Transcript TRANSMISSION MEDIA

Welcome to
Evolution of Networking
Prepared By :
VINAY ALEXANDER
KV JHAGRAKHAND
What is a Computer Network?
Two or more computers or communications devices connected
by transmission media and channels and guided by a set of rules
for communication purposes that allow users to communicate
with each other and share applications and data.
Hardware:
Computer
Network card
Routers
Modem …
Media:
Cable
Wire
Microwave …
Components of a Computer Network
Software:
Network OS
Utilities …
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Network Design:
Logical layout
Physical layout …
Advantages of NETWORK
• Share Resource
• Can Share Software
• Share storage
• Improve Communications
Disadvantages of NETWORK
• The system are more sophisticated and
complex to run. This can add to costs and
you may need specialist staff to run the
network.
• If s/w and files are held centrally, it may be
impossible to carry out any work if the
central server fails.
• If networks are badly managed services can
becomes unusable and productivity falls.
• File security is more important especially if
connected to WAN.
Application of NETWORK
• Sharing :
• Access to remote database
• Communication facilities
Evolution of NETWORK
Evolution of networking started way back
1969 by the development of Internet.
ARPANET, NSFnet, Internet
ARPANET (Advanced Research Projects Agency
NETwork): In 1969, ARPANET was started to
connect computers at US defense & different
universities.
NSFnet (National Science Foundation Network) :
In 1980 NSFnet was started to make a highcapacity network to be used strictly for
academic and engineering research.
Internet : In 1990 the internetworking of
ARPANET , NSFnet and other private
networks resulted into Internet.
Gateway & Backbone Network
A Gateway is a device that connects
dissimilar networks.
A Backbone is central interconnecting
structure that connects one or more
networks just like the trunk of a tree or
the spine of a human being
Internet Functioning
=>A protocol is a set of rules which is used by
computers to communicate with each other across a
network. A protocol is a convention or standard that
controls or enables the connection, communication,
and data transfer between computing endpoints
The communication protocol used by internet is
TCP/IP.
The TCP ( Transmission Control Protocol) part is responsible
dividing the files/massage into packet on the source
computer. It is also responsible for reassembling the
received packet at the destination computer.
The IP (Internet Protocol) part is responsible for handling the
address of destination computer so that each packet is
routed to its proper destination.
Interspace
The future of internet is said to be in
Interspace.
Interspace is a client/server software
program that allows multiple users to
communicate online with real-time
audio, video and text chat in dynamic
3D environments.
Elementary Terminology of Networks
Nodes: the term nodes refers to the
computers that are attached to a
network and are seeking to share the
resources of the network.
A computer becomes a workstation of a
network as soon as it is attached to a
network.
=> A server is any combination of hardware or software designed to
provide services to clients.
=>A server is primarily a program that runs on a machine, providing a
particular and specific service to other machines connected to the
machine on which it is found
=> A computer, or a software package, that provides a specific kind
of service to client software running on other computers.
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Figure 15.1 Client/Server interaction
• TYPES OF SERVER
 Non-Dedicated Server: A Non-dedicated server can be used
as a workstation as well as a server. Using a server as a
workstation has several disadvantages and is not advisable for
larger networks
 Dedicated Server: Dedicated servers are used only as a
server, not as a workstation. Dedicated servers cannot be
used for ordinary work. In fact, access to the server is often
limited to prevent any access by unauthorized users. Most of
the high-end network packages assume you are using a
dedicated server. If the network has a dedicated server, it is
most likely a file server.
 Differences: Non-dedicated servers are used both as a server
and a workstation. Networks with a dedicated server are
known as server-based networks; those with non-dedicated
servers are known as peer-to peer networks
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Elementary Terminology of Networks
NIU (Network Interface Unit) : A
network interface unit is an
interpreter that helps establish
communication
between
the
server and workstation.
MAC address : The MAC address
refers to the physical address
assigned by NIC manufacturer.
Switching Techniques
Switching Techniques are used for
transmitting data across networks.
Circuit Switching : 1st the complete
physical
connection
between
two
computers is established and then data
are transmitted from source computer to
the destination computer.
Switching Techniques
MMessageSwitching:
The
source
computer sends data or the message to
the switching office first, which stores
the data in its buffers. It then looks for
free link to another switching office and
then send the data to this office. This
process is continued until the data are
delivered to the destination computers. It
is also known as store and forward.
Switching Techniques
PPacket Switching: With message switching,
there is no limit on block size, in contrast,
packet switching places a tight upper limit on
block size. A fixed size of packet which can
be transmitted across the network is
specified. Packets are stored in main memory
whereas in massage switching the data are
stored on the disk. This improves the
performance as the access time is reduced,
thus the throughput of the network is
improved.
Transmission Media
 Sending of data from one device to another
is called transmission of data
 Medium used to transmit the data is called
Media
 Transmission of data through Medium is
called Transmission Media
 Transmission media or communication
cannels meant that the ‘connecting cables’
or ‘connection media’.
Topic Included
Tranmission media
 Definition
 Types of Transmission Media
 Guided Media
1. Twisted Pair cable
2. Coaxial Cables
3. Optical Fiber
 Unguided media
1.
Microwave
2.
Infrared
3.
Bluetooth
4.
WI-FI (Wireless Fidelity)
 Applications
Types Of Transmission Media
• Guided (Wired)
– Twisted Pair
– Coaxial cable
– Fiber Optics
• Unguided (Wireless)
– Wi-Fi
– Bluetooth
– Infrared
– Microwave
– Lasers
Guided ( Wired )
• The medium itself is more important in
determining the limitations of transmission.
• The transmission capacity, in terms of
either data rate or bandwidth, depends
critically on the distance and on whether
the medium is point-to-point or multipoint.
Twisted Pair
• A twisted pair consists of two insulated copper wires arranged
in a regular spiral pattern.
• The twisting tends to decrease the crosstalk interference
between adjacent pairs in a cable.
• Twisted pair may be used to transmit both analog and digital
transmission.
• Twisted pair is limited in distance, bandwidth, and data rate.
• The attenuation for twisted pair is a very strong function of
frequency
Twisted-Pair Cables
• If the pair of wires are not twisted,
electromagnetic noises from, e.g., motors,
will affect the closer wire more than the
further one, thereby causing errors
CROSSTALK
• The bleeding of a signal from one wire to another and
which can corrupt signal and cause network errors.
This form of signal interference is called CROSSTALK
• Advantages:
• It is Simple
• It is Physically flexible
• It can be easily connected
• It is easy to install and maintain
• It has a low weight
• It is very inexpensive.
• Disadvantage:
• 1.High Attenuation, it is incapable carrying a
signal over long distances without the use of
repeater.
• 2. Its low bandwidth capabilities make it
unsuitable for broadband application.
