Lecture 3:
Introduction to Netcentric Computing
CSCI102 - Introduction to Information Technology B
ITCS905 - Fundamentals of Information Technology
Overview
This Week
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Background and history of networking and the
Internet
Network architectures
The range of specializations within net-centric
computing
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Networks and protocols
Networked multimedia systems
Distributed computing
Mobile and wireless computing
Background Discussion
Topics
Definitions
Describing a telecommunications
system
Requirements for voice and data
communications
History of telecommunications
Forces for change
Definitions
Communication
“A process which allows information to
pass from a sender to one or more
receivers”
 “The science of transmitting information,
especially symbols”
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Tele
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At a distance
Definitions
Telecommunications
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“Communications over a distance”
Definitions
Circuit:
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" A path over which two-way communications in
any media occurs"
Line:
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" A communications circuit which invariably uses a
physical wire connection"
Link:
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"A communications circuit is subdivided into
segments known as links ”
Definitions
Channel:
A general definition would be "the part of a
communications system that connects a
message source with the message sink"
 In this context a channel is "a one-way
communications path“
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Sound
If a tree falls in a forest far from any
sound detector (such as a human ear or
a microphone), does the tree's crash
make any noise?
Sound
Sound depends on three things
There must be a vibrating source to set up
sound waves
 A medium (such as air) to carry the waves
 A receiver to detect them
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Sound
If a tree falls in a forest far from any
sound detector (such as a human ear or
a microphone), does the tree's crash
make any noise?
Sound
The answer, of course, depends on how
sound is defined
Sound
If it is thought of as the waves that are carried
by the air, the answer is yes

Wherever there are sound waves there is sound
However, if sound is defined subjectively, as a
sensation in the ear, for example, the answer
must be no

In that case sound does not exist unless there is a
receiver present to detect it
The two definitions are equally correct
Transmission Types
Analog:

" An analog signal is represented in the
form of continuously varying physical
quantities"
Transmission Types
Characteristics of analog signals:
Frequency (constant or varying over time)
 Frequency range or bandwidth ( difference
between the upper and lower frequencies)
 Amplitude (varying over time)

Transmission Types
Analog signals are affected by a
number of different types of noise and
interference

These affect the signal clarity and include
White noise
 Impulse noise
 Signal to noise ratio
 Distortion
 Crosstalk
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Transmission Types
Amplification of analog signals is necessary
to counter signal distortion and attenuation
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Transmission cables are likely to act as antennas
and pick up background noise
This background noise is amplified as well as the
signal
This noise is cumulative so the further an analog
signal travels the more amplifiers it travels through
 increased noise
Transmission Types
Digital:

"A signal whose states are discrete
intervals apart“
Characteristics of digital signals:
Discrete and discontinuous
 Unipolar or bipolar
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1 0 1 1 1 0 0 0 1
1 0 1 1 1 0 0 0 1
Transmission Types
Any distortion that occurs while transmitting
digital signals is recovered by regeneration
using repeaters
Advantages of digital transmission:
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Lower signal error
Lower noise levels
Increases line capacity
Less complexity
Integration of voice, data and images
Transmission Types
What type of signals are sound waves?
Describing a
Telecommunications
System
A telecommunications system can be
described by its key components
Transmitter
 Medium
 Receiver
 Communication network

