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DESIGN AND ANALYS YS OF WIRELESS NETWORK
PROTOCOLS

TABLE OF CONTENTS
TABLE OF CONTENTS ………………………….. ………………………….. ………… 6
LIST OF TABLES ………………………….. ………………………….. …………………. 7
LIST OF FIGURES ………………………….. ………………………….. ……………….. 8
INTRODUCTION ………………………….. ………………………….. ………………….. 5
CHAPTER I – DESIGN O F WIRELESS NETWORKS …………………… 7
1.1. The OSI model ………………………….. ………………………….. ………………………….. ….. 7
1.2. Network technologies ………………………….. ………………………….. ……………………. 10
1.3. Wireless network topologies ………………………….. ………………………….. ………….. 12
BIBLIOGRAPHY ………………………….. ………………………….. ………………… 18

LIST OF TABLES
Table 1.1.1 – The layers of OSI model ………………………….. ……………………. 8
Table 1.3.4 – MANET routing example ………………………….. …………………. 16

LIST OF FIGURES
Figure 1.3.1 – Peer – to – peer wireless network ………………………….. …….. 13
Figure 1.3.2 – Star topology of wireless networks ………………………….. ….. 14
Figure 1.3.3 – Mesh network topology ………………………….. ………………….. 15

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INTRODUCTION
One of the biggest innovations in computer science are, without doubt, the
computer networks . Nearly every human act ivity implies (more or less) a form
of collaboration (in most situations, exchang ing data or information ). For a long
period of time, this was possible only by passing them written on a certain support
(papyrus, clay, paper, etc.) which was a difficult and time -consuming operation .
The invention of the telegraph and telephone allowed peop le to communicate
quicker and easier, but only things that can be written or sounds could be
transmitted (it was impossible to send images or other stuff ).
A major breakthrough was the development and usage of computers, which
proved to be very useful to collect, analyze, modify or store large amounts of
information in a safer and faster way. Thanks to this fact, they become very wide
spread in short time. At their beginning, the computers had limited storage and
processing capacities, so, in order to acco mplish more complex tasks , they started
to be linked together, forming the first networks. Soon, the networks started to
include other devices (such as printers or scanners) which deserved all the
computers. Another facility provided by a network is the po ssibility to share files
and other data in a simple and fast way. This is why the computer networks
become more and more popular. Nowadays, w e can deal with networks that cover
a building, a group of buildings (like a factory), a city, or a region.
The bi ggest network is considered to be the Internet. It is a global system
formed from a lot of interconnected computer networks. The Internet is a network
of networks consisting of public or private networks with different sizes and
complexities (starting from personal networks and reaching national networks).
At the beginning, all the devices from a network were connected by using
cables , but with the development of portable devices (such as laptops, PDAs and
smartphones), appeared the necessity of being able to connect a device to a

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network without using a cable. The first network which had the devices
connecting by radio, was developed in the 1970s at the University of Hawaii and
was named ALOHANET. The wireless networks are one of the technologies with
the fastest growing from the 21st century thanks to (according to Steve Rackley)
the ratification of the IEEE 802.11 standard (1997) and to the development of
interoperability certification by the Wi -Fi Alliance.
In this thesis, we will present and analyze a part of the most important facts
related to wireless networks. The major topics that will be treated are:
– the design of a wireless network (including a classification of networks);
– the security of a wireless network;
– ways to perform a formal verification o f a wireless network.
These are the most important things that should be considered when a new
wireless network is implemented in order to obtain a safe, scalable and reliable
one.
Before starting

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CHAPTER I – DESIGN OF WIRELESS NETWORKS
The first step to be performed in order to build a wireless network (or any
other type of network) is to perform a detailed analysis of the requirements and to
establish its design. So, i n this chapter, we will present some facts concerning the
design of wireless networks such as logical and physical architecture.
1.1. The OSI model
This model was introduced by the International Standards Organization
(ISO) mainly as a framework for developing new standards. It is considered that
networking is too complex to be regulated by a si ngle standard1, so, by using the
guidelines of this framework, multiple standards can be develo ped and the
networks created according to these standards can interoperate without major
problems . The name OSI stands for Open Systems Interconnect .
The OSI mod el consists of seven layers, every layer having a well – defined
role into the whole system and they interoperate in order to send (or receive) data.
Table 1.1.1. shows the layers of this model together with short descriptions and
the protocols they are using1.
Layer Description Standards/
protocols
1 – Physical layer Standards to control transmission of the
data stream over a particular medium, at
the level of coding and modulation
methods, voltages, signal durations and
frequencies. Ethernet,
Wi-Fi,
Bluetooth,
WiMAX
2 – Data link layer Standards to specify the way in which
devices access and share the transmission
medium (known as Media Access Control ARP,
Ethernet
(IEEE