• 3.It supports max data rates 1Mbps without
conditioning and 10 Mbps with conditioning.
• TYPES OF TWISTED PAIR CABLES
Unshielded Twisted-Pair (UTP)
• Typically wrapped inside a plastic cover (for
mechanical protection)
• A sample UTP cable with 5 unshielded twisted pairs
of wires
Insulator
Metal
Shielded Twisted-Pair (STP)
• STP cables are similar to UTP cables, except there
is a metal foil or braided-metal-mesh cover that
encases each pair of insulated wires
Twisted Pair Types
• Unshielded Twisted Pair (UTP)
– ordinary telephone wire
– cheapest
– easiest to install
– suffers from external EM
interference
• Shielded Twisted Pair (STP)
– metal braid or sheathing
that reduces interference
– more expensive
– easiest to install
– harder to handle (thick,
heavy)
Coaxial cable
Coaxial cable
It consists of solid wire core surrounded
by one or more foil or wire shield, each
separated by some kind of plastic
insulator. the inner core carries the signal ,
and outer shield provides the ground. the
coaxial cable has high electrical properties
and is suitable for high speed
communication. it is used in television
signal.
 In general, coaxial cables, or coax, carry
signals of higher freq (100KHz–500MHz) than
UTP cables.
Outer metallic wrapping serves both as a shield
against noise and as the second conductor that
completes the circuit.
=>versatile transmission medium, used in a wide
variety of applications, including:
• Television distribution - aerial to TV
systems.
Advantages
• Better than twisted pair cable.
• Used as shared cable network
• Used for broadband transmission.
• Higher bandwidth upto 400 MBPS
Disadvantages
• Expensive compared to twisted pair cables
• The coaxial cables are not compatible with
twisted pair cables.
BNC connectors
•
BNC Connectors are used for connecting to co-axial cables together
at connecting points is when repeaters are required
TYPES OF COAXIAL CABLES
• There are two types .
1.Thicknet: It is a thicker than thinner. It is used
upto 500 meters long.
2. Thinner: It is used upto 185 meters long.
Optical-Fiber Cables
• Light travels at 3108 ms-1 in free space and is
the fastest possible speed in the Universe
• Light slows down in denser media, e.g. glass
• Refraction occurs at interface, with light
bending away from the normal when it enters a
less dense medium
• Beyond the critical angle  total internal
reflection
• An optical fiber consists of a core (denser material)
and a cladding (less dense material)
• Simplest one is a multimode step-index optical fiber
• Multimode = multiple paths, whereas step-index =
refractive index follows a step-function profile (i.e.
an abrupt change of refractive index between the
core and the cladding)
• Light bounces back and forth along the core
• Common light sources: LEDs and lasers
Fiber Optics
Optical Fiber - Transmission Characteristics
 uses total internal reflection to transmit light
 effectively acts as wave guide for 1014 to 1015 Hz
 can use several different light sources
 Light Emitting Diode (LED)
cheaper, wider operating temp range, lasts
longer
 Injection Laser Diode (ILD)
more efficient, has greater data rate
 relation of wavelength, type & data rate
• Fiber optic cable is known as most sophisticated
cables used in long distance network connection.
• Through this cable data transmission is done through
Light ray signal transmission rather than electrical
signal transmission.
• It has inner core of glass that conducts light.This
inner core is surrounded by cladding.
• Cladding is nothing but layer of glass material that
reflects light back into the core.
• Each fiber is then surrounded by plastic sheath
Advantages
•
Immune(प्रतिरक्षिि ) to electrical and magnetic interference.
• Highly suitable for harsh industrial environments.
• Secure transmission and very high transmission capacity.
• Used for broadband transmission.
Disadvantages
• Installation problem.
• Connecting two fibers together is a difficult process.
• Because of noise immunity, they are virtually impossible to
tap.
• Light can reach the receiver out of phase.
• Connection losses are common problem
• Difficult to solder
• Most expensive.
Optical Fibre Transmission Mode
Types of fibre optic cable
1.single node: It is used upto 2kms and band
width of upto 100Mbps
2. Multinode: It is used upto 100kms and band
width of 2Gbps.
microwave
• A microwave is an electromagnetic wave with a very
short wavelength, between .039 inches (1 millimeter)
and 1 foot (30 centimeters). Within the
electromagnetic spectrum, microwaves can be found
between radio waves and shorter infrared waves.
Their short wavelengths make microwaves ideal for
use in radio and television broadcasting. They can
transmit along a vast range of frequencies without
causing signal interference or overlap.
• It consist of a transmitter, receiver and atmosphere.
• Microwave technology was developed during World
War II (1939–45) in connection with secret military
radar research. Today, microwaves are used primarily
in microwave ovens and communications. A
microwave communications circuit can transmit any
type of information as efficiently .
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Advantages:
No cables needed
Multiple channels available
Wide bandwidth
It have the ability to communicate over oceans and
difficult terrain.
Cheaper
Disadvantages:
Line-of-sight will be disrupted if any obstacle, such as
new buildings, are in the way
Signal absorption by the atmosphere. Microwaves suffer
from attenuation due to atmospheric conditions.
Towers are expensive to build line of sight requirement
expensive towers and repeaters
subject to interference such as passing airplanes and
rain
It is insecure communication.
Radio Transmission
• Radio transmission works with or without line of sight. If line of
sight is possible then transmission can take place between
sending antenna and receiving antenna. The placement of
antenna has to take into account the curvature of the Earth
with antenna being built taller accordingly. This will also allow
for greater transmission distances. If line of sight cannot be
implemented then signals can be broadcast to the upper layers
or the atmosphere or space and then transmitted back to
Earth.
• The electromagnetic spectrum used for radio communication
consists of eight distinct ranges which are regulated by
government authorities:
• It consist of two parts
1. The Transmitter 2. The Receiver
• Advantages
• Disadvantages
• It offers mobility
• Cheaper
• Offers freedom from
land acquisition rights
• Ease of communication
over difficult terrain
• Insecure communication
• It effects from rain,
thunder storms
• Satellite Microwave
Satellite communication is special case of microwave
relay system. Satellite communication use the
synchronous satellite to relay the radio signal
transmitted from ground station.
• A satellite is any object that revolves around a planet
in a circular or elliptical path. The moon is Earth's
natural satellite at 240,000 miles distant. Other
satellites that fulfill this definition are man made and
have been launched into orbit to carry out specific
functions. These satellites are typically between 100
and 24,000 miles away.
Satellite Microwave


Satellite is relay station
Receives on one frequency, amplifies or repeats signal
and transmits on another frequency
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Typically requires geo-stationary orbit
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Eg. Uplink 5.925-6.425 ghz & downlink 3.7-4.2 ghz
Height of 35,784km
Spaced at least 3-4° apart
Typical uses
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Television
Long distance telephone
Private business networks
Global positioning
• Advantages:
• High bandwidth
• Develop stronger relationships with
classmates
• Area coverage through satellite is quire large.
