Email: chanaka.lasantha@gmail.com

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DATA COMMUNICATION ASSIGNMENT
Author: Chanaka Lasantha Nanayakkara Wawage
Kingston University ID: K1658833
ABSTRACT
Digital communication for the modern world is
stated nearby when communication
equipment’s that are in the equal constructing
and further limited physical location wise areas.
the certain information sending equipment
transmitting set of data is generally called, the
source equipment device. at the other far end
listing to receive information data from the
source equipment device is called the receiver.
data intercommunication inter exchanges
ambitions at the transfer of statistics and
preservation of the data at some important point
of the procedure however no longer the actual
technology of the statistics at the source and
receiver. Digital communication device collects
data from far-flung places through information
transmission circuits, after which outputs
processed results to far away remote places.
The special data communication strategies
which are presently in the widespread use
advanced regularly to improve the data
communication techniques which are already
present and to replace an identical with better
options and functions.
Within the design of large and complicated
Digital Systems, it's miles regularly vital to have
one device intercommunicate digital information
data from different devices. one advantage of
digital data is that it has a tendency to long way
greater immune to transmitted and interpreted
errors than records symbolized in an analogue
medium. This accounts for the clarity of digitally
encoded phone connections, audio disks, and
for a lot of the keenness inside the engineering
network for digital communications era.
However digital communication has its personal
specific pitfalls, and there are multitudes of
different and incompatible ways in which it can
be dispatched.
The Transmission Control Protocol is the
language a computer construct used to get entry
to the different internetworking regions
resources called the Internet. It consists of the
different internetworking regions resources
(Internet) consists of some well-known protocols
sets designed to structure different
internetworking regions of different
internetworking regions to provides a bunch with
connectivity access towards to the internet.
TCP/IP mainly act the major role of responsibility
for the complete fledged data interconnectivity
such as acknowledgement, addressing and
shortest path soon. In conversation systems and
TCP/IP is communicating over the noisy
transmission medium in a different manner.
noise is an undesired random disturbance of a
user data of a signal. the noise is a summation
of undesirable or traumatic power from natural
and once in a while man-made devices. Noise
is, however, normally distinguished from
interference, inside the signal to noise ratio and
interference ratio measures. Noise is likewise
typically prominent from distortion, which is an
unwanted systematic alteration of the sign
waveform by using the communique equipment,
as an instance in the signal to noise (SNR) and
distortion ratio and overall harmonic distortion
noises.

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1. INTRODUCTION
The encoding and well-known standard
encryption methodologies in different forms are
established over Digital Communication
Technologies which provide us secure
communication mechanism.
The major drawback of the transmission media
is the different types of noses. Therefore, to
obtain noise less correct data is the major
challenge in the modern world over TCP/IP
using security protocols.
“Band Pass Filter (BPF) removes the
fundamental frequency component of the output
signal to overcome dynamic range limitations.”
Komuro et al. (2008).
2. DIGITAL COMMUNICATION
The total harmonic distortion is a major negative
disadvantage of a Digitally Modulated signal
over the transmission media. Specifically, in
High sensitive digital signal receivers and signal
transmitters based communication media type
such as copper, wireless and optical fibre. In
practically bandpass fillers take place to remove
unwanted harmonic frequencies from the
original signal. Harmonic currents especially
affect the energy distribution by adding
additional sides frequencies over the copper
transmission media due to inductors, capacitors
and semiconductor devices in additionally
transformers, harmonics frequencies rather than
fundamental frequency growth the important
impartial contemporary and amplitude, erratic
operation of telecommunication structures,
computer devices, electronic experimental
testing equipment’s. resonance with strength
thing correction capacitors and Digital
Modulators, Modems and Low noise amplifier in
data communication.
Figure 2.1 Representation of Harmonics
Signals
• Direct Current(DC) voltage 0.5V of the
Signal.
• The Signal Amplitude of the Fundamental
Frequency is 2V.
• The 2nd Harmonic Frequency has 0.5V.
1. The amplitude of 2nd Harmonics Fre(Vol2nd)
2. The amplitude of the Fundamental Fre(
Vol_fund)
3. % 2nd Harmonics Distortion (2ndDistro%)
Vol2nd
% 2nd Harmonics Distortion = -----------x 100
Vol_fund
= (1/2)/2
% 2nd Harmonics Distortion = 25%
Therefore, the bundle of harmonics is simply
called the total harmonic distortion(THD) is used
to calculate by following simplified equation,
THD=√[(2nd Har. Dist) 2 + (3rd Har. Dist) 2 ]
Analyzing a sinewave signal to test with
harmonics distortions scrambled on the signal
by expressing the answer with MATLAB
simulations and in this example, was discovered
the resultant amplified signal of a sine wave has
been added noise levels in addition to the
fundamental frequency coupled with an amplifier
pre-amplifier, attenuation on the input frequency
into the amplifier can reduce harmonic
distortion.
Figure 2.2 2kHz Sinewave Frequency

