existing voice
telephone network – require a modem and a piece of
communication software
The Global Internet
 Internet starts from the USA …expanded to
the globe
 In the UK … JANET
The Global Internet
 Internet starts from the USA …expanded to
the globe
 In Europe … Ebone
The Global Internet
 Internet starts from the USA …expanded to
the globe
 In Hong Kong … HARNET
The Global Internet
1998, every populated
country in the world is
connected
Internet: A Global Information Infrastructure
 Infrastructure – basic foundations on which
society depends on – electricity power
stations and supply facilities, railways, roads
…
 New infrastructure makes new industries
possible
Internet: A Global Information Infrastructure
 Communication Infrastructure
 Postal mail services adopted the nation of universal
access and delivery; and individual and send a letter to
any other individual.
 The telegraph changed the basic communication
infrastructure because it introduced high speed delivery
 Telephone changed the communication infrastructure by
extending communication services to individual homes
and offices, and by providing the instantaneous
communication needed for interactive conversation
Internet: A Global Information Infrastructure
 The Internet Infrastructure
 The basic Internet communication facilities are both
general and efficient, almost any network applications can
use the Internet
 The Internet offers a wide variety of services. Most of the
services currently available had not been invented when
the Internet was first designed.
 The Internet is a global infrastructure. Although it offers
many services, the Internet’s chief advantage lies in the
design of TCP/IP software that has accommodated
changes in computers, networks, and services
Summary
 Many different LAN technologies that are completely
incompatible.
 WANs exist
 Few WANs, Many LANs
 WAN and LAN are incompatible
 Desirable to have a single seamless network
Summary
 ARPANET
 ICP/IP
 Open Systems
 Computer science research, UNIX, NSFNET, TCP/IP …
contributed to the rapid growth of the Internet.
 Internet is a global information infrastructure.
Sharing transmission path
Communication Path
Sharing transmission path
Sharing saves
cost
Communication Path
Sharing transmission path
Sharing
introduces delay
Communication Path
Sharing transmission path
Sharing
introduces delay
Communication Path
Sharing using Selectable Channels
Carrier 1
Communication Path
Carrier 2
Sharing using Selectable Channels
Carrier 1
Each channel is assigned
a unique carrier which
encodes the information
of that communication
channel
Communication Path
Carrier 2
Sharing by Taking Turns
C
A
Divide data to be
transmitted into
small trunks, call a
packet; and
transmit one
packet at a time
B
Data to be transmitted
D
Sharing by Taking Turns
1st packet
from B to D
A
B|C
C
A|C B|D A|C
D
B
1st packet
from B to C
2nd packet
from A to C
1st packet
from A to C
Packet
Sharing by Taking Turns
Switching
1st packet
from B to D
A
B|C
C
A|C B|D A|C
D
B
1st packet
from B to C
2nd packet
from A to C
1st packet
from A to C
Packet Switching Avoids Delay
Packet Switching Avoids Delay
A customer
ordered a
single item
Another
ordered 50
items
Each packet must be labeled
1st packet
from B to D
A
B|C
C
A|C B|D A|C
D
B
1st packet
from B to C
2nd packet
from A to C
1st packet
from A to C
Computers Have Addresses
C
A
10.0.0.1
B|C
B
A|C B|D A|C
Each computer attached
to the network is
assigned a unique
number called address
D
Computers Have Addresses
C
A
10.0.0.1
B|C
B
A|C B|D A|C
Each packet contains the
address of the computer
that send it and the address
of the computer to which it
is sent
D
Packets are Not All the Same Size
C
A
10.0.0.1
B|C
B|D
A|C
D
B
Packets can have different
sizes
Packets Transmission Seems Instantaneous
C
A
B|C
B
B|D
A|C
A packet switching system permits
multiple computers to communicate
across a shared network with minimal
delay because it divides each
conversation into small packets and
arranges for the computer that sharing
a network takes turns sending packets
D
Sharing is Automatic
C
A
B|C
B|D
A|C
D
B
From a computer’s point of view,
obtaining fair access to a shared
network is automatic – the network
hardware handles the details.
Many Devices Can Use Packet Switching
C
A
B|C
B|D
A|C
D
B
Many type of devices can connect
directly to a computer network,
each such device must contain a
small computer that handles
communication
Relevance to the Internet
All data is transferred across
the Internet in packets
Relevance to the Internet
A sender divides a message or
document into packets and
transfer the packets across the
Internet
Relevance to the Internet
A receiver re-assembles the
original message from the
packets that arrive.
Relevance to the Internet
Packets from many machines
traverse the Internet at the
same time.