• The laying and maintenance is easy and
inexpensive.
• Heavy usage of intercontinental traffic makes
it commercial attractive.
• Disadvantages:
• Huge initial cost
• Technological limitation preventing the deployment
of large, high gain antennas on the satellite platform.
• Over-crowding
• High investment and insurance cost associated with
significant probability of failure.
• High atmospheric losses.
Satellite Point to Point Link
Satellite Broadcast Link
Continue….
Comparisiom of Major
Wireless Transmission Media
Medium
Description and
Advantages
Limitations and
Drawbacks
Microwave
Point-to-point communication in
lineof-sight path.
Must have visual contact between
antennas.
Antennas are used (30 miles apart).
Susceptible to environmental
interferences
THANK YOU
Provide large capacity.
Can be done quickly at lower cost
Satellites
Can be at high, medium, or low orbit;
used in GPSs.
Expensive to build and maintain.
Complete global coverage is available
with three satellites.
Radio/electromagnetic
Effective for short ranges; used in LANs
Limited range; difficult to secure.
Inexpensive and easy to install.
Can create interference with
communication devices.
Applications
Wireless Transmission Frequencies
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2GHz to 40GHz
– microwave
– highly directional
– point to point
– Satellite
30MHz to 1GHz
– Omni directional
– broadcast radio
3 x 1011 to 2 x 1014
– infrared
– local
Continue….
Infrared
“Infrared technology allows computing
devices to communicate via short-range wireless
signals. With infrared, computers can transfer files
and other digital data bidirectionally. The infrared
transmission technology used in computers is
similar to that used in consumer product remote
control units.”
Modulate noncoherent infrared light
End line of sight (or reflection)
Are blocked by walls
No licenses required
Typical uses
 TV remote control
Infrared
Installation and Usage - Infrared light lies between the
visible and microwave portions of the electromagnetic
spectrum. Infrared light has a range of wavelengths, just
like visible light has wavelengths that range from red
light to violet. "Near infrared" light is closest in
wavelength to visible light and "far infrared" is closer to
the microwave region of the electromagnetic spectrum.
The longer, far infrared wavelengths are about the size
of a pin head and the shorter, near infrared ones are the
size of cells, or are microscopic . Infrared adapters are
installed in many laptops and handheld personal
devices.
• Range - Infrared communications span very short distances.
Place two infrared devices within a few feet (no more than 5
meters) of each other when networking them. Unlike Wi-Fi
and Bluetooth technologies, infrared network signal cannot
penetrate walls or other obstructions and work only in the
direct "line of sight.“
• Performance - Infrared technology used in local networks
exists in three different forms:
• IrDA-SIR (slow speed) infrared supporting data rates up to 115
Kbps
• IrDA-MIR (medium speed) infrared supporting data rates up
to 1.15 Mbps
• IrDA-FIR (fast speed) infrared supporting data rates up to 4
Mbps
• Humans, at normal body temperature, radiate most
strongly in the infrared at a wavelength of about 10
microns. (A micron is the term commonly used in
astronomy for a micrometer or one millionth of a
meter.) This image ( which is courtesy of the
Infrared Processing and Analysis Center at CalTech),
shows a man holding up a lighted match! Which
parts of this image do you think have the warmest
temperature? How does the temperature of this
man's glasses compare to the temperature of his
hand?
IR Advantages:
• Low power requirements: therefore ideal for laptops,
telephones, personal digital assistants
• Low circuitry costs: $2-$5 for the entire
coding/decoding circuitry
• Simple circuitry: no special or proprietary hardware is
required, can be incorporated into the integrated
circuit of a product
• Higher security: directionality of the beam helps
ensure that data isn't leaked or spilled to nearby
devices as it's transmitted
• Portable
IR Disadvantages:
• Line of sight: transmitters and receivers must be
almost directly aligned (i.e. able to see each
other) to communicate
• Blocked by common materials: people, walls,
plants, etc. can block transmission
• Short range: performance drops off with longer
distances
• Light, weather sensitive: direct sunlight, rain, fog,
dust, pollution can affect transmission
• Speed: data rate transmission is lower than
typical wired transmission
Laser wave
• It Requires direct line of sight. it is
unidirectional like microwave, but has higher
speed than microwaves. It requires the use of
laser transmitter and a photo-sensitive
receiver at each end
• Disadvantages
• It effected by weather.
Data communication technologies
1. Data Channel: is the medium to carry information
from one point to another.
2. Baud: is the unit of measurement for the
information carrying capacity.
3. Bits per second: it refers to a thousand bit
transmitted per second.
4. Bandwidth: it refers to the difference between the
highest and lowest frequencies of transmission
channels.
5. Data transfer Rate: Amount of data transfer per
second.
• Local area network: A local area network
(LAN) is a network that connects computers
and devices in a limited geographical area
such as home, school, computer laboratory,
office building, or closely positioned group of
buildings. Each computer or device on the
network is a node. Current wired LANs are
most likely to be based on Ethernet
technology
• Metropolitan area network :A
metropolitan area network (MAN) is a
network that connects two or more local
area networks or campus area networks
together but does not extend beyond the
boundaries of the immediate town/city.
Routers, switches and hubs are connected
to create a metropolitan area network.
• Wide area network :A wide area network
(WAN) is a computer network that covers a large
geographic area such as a city, country, or
spans even intercontinental distances, using a
communications channel that combines many
types of media such as telephone lines, cables,
and air waves. A WAN often uses transmission
facilities provided by common carriers, such as
telephone companies. WAN technologies
generally function at the lower three layers of the
OSI reference model: the physical layer, the data
link layer, and the network layer.
Personal Area Network (PAN)
• A personal area network is the
interconnection of information technology
deice within the range of an individual person,
within a range of 10 meters.
• Laptop connect to a portable printer using
wifi technologies
The pattern of interconnection of nodes in a network is called
the Topology.
The selection of a topology for a network cannot be
done in isolation as it affects the choice of media and the
access method used. There are a number of factors to
consider in making this choice, the most important of which are
set out below:
1. Cost. For a network to be cost effective, one would try to
minimize installation cost. This may be achieved by using
well understood media and also, to a lesser extent, by
minimizing the distances involved.
2. Flexibility. Because the arrangement of furniture,
internal walls etc. in offices is often subject to change,
the topology should allow for easy reconfiguration of the
network. This involves moving existing nodes and
adding new ones.
3. Reliability. Failure in a network can take two forms.
Firstly, an individual node can malfunction. This is not
nearly as serious as the second type of fault where the
network itself fails to operate. The topology chosen for the
network can help by allowing the location of the fault to be
detected and to provide some means of isolating it.
