Toni Ryynänen DESIGN AND IMPLEMENTATION OF A SMALL- …

Bachelor’s thesis

Degree Programme in Information Technology

2020

Toni Ryynänen

DESIGN AND IMPLEMENTATION OF A SMALL- AND MEDIUM-SIZED TCP/IP ENTERPRISE NETWORK

BACHELOR’S THESIS | ABSTRACT

TURKU UNIVERSITY OF APPLIED SCIENCES

Degree Programme in Information Technology

2020 | 28 pages

Toni Ryynänen

DESIGN AND IMPLEMENTATION OF A SMALL- AND MEDIUM-SIZED TCP/IP ENTERPRISE NETWORK

In the modern era we’re living in, a flawless functionality and security of the IP network are one of the largest concerns of any company that aims to maximize the productivity of their employees. These qualities are achieved surprisingly easily through a proper planning and design process for the internal network infrastructure.

TCP/IP protocol suite is the worldwide standard in networking in today’s world, as it possesses the ability to interconnect hardware and operating systems from different manufacturers and is established the worldwide standard for internetworking. TCP/IP is the foundation of the massive communications network that spreads around the whole earth, the Internet. The main focus of the thesis is to shed light on the functionality of TCP/IP protocol suite and on a few different aspects of designing a smaller scale company network and the solutions generally to be implemented in networks.

This thesis was done partially in conjunction of a project of designing and implementing the internal network of a medium-sized company in Southern Finland.

KEYWORDS:

TCP/IP, Network, Implementation, Design, Reliability, Scalability, Topology

OPINNÄYTETYÖ (AMK) | TIIVISTELMÄ

TURUN AMMATTIKORKEAKOULU

Koulutus

2020 | 28 sivua

Toni Ryynänen

PIENEN JA KESKIKOKOISEN TCP/IP-YRITYSVERKON SUUNNITTELU JA TOTEUTUS

Nykymaailmassa yritysten yksi suurimpia huolenaiheita on IP-verkon virheetön toiminnallisuus sekä turvallisuus. Ne ovat yksi yrityksen toiminnallisuuden ja tuottavuuden tukipilareista. Nämä arvot ovat yllättävän helppo saavuttaa asianmukaisen sisäverkon suunnittelu- sekä kaavoitusprosessin avulla.

TCP/IP protokollayhdistelmä on nykyajan tietoverkkojen perusta ja maailmanlaajuinen standardi, koska yksi sen tärkeimmistä ominaisuuksista on kyky yhdistää eri valmistajien laitteisto ja ohjelmisto tietoverkossa. Tämän opinnäytetyön tavoitteena on tähdentää TCP/IP:n ominaisuuksia ja toiminnallisuutta, sekä sisäverkon suunnittelun eri vaiheita mukaanlukien asioita, jotka suunnitteluprosessin aikana tulee ottaa huomioon.

Opinnäytetyö on tehty osittain asiakasprojektin yhteydessä, jossa Suomessa aloittavalle keskikokoiselle yritykselle suunniteltiin ja toteutettiin täysin uusi verkko.

ASIASANAT:

TCP/IP, IP-verkko, Sisäverkko, Suunnittelu, Toiminnallisuus, Toimintavarmuus, Topologia

CONTENT

LIST OF ABBREVIATIONS (OR) SYMBOLS 6

1 INTRODUCTION 1

2 NETWORK FOUNDATIONS 2

2.1 The OSI Model 2

2.1.1 Structure of the OSI Model 2

2.2 TCP/IP 3

2.2.1 History of TCP/IP 4

2.2.2 Features of TCP/IP 4

2.3 Network Hardware in TCP/IP networks 5

2.4 Functionality of 5-Layered TCP/IP stack 7

2.4.1 Data Encapsulation and Decapsulation Process 9

2.5 Transport Layer (Layer 4) 10

2.5.1 Three-way Handshake of TCP 11

2.6 Network Layer (Layer 3) 11

2.6.1 Internet Protocol Addressing 12

2.6.2 Routing 14

2.7 Data Link Layer (Layer 2) 15

2.8 Physical Layer (Layer 1) 16

3 PLANNING, DESIGN AND IMPLEMENTATION 18

3.1 Understanding the Customer’s Needs 18

3.2 Designing the Topology 18

3.2.1 Basic network topologies 19

3.2.2 Hierarchical network model 22

3.3 Documenting Details of the Network 25

3.3.1 How to Document Your Network with a Network Topology Diagram 25

3.4 Testing and Backing Up before launching Production Networks 26

4 CONCLUSION 27

REFERENCES 28

FIGURES

Figure 1. OSI Model layers and examples of the components contained in them. 3 Figure 2. Layers and Components of the original four-layered TCP/IP Model. 8 Figure 3. A five-layered TCP/IP Model. 8 Figure 4. Illustration of how devices on TCP/IP layers interact with each other 9 Figure 5. Bus topology 19 Figure 6. Star topology 20 Figure 7. Ring topology 20 Figure 8. Full mesh topology (left) and partial mesh topology (right). 21 Figure 9. Tree topology 22 Figure 10. Layers of Hierarchical Network Model 23 Figure 11. Collapsed core design 24 Figure 12. A network topology summary diagram of a Local Area Network 26

LIST OF ABBREVIATIONS (OR) SYMBOLS

Abbreviation Explanation of abbreviation (Source)

TCP/IP The Internet Protocol suite that consists of several different

communications protocols, most importantly TCP and IP.

TCP Transmission Control Protocol

IP Internet Protocol

ARPANET Advanced Research Projects Agency Network

UDP User Datagram Protocol

DCCP Datagram Congestion Control Protocol

ICMP Internet Control Message Protocol

IGMP Internet Group Management Protocol

IPsec Internet Protocol Security – a protocol that authenticates and

encrypts packets for secure communication over an IP

network.

ISP Internet Service Provider - A company supplying internet

connection through their infrastructure.

VoIP Voice over IP – Technologies for voice communication and

multimedia sessions over IP networks.