1 Rackley, S., 2007, “ Wireless Network Logical Architecture ”, in Wireless Networking Technology – From
Principles to Successful Implementation , Elsevier Press , Oxford.

8
or MAC) and to ensure reliability of the
physical connection (known as Logical
Link Control or LLC). 802.3), Wi –
Fi (IEEE
802.11),
Bluetooth
(802.15.1)
3 – Network layer Standards to define the management of
network connections – routing, relay ing,
and terminating connections between
nodes in the network. IPv4, IPv6,
ARP
4 – Transport layer Standards to ensure reliable completion of
data transfers, covering error recovery,
data flow control, etc. Makes sure all data
packets have arrived. TCP, UDP
5 – Session layer Standards to manage the communication
between the presentation layers of the
sending and receiving computers. This
communication is achieved by
establishing , managing and terminating
“sessions”. ASAP,
SMB
6 – Presentation
layer Standards to control the translation of
incoming and outgoing data from one
presentation format to another. SSL
7 – Application
layer Standards to define the provision of
services to applications – such as checking
resource availability, authenticating users,
etc.. HTTP,
FTP,
SNMP,
POP3,
SMTP
Table 1.1.1 – The layers of OSI model

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In order to have a better understanding of the way a transaction runs
according to this model, we will present a simple example to illustrate the
interaction between the layers. Supposing that someone want s to send a picture to
another user, these are the main steps that will be executed in order to get th e job
done:
– When the user presses the SEND button, his operating system composes
the message that will be sent. This is formed from the image itself and
one set of instructions for Layer 7 . These instructions will be read and
used by the application level of the receiver’s machine.
– The message obtained after the previous step is now passed to the next
levels where it is translated from application formats (here we can have
also some security encryption such as SSL) in to a simpler form in order
to be transported to destination . When passing t hrough each layer, it
receives some additional headers or control sequences for ensuring the
integrity and for obtaining a secure transmission.
– In the Network layer , the message is divided into data packets that will be
sent, each one of them containing the IP addresses of sender and receiver.
The IPs are needed because in the Data link layer , they will be resolved
in order to obtain the MAC address.
– The last layer ( physical or PHY layer) encodes the packets and sends
them to the receiver (by using its MAC address obtained previously).
– When the packets reach their destination, they are processed again in
reversed order (if when the message is being sent, it passes through layers
in de scending order, now, the layers are traversed ascending) for
converting it into a form that can be read by the user or can be used by
other software.
We should mention here that when the message arrives at its destination a
check is performed to ensure tha t is has been transmitted correctly.

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1.2. Network technologies
As we saw in the example that has been presented in previous section, a
message is decomposed into packets that are transmitted from origin to
destination. So, it is extremely important to know wher e these packets should
arrive. This information is obtained from the receiver’s IP address, based on
which we can calculate its MAC address. During this section, we will see the
meaning of which one of these addresses and their importance. The packets can
be transported by using either the TCP or UDP protocol (as described in Table
1.1.1. ), also known as transport layer protocols . The routing of data packets in a
session is done by the Internet Protocol.
The most important part of Internet Protocol is the IP address , which is a
number (defined at the Network layer) which uniquely identifies a host (computer
or other s device) into a network and the network itself . This is because an address
consists of two parts: the host ID and the network ID. An IP address (IPv4) is
represented as a series of four decimal numbers between 0 and 255. Lately,
because of the massive increase of computers’ number, the number of possible
IPv4 addresses was not enough, so , it was adopted and used the IPv6 standard
which enables muc h more addresses than IPv4 (IPv4 uses 32 -bit addresses, IPv6
uses 128 -bit).
The MAC address is a unique identifier of a network adapter set to each
adapter when it is manufactured. It is used by the Data link layer, is represented
as a six digits hexadecimal number, is hard – coded and it cannot be modified.
Another important element is the Address Resolution Protocol (ARP)
which performs the mapping of an IP to corresponding device’s MAC address. In
order to obtain the MAC address by using an IP, the sender sends a message to all
devices from a network (by using its broadcast address), in which the node that
has the specified IP (the IP from the request) is asked to respond with its MA C.
This process has been optimized, so each device keeps a record of the MAC

