\documentclass[10pt,a4paper]{article}

% Packages
\usepackage{fancyhdr}           % For header and footer
\usepackage{multicol}           % Allows multicols in tables
\usepackage{tabularx}           % Intelligent column widths
\usepackage{tabulary}           % Used in header and footer
\usepackage{hhline}             % Border under tables
\usepackage{graphicx}           % For images
\usepackage{xcolor}             % For hex colours
%\usepackage[utf8x]{inputenc}    % For unicode character support
\usepackage[T1]{fontenc}        % Without this we get weird character replacements
\usepackage{colortbl}           % For coloured tables
\usepackage{setspace}           % For line height
\usepackage{lastpage}           % Needed for total page number
\usepackage{seqsplit}           % Splits long words.
%\usepackage{opensans}          % Can't make this work so far. Shame. Would be lovely.
\usepackage[normalem]{ulem}     % For underlining links
% Most of the following are not required for the majority
% of cheat sheets but are needed for some symbol support.
\usepackage{amsmath}            % Symbols
\usepackage{MnSymbol}           % Symbols
\usepackage{wasysym}            % Symbols
%\usepackage[english,german,french,spanish,italian]{babel}              % Languages

% Document Info
\author{{[}deleted{]}}
\pdfinfo{
  /Title (computer-networks-aqa-computer-science.pdf)
  /Creator (Cheatography)
  /Author ({[}deleted{]})
  /Subject (Computer Networks - AQA Computer Science Cheat Sheet)
}

% Lengths and widths
\addtolength{\textwidth}{6cm}
\addtolength{\textheight}{-1cm}
\addtolength{\hoffset}{-3cm}
\addtolength{\voffset}{-2cm}
\setlength{\tabcolsep}{0.2cm} % Space between columns
\setlength{\headsep}{-12pt} % Reduce space between header and content
\setlength{\headheight}{85pt} % If less, LaTeX automatically increases it
\renewcommand{\footrulewidth}{0pt} % Remove footer line
\renewcommand{\headrulewidth}{0pt} % Remove header line
\renewcommand{\seqinsert}{\ifmmode\allowbreak\else\-\fi} % Hyphens in seqsplit
% This two commands together give roughly
% the right line height in the tables
\renewcommand{\arraystretch}{1.3}
\onehalfspacing

% Commands
\newcommand{\SetRowColor}[1]{\noalign{\gdef\RowColorName{#1}}\rowcolor{\RowColorName}} % Shortcut for row colour
\newcommand{\mymulticolumn}[3]{\multicolumn{#1}{>{\columncolor{\RowColorName}}#2}{#3}} % For coloured multi-cols
\newcolumntype{x}[1]{>{\raggedright}p{#1}} % New column types for ragged-right paragraph columns
\newcommand{\tn}{\tabularnewline} % Required as custom column type in use

% Font and Colours
\definecolor{HeadBackground}{HTML}{333333}
\definecolor{FootBackground}{HTML}{666666}
\definecolor{TextColor}{HTML}{333333}
\definecolor{DarkBackground}{HTML}{E80046}
\definecolor{LightBackground}{HTML}{FDEFF3}
\renewcommand{\familydefault}{\sfdefault}
\color{TextColor}

% Header and Footer
\pagestyle{fancy}
\fancyhead{} % Set header to blank
\fancyfoot{} % Set footer to blank
\fancyhead[L]{
\noindent
\begin{multicols}{3}
\begin{tabulary}{5.8cm}{C}
    \SetRowColor{DarkBackground}
    \vspace{-7pt}
    {\parbox{\dimexpr\textwidth-2\fboxsep\relax}{\noindent
        \hspace*{-6pt}\includegraphics[width=5.8cm]{/web/www.cheatography.com/public/images/cheatography_logo.pdf}}
    }
\end{tabulary}
\columnbreak
\begin{tabulary}{11cm}{L}
    \vspace{-2pt}\large{\bf{\textcolor{DarkBackground}{\textrm{Computer Networks - AQA Computer Science Cheat Sheet}}}} \\
    \normalsize{by \textcolor{DarkBackground}{{[}deleted{]}} via \textcolor{DarkBackground}{\uline{cheatography.com/56036/cs/15127/}}}
\end{tabulary}
\end{multicols}}