OSI Model Open Systems Interconnection Model – A conceptual model

that standardizes telecommunication between computing

devices without considering the properties of the actual

techonogies.

PDU Protocol Data Unit – a generalized name for data packets on

different layers of the OSI Model.

Packet A generalized name for formatted unit of data which is carried

over a network.

VPN Virtual Private Network – A private encrypted connection

between points traversing through public ISP network.

L2L VPN LAN-to-LAN VPN – A Virtual private network traversing from

one site to another.

Telnet (TN) A protocol that allows accessing a computer virtually in a two-

way channel between two machines, allowing the creation of

remote sessions.

TCP Flags TCP flags indicate state of connection or provide details

about the transferred packets.

TCP SYN TCP Synchronization flag, used in establishing a reliable

connection between devices in three-way handshake

method.

TCP ACK TCP Acknowledgment flag, used to acknowledge packets

received.

NIC Network Interface Controller – hardware component that

connects a device to a network.

MAC Address Media Access Control address – unique and permanent 48-

bit identifier that each NIC has which is presented in

hexadecimal.

LAN Local Area Network – a group of devices on the same

physical network

WAN Wide Area Network – a network that spans a large

geographical area

VLAN Virtual LAN – A logical group of devices possibly on separate

physical LANs.

LSA Link State Advertisement – A packet used in OSPF routing

protocol to advertise link states to neighboring routers.

NGFW Next Generation Firewall – A common term for a modern

firewall that performs layer 7 application control

IPv4 Internet Protocol version 4

IPv6 Internet Protocol version 6

DHCP Dynamic Host Configuration Protocol – a network

management protocol used on IP networks where a DHCP

server assigns end devices network configurations such as

IP addresses.

IoT Internet of Things – concept of connecting all possible

devices in a household to the internet

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TURKU UNIVERSITY OF APPLIED SCIENCES THESIS | Toni Ryynänen

1 INTRODUCTION

This thesis is inspired by a project of building a completely new network from scratch for

a medium-sized company in Southern Finland.

The thesis aims to objectively describe the basic functions of Transmission Control

Protocol and Internet Protocol, better known as TCP/IP protocol stack. The first chapter

of the thesis is laying foundation on the basic structure and functionality of a TCP/IP

network by expanding on some of the more important core concepts of TCP/IP

networking, as well as shortly about the history of TCP/IP networking. In the second

chapter I am examining the views I learned about planning and designing a network

during the project, as well as implementation and maintenance of a network. Best

practices and details of the planning, designing and implementation process of a TCP/IP

network are briefly covered in the second chapter of the thesis. These measures ease

explaining and helping any reader fully understand the reasoning behind some of the

decisions during the network planning and designing process without having previous

experience in networking topics.

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2 NETWORK FOUNDATIONS

The first chapter is aiming to provide plentiful basic information of vital concepts in

TCP/IP networking to help the reader understand the overall complexity of an IP network

without any previous knowledge of the topic. This way it will be a lot easier to understand

the reasoning behind decisions made during the network planning, design and

implementation phases.

2.1 The OSI Model

The Open Systems Interconnection reference model, better known as the OSI Model, is

a seven-layered reference model that describes the operations of different components

and protocols in a communications network. Originally conceived in the late 1970s by

the International Organization for Standardization (ISO), the OSI model reached its final

form in 1984 when ISO published the “ISO 7498” standard (Shaw, 2018).

2.1.1 Structure of the OSI Model

The Open Systems Interconnection model is a seven-layered reference model. Each of

the layer is promptly named to describe its function in the overall picture. Each layer

transfers data to the next layer in order, and they do not operate in parallel to each other.

The OSI model can be referenced to top-down from Layer 7 towards Layer 1 or from

Layer 1 up towards Layer 7. In this thesis, it is referenced top-down because it represents

the flow of the communication from the end-user towards the network medium. Table 1

below presents a brief summary of the layers of the OSI model and examples of the

systems or protocols that each layer contains.

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Layer Name Components and

Protocols

7 Application WebSocket, HTTP, FTP,

Telnet, SMTP

6 Presentation TLS, SSL, ASCII,

5 Session Sockets, NetBIOS, SAP

4 Transport TCP, UDP, DCCP

3 Network IP, IPsec, ICMP, IGMP,

OSPF, IS-IS

2 Data Link

PPP, ARP, NDP, Fibre

Channel, Frame Relay,

IEEE802.11

1 Physical Ethernet, RS-232, RJ45,

1000BASE-T,

Figure 1. OSI Model layers and examples of the components contained in them.

Each layer of the OSI Model represents a group of protocols that operate on the same

level of the network. It is often used as a quick reference to a certain point of the network

during a troubleshooting process when trying to trace the data transportation in the

network. It can also be utilized easily to pinpoint a certain section of the network

framework to any network professional when describing functions of devices and

protocols, because it’s a known standard worldwide.

2.2 TCP/IP

TCP/IP protocol suite is the backbone of modern networking. On different layers of

TCP/IP stack, application data is being packed, unpacked and repacked for smooth flow

of communication. It is a collection of communications protocols that enables devices to

communicate across networks regardless of the hardware or the operating system.

TCP/IP protocol suite consists of several different protocols, Transmission Control

Protocol and Internet Protocol being the main components.

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2.2.1 History of TCP/IP

TCP/IP Protocol suite was designed by Robert Kahn and Vinton Cerf in the early 1970s

as a successor to ARPAnet protocol called Network Control Protocol. ARPAnet was the

precursor of the Internet. ARPAnet was created by Advanced Research Projects Agency

(ARPA) during the ‘Cold War’ -era as a secure network for military communications in a

possible nuclear warfare scenario (Thomas, TCP/IP Introduction 2020). The protocol to

direct traffic in the ARPAnet was called Network Control Protocol (NCP). As the ARPAnet

was growing larger and larger, the NCP couldn’t sustain the demands of the network.

For that reason, the development of TCP/IP began and in 1974 Robert Kahn and Vinton

Cerf first published a paper “A Protocol for Packet Network Interconnection”, which

introduced the idea of Transmission Control Protocol (TCP). Kahn and Cerf took after a

French research network CYCLADES which utilized the concept of packet switching.

