\documentclass[10pt,a4paper]{article}

% Packages
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\usepackage{multicol}           % Allows multicols in tables
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\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{Sywise98}
\pdfinfo{
  /Title (computer-communiation-exam1.pdf)
  /Creator (Cheatography)
  /Author (Sywise98)
  /Subject (Computer Communiation Exam1 Cheat Sheet)
}

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% This two commands together give roughly
% the right line height in the tables
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% 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
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% Header and Footer
\pagestyle{fancy}
\fancyhead{} % Set header to blank
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\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}}
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\columnbreak
\begin{tabulary}{11cm}{L}
    \vspace{-2pt}\large{\bf{\textcolor{DarkBackground}{\textrm{Computer Communiation Exam1 Cheat Sheet}}}} \\
    \normalsize{by \textcolor{DarkBackground}{Sywise98} via \textcolor{DarkBackground}{\uline{cheatography.com/116841/cs/21786/}}}
\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}Sywise98 \\
  \uline{cheatography.com/sywise98} \\
  \end{tabulary}
\vfill
\columnbreak
\begin{tabulary}{5.8cm}{L}
  \SetRowColor{FootBackground}
  \mymulticolumn{1}{p{5.377cm}}{\bf\textcolor{white}{Cheat Sheet}}  \\
   \vspace{-2pt}Not Yet Published.\\
   Updated 16th February, 2020.\\
   Page {\thepage} of \pageref{LastPage}.
\end{tabulary}
\vfill
\columnbreak
\begin{tabulary}{5.8cm}{L}
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  \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*}{4}

\begin{tabularx}{3.833cm}{p{0.3433 cm} p{0.3433 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{2}{x{3.833cm}}{\bf\textcolor{white}{Protocols}}  \tn
% Row 0
\SetRowColor{LightBackground}
\mymulticolumn{2}{x{3.833cm}}{define format, order of messages sent and received among network entities, and actions taken on message transmission, receipt} \tn 
% Row Count 3 (+ 3)
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\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{3.833cm}{x{1.7165 cm} x{1.7165 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{2}{x{3.833cm}}{\bf\textcolor{white}{network structure}}  \tn
% Row 0
\SetRowColor{LightBackground}
access networks, physical media:wired, wireless communication links & TDM = time division multiplexing time divided into frames fixed duration fixed number time slots \tn 
% Row Count 5 (+ 5)
% Row 1
\SetRowColor{white}
\mymulticolumn{2}{x{3.833cm}}{network core: •interconnected routers•network of networks} \tn 
% Row Count 7 (+ 2)
% Row 2
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\mymulticolumn{2}{x{3.833cm}}{FDM = frequency division multiplexing: diff CHs transmitted in diff frequency bands} \tn 
% Row Count 9 (+ 2)
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\par\addvspace{1.3em}

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% Row 0
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4 Sources of packet delays & dnodal = dproc + dqueue + dtrans +dprop \tn 
% Row Count 2 (+ 2)
% Row 1
\SetRowColor{white}
dproc : nodal processing, check bit errors, determine output link & dqueue: queueing delay, time waiting at output link for transmission, depends on congestion of router \tn 
% Row Count 8 (+ 6)
% Row 2
\SetRowColor{LightBackground}
dtrans: how long it takes to get on link & L (bits)/R(bps) \tn 
% Row Count 10 (+ 2)
% Row 3
\SetRowColor{white}
dprop: propagation delay & d (m)/s \tn 
% Row Count 12 (+ 2)
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\par\addvspace{1.3em}

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\mymulticolumn{2}{x{3.833cm}}{\bf\textcolor{white}{Stacks}}  \tn
% Row 0
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IP & application(http), transport(TCP), network(IP),  link(WiFi), physical(bits) \tn 
% Row Count 3 (+ 3)
% Row 1
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\seqsplit{ISO/OSI} & app, session(checkpointing), transport, network, link, physical \tn 
% Row Count 5 (+ 2)
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\par\addvspace{1.3em}

\begin{tabularx}{3.833cm}{x{1.81949 cm} x{1.61351 cm} }
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\mymulticolumn{2}{x{3.833cm}}{\bf\textcolor{white}{TCP / UDP}}  \tn
% Row 0
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transmission control protocol & user datagram protocol \tn 
% Row Count 2 (+ 2)
% Row 1
\SetRowColor{white}
reliable transport, flow control, congestion control, DNP( timing, minimum throughput guarantee, security), connection-oriented & unreliable data transfer, DNP \tn 
% Row Count 9 (+ 7)
% Row 2
\SetRowColor{LightBackground}
 & 1 IP \& 1 port \tn 
% Row Count 10 (+ 1)
% Row 3
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 & streaming, DNS (domain name system) \tn 
% Row Count 12 (+ 2)
\hhline{>{\arrayrulecolor{DarkBackground}}--}
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\par\addvspace{1.3em}


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

\end{document}