In networking, the term “topology” refers to the layout of connected
devices on a network. One can think of a topology as a network’s
virtual shape or structure. This shape does not necessarily correspond
to the actual physical layout of the devices on the network. For
example, the computers on a home LAN may be arranged in a circle in
a family room, but it would be highly unlikely to find an actual ring
topology there. Network topologies are categorized into the following
basic types : bus, ring, star, tree, mesh. More complex networks can be
built as hybrids of two or more of the above basic topologies.
Point-to-Point Topology
Transmit
X
• Point-to-point (PTP)
topology connects
two nodes directly
together. The
following examples
are pure point to
point links:
• Two computers
Receiver
communicating via
modems.
Y
In Star, all computers are connected to central device
called hub, router or switches using Unshielded Twisted
Pair (UTP) or Shielded Twisted Pair cables.
In star topology, we require more connecting devices like
routers, cables unlike in bus topology where entire
network is supported by single backbone. The most
practical point of Star topology success is that the entire
network does not go down incase of failure of a
computer or cable or device, it will only affect the
computer whose wire failed rest of the network will be
working fine.. Star topology is widely used in homes,
offices and in buildings because of its commercial
success.
Star Topology
• Advantages
• Easy to add devices as the
network expands
• One cable failure does not
bring down the entire
network (resilience)
• Hub provides centralised
management
• Easy to find device and
cable problems
• Can be upgraded to faster
speeds
• Lots of support as it is the
most used
• Disadvantages
• A star network
requires more cable
than a ring or bus
network
• Failure of the
central hub can
bring down the
entire network
• Costs are higher
(installation and
equipment) than for
most bus networks
each node is daisy-chained (connected one right after the
other) along the same backbone. Information sent from a
node travels along the backbone until it reaches its
destination node. Each end of a bus network must be
terminated with a resistor.
=>Network maintained by a single cable
=>Uses thin coaxial cable (backbones will be thick coaxial
cable)
=>Extra stations can be added in a daisy chain manner
=>Simple and low-cost
=>A single cable called a trunk (backbone, segment)
=>Only one computer can send messages at a time
Passive topology - computer only listen for, not
regenerate data
• Thick Ethernet (10Base5) used for
backbones
• Limited to 500m
• Max of 100 nodes per segment
• Total of four repeaters , 2500m,
with a total of 488 nodes
Bus Topology
•
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Advantages
Inexpensive to install
Easy to add stations
Use less cable than other
topologies
Works well for small
networks
A single node failure
does not bring the
network down
Most widely implemented
topology
Network can be added to
or changed without
affecting other stations
Disadvantages
• No longer recommended
• Backbone breaks, whole
network down
• Limited no of devices can be
attached
• Fault diagnosis is difficult
• Fault isolate is Difficult
• Sharing same cable slows
response rates (Repeater
Configuration)
• Collisions can occur
easily
• Only one device can
access the network
media at a time.
Each node is connected to two and only two neighboring nodes.
data is accepted from one of the neighboring nodes and is
transmitted onwards to another. thus data travels in one direction
only, from node to node around the ring . After passing through
each node, it returns to the sending node, which removes it
=>USES A TOKEN TO PASS INFORMATION FROM 1
COMPUTER TO THE OTHER.
A TOKEN IS ATTACHED TO THE MESSAGE BY THE SENDER
TO IDENTIFY WHICH COMPUTER SHOULD RECEIVE THE
MESSAGE. AS THE MESSAGE MOVES AROUND THE RING,
EACH COMPUTER EXAMINES THE TOKEN. IF THE
COMPUTER IDENTIFIES THE TOKEN AS ITS OWN, THEN IT
WILL PROCESS THE INFORMATION.
•Short cable length.
•No wiring closet space required.
•Suitable for optical fibers.
•Node failure causes network failure.
•Difficult to diagnose faults.
•Network reconfiguration is difficult.
=>Tree topology is a variation of bus topology
=>A special node is designated as root
=>The primary reason for this topology is to segment
nodes so that not all nodes need to listen to packets
broadcast on a segment
=>This adds a layer of security in the form of
unwanted nodes not listening to the network traffic.
=>Looks like an upside-down tree where end nodes
are linked to interior nodes that allow linking through
to another end node.
Tree topology diagram
Root
PC 7
PC 1
PC 6
PC 2
PC 3
PC 4
PC 5
In this topology, nodes are connected
together in an arbitrary fashion. A link
may or may not connect two or more
nodes. There may be multiple links also.
It is not necessary that all the nodes are
connected. But if a path can be
established in two-nodes via one or
more links, it is called a connected
graph.
In this topology, each node is connected to more
than one node to provide an alternative route in
the case the host is either down or too busy. It is
an extension to P-P network.
=>The mesh topology is excellent for long distance
networking because it provides extensive back-up,
rerouting and pass-through capabilities.
Communication is possible between any two
nodes on the network either directly or by passing
through.
Mesh Topology
FULL CONNECTED
Each node is connected to every other
node directly i.e. , there is a direct link
between each host , then the network is
called fully connected.
• Allows communication to continue in the
event of a break in any one connection
FULL CONNECTED
Topologies are essence of computer networks design.
Efficient networks can only be built based on the complete
knowledge and understanding of above mentioned
topologies. Knowledge of every communication device is of
equal importance to help you find the best option for your
network requirements. Optimum networks can be built with
complete knowledge and understanding of computer
network devices and how they are designed, any mistake in
choosing inappropriate techniques, device etc can only be
the waste of time, resources and efforts.
NETWORK DEVICES
=>MODEM (modulator-demodulator): It
is a device that allows you to connect and
communicate with other computer via
telephone lines.
=>Modem changes the digital data from
your computer into analog data, a format
that can be carried over telephone lines.
=>In the same the modem receiving the
call then changes the analog signal back
into digital data that the computer can
understand.
=>Modulation:
•
•
•
•
It is process of sending data
on a wave form
Type of modulation
1.Amplitude modulation (AM), in which
the voltage applied to the carrier is varied
over time
2.Frequency modulation (FM), in which
the frequency of the carrier waveform is
varied in small but meaningful amounts
3.Phase modulation (PM), in which the
natural flow of the alternating current
waveform is delayed temporarily
Internal Modem: The modem that are fixed within
the computer
External Modem: The modem that are connected
externally to a computer
RJ-45 :RJ-45 is short of registered jack45. RJ-45 is an eight-wire connecter, which is
commonly used to connect computers on the
LAN especially Ethernets.( Ethernet is a LAN
architecture developed by Xerox Corp along
with DEC and Intel. Ethernet uses either a
bus or star topology and supports data
transfer rates of upto 10Mbps)
Ethernet Card :Ethernet is a LAN architecture
developed by Xerox Corp along with DEC and Intel.