They took the core concepts from project CYCLADES and baked it into their own

protocol. (“Complete History of the TCP/IP Protocol Suite”, 2020). After more

development and testing, TCP/IP eventually ended up replacing the Network Control

Protocol altogether in 1983 (Thomas, 2020). After pioneering its way through ARPANET

era, TCP/IP has become one of the most widely used protocols in the world (Tim Keary,

The Ultimate Guide to TCP/IP 2018). Vinton Cerf and Robert Kahn went on to win the

Turing award in 2004 for their pioneering work on internetworking and the development

of TCP/IP (Association for Computing Machinery, A.M. Turing Award Recipients, 2020).

2.2.2 Features of TCP/IP

Some of the key features of the TCP/IP protocol suite are the reason why it grew so

popular over the years. As it has grown to be a standard of the industry, it is utilized by

most of the hardware and software vendors. This multi-vendor support enables fluent

interoperability between devices using distinct hardware or operating systems, meaning

i.e. that using TCP/IP a user on a Windows -device can just as easily connect with a

Unix-server as to a Windows-server. (Thomas, TCP/IP Introduction, 2020). Craig Hunt

(2002) states that “Because it is so widely supported, TCP/IP is ideal for uniting different

hardware and software components, even if you don’t communicate over the internet”.

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The logical addressing in TCP/IP protocol stack is better known as the IP Address. This

feature is a cornerstone of dividing large networks into smaller networks by subnetting.

Subnetting is a key element of connecting a vast number of networks together and still

being able to have messages traverse fluently through the entire network.

The data transfer of Transmission Control Protocol is considered a reliable way of

transferring the data. The recipient of TCP packets always confirms that the data has

been reliably transferred by checking the checksum of a TCP header. If the packet

doesn’t pass the check, the recipient will not return the sender an acknowledgement of

receiving the packet. This way the sender has to assume, that the recipient has not

received the packet and will resend the packet that was lost on the way. If not receiving

the acknowledgment message after several attempts, TCP assumes that the recipient is

unreachable (Kowalczyk, TCP/IP Protocols 2020).

2.3 Network Hardware in TCP/IP networks

An entirety of a network consists of a wide variety of different types of physical network

hardware. Their functions are shortly summarized in this subchapter and are further

described layer-specifically in later subchapters.

Routers

Routers are layer 3 devices utilized at network edges to direct packets from one network

to another. Routers utilize routing tables to determine the most efficient ways to route

packets into their destination networks. Static routes can be configured in routers, but

routers also utilize various dynamic routing protocols to determine the most efficient

routes. This is due to the continuously changing network infrastructures and certain

connections being unavailable at times. Dynamic routing protocols can maintain up-to-

date routing information to be able to choose the most efficient paths to destination

networks even when a previously used path becomes unavailable.

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Switches

Switches are generally utilized within a local area network performing layer 2 packet

switching, directing packets to correct end devices within the network. Switches utilize

the Media Access Control (MAC) addresses of the end devices connected to the switch

to determine which host the specific switchport is connected to. Switches keep a

database of these combinations of MAC addresses and switchport and direct incoming

packets based on the information in these MAC address tables.

Since modern switches combine and enhance the functions of older layer 2 devices,

switches have replaced deprecated layer 2 devices such as hubs and bridges completely

in modern networks.

Access Points

Access points are devices that are used to create a wireless entry point to the network

for end devices such as laptops or mobile devices. This is called a wireless LAN (WLAN).

Standard wireless access points are usually directly connected to a switch or a router in

the network. To optimize wireless coverage, several wireless access points are often

required to blanket a larger area with wireless coverage. In many cases several wireless

access point across a building can be clustered into a single entity for easier

configuration and deployment.

Firewalls

Firewalls are devices that are utilized to manage the access and communications in an

out of networks. Firewalls are traditionally used for layer 3 packet filtering based on IP

addressing, port numbering and protocols used for communications. These are

commonly called network firewalls. Layer 4 firewalls add the capability of tracking active

connections and deciding whether to allow traffic based on the states of connections.

More modern iterations of firewalls, also commonly known as New Generation Firewalls

(NGFW), are applying policies to also layer 7 regarding communications of specific,

defined applications through the network. This type of approach is generally called

application firewall. Layer 7 firewalls address issues that layer 3 firewalls have regarding

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lack of protocol awareness (Morello, 2020). As an example, because HTTP is a universal

web application protocol, a layer 3 firewall might just allow all traffic to port 80, leaving

the network open to vulnerabilities and exploitations within the application layer. A layer

7 firewall can address these issues by investigating the app layer and allowing traffic on

further information regarding the requests, not just port information (Morello, 2020). For

maximum security to counteract as many threats as possible, a network should be

utilizing both layer 3 and layer 7 firewall functionalities.

End Devices

End devices are a broad category of devices that are connected to the network through

the access layer of the network. End devices are either the end or the starting point of

data transmission in a network, connected to the network either wired or wireless.

Examples of end devices would be all computers, workstations, servers, laptops, mobile

phones, VoIP phones, security cameras, handheld devices such as scanners or credit

card readers. The list of end devices is long, with the concept of Internet of Things

constantly expanding the category.

2.4 Functionality of 5-Layered TCP/IP stack

The functionality of TCP/IP is best described by chopping it into several layers. Referring

to the OSI Model, TCP/IP protocol suite condenses the seven layers into four of the

layers, thus it was originally considered to be a 4-layer system (Stevens & Wright, 1994).

In a modern TCP/IP model, the bottom-most layer is divided into separate physical (layer

1) and datalink layers (layer 2), making it a 5-layer model. The OSI reference model has

been utilised to a great extent when developing TCP/IP protocol suite which is partial

reason to why a lot of the terms associated with OSI Model are also associated with

TCP/IP (Thomas, 2020).

The four above-mentioned layers are Application Layer, Transport Layer, Network Layer

and Data-link layer. Below table shows which protocols and components operate on

which layer of the TCP/IP model.