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addresses of other nodes, so it does not have to broadcast the request at every
message sent. This is known as ARP table or ARP cache .
The routing process enables the packets to reach their destination. It is done
by using some special devices called routers which redirect the information to its
destination host or to another router. Each one has in its memory a special table
(the routing table) which contains a list of addresses. When a router receives a
packet, it compares the destination address of that packet with the ones from the
table. If a match is found, the packet is forwarded to the corresponding device (a
computer, printer, or another router). If not, the search is repe ated, but, this time
is checked only the network part of the IP. If the second search has no success,
the router tries to redirect the packet to a default destination. If all redirecting
attempts fail, a “Host Unreachable” or “Network Unreachable” error me ssage is
returned to the sender.
An important step related to the routing process is how the routing table is
being built. At the beginning of networking, when only few nodes were
connected , a list was loaded from a startup file . Nowadays, this approach is not
suitable anymore because the networks are getting more and more complex and
their devices number keeps increasing. So, at this moment, the routing tables are
composed by broadcasting messages in the network and waiting for a response .
There are also messages that allow routers to discover the shortest path to each
node in order to build optimum tables or to spot some devices or paths that are
not valid anymore . So, the routing process can be considered a continuous one. A
serious challenge is the routing in wireless networks because their topology can
be modified constantly and the routing table has to be updated continuously.
Considering that this paper aims to present information especially regarding
the wireless netwo rks, we will see an example of how the routing is made in a
wireless mesh network after we will present some notions referring to the physical
architecture of a network.

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1.3. Wireless network topologies
When referring to the topology of a network, we discuss ab out the way in
which its nodes are arranged and are interoperating. The topologies used for
wireless networks are mainly the same as the ones used in wired networks. In this
section we will present some of these topologies and their main characteristics.
Peer – to – Peer connections
“A distributed computer system or architecture is called peer to peer that is
basically intended to enable computer for sharing resources in such a way that
they can exchange data directly without the help of any centralized sy stem or
server.”2 From this definition we can easily find out some major benefits of this
topology:
– This kind of network is composed only from its nodes, no other auxiliary
machine (such as a server) is involved;
– All the nodes work together to “achieve” a certain “goal” ;
– It has a very high fault tolerance i.e. if a node stops working or becomes
unavailable (it is not possible to establish a connection with it), the rest
of the networks keeps functioning ;
– They do not imply massive costs to be implemented an d / or maintained.
This kind of networks can be divided into three main categories2, considering
their logical structure:
– Centralized – the peers rely on a central host for some services;
– Decentralized but structured – this type of network is ruled by a se ries
of constraints (in most of the cases , these rules are regarding the

2 Md. Sajjatul Islam , Md. Zainal Abedin, Sudam Das, 2014, “ Mobile Wireless Peer -To-Peer Network with
Higher End -To-End Throughput And Lower End -To-End Delay ”, American Journal of Engineering Research
(AJER) , Volume -03, Issue -02, pp -08-21, accessed online in April 2018 on the following link:
[http://www.ajer.org/papers/v3(2)/B0320821.pdf ]

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members’ topologies ) The messages are broadcasted taking into
consideration the topology of the nodes;
– Decentralized and unstructured – this type of network does not imply
a reliance on a central host nor a set of rules (constraints). In this context,
we do not have any restrictions related to content distribution.
An example illustrating this topology can be seen in Figure 1 .3.1, which
shows a decentralized and unstructured network.