Summary
 Packet switching – a fundamental technique used to
ensure faire access to shared network resources.
 Before data can be transferred across a network, it
must be divided into small trunks – packets
 Each computer connected to a network has a unique
address
 Each packet contains a header – records the sending
and receiving computers’ addresses
 Each computer takes turns to send its packet. One
each turn, a computer sends one packet.
Internet: A Network of Networks
How multiple packet switching networks can be
interconnected to form an Internet that function like a
single, large network.
Use A Computer to Interconnect Networks
Interconnecting
Computer
Computers that interconnect networks are
dedicated to the interconnection task.
Use A Computer to Interconnect Networks
They can use conventional hardware and
run on special-purpose software that starts
automatically when the system is powered
on and remains operating all the time.
Interconnecting
Computer
Interconnection Computers Pass Packets
Interconnecting
Computer
Interconnection Computers Pass Packets
Interconnecting
Computer
Interconnection Computers Pass Packets
Interconnecting
Computer
Interconnection Computers Pass Packets
Interconnecting
Computer
Interconnection Computers Pass Packets
Interconnecting
Computer
An
interconnect
ing
computer is
call router
Routers are Building Blocks of the Internet
 The Internet is not a single computer network
 It consists of thousands of computer networks
interconnected by dedicated, special purpose
computers called routers
Routers are Building Blocks of the Internet
 The Internet is not a single computer network
 It consists of thousands of computer networks
interconnected by dedicated, special purpose
computers called routers
The Hierarchical Structure of the Internet
Major ISP
Major ISP
Regional
ISP
Regional
ISP
Local
ISP
subscribers
Regional
ISP
Local
ISP
Local
ISP
subscribers
subscribers
Where Packets Travel
Major ISP
Major ISP
Regional
ISP
Regional
ISP
Local
ISP
Local
ISP
Local
ISP
Regional
ISP
Where Packets Travel
Major ISP
Major ISP
Regional
ISP
Regional
ISP
Local
ISP
Local
ISP
Local
ISP
Regional
ISP
Where Packets Travel
Major ISP
Major ISP
Regional
ISP
Regional
ISP
Local
ISP
Local
ISP
Local
ISP
Regional
ISP
Where Packets Travel
Major ISP
Major ISP
Regional
ISP
Regional
ISP
Local
ISP
Local
ISP
Local
ISP
Regional
ISP
Where Packets Travel
Major ISP
Major ISP
Regional
ISP
Regional
ISP
Local
ISP
Local
ISP
Local
ISP
Regional
ISP
Where Packets Travel
Major ISP
Major ISP
Regional
ISP
Regional
ISP
Local
ISP
Local
ISP
Local
ISP
Regional
ISP
Where Packets Travel
Major ISP
Major ISP
Regional
ISP
Regional
ISP
Local
ISP
Local
ISP
Local
ISP
Regional
ISP
Interconnecting Networks was Revolutionary
Interconnecting
Computer
(Router)
Summary
 To the user the Internet seems to be a single network
 It in fact consists of thousands of networks
interconnected by a dedicated device known as routers.
 A router can connect LAN/LAN, LAN/WAN, WAN/WAN
 Networks in the Internet are arranged into a conceptual
hierarchy of ISPs.
 Using routers to interconnect networks produced a
revolution.
ISPs: Broadband and Wireless Access
 How your compute can connect to and use the
Internet
ISPs: Broadband and Wireless Access
 How your compute can connect to and use the
Internet
Internet Service Providers and Fees
 A company that provides Internet access is
known as an Internet Service Provider (IPS)
 ISP levy two types of fees
 A charge for using the Internet
 A charge for a physical connection to the Internet
Leased Line
 Dedicated connection, available all the time
(24/7)
 Expensive
 Large business users
Dial-Up Access
ISP’s
Computer
Attached
To the Internet
User’s Computer
Modem
Voice
Telephone
system
Modem
ISP’s
Permanent
Connection to
The Internet
Modern Technologies Offer Inexpensive Dedicated
Access
 Cable Modem – From cable TV …
 DSL (ADSL) – Digital subscriber line
(Asynchronous digital subscriber line)
 Wireless Access
Modern Technologies Offer Inexpensive Dedicated
Access
 DSL (ADSL) for residential users
 A separate pair of copper wires connects each
residence to the telephone office
 The technology sends digital data over the same
wires that are used for conversational telephone
service, there is no interference. Telephone calls do
not interfere with Internet use, and Internet use
does not interfere with telephone calls.
Wi-Fi and 3G …
 Most laptop has Wi-Fi …
 3G …Mobile phone access to the Internet …