Transmitter
Telephone, voicebox, terminal etc
Medium
Cable, air, data circuits etc
Receiver
Telephone, ear, computer etc
Requirements for Voice
and Data
Communications
Voice communications
Fast
 < 200ms delay
 Telco’s <70ms round-trip-delay
 Speed more important than integrity
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Data communications
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Data integrity vs real-time
History of
Telecommunications
1837 – Wheatstone and Cooke
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five needle telegraph
1838 - Govt declines use of telegraph
1843 - First demonstration of Telegraph and
FAX in US
1845 - Morse forms company
1851 - 50 telegraph companies operating
1856 - Western union telegraph (WUT)
established
History of
Telecommunications
1876 - WUT becomes the largest communications
company
- Alexander graham bell - patent on telephone
1876 - WUT decline to pay $100,000 for telephone
1877 - Bell company formed
1878 - Worlds first telephone exchange
- Bell sues WUT and takes it over
1885 - AT&T established interconnections between
regional telephone companies
1889 – First automatic telephone system
History of
Telecommunications
1893/94 - Bell’s patent expires
- Independent telephone companies
enter the market
1911 - Bell associated companies formed
1913 - Vacuum tube patent
History of
Telecommunications
1943 - Amplifiers and repeaters
1947 - Transistors
1956 - First trans-Atlantic cable laid
1957 - Launch of first satellite
1977 - Internet services provided by
public carriers
History of
Telecommunications
1984 - Divestiture in the US
1988 - Internet provides multimedia
services
- Global digital interconnectivity
standards converge
1993 - Formation of global consortium for
the development of global satellite and
optical digital networks
What Caused the
Internet ?
Sputnik I 
US government felt vulnerable 
Creation of Advanced Research
Projects Agency
The Early Years
1961 - First paper on packet-switching (PS)
theory
1962 - J.C.R. Licklider & W. Clark, MIT: "OnLine Man Computer Communication“
(August)
1962 ARPA opened a computer research
program and appointed to its head John
Licklider to lead it
1964 - Packet-switching networks;
no single outage point
The Early Years
1966/67 - plan for computer network
system called ARPANET published
Independent teams at MIT, the National
Physics Laboratory (UK) and RAND
Corporation had all been working on the
feasibility of wide area networks
Their best ideas were incorporated into
the ARPANET design
The Early Years
Final requirement was to design a
protocol to allow the computers to send
and receive messages and data, known
as an interface message processor
(IMPs – see RFC 1)
Work on this was completed in 1968
In October 1969, IMPs installed in
computers at both UCLA and Stanford.
The Internet – 1969
The Internet – Later that
year
see RFC 4: Network
Timetable
The First Login
LOG
ERROR MESSAGE:
The Early Years
UCLA students would 'login' to
Stanford's computer, access its
databases and try to send data
The experiment was successful and the
fledgling network had come into being
The Early Years
By December 1971 ARPANET linked 23
host computers to each other
From Arpanet to
Internet
1972, direct person-to-person
communication that we now refer to as
e-mail
host-to-host protocols (Telnet)
In October 1972 ARPANET went 'public'
TCP/IP design concepts
Crucial concept was that the system should
have an 'open architecture‘
Each network should be able to work on its
own, developing its own applications without
restraint and requiring no modification to
participate in the Internet
Within each network there would be a
'gateway', which would link it to the 'outside
world'
TCP/IP design concepts
The gateway software would retain no
information about the traffic passing
through
Packages would be routed through the
fastest available route
TCP/IP design concepts
The gateways between the networks
would
always be open
 route the traffic without discrimination