Figure 1.3.1 – Peer – to – peer wireless network
Star topologies
They are also known as hub topologies . This name has been given because
of their central node which acts like a hub. In this type of network, the message
goes from the hub to all the points of the star. The major advantage of this type of
network is its fault tolerance: if a marginal node crashes or becomes unreachable ,
the rest of the network remains functional. On the other hand, if the hub stops
working, the network becomes unusable. We sh ould note that all nodes can
interact between them, but the message will pass through the hub which will
redirect to its destination. A diagram of this type of system is represented in
Figure 1.3.2 .

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Figure 1.3.2 – Star topology of wireless networks
Mesh network (MANET)
Mesh networks (which are also known as mobile ad hoc networks or
MANET s) are local or metropolitan networks in which nodes are mobile and
communicate directly with adjacent nodes without needing a central controlling
device3. These networks’ topologies can change constantly as well as a lot of
devices can connect or disconnect every moment. The routing technique used by
this kind of networks imitates the one used in Internet, the data being redirected
from node to node, no usa ge of a dedicated router being necessary. Every node
has to have routing capabilities. The following figure ( Figure 1.3.3 ) shows a
generic topology for this kind of network.
These networks have a high fault -tolerance, as well as a self – healing
capacity t hanks to the dynamic routing and configuring process: if a device stops
functioning, its duties are taken by the neighbors and the entire system continues
to work without flaws. The only condition for having this capacity is to ensure
enough devices that c an back -up the disabled ones. For obtaining this goal, more
and more networks are inspired from biology (they simulate some natural

3Adapted from Rackley, S., 2007, “ Wireless Network Logical Architecture ”, in Wireless Networking Technology
– From Principles to Successful Implementation , Elsevier Press, Oxford.

15
environments).

Figure 1.3. 3 – Mesh network topology
Despite the advantages mentioned previously, this kind of network has a
major challenge that has to be resolved: the security . Because of the structure
which is changing very quick, it’s hard to allow some devices’ access or to restrict
the connection of o ther unwanted ones.
In this paragraph (as it was an nounced previously ), we will present a routing
technique using by MA NET s which in inspired from nature ( from ants ’ word,
more exactly ). This example is ada pted from [ 2]. Ants use a clever method called
stigmergy . Each ant leaves a chemical substance ( pheromone ) which can be
smelled by the others, so the behavior of the colony is organized and coordinated
by the usage of these traces. Basically, the most u sed and crowded routes have
stronger smells than the other ones and these will continue to be developed and
maintained. The way in which thi s technique has bee n implemented into the
networks is presented in the following table ( Table 1.3 .4) which contains multiple
features of the algorithm a nd their importance for the entire system ’s behavio r.

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Feature Description
Pheromone tables A table ( stored in each node ) which contains information
regarding the q uality of its neighbors. The quality score
is being computed based on the percentage of data
packets deli vered correctly and the distance between
nodes.
Reactive routing
table update This step is triggered by an event that causes a change of
the network ’s structure (such as insertion of a new
station or failure of another one ). All the tables are being
updated by using some agents ( also known as “ants”)
which go through each route and evaluate its quality.
There are u sed two agents, one for each direction.
Proactive routing
table update This is also done by using agents but does not need an y
trigger . From time to time, “ants” are generated and sent
to evaluate the routes and eventu ally d iscover new ones.
The information obtain is used for updating the existing
tables in order to optimize the transmission of data
packets and / or to discover backup routes for the case of
some faults.
Stochastic routing
decisions When multiple paths are available, the selection is made
in a stochastic way : the path which has the greatest
quality score is being chosen. Despite th e fact that this
greedy strategy seems the best one, in time, this route
will become more and more used and busy , so new
routes have to be discovered and used until the best one
becomes clear again and can be used without prob lems.

Table 1.3.4 – MANET routing example

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BIBLIOGRAPHY
[1] Rackley, S., 2007, “ Wireless Network Logical Architecture ”, in Wireless
Networking Technology – From Principles to Successful Implementation ,
Elsevier Press, Oxford.
[2] Md. Sajjatul Islam, Md. Zainal Abedin, Sudam Das, 2014, “Mobile Wireless
Peer-To-Peer Network with Higher End -To-End Throughput And Lower End -To-
End Delay”, American Journal of Engineering Research (AJER), Volume -03,
Issue -02, pp -08-21, accessed online in April 2018 on the following link:
[http://ww w.ajer.org/papers/v3(2)/B0320821.pdf]