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Layer Name Notes

4 Application layer DNS, HTTP, Telnet, SSH, FTP,

TFTP, SNMP, SMTP, DHCP

3 Transport layer TCP, UDP

2 Internet layer IP, ICMP, IGMP, ARP

1 Network Interface layer Ethernet, X.25, Frame Relay

Figure 2. Layers and Components of the original four-layered TCP/IP Model.

The newer, more modern 5-layered version of the TCP/IP model divides the network

interface layer into separate physical (layer 1) and datalink (layer 2) layers, where the

layer 1 is purely responsible for the transfer of bits from an end device to another in the

network as streams of bits (Thomas, 2020).

Layer Name Short Description

5 Application layer

Provides the protocols and interfaces for end

users. Data from application layer is passed

down to transport layer.

4 Transport layer

Encapsulates data from Application layer for

outgoing transmission, using primarily TDP and

UDP as transmission protocols.

3 Network layer Encapsulation of IP addressing and delivery of IP

datagrams over a network.

2 Data Link layer Encapsulates outgoing IP datagrams into

Ethernet frames

1 Physical layer

Converts an Ethernet frame into stream of bits

over a transmission medium as electrical signals,

radio waves or light signals.

Figure 3. A five-layered TCP/IP Model.

In the following subchapters the functions of each layer of the TCP/IP model are

described to pinpoint specify each layer’s function in data transfer and the components

and protocols that they populate. The five-layered model is nowadays the standard

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model for TCP/IP and is being used here to better describe the functions of the TCP/IP

-stack because it provides a more accurate overall picture of the operation of the protocol

stack as a whole.

2.4.1 Data Encapsulation and Decapsulation Process

The basis of the layered model of the TCP/IP stack is encapsulation and decapsulation

of the data while traversing the layers of the protocol stack. Generally, when moving data

from a higher layer to a lower layer, each layer adds something new to the pre-existing

data by encapsulating the original protocol data unit (PDU) with a header or a trailer that

includes new data and forms a new type of PDU. At the recipient device the process is

done in reversed order, decapsulating the headers one by one to access the data stored

in the packet.

Figure 4. Illustration of how devices on TCP/IP layers interact with each other

Application Layer (Layer 5)

The application layer is the top-most layer of the TCP/IP stack model which facilitates

the user interface for sending data between devices and applications. It includes all the

functions of the OSI Model’s layers 5 to 7; application, presentation and session layers.

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The application layer facilitates all the applications in addition to the protocols that are

being used in conjunction to them (Thomas, 2020). Some of the most common protocols

that function on the application layer are Telnet, HTTP, FTP, DNS, DHCP and SMTP.

While the application layer protocols are very important for multiple reasons, there is not

much to be considered regarding the application layer while designing a network.

2.5 Transport Layer (Layer 4)

Transport layer is the second-uppermost layer of the TCP/IP model. It is the layer that

facilitates the protocols that are responsible for initially encapsulating data from the

application layer for outgoing transmission and decapsulating data for incoming

transmission. The protocols that encapsulate data on the transport layer are

Transmission Control Protocol (TCP) and User Datagram Protocol (UDP). These two

protocols perform the same operation; they transfer the data through the network to

another device. They perform the operation in different ways, therefore one or the other

is the preferred method of data transfer for certain applications and services. TCP is

considered a reliable protocol, because it establishes a virtual end-to-end connection to

the endpoint by performing a three-way handshake. Before passing the data to the

network layer, TCP divides the data into smaller, more easily transferable data units

called segments, which are transferred separately to the destination and reassembled

into readable form. UDP is a connectionless protocol that encapsulates the data into

UDP datagrams that contain a source and destination ports, datagram length and a

checksum, then passes the datagrams to the network layer for transfer without any error-

checking or assurances that the data was received. Both of these protocols utilize ports,

which is a concept that allows to differentiate network communications between different

applications and protocols. A network port is a certain 16-bit numerical value that is

assigned to an application or a service running on the computer. The values of these

ports range from 0 to 65535. Port numbers 0 to 1023 are called well known ports, which

means that they have been assigned to specific services by Internet Assigned Numbers

Authority (Cotton et al., 2011). In addition, ports 1024 to 49151, also assigned by IANA,

are called registered ports, which means that they can be registered for a specific

application or service at the IANA (Cotton et al., 2011). The remainder of the ports, 49152

through 65535 are called dynamic ports (also known as Ephemeral ports), which are

temporary ports and can be freely used by any application.

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2.5.1 Three-way Handshake of TCP

The three-way handshake of Transmission Control Protocol (also known generally as

TCP-handshake) is a method performed by TCP to establish a reliable connection

between devices for transferring data. In this method the initiating client sends a TCP

segment to the destination with a SYN flag (Synchronization) set to 1 and all the other

TCP flags set to 0. Other contents that the TCP SYN-request includes are the sequence

number, source and destination IP addresses, and source and destination TCP port

numbers (Thomas, 2020). By receiving this TCP segment, the destination device

recognizes that the initiator wants to establish a connection to the destination. The

second step after receiving the SYN request from initiator, the destination device replies

with a TCP SYN-ACK (synchronization-acknowledgement) packet. This means that in

addition to the TCP SYN flag being set to 1, the ACK flag (Acknowledgment) is also set

to 1. In addition to the contents of the SYN packet, SYN-ACK packet includes an

acknowledgement number. In the final third step of the three-way handshake, the initiator

sends an ACK-packet to the destination with the previously established sequence and

acknowledgement numbers. The SYN flag in this packet is set to 0 and the ACK flag to

1. Once the destination device receives the ACK-packet, the TCP connection between

these two devices is established and they can communicate with each other reliably for

data transfer.

2.6 Network Layer (Layer 3)

The network layer of the TCP/IP stack is the layer where Internet Protocol, IPv4 and

IPv6, operate on. Along with Internet Protocol the important protocols operating on the

Network layer are Internet Control Message Protocol (ICMP), Internet Group

Management Protocol (IGMP), Address Resolution Protocol (ARP) and Reverse

Address Resolution Protocol (RARP).