Operating principles would be freely
available to all the networks
Going Global - 1973
First international connections to the
ARPANET: university college of London
(England) via NORSAR (Norway)
Ethernet
RFC 454: file transfer specification
Christmas day lockup
The Rest of the
Seventies
1974 - transmission control protocol/internet
protocol (TCP/IP)
1975
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Operational management of Internet transferred to
DCA (now DISA)
First ARPANET mailing list is created by Steve
Walker
1978 - TCP split into TCP and IP (March)
The Rest of the
Seventies
1979
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Computer science department research computer
network
Usenet
First MUD, MUD1
Internet configuration control board (ICCB)
Packet radio network (PRNET) experiment starts
with DARPA funding
April 12 emoticons
1980’s Expansion
The 1980’s saw a period of expansion
in the internetworking community
1981
BITNET, the "because it's time network"
 CSNET (computer science network)
 True names by Vernor Vinge
 RFC 801: NCP/TCP transition plan
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1980’s Expansion
1982
DCA and ARPA establish the transmission
control protocol (TCP) and internet protocol
(IP), as the protocol suite for ARPANET
 DoD declares TCP/IP suite to be standard
for DoD
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1980’s Expansion
1983
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Cutover from Network Control Protocol
(NCP) to TCP/IP (1 January)
1984 - Domain Name System (DNS)
introduced
1980’s Expansion
1986
NSFNET created (backbone speed of
56Kbps)
 Internet Engineering Task Force (IETF)
 Internet Research Task Force (IRTF)
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1987
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Number of hosts breaks 10,000
1980’s Expansion
1988
2 November - Internet worm
 CERT (Computer Emergency Response
Team)
 DoD chooses to adopt OSI and sees use
of TCP/IP as an interim
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1980’s Expansion
1989
Number of hosts breaks 100,000
 AARNET - Australian Academic Research
Network
 ARPANET's 20th anniversary
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The ‘Information Age’
Explodes
1990
ARPANET ceases to exist
 First remotely operated machine to be
hooked up to the Internet
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The ‘Information Age’
Explodes
1991
NSF lifts restrictions on the commercial
use of the Net (March)
 Wide Area Information Servers (WAIS)
 Gopher released
 World-Wide Web (WWW) released
 PGP (Pretty Good Privacy) released
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The ‘Information Age’
Explodes
1992
Internet Society (ISOC) is chartered
(January)
 IAB reconstituted as the Internet
Architecture Board and becomes part of
the Internet Society
 Number of hosts breaks 1,000,000
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The ‘Information Age’
Explodes
1993
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Mosaic takes the Internet by storm
WWW proliferates at a 341,634% annual
growth rate of service traffic
 Gopher's growth is 997%
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The ‘Information Age’
Explodes
1994 – The World discovers ‘the net’
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Shopping Mall
Internet Radio
Spamming
Governments
Banking
1995
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Registration of domain names is no longer free
The ‘Information Age’
Explodes
1996
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A malicious cancelbot is released on USENET
wiping out more than 25,000 messages
Restrictions on Internet use around the world:
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China: requires users and ISPs to register with the police
Germany: cuts off access to some newsgroups carried
on Compuserve
Saudi Arabia: confines Internet access to universities and
hospitals
Singapore: requires political and religious content
providers to register with the state
New Zealand: classifies computer disks as "publications"
that can be censored and seized
The ‘Information Age’
Explodes
1997
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101,803 Name Servers in whois database
1998
Network Solutions registers its 2 millionth
domain on 4 May
 Electronic postal stamps
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The ‘Information Age’
Explodes
1999
Technologies of the Year: E-Trade, Online
Banking, MP3
 Emerging Technologies: Net-Cell Phones,
Thin Computing, Embedded Computing
 Viruses of the Year: Melissa (March),
ExploreZip (June)
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The ‘Information Age’
Explodes
2000
RFC 2795: The Infinite Monkey Protocol
Suite
 Hacks of the Year: RSA Security (Feb),
Apache (May), Western Union (Sep),
Microsoft (Oct)
 Technologies of the Year: ASP, Napster
 Emerging Technologies: Wireless devices,
IPv6
 Viruses of the Year: Love Letter (May)
 Lawsuits of the Year: Napster, DeCSS
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The ‘Information Age’
Explodes
2001
Viruses of the Year: Code Red (Jul), Nimda
(Sep), SirCam (Jul), BadTrans (Apr, Nov)
 Emerging Technologies: Grid Computing,
P2P
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The ‘Information Age’
Explodes
2002
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New Top level Domains
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Abilene (Internet2) backbone deploys native IPv6 (5 Aug)
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.name (15 Jan), .coop (30 Jan), .aero (18 March) 2 September
Internet2 now has 200 university, 60 corporate, and 40 affiliate