\fancyfoot[L]{ \footnotesize
\noindent
\begin{multicols}{3}
\begin{tabulary}{5.8cm}{LL}
  \SetRowColor{FootBackground}
  \mymulticolumn{2}{p{5.377cm}}{\bf\textcolor{white}{Cheatographer}}  \\
  \vspace{-2pt}{[}deleted{]} \\
  \uline{cheatography.com/deleted-56036} \\
  \end{tabulary}
\vfill
\columnbreak
\begin{tabulary}{5.8cm}{L}
  \SetRowColor{FootBackground}
  \mymulticolumn{1}{p{5.377cm}}{\bf\textcolor{white}{Cheat Sheet}}  \\
   \vspace{-2pt}Published 16th May, 2018.\\
   Updated 16th May, 2018.\\
   Page {\thepage} of \pageref{LastPage}.
\end{tabulary}
\vfill
\columnbreak
\begin{tabulary}{5.8cm}{L}
  \SetRowColor{FootBackground}
  \mymulticolumn{1}{p{5.377cm}}{\bf\textcolor{white}{Sponsor}}  \\
  \SetRowColor{white}
  \vspace{-5pt}
  %\includegraphics[width=48px,height=48px]{dave.jpeg}
  Measure your website readability!\\
  www.readability-score.com
\end{tabulary}
\end{multicols}}




\begin{document}
\raggedright
\raggedcolumns

% Set font size to small. Switch to any value
% from this page to resize cheat sheet text:
% www.emerson.emory.edu/services/latex/latex_169.html
\footnotesize % Small font.