As data encapsulated by a transport protocol (TCP or UDP) is passed to the network

layer as a TCP segment or an UDP datagram, the IPv4 or IPv6 protocols are

encapsulating the segments or datagrams respectively with IPv4 headers or IPv6

headers into network packets that contain the previously added TCP/UDP headers and

the newly added source and destination IP addresses. These addresses enable an

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important network function called routing, which means that layer 3 networking devices

such as routers direct the packets to correct recipients in a remote network.

2.6.1 Internet Protocol Addressing

Internet Protocol addressing is one of the cornerstones of communicating outside of the

local network and layer 3 routing would not be possible to accomplish without proper

addressing. IP addressing is a logical addressing system utilized by Internet Protocol on

layer 3 communications, assigning a unique identifier for a device on a network. These

unique addresses are utilized by the layer 3 network devices for routing traffic from one

network to another. IP addresses are manually configurable or automatically assigned

to end devices by a network management protocol called Dynamic Host Configuration

Protocol (DHCP).

Since its publishing in 1981, IPv4 (Internet Protocol version 4) has set the standard for

Internet Protocol addressing. It is followed by its successor, the most recent version of

Internet Protocol, IPv6 (Internet Protocol version 6) which was developed in the mid-

1990s due to the inevitable global exhaustion of IPv4 addresses. In modern networks,

IPv4 and IPv6 are often both utilized, and devices can simultaneously have both IPv4

and IPv6 addresses.

Internet Protocol version 4

While IPv4 is already nearly a forty-year-old technology, it still routes majority of today’s

global internet traffic. IPv4 addresses are 32-bit binary addresses that are most

commonly expressed in a dotted decimal format, x.x.x.x, in which each x represents an

eight-bit binary number known as an octet, each of them having a value between 0 and

255. As example, 192.168.178.1 is an IPv4 address expressed in it’s dotted decimal

format, while it in binary form actually is 11000000.10101000.10110010.00000001. The

dotted decimal format is used mainly for simplicity, for humans to read and configure

while all the actual interactions in the network are happening in the binary format. The

address has two dynamic parts, network part and host part. A subnet mask is a value

that defines which bits of the 32-bit address belong to the network part and the host part

of the IP address, i.e. an address with subnet mask 24 has 8 bits left in the host part.

Subnet mask is often indicated as a prefix after an IP address, such as 192.168.178.1/24.

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IPv4 addresses are assigned to each NIC in a network including links on layer 3 devices

such as routers. These addresses are used to deliver packets over networks by layer 3

protocols that are discussed in chapter 2.7.2.

IP addresses are divided in classes depending on their capability of containing host

addresses. These are called Class A, Class B, Class C and Class D addresses. Class A

addresses are big chunks of networks where only 8 bits belong to the network part,

leaving 24 bits in the network part, resulting in 127 networks with over 16 million available

addresses within the Class A network. Class B addresses have 16 host address bits,

producing 16,384 different networks with 65,534 hosts in them. Class C addresses are

commonly used for small scale networks, having only 8 host address bits, producing

about 2 million networks with 254 possible host addresses within them. Class D

addresses are mainly reserved for multicasting, which is a technique of sending packets

from one device to many destination devices. Class D IPv4 addresses cannot be

assigned to be successfully used in end devices.

Internet Protocol version 6

IPv6 was developed in the mid-90s because it came to common understanding that the

IPv4 address range is inevitably going to exhaust eventually, leaving future devices

without any viable IP addresses. While IPv4 addresses have a 32-bit address space,

IPv6 has a 128-bit address space, making it virtually impossible to exhaust. IPv6 also

specified a new packet format that helps to minimize packet header processing by

routers (Thomas, 2020).

IPv6 are expressed in hexadecimal numbers because they are so much longer than IPv4

addresses. One hexadecimal number represents 4 bits and they are grouped in 8 blocks

of 4, so an example of an IPv6 address looks like

2001:0000:9d38:6ab8:1c48:3a1c:a95a:b1c2. Since IPv6 addresses are so long, there

are a few methods to shorten them. Long series of 0s can be omitted as a single 0, in

the above-mentioned address being 2001:0:9d38:6ab8:1c48:3a1c:a95a:b1c2. If there

are several subsequent blocks of only series of 0s, they can be replaced with a double

colon. An address 2001:0db8:0000:0000:0022:f472:ff2a:ab99 would be

2001:0db8::0022:f472:ff2a:ab99.

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IPv6 has several functions distinct from IPv4, but the usage of IPv6 addresses works

practically in the same way as IPv4 addresses.

Subnetting

Subnetting is a concept of preventing the waste of IP addresses and reducing network

congestion by chopping IP address spaces into smaller sections. Subnet is plainly a

smaller set of addresses within a Class A, B or C address. Subnetting is performed by

converting the decimal value of the address into binary and then “borrowing” bits from

the host portion to create subnets. Borrowing bits from the host portion into the network

portion reduces the amount of IP addresses within the subnet, allowing less of them

going into waste. This way for example an address block of 254 IP addresses can easily

be split into several smaller blocks with less hosts, leaving the rest of the addresses

easily usable for other parts of the network.

2.6.2 Routing

Routing is a layer 3 function which is responsible for forwarding packets from one

network to another as IP packets. Routing is performed by layer 3 network devices,

primarily on routers and occasionally on multilayer switches. Simply explained the

process of routing has one objective, which is getting a packet from source point to a

destination point. Routers are the gateway devices on edges of local area networks and

their purpose is to direct packets towards their destination. Routers maintain a routing

table, which is a dynamic data storage containing information about all the known

destination networks, the next hops towards the specific network destinations and

metrics that determine the quality of the route towards the network. Static routes can be

configured into the router by system administrators to add specific routes to the table. In

addition, routers gather and share information about routes to different networks between

each other by utilizing routing protocols, for example such as OSPF, EIGRP, BGP or IS-

IS. Routers usually always have also a default route configured to them, so they can

direct packets towards the default route if the destination network for a packet is not

included in the routing table of the router.