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• Sinewave frequency is 2 kHz
• Duration of 50ms
• Maximum operating voltage is 2V
• The sample rate of the Frequency is
44.1kHz
“A periodogram is a graphical data analysis
technique for examining frequency-domain
models of an equi-spaced time series.” (The
Pennsylvania State University 2017)
Figure 2.3 Periodogram
Noted that rather than seeing simply the 2-kHz
sinewave, we placed on the input that can
observe there are extra sine waves including
between at 4 kHz and 10 kHz. All are the sine
waves frequencies are multiples of Primary
signal, 2 kHz frequency in addition to the non-
linearity of the amplifier with the highly flat band
of noise power.
2.1 Identifying the Nonlinear Distortions
“The nonlinear distortion energy is not random,
and can be quantified with knowledge of the
input signal that created it.” Campos et al.
(2013).
The simulation which was shown in bellow
image represented the periodogram conduct
described harmonics of the fundamental signal,
the THD of the fundamental sinewave which are
added harmonic components into the
fundamental signal. the Simplified Expression
for the case is,
THD is,
√[(2nd H. D) 2 + (3rd H. D) 2 + (nth H. D) 2 ]
Figure 2.4 Nonlinear Distortions in Frequency
Domain
Observed the 3rd harmonics frequency and the
maximum harmonic level is approximate to
60Decibel down compared with the original
fundamental essential waveform. this is wherein
unwanted additional distortions take place at the
resultant in Frequency domain. as an end result,
it is possible degree and obtains an estimate of
the full noise found in entering the segment of
the amplifier. therefore, the Signal over noise
ratio(SNR) obtains, the ratio regarding the
strength of the fundamental waveform to the all
are non-harmonic contents.
Figure 2.5 SNR

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“SINAD is a receiver audio quality measurement
that is typically used for mobile stations
operating on an analogue system, such as
AMPS.” (Keysight Technologies 2013)
Figure 2.6 SINAD
The above Figure 2.6 SINAD shows the
representation of nose added content over the
fundamental frequency within the resultant
waveform.
Figure 2.7 signal distortion Vs Input signal
attenuation
Figure 2.7 indicates the usable dynamic variety
of signal distortion Vs input signal attenuation.
THD is,
√[(2nd H. D) 2 + (3rd H. D) 2 + (nth H. D) 2 ]
the significance of THD corresponds only on
Harmonics components extraction excluding
fundamental frequency component. SINAD
speaking to the specific element scope of whole
resultant that is liberated from signal distortion.
In additionally the signal to noise ratio debases
as enter signal lessening will increment. that is
because even as attenuate the sinewave, best
signal is attenuated but the noise parent of the
amplifier remains the same. In moreover that the
significance of the overall harmonic distortion
improves gradually until it intersects the SNR
curve, and then the size will become volatile. this
takes place while the harmonics have
disappeared beneath the noise of the amplifier.
A realistic manner of amplifier attenuation for the
amplifier is 26dB, that is a reasonable decibel
amount of harmonic and noise distortion.
Advantages of Digital Transmissions
• Ability to archived better noise immunity
compared to the analogue transmission.
• It is very supporting to implement and
integrate secured encryption algorithms.
• Channel utilization is too lowest for a
higher degree of multiplexing
applications Example is a 64QAM
Modulation technique.
Shannon's Theorem
“Shannon's Theorem gives an upper bound to
the capacity of a link, in bits per second (bps),
as a function of the available bandwidth and the
signal-to-noise ratio of the link.
The Theorem can be stated as C = B * log2(1+
S/N)” (Kaufmann 1996)

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3. TCP/IP NETWORKS
“The TCP provides reliable transmission of data
in an IP environment. TCP corresponds to the
transport layer (Layer 4) of the OSI reference
model. Among the services TCP provides are
stream data transfer, reliability, efficient flow
control, full-duplex operation, and multiplexing.”
(IT's Center for Bits and Atoms 1999)
Figure 3.1 Functionality of OSI Layers
Communications through the computer network
are accomplished through protocol
methodologies. The maximum extensively used
and maximum extensively available protocol
suite is the TCP/IP protocol methodology. a
protocol includes a layered structure in which
every layer depicts a few capabilities which
should achieve by the usage of a protocol. each
multiple protocols optional of the top and bottom
Layers has unique responsibilities and TCP/IP
commonly pointed with four Layers system.
3.1 Data Switching Techniques
Circuit Switching
Circuit switching is in use when making a
standard telephone call on the public Telephone
network when a call is established, data is
transferred, and then the decision is
disconnected. The time required to set up the
decision is called the setup time. Once the
decision has been hooked up, the circuits
interconnected with the aid of the network
switches are allotted to a single user all through
the call. After a call has been established,
information is transferred in actual time. when a
call is terminated, the circuits and switches are
once again available for another user. Because
there are a limited number of circuits and
switching paths available, blocking can occur.
Blocking occurs when a call cannot be
completed because there are no facilities or
switching paths available between the source
and destination locations. When circuit switching
is used for data transfer, the terminal equipment
at the source and destination must be
compatible; they must use compatible modems
and some bit rate, character set, and protocol. A
circuit switch is transparent. It is transparent to
the data, it does nothing extra than interconnect
the source and destination terminal device. a
circuit switch adds no value to the circuit.
• Dedicated transmission flow path
• Continues data transmission behaviour
• Operate in real time
• Massages not stored
• The path set for the full message
• Call setup delay
• Busy Signal
• Blocking may occur
• No speed conversion
• No code conversion
• Fixed bandwidth transmission
• No overhead bits-after initial setup
Massage Switching
Message switching is a form of store-and-
forward network. Data including source and
destination identification codes are transmitted
into the network and stored in a switch. Each
switch inside the network has message garage
abilities. The network transfers the statistics
from switch to interchange whilst it's miles
convenient to do so. Consequently, information
re no longer transferred in actual time; there are
put off at each transfer. With message switching,
blockading cannot arise.
However, the postpone time from message
transmission to reception varies from call to call
and can be pretty long (every so often so long
as 12 hours). With message switching, as soon
as the records have entered the network, it's far
transformed into a greater suitable layout for
transmission through the network. At the acquire