\begin{multicols*}{2}

\begin{tabularx}{8.4cm}{X}
\SetRowColor{DarkBackground}
\mymulticolumn{1}{x{8.4cm}}{\bf\textcolor{white}{What is a Computer Network?}}  \tn
\SetRowColor{white}
\mymulticolumn{1}{x{8.4cm}}{A digital telecommunications network which allows nodes (i.e. computers) to share resources.% Row Count 2 (+ 2)
} \tn 
\hhline{>{\arrayrulecolor{DarkBackground}}-}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{8.4cm}{x{2.08 cm} x{5.92 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{2}{x{8.4cm}}{\bf\textcolor{white}{Pros and Cons of Networks}}  \tn
% Row 0
\SetRowColor{LightBackground}
\seqsplit{Advantages:} & {\bf{Communication}}: becomes easier as a result of technology like texting, emailing, etc. \tn 
% Row Count 4 (+ 4)
% Row 1
\SetRowColor{white}
 & {\bf{Flexibility}}: if information is stored on a network, it means users can access it from anywhere in the world. \tn 
% Row Count 8 (+ 4)
% Row 2
\SetRowColor{LightBackground}
 & {\bf{Sharing resources}}: sharing files and information over a network, including software (can be streamed using web applications) and access to printers. \tn 
% Row Count 14 (+ 6)
% Row 3
\SetRowColor{white}
\seqsplit{Disadvantages:} & {\bf{Hardware}}: routers, network cards etc are required to set up a network. This is expensive and requires professional expertise to set up. \tn 
% Row Count 19 (+ 5)
% Row 4
\SetRowColor{LightBackground}
 & {\bf{Vulnerability}}: hackers can break into networks. Malware can spread and damage files on many computers via a network. \tn 
% Row Count 24 (+ 5)
% Row 5
\SetRowColor{white}
 & {\bf{Dependence}}: users relying on a network might be stuck without access to it. \tn 
% Row Count 27 (+ 3)
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{8.4cm}{X}
\SetRowColor{DarkBackground}
\mymulticolumn{1}{x{8.4cm}}{\bf\textcolor{white}{Wired vs Wireless}}  \tn
% Row 0
\SetRowColor{LightBackground}
\mymulticolumn{1}{x{8.4cm}}{Wired Networks} \tn 
\mymulticolumn{1}{x{8.4cm}}{\hspace*{6 px}\rule{2px}{6px}\hspace*{6 px}The computers are physically connected by wires (e.g. coaxial copper cables, fibre optics). They are arranged in {\bf{topologies}}.} \tn 
% Row Count 4 (+ 4)
% Row 1
\SetRowColor{white}
\mymulticolumn{1}{x{8.4cm}}{Wireless Networks} \tn 
\mymulticolumn{1}{x{8.4cm}}{\hspace*{6 px}\rule{2px}{6px}\hspace*{6 px}There is no physical connection, as radio waves (e.g. in the form of WiFi) are used to communicate data instead.} \tn 
% Row Count 8 (+ 4)
% Row 2
\SetRowColor{LightBackground}
\mymulticolumn{1}{x{8.4cm}}{Which is Better?} \tn 
\mymulticolumn{1}{x{8.4cm}}{\hspace*{6 px}\rule{2px}{6px}\hspace*{6 px}It is dependent on situation. Wired networks are more reliable, as there is less interference. Security is also easier to manage. However, cabling and other physical components can make it very expensive. Wireless networks allow mobility and flexibility, but are much less secure and interference can occur. Data transfer may also be slower.} \tn 
% Row Count 17 (+ 9)
\hhline{>{\arrayrulecolor{DarkBackground}}-}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{8.4cm}{X}
\SetRowColor{DarkBackground}
\mymulticolumn{1}{x{8.4cm}}{\bf\textcolor{white}{Why is network security important?}}  \tn
\SetRowColor{white}
\mymulticolumn{1}{x{8.4cm}}{{\bf{Network security}} is a broad term for any measures that protect a network from unauthorized access, misuse, destruction, or the sharing of confidential information. It is important because otherwise sensitive data may be shared or lost. It is also essential from a legal persepctive. For businesses, corporate espionage is another a potential issue.% Row Count 8 (+ 8)
} \tn 
\hhline{>{\arrayrulecolor{DarkBackground}}-}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{8.4cm}{x{3.04 cm} x{4.96 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{2}{x{8.4cm}}{\bf\textcolor{white}{Methods of Network Security}}  \tn
% Row 0
\SetRowColor{LightBackground}
{\bf{Authentication}} & Checking the identity of a user, usually by requiring them to input a password or biometric ID. \tn 