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Routing Protocols

The objective of different routing protocols is collectively the same. The goal is to have

every router in the network have an up-to-date information concerning the routes to all

the destinations available. Routing protocols are divided in two primary categories,

distance vector protocols and link-state protocols. Distance vector protocols share their

routing table to all of the directly connected routers at intervals to update information

about routes being available or unavailable (Wilson, 2010). Examples of widely used

distance-vector protocols are EIGRP and BGP.

Open Shortest Path First, better known as OSPF, is one of the most widely used link-

state routing protocols. Link state protocols allow a router to observe the states of links

in the whole network by sharing information about the router itself and its directly

connected links to its peers. This information is passed along the network in packets

called Link State Advertisements (LSAs). This way all the routers in the network have

an up-to-date image of the route map in the whole network and can calculate the best

paths towards a destination network.

2.7 Data Link Layer (Layer 2)

The data-link layer is theoretically divided into two sublayers; Logical Link Control (LLC)

and Media Access Control (MAC). Logical link control is considered the upper sublayer

of the data link layer as it functions as a software-implemented interface between the

network layer and physical data link medium. The data link layer is responsible for

converting the IP datagrams arriving from the network layer into ethernet frames. In the

encapsulation process, the pre-existing IP header, TCP header, and the data from upper

layer protocols are encapsulated most importantly with source and destination Media

Access Control (MAC) addresses. These addresses are used by layer 2 network devices

such as switches to determine which device to deliver packets to in a Local Area

Network. In addition to the MAC addresses, ethernet frames consist of a preamble (7

bytes), start of frame delimiter (SFD, 1 byte), a type indicator (2 bytes), payload data

(minimum of 46 bytes and up to 1500 bytes), and a frame check sequence (FCS, 4

bytes). The preamble and start of frame delimiter are a sequence in format of

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1010…10101011, which is used for synchronization between the frame sender and

receiver and to recognize a new incoming frame by the receiving device.

Data Link Layer Switching

Data link layer switching is a layer 2-equivalent function of routing. Data link layer

switching is primarily carried out by layer 2 or multilayer switches in modern networks.

The difference is that whereas routers route packets based on IP addressing, in layer 2

switching the devices do not examine nor utilize the IP addresses of the packets. In data

link layer switching forwarding frames from a switchport to another happens only within

a Local Area Network, using the device-specific MAC addresses to determine which port

to forward the ethernet frames to.

Layer 2 and multilayer switches generate tables that contain information about the MAC

addresses of the devices connected to them in the network. The table includes also

information about the type of the link (whether it’s an assigned static MAC or a dynamic),

which switchport the mac address is associated with and the Virtual Local Area Network

(VLAN) associated with the MAC. The same MAC address may have several entries in

the MAC address table indicating that it exists in several different VLANs in the network.

Whenever the switch receives frames, it examines the source MAC address information

of the frame to add new information to add to the table. By populating the MAC address

table, the switch learns which ports to forward frames to. If the destination MAC address

of the frame is not in the MAC table, the switch will forward the frame into every port

except the port where the frame arrived from.

2.8 Physical Layer (Layer 1)

Physical layer is the concrete layer of medium that is responsible for transferring the

stream of bits passed from data layer as electric signals from the sending computer to

the destination computer. Common ways of transferring the data between the computers

are twisted cable pairs or optic fibre connections. Twisted pair cables have several

internal twisted pair wires wrapped into a coating and a RJ45 (Registered Jack 45)

connector attached in both of the ends of the cable, making them capable of being

plugged into the ethernet network interface card’s ports. RJ45 is a common standard

used widely in almost all network devices. Ethernet cables are categorized based on

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their performance into several categories, the current highest performing category being

Category 8 ethernet cable.

Fibre optic cables are data transferring medium that utilize pulses of light instead of

electric signals to transfer data through the cable. Each side of the cable has a

transceiver and a receiver attached to send and receive the lights (Thomas, 2020). Fibre

optic cables allow the highest possible bandwidth compared to twisted copper pairs and

allow a longer cable length. Usage of optic fibre also eliminates electrical interference

and noise that can disturb data transfer on twisted pairs from the electric signals. The

limiting factor on using optic fibre cables for all data transferring is that it can be damaged

rather easily, and it cannot be bent much, causing it to be difficult to install into certain

structures inside buildings. Optic fibre is also still rather expensive to install compared to

copper cables and requires training to install. All in all in this category, all ethernet and

serial connections and physical network interface cards are a part of the physical layer.

In addition, wireless connections that transfer data as radio wave signals are a part of

the physical layer.

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3 PLANNING, DESIGN AND IMPLEMENTATION

The design process is the most crucial part of planning the structure of a network. Most

of the pitfalls of a flawed network can be avoided with proper design, planning and

documentation of the network.

3.1 Understanding the Customer’s Needs

The design for the structure of a network should always be based on the needs. It is at

utmost importance to set up meetings with the customer to get immediately on the same

page about the requirements for their network. Predetermining a floor plan for the

network’s destined building will ease the implementation process by far by being able to

determine optimal spots for switching cabinets and figuring out where to place access

points for optimizing wireless coverage throughout the building. Seeing the dimensions

and materials of the building is also helpful in determining the cabling requirements for

implementing the network and seeing which links are viable for fiber optics for faster data

transfer.

It is important to discuss approximately how many end devices the network needs to be

able to house initially and how likely it is for the network to need upscaling soon. In

addition to the capacity of the devices, different services such as internal VoIP usage,

surveillance systems or control systems might require special consideration when

constructing the IP network.

3.2 Designing the Topology

When designing the topology, one should know the basics of network topologies to begin

with. The network topology means the way the network devices are sorted within the

network, and it can be presented in two ways: a physical topology or a logical topology.

The difference between physical and logical topology is quite distinct. The purpose of

physical topology is to illustrate the pattern how the physical devices are interconnected

and placed, including cablings between devices. Having a physical topology gives a

rough image of the actual placement of the devices and the distance of the cabling

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between them. Logical topology is a construct that reflects the communication between

the devices and the data flow within the network. While logical topology does not

consider the physical distance of the devices, it gives more attention to the device details

and the protocols that control the flow of the data in the network.