Ethernet uses either a bus or star topology and
supports data transfer rates of upto 10Mbps
The computers that are part of Ethernet, have to
install a special card called Ethernet card.
HUB :A hub is a hardware device used to
connect several computers together.
Active Hub: An electrically amplify the signal
as it moves from one connected device to
another. Active Hubs used like a repeater.
Passive Hub : It allow the signal to pass from
one computer to another without any change.
Concentrator : A concentrator is a device that
provides a central connection point for cables
from workstations, servers, and peripherals.
•Function of HUB:
•A hub is a common connection point for devices
in a network. Hubs are commonly used to
connect segments of a LAN. A hub contains
multiple ports. When a packet arrives at one
port, it is copied to the other ports so that all
segments of the LAN can see all packets.
•The functions of a hub within a network is so
they produce packets to the location of the
service required to load or view a webpage or
document
Switch :A switch is a device that is used to
segment networks into different sub-networks
called subnets or LAN segments.
A switch is responsible for filtering that is
transforming data in a specific way and for
forwarding packets between LAN segments.
 Network switches are capable of
inspecting data packets as they are received,
determining the source and destination
device of that packet, and forwarding it
appropriately
Repeater : A repeater is a network device
that amplifies and restores signals for longdistance transmission.
There are two types of repeator.
1. Amplifier: It amplifies both the sinal and
concurrent noise.
2. Signal Repeater: It collect the inbound
packet and then retransmits the packet as if
were starting from the source station.
Repeater
REPEATER
Bridge : A bridge is a network device that
establishes an intelligent connection between
two local networks with the same
standard(protocol) but with different types of
cables.
=> Bridges are smart enough to know which
computers are on which side of the bridge , so they
only allow those messages that need to get the
other side to cross the bridge. This improves
performance on both sides of the bridge. As a
packet at the bride , the bridge examines the
physical address of the packet. The packet then
decides whether or not to let the packet cross.
Router : A Router is a network device that is
used to separate different segments in a
network to improve performance and reliability. A
router works like a bridge but can handle
different protocols.
How a router Functions:
=> A router forwards data packets from one
connected network to another depending upon
their IP address and not their MAC addresses.
=>A router is a device that determines the next
network point to which a packet should be
forwarded toward its destination.
=>A router creates and maintain a table
of the available routes and their
conditions and uses this information
along with distance and cost
algorithms to determine the best route
for a given packet.
=>A packet will travel through a number
of network points with routers before
arriving at its destination.
Gateway :A Gateway is a network device that
connects dissimilar networks. It establishes an intelligent
connection between a local networks and external networks
with completely different structure
e.g. to connect a LAN with Novell Netware with another
LAN with Microsoft NT.
=>In enterprises, the gateway is the computer that routes the
traffic from the workstation to the outside world.
=>In homes, the gateway is the ISP that connects the user to
the Internet.
=>In enterprises, the gateway node acts as a proxy server( a
machine that is not actually a server but appear as a server)
and a FIREWALL (a system designed to prevent
unauthorized access to or from a private network
Network Design
Access Need and costs
Select topologies and
technologies to satisfy needs
Model network workload
Simulate behavior under expected load
Perform sensitivity tests
Rework design as needed
Connecting Networks
• Repeater:
physical layer
• Bridge:
data link layer
• Router:
network layer
• Gateway:
network layer and above.
Communication Protocols
A protocols means the rules that are
applicable for a network. Protocol defines
standardized formats for data packets,
techniques for detecting and correcting
errors and so on.
It is a formal description of massage formats
and the rules that two or more machines
must follow to exchange those message.
HTTP (Hypertext Transfer Protocol) : IT is the
set of rules for transferring hypertext( text,
graphic , image , sound , video etc ) on W W W
=>The Hypertext Transfer Protocol (HTTP) is an
application-level protocol for distributed, collaborative,
hypermedia information systems. Its use for retrieving
inter-linked resources, called hypertext documents, led
to the establishment of the World Wide Web in 1990
by English physicist Tim Berners-Lee. There are two
major versions, HTTP/1.0 that uses a separate
connection for every document and HTTP/1.1 that can
reuse the same connection to download, for instance,
images for the just served page. Hence HTTP/1.1 may
be faster as it takes time to set up such connections
FTP (File Transfer Protocol) : File Transfer
Protocol (FTP) is a standard network
protocol used to exchange and manipulate
files over a TCP/IP based network, such as
the Internet. FTP is built on a client-server
architecture and utilizes separate control and
data connections between the client and
server applications. Client applications were
originally interactive command-line tools with
a standardized command syntax, but
graphical user interfaces have been
developed for all desktop operating systems
in use today.
Objectives of FTP are:
1. To promote sharing of files.
2. To encourage indirect or implicit use of
remote computer.
3. To shield a user from variations in file
storage systems among hosts.
4. To transfer data reliably and efficiently.
FTP, through usable directly by a user at
a terminal , is designed mainly for use by
program.
TCP/IP (Transmission Control Protocol / Internet Protocol)
TCP and IP were developed by a Department of
Defense (DOD) research project to connect a number
different networks designed by different vendors into a
network of networks (the "Internet"). It was initially
successful because it delivered a few basic services
that everyone needs (file transfer, electronic mail,
remote logon) across a very large number of client and
server systems. Several computers in a small
department can use TCP/IP (along with other
protocols) on a single LAN. The IP component provides
routing from the department to the enterprise network,
then to regional networks, and finally to the global
Internet. As with all other communications protocol,
TCP/IP is composed of layers:
On the battlefield a communications network
will sustain damage, so the DOD designed
TCP/IP to be robust and automatically recover
from any node or phone line failure. This
design allows the construction of very large
networks with less central management.
However, because of the automatic recovery,
network problems can go undiagnosed and
uncorrected for long periods of time.
TCP/IP (Transmission Control Protocol / Internet Protocol) :
As with all other communications protocol, TCP/IP is composed of
layers:
IP - is responsible for moving packet of data from node to node. IP
forwards each packet based on a four byte destination address
(the IP number). The Internet authorities assign ranges of
numbers to different organizations. The organizations assign
groups of their numbers to departments. IP operates on gateway
machines that move data from department to organization to
region and then around the world.
TCP - is responsible for verifying the correct delivery of data from
client to server. Data can be lost in the intermediate network. TCP
adds support to detect errors or lost data and to trigger
retransmission until the data is correctly and completely received.
Sockets - is a name given to the package of subroutines that
provide access to TCP/IP on most systems.
Datagram: It is a collection of the data is send as a single
message
SLIP/PPP (Serial line internet Protocol /
Point to Point Protocol) :
SLIP is for delivering IP packets over dialup lines.