% Row Count 4 (+ 4)
% Row 1
\SetRowColor{white}
{\bf{Encryption}} & Encoding data it using a key, meaning that the same key is needed to decrypt the data. This is how HTTPS works. \tn 
% Row Count 9 (+ 5)
% Row 2
\SetRowColor{LightBackground}
{\bf{Firewalls}} & Protects a network from unauthorised access. \tn 
% Row Count 11 (+ 2)
% Row 3
\SetRowColor{white}
{\bf{MAC Address Filtering}} & Allows devices to access or be blocked from accessing a network based on their physical address embedded within the device's network adapter. \tn 
% Row Count 17 (+ 6)
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{8.4cm}{x{2.72 cm} x{5.28 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{2}{x{8.4cm}}{\bf\textcolor{white}{TCP/IP}}  \tn
% Row 0
\SetRowColor{LightBackground}
{\bf{TCP}} & {\bf{T}}ransmission {\bf{C}}ontrol {\bf{P}}rotocol, a protocol dictating how to establish and maintain a network conversation. \tn 
% Row Count 5 (+ 5)
% Row 1
\SetRowColor{white}
{\bf{IP}} & {\bf{I}}nternet {\bf{P}}rotocol \tn 
% Row Count 6 (+ 1)
% Row 2
\SetRowColor{LightBackground}
{\bf{TCP/IP}} & A 4-layer model that is essential to networking. \tn 
% Row Count 8 (+ 2)
% Row 3
\SetRowColor{white}
{\bf{Application Layer}} & Where the network applications, such as web browsers or email programs, operate. Examples: HTTP, HTTPS \tn 
% Row Count 12 (+ 4)
% Row 4
\SetRowColor{LightBackground}
{\bf{Transport Layer}} & Sets up the communication between the two hosts and they agree settings such as 'language' and size of packets. \tn 
% Row Count 17 (+ 5)
% Row 5
\SetRowColor{white}
{\bf{Network Layer}} & Addresses and packages data for transmission. Routes the packets across the network. \tn 
% Row Count 21 (+ 4)
% Row 6
\SetRowColor{LightBackground}
{\bf{Data Link Layer}} & This is where the network hardware such as the NIC (network interface card) is located. OS device drivers also sit here. \tn 
% Row Count 26 (+ 5)
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{8.4cm}{X}
\SetRowColor{DarkBackground}
\mymulticolumn{1}{x{8.4cm}}{\bf\textcolor{white}{TCP/IP Diagram}}  \tn
\SetRowColor{LightBackground}
\mymulticolumn{1}{p{8.4cm}}{\vspace{1px}\centerline{\includegraphics[width=5.1cm]{/web/www.cheatography.com/public/uploads/danielles_1526012153_tcpip_5_layer_overview.png}}} \tn 
\hhline{>{\arrayrulecolor{DarkBackground}}-}
\SetRowColor{LightBackground}
\mymulticolumn{1}{x{8.4cm}}{\seqsplit{http://microchipdeveloper}.com/tcpip:tcp-ip-five-layer-model}  \tn 
\hhline{>{\arrayrulecolor{DarkBackground}}-}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{8.4cm}{x{2.72 cm} x{5.28 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{2}{x{8.4cm}}{\bf\textcolor{white}{Network Protocols}}  \tn
% Row 0
\SetRowColor{LightBackground}
{\bf{Ethernet}} & A family of protocols that dictate how devices on the same network segment format and transmit data. \tn 
% Row Count 4 (+ 4)
% Row 1
\SetRowColor{white}
{\bf{Wi-Fi}} or {\bf{WLAN}} & A family of protocols that deal with wireless transmission. \tn 
% Row Count 7 (+ 3)
% Row 2
\SetRowColor{LightBackground}
{\bf{TCP}} & {\bf{T}}ransmission {\bf{C}}ontrol {\bf{P}}rotocol: splits (and later reassembles) data into packets. Also involves error checking, as expects an acknowledgement transmission within a set time frame. \tn 
% Row Count 15 (+ 8)
% Row 3
\SetRowColor{white}
{\bf{UDP}} & {\bf{U}}ser {\bf{D}}atagram {\bf{P}}rotocol: \tn 
% Row Count 17 (+ 2)
% Row 4
\SetRowColor{LightBackground}
{\bf{IP}} & {\bf{I}}nternet {\bf{P}}rotocol: each device has an IP address. Packets are 'addressed' to ensure they reach the correct user. \tn 
% Row Count 22 (+ 5)
% Row 5
\SetRowColor{white}
{\bf{HTTP}} & {\bf{H}}ypertext {\bf{T}}ransfer {\bf{P}}rotocol: used to access a web-page from a web server. \tn 
% Row Count 26 (+ 4)
% Row 6
\SetRowColor{LightBackground}
{\bf{HTTPS}} & {\bf{H}}ypertext {\bf{T}}ransfer {\bf{P}}rotocol {\bf{S}}ecure: u7ses encryption to protect data. \tn 
% Row Count 30 (+ 4)
\end{tabularx}
\par\addvspace{1.3em}