3.2.1 Basic network topologies

Basic network topologies include topologies such as bus topology, star topology, ring

topology, mesh topology, tree topology or hybrid topology.

A bus topology is a topology that consists of a main cable, where all nodes are linearly

connected to. While bus topology is rather easy to install and maintain, it is susceptible

to collisions if the computers connected try to communicate simultaneously. Also, the

entire network will be unable to operate if there are any issues on the main cable.

Figure 5. Bus topology

A star topology is a topology where all the nodes are connected to a centralized network

device such as a switch. It requires more cabling than a bus topology, but as an

advantage it is a lot easier to pinpoint the point of fault when having network issues on a

certain end device. Also when the connection of one device fails, the rest of the network

is unaffected by the issue.

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Figure 6. Star topology

In a ring topology all the devices of the network are connected in a circular loop, where

each device in the network is connected to two others to form the full loop. The data

travels through all devices in the network but in only one direction. Adding devices to a

ring topology is not burdensome and the data transmission speed between nodes can

be optimized well. While the chance of data collision in ring topology is very low, the

whole network is impacted if one node shuts down.

Figure 7. Ring topology

Mesh topology is a redundant type of topology where the network devices are

interconnected to each other. A mesh topology can be either a full mesh topology, where

every single device in the network is connected to all the others. Mesh topology can also

21


be partial mesh topology meaning that not every single device is connected to each

other, but interconnectivity exists in the network. The main purpose of a mesh topology

is the redundancy and fault tolerance. If a single point of the network fails, there are still

multiple paths for the data to travel through and it is ultimately rare to have the whole

network fail. Managing a full mesh topology in a large network can be very troublesome

and gets expensive quickly in cabling costs when several devices are added to the

network. In addition, in a large full mesh topology, troubleshooting an issue is often a

very long and tedious process. A partial mesh topology is a good way of reducing costs

of the network but still maintaining some of the redundancy provided by mesh topology.

Figure 8. Full mesh topology (left) and partial mesh topology (right).

Tree topology is a type of hybrid, hierarchical network structure that looks like a tree,

starting from a backbone device that splits into several branches that eventually facilitate

the end devices. A tree topology is great for scalability for larger networks because it is

easy to add new devices into branches to make space for more hosts. While a tree

topology upscales very easily, it is also very expensive to implement especially when

taking redundancy solutions into consideration. Without proper redundancy measures,

the backbone node poses a great risk as a point of failure, because the whole network

depends on it. A tree topology should rarely or never be considered for any smaller scale

networks because of the building costs and because it is in most cases not necessary if

there are not several branches required for the network.

22


A tree topology consists of a combination of a star topology and a bus topology; thus, it

can be considered a hybrid topology.

Figure 9. Tree topology

A hybrid topology is a topology that has several types of topologies combined within one.

Common examples of a hybrid topology are a Star-Bus topology or a Star-Ring topology,

but a hybrid topology can be implemented using any of the existing topologies. Building

a hybrid topology is a great way to improve the network’s efficiency, make it more reliable

and redundant and to boost the network’s scalability. Designing a hybrid topology takes

substantially more effort and time and the implementation, such as installation and

configuration needs to be precisely planned. Hybrid network topologies often turn out to

be larger scale networks, so managing the costs of the network is a crucial part of the

design process as well.

3.2.2 Hierarchical network model

The hierarchical network model is a conceptual model for designing modern networks

while keeping in mind qualities such as scalability and costs of implementing the network.

Hierarchical network model is one of the core concepts of modern enterprise network

design, because utilizing it is the best way to reach crucial network qualities such as

23


hierarchy, modularity, resiliency and flexibility, defined by Cisco (Cisco Networking

Academy, 2016).

The base principle of hierarchical network model is that there are three separate

functional layers: core layer, distribution layer and access layer. The model follows a

strict hierarchy, beginning from the core layer on the top of the model.

Figure 10. Layers of Hierarchical Network Model

24


The core layer is considered the backbone of the network, as it is connecting the network

WAN edge routers to distribution devices on site. The core layer consists mainly of fast

layer 2 or multilayer switches that are designed to provide a rapid data transmission

within the network. The core layer is a critical point of failure for the network, so

redundancy measures must be in place to redirect traffic in case of a link failure to ensure

the continuity of the data transmission. Distribution layer acts as the separation point of

access and core layers, providing redundancy for both, the core and the access layer

devices. Distribution layer devices can also provide services to both core and access

layers such as route summarization and route filtering. The access layer is the entry point

into the network, allowing network access for all end devices. The access layer is most

commonly implemented as a layer 2 switching environment that can use virtual local

area networks to segment the local area network.

In many cases when the network is not projected to grow large over time a two-tier

collapsed core design is implemented. Two-tier collapsed core means practically that the

distribution and the core layers are merged. The main purpose of using a collapsed core

design is to minimize the costs of the network in exchange of the redundancy and

services provided by the separate collapsed core layer.

Figure 11. Collapsed core design

25


3.3 Documenting Details of the Network

From the very beginning, documenting every device added to the network in a network

diagram is massively beneficial for keeping the topology clear and untangled. It might

not feel impactful in a smaller scale networks with only a few devices on them. Scalability,

the ability to fluently increase the capacity of the network, is one of the biggest impact

factors in a company network, where sudden and rapid growth might be required at a

certain point in time. When this growth happens, having up-to-date network diagrams is

vital for keeping track of the flow of data in the network. This becomes especially handy

in any troubleshooting situations when something is not functioning as intended. Being

prepared for the worst-case scenario with your network documentation is almost always

a way to avoid ending up in the worst-case scenario altogether.

In addition to having a network diagram, it is always highly recommended to keep an up-

to-date document of the device models, IP addresses and used interfaces in the network

separately. Descriptions for each device’s used links and their destinations should be

included.

3.3.1 How to Document Your Network with a Network Topology Diagram

The network topology diagram illustrates the size, shape and structure of the network.

