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Week1-ITECH1102Introductiontonetworking1.pptxITECH1102 Networking and Security
Week 1 – Introduction
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Topic 1 – Introduction to Networking and Security
What is computer networking?
-- Some definitions from the Internet --
A computer network is a telecommunications network which allows computers to exchange data.
Computer networking is an engineering discipline that aims to study and analyze the communication process among various computing devices or computer systems that are linked, or networked, together to exchange information and share resources.
In the very early days of computing computers were not networked.
To exchange data it had to be physically transferred from one computer to another on magnetic media (Floppy disks or magnetic tape).
Today almost all computing devices are networked in one form or another. It is their ability to exchange data that underpins many of the services we use daily, for instance Facebook, email, Internet browsing, eBay etc.
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Types of data exchange
Form into small groups and suggest data types that can be exchanged in computer networks.
Google search query (train timetable from Ballarat to Melbourne)
Netflix video
Stream a song from Pandora, Rhapsody, Spotify, Amazon Music & others.
Send a file to the printer for printing
Skype
Upload a file to Dropbox or OneDrive
Make phone calls with Viber
ebay
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My recent experience with eBay
I recently purchased an item on eBay!!!
The item was sent for free (from Hong Kong).
The item cost me $3.12
The item arrived in 18 days.
Similar items cost around $23.00 in Australia.
Being a big spender I purchased two!!!
This example allows us to investigate the technologies that underpin simple networked interactions like an eBay purchase.
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Data exchange in an eBay purchase
Form back into your groups and discuss the types of data exchanges involved in my purchase.
View items on eBay
Select an item for purchase and go to checkout page
Login to eBay (authentication {security})
Pay for my purchase with PayPal {encryption & security}
Even simple interactions can involve complicated exchanges like authentication and encryption.
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What technologies were involved in my ebay transaction?
Assumptions
The eBay web site is hosted in the USA.
I made the purchase from my home using a Desktop computer.
My Desktop computer connects to my home network using a Cat6 (blue) network cable.
-- Limit our discussion to Cat6 cabling technologies --
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Technology surrounding Cat 6 cables
Pairs of wires must be twisted together. Why?
The number of twists per distance must be correct.
Specific wires must be connected to specified connector pins.
So, Do we care about such details?
No way!!!!!
Leave the technical details to Standards organisations and the Engineers who work in such organisations.
The technologies we take for granted, like the cabling we use, WiFi devices and the computers we use are often underpinned by complicated technologies.
As users we are not all that concerned with the Science or Engineering behind the technologies, we leave such concerns to the engineers who specialise in such areas, however we should appreciate that Standards organisations create and maintain the technologies that underpin networking.
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Back to eBay without the Cat 6 cable
If I disconnect my Cat 6 cable from my Desktop computer then I must connect using WiFi.
This creates a whole new set of technologies to use and understand.
What about if I accessed eBay from my Mobile Phone’s mobile data connection.
Now we have a whole new set of technologies that become important.
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Devices involved in eBay exchange
My home PC
eBay Web Server
Communications hardware between my PC and eBay
PayPal server
Servers at my Bank
Lots more
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What is this course about?
This course mainly deals with networking technologies.
We investigate how networking works.
We use standard models (not discussed yet) of networking to help make sense of each part of network conversations like those just discussed in the eBay purchase.
This course also serves as a introduction to some of the technologies that will be expanded upon in later courses of the Networking and Security stream.
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Tool Talk
Some lectures will incorporate a Tool Talk session.
Tool talk sessions will discuss networking and associated tools like:
Wireshark (This is an industry standard protocol analyser) With it we could sniff (capture) plain text passwords. We can also analyse network traffic.
Virtualization tools Virtualization is one of the most useful and important tools used in networking & security.
During some lectures technologies will be demonstrated. Two tools of particular concern to us are Wireshark and VirtualBox.
Wireshark is a Protocol Analyser and as such can capture the binary data that constituted network traffic and then analyse and display that data in ways to help us understand it. Wireshark is use throughout the networking industry and so is not only important to us, but also to network engineers worldwide.
Virtualization underpins data centres worldwide. We are only concerned with its use as a desktop user, however its reach into industry is profound.
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Tool Talk (continued)
Windows calculator (Programmer View)
This is particularly used for working with binary numbers.
Binary underpins all computing and networking (its important).
Linux networking tools
Windows networking tools
Others.
Tool talk demonstrations may also look at simple technologies like the Windows Calculator for converting numbers between number systems, Linux networking utilities and Windows networking tools.
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Week 1 tool talk session – Number systems.
There are 4 number system that are used in networking:
Decimal
Binary
Hexadecimal
Octal
Main areas of usage:
Decimal Represents quantities, IPv4 addresses.
Binary This is how data is stored in computer systems.
It can be used to investigate individual bits in data
Hexadecimal To represent large quantities (also IPv6 addresses)
Octal Linux permissions
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Why not just use the decimal number system?
Sometimes the properties of one number system is more appropriate than the other three number systems.
For instance when looking at subnet masks (discussed later) binary is far more useful and less confusing than decimal.
When working with different number systems you should realise that the different number systems simply represent the same quantity in different ways.
For instance we can represent 25 widgets using all three number systems. Each number system represents the number of widgets in different ways, however the number of widgets stays the same.