\vfill
\columnbreak
\begin{tabularx}{8.4cm}{x{2.72 cm} x{5.28 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{2}{x{8.4cm}}{\bf\textcolor{white}{Network Protocols (cont)}}  \tn
% Row 7
\SetRowColor{LightBackground}
{\bf{FTP}} & {\bf{F}}ile {\bf{T}}ransfer {\bf{P}}rotocol: handles file uploads and downloads, transfers data and programs. \tn 
% Row Count 4 (+ 4)
% Row 8
\SetRowColor{white}
{\bf{SMTP}} & {\bf{S}}imple {\bf{M}}ail {\bf{T}}ransfer {\bf{P}}rotocol: handles outbound email. SMTP servers have databases of user's email addresses. \tn 
% Row Count 9 (+ 5)
% Row 9
\SetRowColor{LightBackground}
{\bf{IMAP}} & {\bf{I}}nternet {\bf{M}}essage {\bf{A}}ccess {\bf{P}}rotocol: handles inbound emails. \tn 
% Row Count 12 (+ 3)
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\SetRowColor{LightBackground}
\mymulticolumn{2}{x{8.4cm}}{A {\bf{network protocol}} is a set of rules/conventions that dictate how a network operates.}  \tn 
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{8.4cm}{X}
\SetRowColor{DarkBackground}
\mymulticolumn{1}{x{8.4cm}}{\bf\textcolor{white}{Network Topologies}}  \tn
% Row 0
\SetRowColor{LightBackground}
\mymulticolumn{1}{x{8.4cm}}{What is {\bf{network topology}}?} \tn 
\mymulticolumn{1}{x{8.4cm}}{\hspace*{6 px}\rule{2px}{6px}\hspace*{6 px}The way that a network is physically structured.} \tn 
% Row Count 3 (+ 3)
% Row 1
\SetRowColor{white}
\mymulticolumn{1}{x{8.4cm}}{What is {\bf{star topology}}?} \tn 
\mymulticolumn{1}{x{8.4cm}}{\hspace*{6 px}\rule{2px}{6px}\hspace*{6 px}A network where there is a central {\bf{server}} that all of the computers and peripherals are connected to.} \tn 
% Row Count 7 (+ 4)
% Row 2
\SetRowColor{LightBackground}
\mymulticolumn{1}{x{8.4cm}}{Advantages of star toplogy:} \tn 
\mymulticolumn{1}{x{8.4cm}}{\hspace*{6 px}\rule{2px}{6px}\hspace*{6 px}1. If a computer fails, there is no impact on the other devices. \{\{nl\}\} 2. Security is good, because the data only passes through the server, not any other devices. \{\{nl\}\} 3. There are no data collisions.} \tn 
% Row Count 13 (+ 6)
% Row 3
\SetRowColor{white}
\mymulticolumn{1}{x{8.4cm}}{Disadvantages of star topology:} \tn 
\mymulticolumn{1}{x{8.4cm}}{\hspace*{6 px}\rule{2px}{6px}\hspace*{6 px}1. If the server fails, it's a catastrophe. \{\{nl\}\} 2. Lots of cabling is need to connect all the devices individually, so it's quite expensive.} \tn 
% Row Count 18 (+ 5)
% Row 4
\SetRowColor{LightBackground}
\mymulticolumn{1}{x{8.4cm}}{What is {\bf{bus topology}}?} \tn 
\mymulticolumn{1}{x{8.4cm}}{\hspace*{6 px}\rule{2px}{6px}\hspace*{6 px}A network where there is a central backbone of cable connecting every computer. At each end of the cable is a {\bf{terminator}} to stop data from continually being moved around.} \tn 
% Row Count 23 (+ 5)
% Row 5
\SetRowColor{white}
\mymulticolumn{1}{x{8.4cm}}{Advantages of bus toplogy:} \tn 
\mymulticolumn{1}{x{8.4cm}}{\hspace*{6 px}\rule{2px}{6px}\hspace*{6 px}1. Cheap. \{\{nl\}\} 2. Easy to add more devices.} \tn 
% Row Count 25 (+ 2)
% Row 6
\SetRowColor{LightBackground}
\mymulticolumn{1}{x{8.4cm}}{Disadvantages of bus topology:} \tn 
\mymulticolumn{1}{x{8.4cm}}{\hspace*{6 px}\rule{2px}{6px}\hspace*{6 px}1. Only appropriate for small networks, otherwise data transmission is too slow. \{\{nl\}\} 2. Data collisions are likely. \{\{nl\}\} 3. If the backbone is severed, all computers are impacted.} \tn 
% Row Count 30 (+ 5)
\hhline{>{\arrayrulecolor{DarkBackground}}-}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{8.4cm}{X}
\SetRowColor{DarkBackground}
\mymulticolumn{1}{x{8.4cm}}{\bf\textcolor{white}{Bus Topology}}  \tn
\SetRowColor{white}
\mymulticolumn{1}{x{8.4cm}}{Image could not be loaded.} \tn 
\hhline{>{\arrayrulecolor{DarkBackground}}-}
\SetRowColor{LightBackground}
\mymulticolumn{1}{x{8.4cm}}{\seqsplit{http://www.bbc.co.uk/schools/gcsebitesize/ict/datacomm/networktopsrev1.shtml}}  \tn 
\hhline{>{\arrayrulecolor{DarkBackground}}-}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{8.4cm}{X}
\SetRowColor{DarkBackground}
\mymulticolumn{1}{x{8.4cm}}{\bf\textcolor{white}{Star Topology}}  \tn
\SetRowColor{white}
\mymulticolumn{1}{x{8.4cm}}{Image could not be loaded.} \tn 
\hhline{>{\arrayrulecolor{DarkBackground}}-}
\SetRowColor{LightBackground}
\mymulticolumn{1}{x{8.4cm}}{\seqsplit{http://www.bbc.co.uk/schools/gcsebitesize/ict/datacomm/2networksrev6.shtml}}  \tn 
\hhline{>{\arrayrulecolor{DarkBackground}}-}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{8.4cm}{x{1.2 cm} x{6.8 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{2}{x{8.4cm}}{\bf\textcolor{white}{Types of Network}}  \tn
% Row 0
\SetRowColor{LightBackground}
{\bf{PAN}} & {\bf{P}}ersonal {\bf{A}}rea {\bf{N}}etwork - a network comprising only a small number of devices belonging to only one individual (e.g. Bluetooth). \tn 
% Row Count 5 (+ 5)
% Row 1
\SetRowColor{white}
{\bf{LAN}} & {\bf{L}}ocal {\bf{A}}rea {\bf{N}}etwork - a network that encompasses a small area (e.g. one company's network). \tn 
% Row Count 8 (+ 3)
% Row 2
\SetRowColor{LightBackground}
{\bf{WAN}} & {\bf{W}}ide {\bf{A}}rea {\bf{N}}etwork - a network comprising many devices and covering a large area (e.g. the Internet). Often under collective ownership. \tn 
% Row Count 13 (+ 5)
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\end{tabularx}
\par\addvspace{1.3em}


% That's all folks
\end{multicols*}

\end{document}