When documenting a network with a network diagram, two key features are clarity and

simplicity. A network diagram should be easy to read and the components should be

easily distinguishable from each other. The network diagram should always contain the

most important information about the devices included in the network, such as the host

name and the model of the device and the management IP address for remote access.

Including physical links between all devices in the network diagram can ease

troubleshooting when having network issues or issues with specific end devices.

Having all information on one diagram might be challenging and get messy very easily.

For that reason, it is advisable to split a network diagram into several pages including

layer 2 and layer 3 information separately, such as VLANs and routing protocol

information within the network.

26


Figure 12. A network topology summary diagram of a Local Area Network

When separating information into different diagrams in larger networks, the most useful

information to display about the network is are for example the DHCP address ranges,

and VLANs. In networks that spread out to multiple locations or branches, including

Layer routing protocol details such as autonomous systems or OSPF areas can prove

useful.

3.4 Testing and Backing Up before launching Production Networks

When the network design is nearing finalization and only small adjustments are required,

it is necessary to conduct network testing after configuring the devices. Initial tests should

include connectivity tests, assuring that connections are fluent from each device of the

network and that everything is working seamlessly together. In addition, in larger

enterprise networks it might be necessary to conduct network security auditing and

stress testing case-by-case.

Backing up device configurations are always necessary in case of a hardware failure or

a sudden need of a rollback after making changes in the network, and backups should

always be kept up to date after making any adjustments in the configurations of the

network devices.

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4 CONCLUSION

TCP/IP protocol stack is the dominant standard in modern communications networks

and is utilized in majority of network implementations worldwide. The functionality of the

protocol stack can be expressed in a five-layer model called TCP/IP model. The

forementioned model illustrates how network devices interact with each other utilizing

the protocols on different layers in a TCP/IP network. On application layer the software

and application layer protocols determine the data to be transferred. On transport layer

the data is encapsulated by a transport protocol, such as TCP, for transmission. On

network layer the segment or datagram received is encapsulated with IP header into an

IP packet. On the data link layer the incoming packet is encapsulated with MAC

information into a data frame. On the physical layer the incoming data frame is

transferred as bits over a physical medium to the destination device. On the destination

device the whole process is reversed to unpack the data for application usage.

When implementing a network, apart from the TCP/IP basics, there are several core

concepts that should be taken into account. The most variable of these is the client

requirements, that changes in every scenario. Efficient, precise and professional design

of the topology by utilizing the standard-setting hierarchical network model ensures that

the network runs as reliably as possible and provides important quality of service and

scalability. Testing the network thoroughly before launching into production and properly

documenting the details of the network is crucial to ease maintenance and

troubleshooting. This is further aided by always keeping up-to-date backups of each

network device’s configurations. Following these steps is a basis for building a modern

enterprise network to facilitate the needs of a company that wants to meet the standard

of flawless and reliable network.

28


REFERENCES

Association for Computer Machinery (2020). A.M. Turing Award. Retrieved September 02, 2020, from https://amturing.acm.org/

CertificationKits. (2013). 1-4 TCP/IP Model. Free CCNA Study Guide. Retrieved December 17, 2020, from https://www.freeccnastudyguide.com/study-guides/ccna/ch1/1-4-tcpip-model/

Cisco Networking Academy. (2016). Hierarchical Network Model. Retrieved December 18, 2020, from https://www.ciscopress.com/articles/article.asp?p=2202410

Complete History of the TCP/IP Protocol Suite (2020). TCP/IP. Retrieved December 17, 2020, from https://history-computer.com/Internet/Maturing/TCPIP.html

Cotton, M., Eggert, L., Touch, J., Westerlund, M., & Cheshire, S. (2011, August). Internet Assigned Numbers Authority (IANA) Procedures for the Management of the Service Name and Transport Protocol Port Number Registry. Retrieved September 16, 2020, from https://tools.ietf.org/html/rfc6335

Hunt, C. (2002). TCP/IP Network Administration. Sebastopol, CA: O'Reilly.

Keary, T. (2018). The Ultimate Guide to TCP/IP. Retrieved September 01, 2020, from https://www.itprc.com/tcpipfaq/

Kowalczyk, C. (2020). TCP/IP Protocols. Retrieved September 02, 2020, from http://www.crypto-it.net/eng/theory/tcp-ip-protocols.html

Morello, J. (2020). Know Your Firewall: Layer 3 vs. Layer 7. Retrieved November 22, 2020, from https://securityboulevard.com/2018/10/know-your-firewall-layer-3-vs-layer-7/

OSI-Model: Open Systems Interconnection model. Retrieved September 03, 2020, from https://osi-model.com/

Shaw, K. (2018). The OSI model explained: How to understand (and remember) the 7-layer network model. Retrieved September 03, 2020, from https://www.networkworld.com/article/3239677/the-osi-model-explained-how-to-understand-and-remember-the-7-layer-network-model.html

Stevens, W. R., & Wright, G. R. (1994). TCP/IP Illustrated. Addison-Wesley.

Thomas, J. (2020). TCP/IP Introduction. Retrieved September 02, 2020, from https://www.omnisecu.com/tcpip/tcpip-introduction.php

https://amturing.acm.org/

https://www.freeccnastudyguide.com/study-guides/ccna/ch1/1-4-tcpip-model/

https://www.ciscopress.com/articles/article.asp?p=2202410%20%20

https://history-computer.com/Internet/Maturing/TCPIP.html

https://tools.ietf.org/html/rfc6335

https://www.itprc.com/tcpipfaq/

http://www.crypto-it.net/eng/theory/tcp-ip-protocols.html

https://securityboulevard.com/2018/10/know-your-firewall-layer-3-vs-layer-7/

https://securityboulevard.com/2018/10/know-your-firewall-layer-3-vs-layer-7/

https://osi-model.com/

https://www.networkworld.com/article/3239677/the-osi-model-explained-how-to-understand-and-remember-the-7-layer-network-model.html

https://www.networkworld.com/article/3239677/the-osi-model-explained-how-to-understand-and-remember-the-7-layer-network-model.html

https://www.omnisecu.com/tcpip/tcpip-introduction.php

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