 PPP is for transmitting Ip packets over
serial lines.
Lets you connect your computer system to
the Internet itself, rather than logging on
through an Internet access provider's host
computer and issuing commands through a
shell. SLIP/PPP connections lets you
communicate directly with other computers
on the network using TCP/IP connections.
Wireless/Mobile Computing
=>Wireless communication is simply data
communication without the use of landlines.
=>Mobile computing means that the computing
device is not continuously connected to the base or
central network.
Wireless Mobil
e
No
No
No
yes
yes
No
yes
yes
yes
yes
examples
Stationary Computer
Notebook in a hotel
Wireless LAN in HS
Personal digital assistant
Smart phones, pagers
=>GSM (Global System for Mobile communications:
It is the most popular standard for mobile phones in the
world. Its promoter, the GSM Association, estimates that
70% of the global mobile market uses the standard.
GSM uses narrowband TDMA, which allows eight
simultaneous calls on the same radio frequency.
 TDMA (Time Division Multiple Access) works by
dividing a radio frequency into time slots and then
allocating slots to multiple calls. In this way , a single
frequency can support multiple, simultaneous data
channels.
 SIM (Subscriber identification Module): Sim cards
are small removable disks that slip in and out of GSM
cell phones.
=>CDMA (Code Division Multiple Access)
:It is a channel access method utilized by
various radio communication technologies.
This allows several users to share a
bandwidth of different frequencies. This
concept is called multiplexing.
=>CDMA uses spread-spectrum technique
where data is sent in small pieces over a
number of discrete frequencies. Each user’s
signal is spread over the entire bandwidth
by unique spreading code. At the receiver .
The same unique code is used to recover
the signal.
WILL (Wireless in Local Loop) or Wireless
local loop (WLL), is a term for the use of a
wireless communications link as the "last mile
/ first mile" connection for delivering plain old
telephone service (POTS) and/or broadband
Internet to telecommunications customers.
Various types of WLL systems and
technologies exist.
=> WLL is a system that connects subscribers
to the public switched telephone network
(PSTN) using radio signals as a substitute for
other connecting media
=>GPRS (General packet radio service) :It
is technology for radio transmission of
small packets of data between mobile
device and internet.
=> HOW does GPRS work: The information
is split into smaller units or packets and
sent through the network and is
reassembled at the receiving end
=>1G, 2G AND 3G NETWOKS: “G” Means
Generation.
1G: First analog cellular systems , which
stated early 1980s. It is designed purely
for voice calls.
 2G(GSM , CDMA) : It is a first digital
cellular system launched early 1990.it
improve sound quality, better security and
higher total capacity it allow users to place
dial-up data call digitally.
2.5G(GPRS CDMA2000): It is
enhance version of 2G network with
theoretical data t\rates up to about
144 kbit/s.
 3G(UMTS, FDD,CDMA2000):
broadband, packet-based transmission of
text, digitized voice, video and
multimedia at data rates up to 2
megabits per second (Mbps), offering a
consistent set of services to mobile
computer and phone users
3G (Third Generation)
• 3G and EDGE (Enhanced Data
Rates for GSM Evolution) : 3G
Mobile communication technology is a
broadband, packet-based
transmission of text, digitized voice,
video and multimedia at data rates up
to and possibly higher then 2Mbps,
offers a consistent set of service to
mobile computer and phone users no
matter where they are located in the
world.
Enhanced Data rates for GSM Evolution (EDGE) (also
known as Enhanced GPRS (EGPRS), or IMT Single Carrier
(IMT-SC), or Enhanced Data rates for Global Evolution) is
a backward-compatible digital mobile phone technology that
allows improved data transmission rates, as an extension on
top of standard GSM. EDGE is standardized by 3GPP as part
of the GSM family, and it is an upgrade that provides more
than three-fold increase in both the capacity and performance
of GSM/GPRS networks. It does this by introducing
sophisticated methods of coding and transmitting data,
delivering higher bit-rates per radio channel.
EDGE can be used for any packet switched application, such
as an Internet connection. EDGE-delivered data services
create a broadband internet-like experience for the mobile
phone user. High bandwidth data applications such as video
services and other multimedia benefit from EGPRS' increased
data capacity.
Chat
• Online textual talk in real time is called chatting.
=>SMS (Short Massage Service ) : It is a communication
service standardized in the GSM mobile communication
system, using standardized communications protocols
allowing the interchange of short text messages between
mobile telephone devices. SMS text messaging is the most
widely used data application on the planet.
Chatting: Online
textual talk, in real time, is
called chatting.
 you type a message on your screen , which is
immediately received by the recipient . The the recipient can
type a message in response to your message , which is
received by you instantly.
 Video Conferencing: A two way videophone
conversation among multiple participants is called video
conferencing.
Video Conferencing
• It is a two-way videophone conversation among
multiple participants.
Email (Electronic Mail)
• Electronic Mail is sending and receiving messages by
computer.
E-Mail (Electronic Mail ) :Electronic mail,
often abbreviated as email, or e-mail, is a
method of exchanging digital messages. E-mail
systems are based on a store-and-forward
model in which e-mail computer server systems
accept, forward, deliver and store messages on
behalf of users, who only need to connect to the
e-mail infrastructure, typically an e-mail server,
with a network-enabled device (e.g., a personal
computer) for the duration of message
submission or retrieval. Originally, e-mail was
always transmitted directly from one user's
device to another's; nowadays this is rarely the
case.
Voice Mail
• It refers to e-mail systems that support audio.
Voice Mail: Voicemail (or voice mail, voice-mail,
vmail or VMS, sometimes called message
bank) is a centralized system of managing
telephone messages for a large group of
people. The term is also used more broadly, to
denote any system of conveying voice
message, including the answering machine.
Protocols for Chat and video conferencing:
 IRC (Internet relay chat)
H.323 and SIP(Session Initiation protocol)
For video conferencing.
 Voice over Internet protocol, VoIP.
“WiFi or Wireless Fidelity refers to the technology surrounding the radio
transmission of internet protocol data from an internet connection
wirelessly to a host computer. Most often the internet connection is a
higher speed one such as satellite, DSL or cable rather than slower dial-up
connections.”
i-Fi
•Basic concept is same as Walkie talkies.
How
Wi-Fiis Network
Works
•A Wi-Fiahotspot
created by installing
an access
point to an internet connection.
•An access point acts as a base station.
•When Wi-Fi enabled device encounters a hotspot
the device can then connect to that network
wirelessly.
•A single access point can support up to 30 users
and can function within a range of 100 – 150 feet
indoors and up to 300 feet outdoors.
•Many access points can be connected to each
other via Ethernet cables to create a single large
network.