Number Systems are just a different way of representing the same quantity. For instance we could represent the decimal number 65520 in the following ways:
Decimal 65,520
Binary 1111 1111 1111 0000
Hexadecimal 0xFFF0
Octal 0 177 760
Notice that the binary representation shows the individual bit pattern of 65,520. The Hexadecimal format is a shorthand way or writing the binary form, and in this case the octal version is of little use.
Irrespective of the number system we use, each is just representing the same quantity (ie. 65520 widgets). The quantity does not change just the way we choose to represent that quantity.
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Decimal number system
The decimal number system has universal use for representing quantities.
Example 73 apples, $264, 4209 years old.
It is has a base of 10 so the weighting of successive digits is 100=1, 101=10, 102=100, 103=1000
Valid digits in the decimal system are 0,1,2 …….9.
4209 decimal means 4 * 1000 + 2 * 100 + zero 10’s + 9 ones.
| 103=1000 | 102=100 | 101=10 | 100=1 |
| 4 | 2 | 0 | 9 |
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Bases and valid digits
The other number system of interest have different bases and associated valid digits.
| Number system | Base | Valid digits |
| Decimal | 10 | 0,1,2,3,4,5,6,7,8,9 |
| Binary | 2 | 0,1 |
| Hexadecimal | 16 | 0,1,2 …..8,9,A,B,C,D,E,F |
| Octal | 8 | 0,1,2,3,4,5,6,7 |
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Binary
Information stored and transmitted by digital computers is stored in binary. Each digit in binary is either 0 or 1.
Analogous to a light switch, either ON (1) or OFF (0).
Because binary has a base of 2, successive digits have a weighting of powers of 2. So the binary number 10110110 has the following format.
10110110 = 1 * 128 + 1 * 32 + 1 * 16 + 1 * 4 + 1 * 2 = 182 (decimal)
| 27 =128 | 26 =64 | 25 =32 | 24 =16 | 23 =8 | 22 =4 | 21 =2 | 20 =1 |
| 1 | 0 | 1 | 1 | 0 | 1 | 1 | 0 |
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Conversion from Decimal to Binary
Knowing the format of a Binary number, conversion from decimal to binary is straightforward.
Example: Convert the decimal number 75 to Binary
75 has no 128’s
75 has one 64 (with a remainder of 11)
The remaining 11 consists of no 32’s, no 16’s, one 8, etc.
| 128 | 64 | 32 | 16 | 8 | 4 | 2 | 1 |
| 0 | 1 | 0 | 0 | 1 | 0 | 1 | 1 |
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Hexadecimal, Octal and Binary
Once we have a number expressed in Binary, representation (conversion to) Octal or Hexadecimal is simple because:
3 binary bits can be represented by one octal digit
4 binary bits can be represented by one hexadecimal digit
Therefore representing numbers in octal or hexadecimal is effectively a shorthand way to write large binary numbers.
For instance, in networking we normally represent 128 bit IPv6 addresses in Hexadecimal (ie. 32 hexadecimal digits)
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Hexadecimal
In networking Hexadecimal is used frequently, particularly for representing large numbers.
Because hexadecimal numbers easily convert to their binary equivalent hexadecimal is often preferred to decimal.
The valid digits in hexadecimal are 0,1,2….9,A,B,C,D,E,F.
Either uppercase or lowercase is acceptable.
Each hexadecimal digit equates to 4 binary digits.
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Hexadecimal
Hex Binary Hex Binary Hex Binary
0 0000 1 0001 2 0010
3 0011 4 0100 5 0101
6 0110 7 0111 8 1000
9 1001 A 1010 B 1011
C 1100 D 1101 E 1110
F 1111
(Each successive binary bit is a power of 2 ( 8,4,2,1 )
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Exercise: Convert hexadecimal numbers to binary
Convert the following 3 digit hexadecimal (hex) numbers to binary. (Note – Hex numbers use the prefix of 0x to distinguish them from binary, octal and decimal numbers.
Hex Binary _
0x123 0001 0010 0011
0xABC 1010 1011 1100
0xFED 1111 1110 1101
We will get practice with number conversions in the lab.
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Octal
3 successive binary bits can be represented by a single octal digit.
Octal Binary equivalent
0 000
1 001
2 010
… …
6 110
7 111
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Using the Windows Calculator program to convert quantities to different number systems.
Run Calculator from Start Menu
Change the View to Programmer
You now have a tool to convert
Numbers (quantities) to the three
required number systems.
----- Demonstration -----
The Windows calculator (and for that matter similar applications on Linux and other platforms) allow us to convert any number from one number system to any other.
Using such calculators allows us to check our proficiency with converting between number systems. To do so:
Choose a number
Convert that number (with pen and paper) to any or all of the other number systems.
Use the calculator to check your answers
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Analysis of a Wireshark traffic dump
The graphic below shows network traffic as captured with Wireshark.
The packet contents are shown in the centre of the display
Packet contents in hexadecimal format
Location within the packet in hexadecimal
Packet contents in ASCII
A period represents a non ASCII character.
This Wireshark capture is that of a http request to a server named phoebe.ballarat.edu.au.
The IP address of phoebe is 141.132.88.82
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Next topic
OSI Model
Internet Model
Reference networks
Home/Small Business network
Campus network
Internet
Network gear
Switches/Hubs/Routers
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Questions ???
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