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and, the facts are transformed to a layout well
suited with the receiving information terminal
transformed to a format compatible with the
receiving statistics terminal gadget. Therefore,
with message switching, the source and
destination information terminal equipment do
no longer want to be well suited.
Message switching is mane’ efficient than circuit
switching due to the fact data that enter the
network throughout busy time may be held and
transmitted later while the weight has reduced.
A message switch is a transaction switch
because it closes greater than in reality transfer
the information from the supply to the
destination. A message switch can keep
statistics or change its layout and bit rate, then
convert the facts back to their authentic form or
a completely distinctive form on the receive
cease. Message switching multiplexes statistics
from distinct assets onto a common facility.
• No dedicated transmission path
• Message transmission
• Not in real time
• Messages stored
• The path set for each message
• Massage transmission delay
• No busy signals occur
• Blocking cannot occur
• Speed conversion
• Code conversion
• Dynamic use of bandwidth
• Overhead bits in each message
Packet Switching
With packet switching, records are divided into
smaller segments known as packets prior to
Transmission Through the Network. Because a
packet can be held in reminiscence at a switch
for a quick period of time, packet switching is
sometimes referred to as a preserve-and-ahead
network. With packet switching, a message is
split into packets and Bath packet can take a
special direction via the Network.
Consequently, all packets do now not always
arrive on the receiving end on the someday or
within the identical order wherein they had been
transmitted. Because packets are small, the
preserving time is generally pretty short and
message transfer is close to actual time and
blockading cannot occur.
However, packet-switching networks require
complicated and luxurious switching
preparations and complicated protocol. A packet
transfer is likewise a transnational transfer.
Circuit, message, and packet switching
strategies are summarized underneath.
• No dedicated transmission path
• Transmission of packets
• Not in real time
• Message hold for short time
• The path set for each packet
• Packet transmission delay
• No busy signals occur
• Blocking cannot occur
• Speed conversion
• Code conversion
• Dynamic use of bandwidth
• Overhead bits in each packet
3.2 The Client and Server Model
In the section of client-server
intercommunication model that are sub divides
capabilities when the one or multiple client
requests send towards to the server, as a result,
the server also has capabilities to reply back to
the certain clients by acknowledging over
TCP/IP combination as well.
“Distribution brings a new design dimension into
the architecture of information systems. It offers
great opportunities for good systems design, but
also complicates the development of a suitable
architecture by introducing a lot of new design
aspects and trapdoors compared to a
centralized system.” Renzel et al. (1997).
This kind of Client-Server architecture obviously
behaving under a hierarchical manner in the
Oder to server lots of TCP/IP communications
from Upper Layers to Bottom Layers. use of a
number and clients, by using the manner a
computer functions inside a machine. The
dividing line between the client and a server can
be anywhere along a broad continuum:

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• Distributed: the distributed system is a
model in which components located on
networked computers communicate and
coordinate their actions by passing
messages from client to server.
• Remote: The presentation is managed
and treated absolutely by using the
requester(client).
• Distributed logic: It is dealt with partially
through the server and partly via the
requester(client). far off statistics control
where control of the database treated
completely by using at the Server end as
well.
• Distributed database: This kind of
Distributed system support to manage
and allowed under a certain level of
security mechanism access the data
which are located in locally and remotely.
TCP
Figure 3.2 Cisco Packet Tracer Simulation
The Client-Server Architecture Shown in Figure
3.2 is the practical representation that interacts
with two different computers communicating
over the TCP/IP.at the server is listening on pre-
defined port address continuously while client
requests using ACK until the connection was
established to serve multiple requests called
data flow which is coming from host towards to
a server end.
The one example to make the concept clearer
which is mentioned in Figure 3.3
Figure 3.3 Client to Server TCP/IP
Communication
The Figure 3.3 shows the client-server
information directions flow from the application
layer to the physical layer and again the physical
layer to the application layer wise versa on
both host and server machines. At the server
end, continuously listening web traffics on
binding port address while the client-server
request-response over the HTTP mainly
sending through the transport layer to interact
both communication servers.
TCP/IP mainly assigned additional information
such as TCP segment, destination and source
port address. Mainly Application layer
information flows through the transport layer as
the TCP segment, the Transport layer going
through Internet Layer as an IP datagram, Data
link layer also sending frames to the physical
layer.
Finally, the same process is happening wise
versa up to the application layer of the
destination server machine to establish the
connection under certain keepalive timeout
value. the information link layer that makes sure
statistics of the switch from the physical layer
properly has carried out, in some random
situation only that the communication flow
unreliability is possible happened. all the
information data flowing through over the copper
ethernet media to reach its final destination
target host, currently at the destination target
host identical for the collection of interactions
occur in opposite order of the previous process.