Wi-Fi Applications
•Home
•Small Businesses or SOHO
•Large Corporations & Campuses
•Health Care
•Wirelests ISP (WISP)
•Travellers
Wi-Fi Gadgets
WiMAX (Worldwide Interoperability for
Microwave Access) is a wireless
communications standard designed to
provide 30 to 40 megabit-per-second
data rates with the 2011 update
providing up to 1 Gbit/s for fixed
stations. The name "WiMAX" was
created by the WiMAX Forum, which
was formed in June 2001 to promote
conformity and interoperability of the
standard.
• Uses
• The bandwidth and range of WiMAX make it
suitable for the following potential applications:
• Providing portable mobile broadband connectivity
across cities and countries through a variety of
devices.
• Providing a wireless alternative to cable and digital
subscriber line (DSL) for "last mile" broadband
access.
• Providing data, telecommunications (VoIP) and
IPTV services (triple play).
• Providing a source of Internet connectivity as part
of a business continuity plan.
• Smart grids and metering
WWW (World Wide Web)
• It is a set of protocols that allows you to
access any document on the net through
a naming system based on URL’s.
• It is a small part of internet.
• WWW Attributes:1. User-friendly
2. Hypertext and Hyperlink
3. Interactive
4. Frames
Internetworking Terms And Concepts
TelNet : Telnet (teletype network) is a network protocol used on the
Internet or local area networks to provide a bidirectional interactive
communications facility. Typically, telnet provides access to a
command-line interface on a remote host via a virtual terminal
connection which consists of an 8-bit byte oriented data connection
over the Transmission Control Protocol (TCP). User data is
interspersed in-band with TELNET control information.
Telnet
Web Browser and Web Server : a Web
Browser is a www client that navigates
through the world wide web and display
web page.
A web server is a www server that responds
to the requests made by web browsers.
Web Site, Web Address and Web Pages : A
location on a net server is called a web server.
Each web site has a unique address called
URL (uniform resource locator) .
URL and Domain : The internet structure of the www is built on a
set of rules called Hypertext Transfer Protocol (HTTP) and a page
description language called Hypertext Markup Language (HTML).
HTTP uses Internet addresses in a special format called a URL.
A URL(Uniform Resources Locator) specifies the distinct
address for each resource on the internet
Type://address/path
An internet address which is character based is called a Domain
Name. the character based naming system by which servers are
identified is also known as domain name system (DNS).
Web Hosting : Web Hosting is a means of hosting web-server
application on a computer system through which electric content on
the internet is readily available to any web-browser.
(i) Free hosting, (ii) virtual or shared hosting, (iii) dedicated hosting,
(iv) co-llocation hosting
HTML(Hyper Text Markup Language):It is a document layout
and hyperlink-specification language.
It tells the browser how to display the contents of a hypertext
document.
It also tells how to make a document interactive through
special hyperlinks.
It provides many layout commands, called tags that let us
control the presentation of information on a web page.
It is written in the form of HTML elements consisting of "tags"
surrounded by angle brackets within the web page content. It
can include or can load scripts in languages such as
JavaScript which affect the behavior of HTML processors like
Web browsers; and Cascading Style Sheets (CSS) to define
the appearance and layout of text and other material. The
W3C, maintainer of both HTML and CSS standards,
encourages the use of CSS over explicit presentational
markup
Internetworking Terms And Concepts
XML : XML (Extensible Markup Language) is a set of rules for
encoding documents electronically. It is defined in the XML 1.0
Specification produced by the W3C and several other related
specifications; all are fee-free open standards
DHTML : Dynamic HTML, or DHTML, is a collection of technologies
used together to create interactive and animated web sites by using a
combination of a static markup language (such as HTML), a client-side
scripting language (such as JavaScript), a presentation definition
language (such as CSS), and the Document Object Model.
DHTML allows scripting languages to change variables in a web page's
definition language, which in turn affects the look and function of
otherwise "static" HTML page content, after the page has been fully
loaded and during the viewing process. Thus the dynamic characteristic
of DHTML is the way it functions while a page is viewed, not in its
ability to generate a unique page with each page load.
Web Scripting : The process of creating and
embedding scripts in a web page is known as webscripting. Script are interpreted and executed by a certain
program of scripting-engine.
Client-side scripting generally refers to the class of
computer programs on the web that are executed clientside, by the user's web browser, instead of server-side (on
the web server). This type of computer programming is an
important part of the Dynamic HTML (DHTML) concept,
enabling web pages to be scripted; that is, to have different
and changing content depending on user input,
environmental conditions (such as the time of day), or
other variables.
Web authors write client-side scripts in languages such as
JavaScript (Client-side JavaScript)
• Server-side scripting is a web server
technology in which a user's request is fulfilled
by running a script directly on the web server to
generate dynamic web pages. It is usually used
to provide interactive web sites that interface to
databases or other data stores. This is different
from client-side scripting where scripts are run
by the viewing web browser, usually in
JavaScript. The primary advantage to server-side
scripting is the ability to highly customize the
response based on the user's requirements,
access rights, or queries into data stores.
Welcome to
Open Source Terminologies
Free software: The software is freely
accessible and can be freely used, changed,
improved, copied and distribute by all who wish
to do it.
 No payments are needed to be made for free
software.
 There are four kinds of freedom for the
users of the software.
1.The freedom to run the program , for any
purpose
2. The freedom to study how the program work,
and adapt it to your needs. Access to the
source code is a precondition for this.

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3.The freedom to redistribute copies
so you can help your neighbor.
4.The freedom to improved the
program, and release your
improvements to the public, so that
the whole community benefits.
Access to the code is a
precondition for this.
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166
=>Open Source Software: The
software/programs whose licenses do
not impose much conditions.
=>Software give users freedom to run/use
the software for any purpose, to study
and modify the program, and to
redistribute copies of either the original or
modified program (without having to pay
royalties to previous developers).
=> Open Source Software can be freely used
but it not have to be free of charge.
=>Open Source doesn’t just access to the
source code. the distribution terms of
Open Source Software must comply with
the following criteria.
1.Free Redistribution: The license shall not
restrict any party from selling or giving away
the software as a component of an
aggregate software distribution containing
programs from several different source. The
license shall not require a royalty or other
fee for such safe.
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2. Source Code: The program must
include source code and must allow
distribution in source code as well as
compiled form.
3. Derived works: The license must allow
modifications and derived works and
allow them to be distributed under the
same terms as the license of the
original software.
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4. Integrity of the Author’s Source Code: The
license may restrict source-code from
being distributed in modified from only if
the license allows the distribution of “patch
files” with the source code for the purpose
of modifying the program at build time.
5.No Discrimination Against persons or
groups: The license must not discriminate
against any person or group of persons.
6.No Discrimination Against Fields or
Groups: The license must not restrict
anyone from making use of the program in
a specific field of endeavor.