members (2 Sep)
A distributed denial of service (DDoS) attack struck the 13
DNS root servers knocking out all but 5 (21-23 Oct). Amidst
national security concerns, VeriSign hastens a planned
relocation of one of its two DNS root servers
A new US law creates a kids-safe "dot-kids" domain (kids.us)
to be implemented in 2003 (3 Dec)
RFC 3251: Electricity over IP
The ‘Information Age’
Explodes
2003
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Public Interest Registry (PIR) takes over as .org registry
operator on 1 Jan
By giving up .org, VeriSign is able to retain control over .com
domains
The first official Swiss online election takes place in Anières
(7 Jan)
The SQL Slammer worm causes one of the largest and
fastest spreading DDoS attacks ever.
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Taking roughly 10 minutes to spread worldwide, the worm took
down 5 of the 13 DNS root servers along with tens of
thousands of other servers, and impacted a multitude of
systems ranging from (bank) ATM systems to air traffic control
to emergency (911) systems (25 Jan)
RFC 3514: The Security Flag in the IPv4 Header (The Evil
Bit)
Growth Chart
Growth Chart
Growth Chart
Growth Chart
Growth Chart
Growth Chart
Definitions
Architecture
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From Merriam Webster’s dictionary
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“A unifying or coherent form or structure”
“A set of rules or outlines needed to perform
functions according to user needs”
A design
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The term architecture can refer to either hardware or
software, or to a combination of hardware and software
The architecture of a system always defines its broad
outlines, and may define precise mechanisms as well
Definitions
Communications network architecture:
“A set of design principles on the basis of
which a communications network is
designed and implemented to satisfy enduser needs over a period of time”
 “A set of layers and protocols”
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Telecommunication
Network Architectures
A telecommunications network
architecture is a set of design principles
used as a basis for the designing and
implementation of a network
It simply describes ‘what’ will be built - it
does not say ‘how’
Telecommunication
Network Architectures
An architecture can be
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A reference model such as the open systems
interconnection (OSI) reference model
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Intended as a model for specific product architectures
A specific product architecture, such as that for an
Intel Pentium microprocessor or for IBM's OS/390
operating system
A vocabulary for describing a protocol
An example of a network architecture is RFC
2271: an architecture for describing SNMP
management frameworks
Internetworking
Internetworking is the ability to communicate
across networks, with connection between
networks provided at the network layer [next
week] by routers or, at the data link layer, by
bridges and by switches
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An internet is a collection of internetworked
networks
The Internet is the name for the global, public
internet connecting most networks and using the
TCP/IP family of protocols
Classification of
Network Architecture
Open vs Closed
Extent
Ownership
Service
Quality of Service(QoS)
Classification of
Network Architecture
Open architecture

An open architecture allows the system to
be connected easily to devices and
programs made by other manufacturers
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Open architectures use off-the-shelf
components and conform to approved
standards
Closed architecture

A closed architecture network is one whose
design is proprietary
Classification of
Network Architecture
Extent

The physical space covered by the network
Pan, LAN, man, wan
 Internet, intranet, extranet
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Classification of
Network Architecture
Ownership
Public
 Private
 Virtual private networks
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Classification of
Network Architecture
Service:
Connection-oriented
 Connectionless
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Quality of service(QoS)
Delay
 Reliability
 Jitter
 Throughput
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Classification of
Network Architecture
Topology
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Star
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Hierarchal
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Mesh
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Bus
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Ring
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Hybrid
Network Basics
Networks
Encompass a variety of technologies
 Are created and maintained by large
number of ever changing industries
 Must satisfy a significant number of often
conflicting requirements
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Network Basics
"No single networking technology is best for
all needs“ - Comer
Universal Service
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to allow any two computer to communicate
Regardless of
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technologies they use
specific networks they are directly connected to,
as long as there exists a communication path
between them
References
Hobbs Timeline
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http://www.zakon.org/robert/internet/timeline/
RFC Index
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http://www.rfc-editor.org/rfc-index.html