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the data packet has been initially received on the
OSI Layer 2.
Due to this incident situation, the received
certain information’s are identified and other
remaining information statistics also handed
over into the upper layer. On the other hand on
the Network layer, also settled the data of the
Network layer protocol of the host system while
examining all the records are surpassed by the
subsequent higher layer. the same scenario
again happens on the transport layer also and
sooner or later the HTTP client request that is
sent over the Simulation software called
MATLAB Console. that is acquired by the target
software (Server on Separate MATLAB
Instance).
TCP protocol representing at the transport layer.
transport layer protocol provides information at
the host machine sequence wide variety to each
packet dispatched by this layer. at the
destination. At this point In the MATLAB
instance packets level transferring process take
place into the scene and TCP protocol at a given
stage of time considering for observation for the
bundle of quantities as the series of packets
which are sending with acknowledgements.on
the other hand, the certain host machine does
not receive proper acknowledgments in between
pre-calculated determined targeted time period,
as a result the host machine should re-sending
the same identical packets again until it settled
down in a reliable manner for the smooth
information throughput, due to this condition
TCP process definitely understand and make
sure that there are no any packet lost happened
during the communication flow.in additionally
the certain protocols levels at the every OSI
layer stages have the responsibility to handle
and reads the what information should
manageable, transferring itself by supporting
other top and bottom layers as well including its
counterpart acquire capability according to it
process role represented.
At the both of server and client MATLAB
Instances machines already configured with
static IP address including the port (socket)
binding only one the server machine Instance to
listen all are the traffics which are coming from
the client MATLAB Console Instance as well, the
mixture of IP address and port address on both
client machine and server machine is called four
tuples. As a result, that the four tuples uniquely
identify a connection. by default, the
international standers refer to the valid port
ranges where beginning from 1 1023
accordingly and also called well-known ports
address. But in our case already used the
port(Socket) address of 5000.
Figure 3.4 Data Received by the Server form
the Client Host
At the Other hand, the client does not need to
bind with specific port(socket) address as static
configuration mode but only on the server side
has been configured the specific port address,
that all are the incoming traffic going to handle,
the client always receiving random widespread
port addresses dynamically to handle the
process. as a result, the client does not require
well-known standards port address to run itself
and it's also called in another word ephemeral
socket address when the Client MATLAB
machine hook up with the server, does not work
after which disconnect in the same dynamic
port, used the time period. as a result, always
connected and listening static ports are not
required at the client MATLAB instance while
establishing the connection. As per disconnect
with the previous session, then the new dynamic
port address will have allocated into the process
at the client side. the client side MATLAB

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instance also has an ability to recognize which
ports number to hook up with the server to
continuously information establishment between
Server and client.
4. NETWORK SECURITY PROTOCOLS
There many security protocols which are used to
protect computer statistics and communication
data interchanging, the primary mechanism
used to protect records because it travels across
a network is called cryptography. Cryptography
makes use of algorithms to encrypt facts in order
that it isn't always readable by unauthorized
customers. typically, cryptography works with a
hard and fast of processes or protocols that
manipulate the trade of information among
gadgets and networks. collectively, these
cryptographic protocols beautify at ease
information switch.
The modern growth of the huge internetworking
Infrastructures need to be protected due to
enterprise business security requirements as
well as normal consumer security expectations
when the computer networks are bigger and
bigger, to mitigate some of the security
weakness and threats from cybercriminals, that
all are the companies, organization and
community should have protected from the
modern cyber-attacks over the certain
applicable Network layers to overcome security
hazards.
The most important requirements form the
cybersecurity to protecting all are the intellectual
properties which are belongs to an organization
as well as focused on the consumer wise versa
when the cybersecurity comes into the
protection strategies, then only the certain
community mitigate the threat hazards from the
attackers, the digitization of most of the legacy
systems, the internal and external cybercrimes
has been affected by the overall business
process as well as personal mobile data.
Therefore, the cybersecurity has highest priority
responsibility to protect all are hackable users'
data into the protected mode instead of
happening cybercrimes accordingly, most of the
Internet Service providers are recently
considering to protect their customers by
providing some virtual private network over the
internet in additionally to the slandered SSL/TLS
web protections against to the Unethical criminal
cybercrimes, to establishing the secured
infrastructure such as VPN Tunnels Services,
Web Tunnels (HTTPS) security, SET card
transaction protection protocols came to the
process.
There are numerous stages that an attacker has
to bypass via to efficaciously perform an attack.
4.1 Samples of Network Security Protocols
Application Layer
• PGP
• S/MIME
• HTTPS
• SET
Transport Layer
• SSL
• TLS
Network Layer
• IPsec
Data Link Layer
• PPP
• RADIUS
“Two schemes stand out as approaches that
enjoy widespread use: Pretty Good Privacy
(PGP) and Secure/Multipurpose Internet Mail
Extension (S/MIME)” (Raptis 1999).
The Impotency of securing email exchanges
using IMAP, POP and SMTP protocols have to
integrate with security enhancements with
SSL/TSL secure layers that can protect email
communication flow channel for the certain
IMAP or POP connectivity between the email
server and the email client application as well.
As per content protection strategies also
implemented to encrypt the email content using
the protocol called Pretty Good Privacy (PGP).
There is a pre-defined combination of hashing
and symmetric key cryptography algorithms in
additionally to the data compression of the email
information content.
“S/MIME or Secure/Multipurpose Internet Mail
Extensions is the industry standard for public