7.Distribution of License: The Right attached to the
program must apply to all to whom the program
is redistributed without the need for execution of
an additional license by those parties.
8.License Must Not be Specific to a Product: The
rights attached to the program must not depend
on the program’s being part of a particular
software distribution.
9.The license must Not Restrict other Software:
The license must not place restrictions on other
software that is distributed along with the
licensed software
10. License Must Be technology Natural: No
provision of the license may be predicted on any
individual technology or style of interface.
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Free Software and Open Source Software
FREE SOFTWARE




freely accessible
freely used, changed,
improved, copied &
distributed
requires no payment
emphasis on freedom




OPEN SOURCE
SOFTWARE
freely used
does not have to be free
of charge
source code is freely
available to customer
emphasis on technical
progress



OSS(open source Software): It refer to
software whose source code is available to
customers and it can be modified and
redistributed without any limitation.
FLOSS(Free Libre and Open Source
Software or to Free Livre and Open Source
Software): A software which is both free
software as well as open source software.
GNU: It refers to GNU’s Not Unix .GNU
Project emphasizes on freedom and thus its
logotype show a gnu, an animal living in
freedom.
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173




GNU: GNU refer to GNU’s Not Unix. It
emphasizes on freedom and its logotype shows
a gnu, an anima living in freedom. objective to
create a system compatible to Unix but not
identical with it.
FSF: Free Software foundation. it is a non-profit
organization created for the purpose of
supporting free software movement.
OSI: Open Source Initiative. It is an organization
dedicated to cause of promoting open software
W3C(World wide Web consortium): W3C is
responsible for producing the software
standards for world wide web.
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174
Proprietory Software
•
•
•
•
Neither open nor freely available
Use is regulated
Further distribution & modification forbidden
Source code is normally not available.
Freeware
•
•
•
•
•
Software available free of
cost
Allows copying and further
distribution, not
modification
Source code not available
Distributed in binary form
without any licensing fee
e.g. Microsoft Internet
Explorer
Shareware
•
•
•
•
•
Right to redistribute
copies
For use after trial period, a
license fee to be paid
Source code not available
Modifications not allowed
Distributed in binary form
OSI (Open Source Initiative)
•
•
Organization
dedicated to cause of
promoting OSS
Specifies criteria for
OSS and properly
defines the terms &
specifications of OSS.
WELCOME TO
Network Security Concepts
Problems
• Physical Security holes: When individuals gain
unauthorized physical access to a computer and
tamper with files.
• Software Security holes: When badly written
programs or privileged software are compromised
into doing things that they shouldn’t be doing.
• Inconsistent usage holes: When a system
administrator assembles a combination of hardware
and software such that the system is seriously flawed
from a security point of view.
Protection Methods
•
•
•
•
•
Authorization- e.g. username
Authentication- e.g. password
Encrypted smart card
Biometric systems- e.g. fingerprint matching
Firewall- e.g. Packet filter, Application
gateway, Circuit-level gateway, Proxy server
Network Security Measures
• Firewall: A System designed to prevent
unauthorized access to or from a private
network.
• It is a mechanism to prevent unauthorized
internet users from accessing private networks
connected to internet.
Related terms
• Cookies: Cookies are messages that a web
server transmits to a web browser so that the
web server can keep track of the user’s
activity on a specific web site.
• Hackers
• Crackers
• Cyber law
• India’s IT Act
• Cyber Crime
Cookies
Hackers & Crackers
• Hackers: interested in
gaining knowledge
about computer
systems & using this for
playful pranks
• Crackers: malicious
programmers who
break into secure
systems for the purpose
of stealing or corrupting
data
Ankit Fadia, famous hacker
Cyber Law & India’s IT Act
• Cyber law: Refers to all the legal and
regulatory aspects of Internet & the World
Wide Web
• India’s IT Act: In India the cyber laws are
contained in the IT Act 2000. Aims to provide
legal infrastructure for e-commerce in India by
governing transactions through internet and
other electronic medium
Cyber Crime
An unlawful act where in a computer is either a tool
or a target or both. classified as:
– Tampering with computer source documents
– Hacking
– Publishing of obscene information in electronic
form
– Child Pornography
– Accessing protected system
– Breach of confidentiality & privacy
IPR(Interllectual property reflect) Issues
• Refers to a number of distinct types of creations of
the mind for which property rights are recognized &
corresponding fields of law.
• Owners are granted certain exclusive rights to a
variety of intangible assets, such as musical, literary,
artistic works, discoveries, inventions, words,
phrases, symbols & designs.
• Common types of intellectual property are
copyrights, trademarks, patents and industrial design
rights
 VIRUS:
A computer virus is a computer
program that can replicate itself and spread from
one computer to another.
 Depend on the nature of a virus, it may cause
damage of your hard disk contents, and/or
interfere normal operation of your computer.
 Characteristics of a computer virus:
 It is able to replicate.
 Reduced memory or disk space.
 Modification of data.
 Files overwritten or damaged.
 Hard drive erased.
 Types

of Virus
File Infectors: Attach themselves to a program
file.
 Boot sector Virus: Install themselves on the
beginning tracks of the hard drive
 Macro Virus : infect data file.
 How Computer Viruses Spread ?
 It moves from computer to computer by attaching
themselves to files or boot records of disks.
 A virus travel from file to another on the same
computer if the infected file executed, from
computer memory to a file on the disk , on a disk
that is carried from one computer to another.
 Damage
Can destroy file allocation table(FAT)
 Can create bad sectors on the disk
 can decrease the space on the hard
disks by duplicating file.
 can format specific tracks on the
disk.
 Can destroy specific executable files
 can cause the system to hang.

=>Trojan Horse: A Trojan Horses is code
hidden in a program such as a game as
spreadsheet that looks safe to run but has
hidden side effects.
SPREAD: It spread through e-mail and
exchange of disks and information
between computers.
Damage: File, memory etc.
 Worm:
A worm is a program designed to
replicate. The program may perform any
variety of additional tasks as well.
 Characteristics:
 It is able to replicate
 It is self-contained and does not required
a host
 It is activated by creating process.
 if it is a network worm, it can replicate
across communication links.
SPAM: It is a electronic junk mail or junk
newsgroup postings.
Avoiding Spam:
=>To create a filter that finds does
something to e-mail that you suspect is
spam.
 Not to register yourself with true id to sign
up for things on the internet.
 Virus Prevention:
=>VIRUS PROTECTION: The following
guidelines to lead virus free computing life.
 Never use a CD without scanning it for
viruses.
 Always scan files downloaded from the
internet.
 Never boot your PC from floppy .
 Write protect your disks.
 Use licensed software.
 Password protect your PC.
 Make regular backup.
 Install and use antivirus software.
 Keep antivirus software up to date.