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key encryption for MIME-based data.”
(Lightowler 1996).
This protocol most popular and widely used
sends an email by digitally signing with message
encryption process in order to archive maximum
outcome of the message security against the
cybercriminals. The mail receiver has trusted
way to obtain certain email message form
specific user instead of receiving bogus emails
form duplicate cyber attacker to overcome the
leakage of personal and business process data
into the third party.
“HTTPS or Secure HTTP some may call it is a
combination of Hypertext Transfer Protocol
(HTTP) with SSL/TLS protocol.” (Azharuddin
2012).
“The first version of SSL was never released
because of problems regarding protection of
credit card transactions on the Web. In 1994.”
(Cisco System 2002).
This Protocol is using to provide the tunnel
security over the HTTP unsecured
communication protocol, the client has to access
a certain web site's document through the
exposed traditional HTTP communication
process is the risk for user in some cases when
an unknown cybercriminal person entered into
the middle attack process such as privacy
stealing, credit card numbers expose, password
expose, images and other private documents.
The mitigation process for the security threats
over the web protocols has been introduced the
encrypted tunnel security protocol called
HTTPS. On the other hand, the HTTPS
tunnelling method provides end to end
encryption between web browser to the web
server. As per well-known port address
standard, the port 443 is used for the all the
incoming HTTPS traffics where coming from the
client browser as well.
The cybercrimes on the online transaction are
the most dangerous financial threats to the
Credit Cardholders that can steal the account
details by phishing attacks into the cookies
stored in the web browser.
“The standard protocol for providing security
services in the context of E-commerce over the
Internet.” Mahboob et al. (2004).
The SET communication encrypted
cryptography enabled protocol use to facilize the
secure service which is securing some of the
important mechanisms such as authentication
security, privacy and confidential security with
the integrity of the transaction over the public
key and digitally signed encrypted connectivity
establishment between the payment gateway
and the customer.
4.2 IPSec Protocol
“There are numerous speculations and
scenarios in which the protocols defined for
operation of IPsec can be challenged.
• Cut-And-Past Attack – This attack will
only be possible on two networks that use
IPSEC as a tunnel between the two
routers that link the networks
• Session Hijacking” (Clark 2002).
IPsec virtual internetworking mechanism is not
more secure under some of the circumstance
and that can further clarify under the different
aspect of technological areas. In the certificate
implementation in Open-VPN using its own
algorithm instead of using exploitable
certificates which are falling into the default VPN
standards of the industry by restricting root CA
certificates as usual. In additionally IPsec
always faced with overhead problems when it is
dealing with clients' certificates while
establishing the VPN initialization connectivity,
the Open-VPN have an ability to set up either
null certificates or PSK among all are the client
users.

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4.3 The Modern SSL-VPN Connectivity
Practical Application
Figure 4.1 SSL Open VPN Site to Multi Sites
Interconnection
NOTE: Already Tested within the Virtual
OpenStack Could Environment to test the
Features, Vulnerabilities and Compression as
well.
“OpenVPN is open source software that uses
the technique of VPN for creating connections
point to point or site to site connection.” (Elena
2014).
4.4 Advantages of The Open-VPN
• L2 and L3
It offers two primary modes, which is
running either as L2 or L3 VPN as a
consequence.
• Internal Firewall
This Technology has inbuilt
programmable firewall systems which
can have configured in two main
methods. All are incoming and outgoing
packets going through VPN server to
outside internet in addition to the intranet
Network access capabilities. (Secured
and Filtered all Inbound and outbound
traffics). Local VPN Intranet access
traffics comes through only on VPN
server and the rest of web surfing traffics
which can flow over the external, the
user’s own internet connections.
• Tunnelling
This special VPN framework is suitable
for processing the connection mode in
two subsections such as TUN mode and
TAP mode, The TUP mode mainly can
describe as a point to point method. On
the other hand, TAP mode configuring
using a virtual Bridge interface
mythology.
• UDP and TCP
There are two different type of
communication methods mainly bind
within the Open VPN interconnection
protocol section such as UDP and TCP.
usually, UDP is very fast but it does not
have acknowledgements request where
sent by the client smoothly compared
with the TCP methodology.
• Port Requirement
This technology allowed us to configure
any suitable port address under
community standards including TCP port
and UDP port addresses.
• No NAT Issues
This NAT configuration cause to set up
different IP address blocks ranges under
certain condition by issuing DHCP IP
address separately to various subnets
without having NAT issues towards
alternative tunnelling endpoints.
• Dynamic Scripting
One of the main advantages is the script
embedded capability of the VPN system
which can create own advanced scripts
as an external plugin for the different
purposes such as authentication, user
activity tracking, database detail
reporting, to establish connectivity for
LDAP and Active Directory and function
creation due to some authentication
failover situations.
• Compression
LZO compression techniques highly
compress the tunnels data before the
transmission and send it over low
bandwidth internet links to provide
maximum relabel connectivity.
• Support for the Mobiles
Provides mobile phone and other mobile
devices support under high-security
mode as a user-friendly application.

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5. CONCLUSION
The proposed assignment become documented
to provide a practical application on theoretical
concepts of records communique arena. The
scope of this challenge turned into to put in force
simulations on such as Digital Communications,
TCP/IP Stack, Network Security Protocols and
contemporary VPN solutions as well.
With the aid of reviewing the practical
requirements that were observed at some stage
in the simulation and theoretical analysis phase.
an architectural version provides a
commonplace frame of reference for discussing
internet communications. it's far used not
simplest to give an explanation for
communication protocols but to increase them
as properly. It separates the capabilities
executed by means of communication exchange
protocols into attainable layers stacked on top of
each different. each layer inside the stack
performs a particular feature in the process of
intercommunicating over a certain network
system.
Within the Digital Communications section in
which step by step defined concerning on
Harmonic Distortion which turned into
scrambled with an entrance sign through
figuring out with MATLAB exercise to overcome
the undesirable potion signal distortion in a sine
wave to archived minimal of the noise level. the
SSL-VPN a brand-new era of VPN introduced
the modern features.
Open VPN enabled the new area of the low cost
and high-end VPN solution with the maximum
security and reliability levels over SSL/TLS
Tunnel security architecture, the Readability is
very high compared to the most complex
Protocols such as IPSec.

13. P a g e 13 | 18
REFERENCES
Komuro, T., Sobukawa, S., Sakayori, H., Kono,
M. and Kobayashi, H. (2008) IEEE
Transactions on Instrumentation and
Measurement. Total Harmonic Distortion
Measurement System of Electronic Devices up
to 100 MHz With Remarkable Sensitivity, 56(6),
pp.2360-2356[Online]. Available at
<https://www.researchgate.net/publication/3094
084_Total_Harmonic_Distortion_Measurement
_System_of_Electronic_Devices_up_to_100_M
Hz_With_Remarkable_Sensitivity/.>. [Access
on 20th Feb 2017].
The Pennsylvania State University. (2017)
Applied Time Series Analysis. A periodogram is
used to identify the dominant periods (or
frequencies) of a time series[Online]. Available
at
<https://onlinecourses.science.psu.edu/stat510/
node/71.>. [Access on 20th Feb 2007].
Campos, A., Hamzeh, B. and Williams, T.
(2013) Testing for Nonlinear Distortion in Cable
Networks. Nonlinear Distortion(Online), pp.5-
41[Online]. Available at
<https://www.cablelabs.com/wp-
content/uploads/2014/05/Testing-for-Nonlinear-
Distortion-in-Cable-Networks.pdf.>. [Access on
20th Feb 2017].
Keysight Technologies. (2013) SINAD
Measurement Description. SINAD[Online].
Available at
<http://rfmw.em.keysight.com/rfcomms/refdocs/
wcdma/wcdma_meas_sinad_desc.html.>.
[Access on 21st Feb 2017].
Kaufmann, M. (1996) Computer Networks: a
systems approach. Shannon's
Theorem(Online), pp.94-95[Online].
Available at <http://www.inf.fu-
berlin.de/lehre/WS01/19548-U/shannon.html.>.
[Access on 21st Feb 2017].
IT's Center for Bits and Atoms. (1999) Internet
Protocol. Internet protocols span the complete
range of OSI model layers. (Online), pp.03-
12[Online].
Available at
<http://fab.cba.mit.edu/classes/961.04/people/n
eil/ip.pdf.>. [Access on 22nd Feb 2017].
Renzel, K. and Keller, W., (1997) Client/Server
Architectures for Business Information
Systems. Distributed Presentation
Architecture(Online), pp.1-5[Online].
Available at
<https://www.hillside.net/plop/plop97/Proceedin
gs/renzel.pdf.>. [Access on 22nd Feb 2017].
Raptis, K., (1999) E-Mail Security. Pretty Good
Privacy & Privacy-Enhanced Mail(Online),
pp.4-5[Online].
Available at
<http://citeseerx.ist.psu.edu/viewdoc/download
?doi=10.1.1.454.745&rep=rep1&type=pdf.>.
[Access on 22nd Feb 2017].
Lightowler, B., (1996) S/MIME Compatibility.
Assessing the compatibility and best practices
of using S/MIME encryption(Online),
pp.3[Online].
Available at
<https://www.globalsign.com/en/resources/whit
e-paper-smime-compatibility.pdf.>. [Access on
22nd Feb 2017].
Azharuddin., (2012) Difference between HTTP
and HTTPS. What is HTTPS(Online)?
Available at
<http://www.thewindowsclub.com/difference-
http-https.>. [Access on 22nd Feb 2017].
Cisco System., (2002) Introduction to Secure
Sockets Layer. Introduction(Online), pp-1-
3(Online).
Available at
http://euro.ecom.cmu.edu/resources/elibrary/ep
ay/SSL.pdf.>. [Access on 22nd Feb 2017].
Mahboob, A. and Ikram, N., (2004) Transport
Layer Security (TLS). A Network Security
Protocol for E-commerce(Online), pp.1-
7[Online].

14. P a g e 14 | 18
Available at
<https://www.researchgate.net/publication/2164
85703_Transport_Layer_Security_TLS--
A_Network_Security_Protocol_for_E-
commerce.>. [Access on 22nd Feb 2017].
Clark, D., (2002) SANS Institute. A Discussion
of Possible Weaknesses in IPSEC
Implementation(Online), pp.2-14[Online].
Available at <https://www.sans.org/reading-
room/whitepapers/vpns/vulnerabilitys-ipsec-
discussion-weaknesses-ipsec-implementation-
pro-760.>. [Access on 22nd Feb 2017].
Elena., (2014) Advantages of using OpenVPN
server. The advantages of OpenVPN are
illustrated(Online).
Available at <http://best.vpn-
revista.com/advantages-of-using-openvpn-
server/.>. [Access on 22nd Feb 2017].

15. P a g e 15 | 18
APPENDIX A – DIGITAL COMMUNICATIONS
%Generating the 2kHz Sinewave Frequency
clc %Clear the Matlab console.
clear %Clear all are the variable that is previously loaded.
PeakVol = 2; %Setting the maximum peak voltage level.
Fi = 2000; %Setting the sinewave frequency of 2 kHz.
Fs = 44.1e3; %Setting the Sample rate frequency at 44.1kHz.
TS_dur = 50e-3; %Assign the duration of sinewave frequency.
t = 0:1/Fs:TS_dur; % Setting the Input time vector Level.
MaxIPVol = PeakVol*sin(2*pi*Fi*t); % Setting the maximum peak voltage on
amplifier.
MaxOPVol = helperHarmonicDistortionAmplifier(MaxIPVol);
%t = 0:0.001:10;
%x = sin(4*pi*t);
figure(1);
subplot(3,1,1) %Prepare subplot box
plot(t, MaxOPVol) %Plotting the maximum peak voltage on amplifier.
xlabel('Time') %Assigned Label in Time X-Axis.
ylabel('Output Voltage') %Assigned Label in Amplitude Y-Axis.
axis([0 5e-3 -2.5 2.5])
title('Amplifier output') %Make a Title on it.
%or Another method to draw the sinewave
%Am=5;
%fa=2000;
%Ta=1/fa;
%t=[0:Ta/999:6*Ta];
%ym=Am*sin(2*pi*fa*t);
%figure(1);
%subplot(3,1,1);
%plot(t,ym);
%A Periodogram Is A Graphical Data Analysis:
clc %Clear the Matlab console.
clear %Clear all are the variable that are previously loaded.
PeakVol = 2; %Setting the maximum peak voltage level.
Fi = 2000; %Setting the sinewave frequency of 2 kHz.
Fs = 44.1e3; %Setting the Sample rate frequency at 44.1kHz.
TS_dur = 50e-3; %Assign the duration of sinewave frequency.
t = 0:1/Fs:TS_dur; % Setting the Input time vector Level.
MaxIPVol = PeakVol*sin(2*pi*Fi*t); % Setting the maximum peak voltage on
amplifier.
MaxOPVol = helperHarmonicDistortionAmplifier(MaxIPVol);
%t = 0:0.001:10;
%x = sin(4*pi*t);
figure(1);
subplot(3,1,2) %Prepare subplot box
plot(t, MaxOPVol) %Plotting the maximum peak voltage on amplifier.
xlabel('Time') %Assigned Label in Time X-Axis.
ylabel('Output Voltage') %Assigned Label in Amplitude Y-Axis.

16. P a g e 16 | 18
axis([0 5e-3 -2.5 2.5])
title(' Periodogram ') %Make a Title on it.
helperPlotPeriodogram(MaxOPVol, Fs, 'power','annotate');
%Nonlinear Distortions
clc %Clear the Matlab console.
clear %Clear all are the variable that are previously loaded.
PeakVol = 2; %Setting the maximum peak voltage level.
Fi = 2000; %Setting the sinewave frequency of 2 kHz.
SampleFRQ = 44.1e3; %Setting the Sample rate frequency at 44.1kHz.
TS_dur = 50e-3; %Assign the duration of sinewave frequency.
t = 0:1/SampleFRQ:TS_dur; %Setting the Input time vector Level.
MaxIPVol = PeakVol*sin(2*pi*Fi*t); %Setting the maximum peak voltage on
amplifier.
MaxOPVol = helperHarmonicDistortionAmplifier(MaxIPVol);
%t = 0:0.001:10;
%x = sin(4*pi*t);
figure(1);
subplot(3,1,3) %Prepare subplot box
plot(t, MaxOPVol) %Plotting the maximum peak voltage on amplifier.
xlabel('Time') %Assigned Label in Time X-Axis.
ylabel('Output Voltage') %Assigned Label in Amplitude Y-Axis.
axis([0 5e-3 -2.5 2.5])
title('Nonlinear Distortions') %Make a Title on it.
helperPlotPeriodogram(MaxOPVol, SampleFRQ, 'power','annotate');
thd(MaxOPVol, SampleFRQ)
%SNR
clc %Clear the Matlab console.
clear %Clear all are the variable that are previously loaded.
PeakVol = 2; %Setting the maximum peak voltage level.
Fi = 2000; %Setting the sinewave frequency of 2 kHz.
SampleFRQ = 44.1e3; %Setting the Sample rate frequency at 44.1kHz.
TS_dur = 50e-3; %Assign the duration of sinewave frequency.
t = 0:1/SampleFRQ:TS_dur; %Setting the Input time vector Level.
MaxIPVol = PeakVol*sin(2*pi*Fi*t); %Setting the maximum peak voltage on
amplifier.
MaxOPVol = helperHarmonicDistortionAmplifier(MaxIPVol);
%t = 0:0.001:10;
%x = sin(4*pi*t);
plot(t, MaxOPVol) %Plotting maximum peak voltage on amplifier.
xlabel('Time') %Assigned Label in Time X-Axis.
ylabel('Output Voltage') %Assigned Label in Amplitude Y-Axis.
axis([0 5e-3 -2.5 2.5])
title('SNR') %Make a 'SNR' Title on it.
helperPlotPeriodogram(MaxOPVol, SampleFRQ, 'power','annotate');
snr(MaxOPVol, SampleFRQ)
%SINAD
clc %Clear the Matlab console.
clear %Clear all are the variable that are previously loaded.
PeakVol = 2; %Setting the maximum peak voltage level.
Fi = 2000; %Setting the sinewave frequency of 2 kHz.

17. P a g e 17 | 18
SampleFRQ = 44.1e3; %Setting the Sample rate frequency at 44.1kHz.
TS_dur = 50e-3; %Assign the duration of sinewave frequency.
t = 0:1/SampleFRQ:TS_dur; %Setting the Input time vector Level.
MaxIPVol = PeakVol*sin(2*pi*Fi*t); %Setting the maximum peak voltage on
amplifier.
MaxOPVol = helperHarmonicDistortionAmplifier(MaxIPVol);
%t = 0:0.001:10;
%x = sin(4*pi*t);
plot(t, MaxOPVol) %Plotting the maximum peak voltage on amplifier.
xlabel('Time') %Assigned Label in Time X-Axis.
ylabel('Output Voltage') %Assigned Label in Amplitude Y-Axis.
axis([0 5e-3 -2.5 2.5])
title('SINAD') %Make a Title on it.
helperPlotPeriodogram(MaxOPVol, SampleFRQ, 'power','annotate');
sinad(MaxOPVol, SampleFRQ)
%Periodogram Output Half Voltage
clc %Clear the Matlab console.
clear %Clear all are the variable that are previously loaded.
PeakVol = 2; %Setting the maximum peak voltage level.
Fi = 2000; %Setting the sinewave frequency of 2 kHz.
SampleFRQ = 44.1e3; %Setting the Sample rate frequency at 44.1kHz.
TS_dur = 50e-3; %Assign the duration of sinewave frequency.
t = 0:1/SampleFRQ:TS_dur; %Setting the Input time vector Level.
MaxIPVol = PeakVol*sin(2*pi*Fi*t); %Setting the maximum peak voltage on
amplifier.
MaxOPVol = helperHarmonicDistortionAmplifier(MaxIPVol);
%t = 0:0.001:10;
%x = sin(4*pi*t);
plot(t, MaxOPVol) %Plotting the maximum peak voltage on amplifier.
xlabel('Time') %Assigned Label in Time X-Axis.
ylabel('Output Voltage') %Assigned Label in Amplitude Y-Axis.
axis([0 5e-3 -2.5 2.5])
title('Periodogram O/P Half Voltage') %Make a Title on it.
inputVhalf = (PeakVol/2) * sin(2*pi*Fi*t);
outputVhalf = helperHarmonicDistortionAmplifier(inputVhalf);
helperPlotPeriodogram(outputVhalf, SampleFRQ, 'power','annotate');
%Signal distortion Vs Input signal attenuation
clc %Clear the Matlab console.
clear %Clear all are the variable that are previously loaded.
PeakVol = 2; %Setting the maximum peak voltage level.
Fi = 2000; %Setting the sinewave frequency of 2 kHz.
SampleFRQ = 44.1e3; %Setting the Sample rate frequency at 44.1kHz.
TS_dur = 50e-3; %Assign the duration of sinewave frequency.
t = 0:1/SampleFRQ:TS_dur; %Setting the Input time vector Level.
MaxIPVol = PeakVol*sin(2*pi*Fi*t); %Setting the maximum peak voltage on
amplifier.
MaxOPVol = helperHarmonicDistortionAmplifier(MaxIPVol);
%t = 0:0.001:10;
%x = sin(4*pi*t);
plot(t, MaxOPVol) %Plotting the maximum peak voltage on amplifier.

18. P a g e 18 | 18
xlabel('Time') %Assigned Label in Time X-Axis.
ylabel('Output Voltage') %Assigned Label in Amplitude Y-Axis.
axis([0 5e-3 -2.5 2.5])
title('Signal distortion')
helperPlotPeriodogram(MaxOPVol, SampleFRQ, 'power','annotate');
% Allocated a MATLAB table with 30 sections of Entry
NumberOfRead = 30;
HMDristroTBL = zeros(NumberOfRead, 3);
% Calculate Total Harmonic Distortion, Signal to noise ratio and SINAD.
for i = 1:NumberOfRead
inputVbestAtten = db2mag(-i) * PeakVol * sin(2*pi*Fi*t);
SigOPAttenu = helperHarmonicDistortionAmplifier(inputVbestAtten);
HMDristroTBL(i,:) = [abs(thd(SigOPAttenu, SampleFRQ))
snr(SigOPAttenu, SampleFRQ)
sinad(SigOPAttenu, SampleFRQ)];
end
plot(HMDristroTBL)
xlabel('Input Attenuation (dB)')
ylabel('Dynamic Range (dB)')
title('Distortion Summarize Metrics vs. Input Signal Attenuation')
APPENDIX B – TCP/IP NETWORKS
%Server Host A
clear
clc
%Assign any IP address for listening,
prot and the network role
t = tcpip('0.0.0.0', 5000, 'NetworkRole',
'server');
fopen(t);
data = fread(t, 50); %Assign timeout
delay
figure(1);
subplot(3,1,1) %Prepare subplot
box
plot(data); %Plot the resultant
xlabel('Time')
ylabel('Output Voltage')
title('Server - Client Sent Data')
%Client Host B
clear
clc
%Assign any 'localhost' for listening,
port and the network role
t = tcpip('localhost', 5000,
'NetworkRole', 'client');
fopen(t);
data = sin(1:64); %Assign data range
%data = 1:10;
fwrite(t, data); %Write to buffer for txd
%figure(1);
%subplot(3,1,2) %Prepare subplot box
plot(data); %Plot the resultant
xlabel('Time')
ylabel('Output Voltage')
title('Client - I/P to the Remote server')