\documentclass[border=2mm]{standalone}

\usepackage[most]{tcolorbox}
\usepackage{lmodern}
\usepackage{lipsum}
%\usepackage{geometry}

\standaloneenv{tcbposter}

%\pagestyle{empty}
\begin{document}

\begin{tcbposter}[%
    poster = {columns=8, rows=9, width=17cm, height=8cm, spacing=1mm},% showframe},
    boxes = {colback=cyan!80!black, 
        boxrule=0pt, arc=2mm,
        colframe=cyan!80!black, 
        halign=center, valign=center,   
        colupper=white,
        fontupper=\sffamily\bfseries, size=small}
]
%1st row
\posterbox{column=1, row=1}{HTTP}
\posterbox{column=2, row=1}{HTTP/2}
\posterbox{column=3, row=1}{MQTT}
\posterbox{column=4, row=1}{CoAP}
\posterbox{column=5, row=1}{FTP}
\posterbox{column=6, row=1}{TFTP}

%2nd row
\posterbox{column=1, row=2}{SMTP}
\posterbox{column=2, row=2}{SNTP}
\posterbox{column=3, row=2}{DNS}
\posterbox{column=4, row=2}{NetBIOS}
\posterbox{column=5, row=2, span=2}{SNMPv1/v2c/v3}

%3rd row
\posterbox{column=1, row=3, span=2}{WebSocket}
\posterbox{column=3, row=3}{mDNS}
\posterbox{column=4, row=3}{DNS-SD}
\posterbox{column=5, row=3}{DHCP}
\posterbox{column=6, row=3}{DHCPv6}

%4th row
\posterbox{column=1, row=4,span=6}{Socket}

%5th row
\posterbox{column=1, row=5, span=2.5}{TCP}
\posterbox{column*=5, row=5, span=2.5}{UDP}
\posterbox{column=6, row=5}{RAW}

%6th row
\posterbox{column=1, row=6, span=3}{IPv4}
\posterbox{column=4, row=6, span=3}{IPv6}

%7th row
\posterbox{column=1, row=7, span=1.5}{ARP}
\posterbox{column*=3, row=7, span=1.5}{Auto-IP}
\posterbox{column=4, row=7, span=1.5}{NDP}
\posterbox{column*=6, row=7, span=1.5}{SLAAC}

%8th row
\posterbox{column=1, row=8, span=1.5}{ICMP}
\posterbox{column*=3, row=8, span=1.5}{IGMPv2}
\posterbox{column=4, row=8, span=1.5}{ICMPv6}
\posterbox{column*=6, row=8, span=1.5}{MLDv1}

%9th row
%5 boxes and 4 separations should use 
%equivalent to 6 original boxes plus 5 
%separations 
\newlength{\mylength}
\pgfmathsetlength{\mylength}{(6*\tcbpostercolwidth+\tcbpostercolspacing)/5}%

%Use `width` instead of `span` to fix box size
\posterbox[width=\mylength]{name=91, column=1, row=9}{Ethernet}
\posterbox[width=\mylength]{name=92, column=1, row=9, xshift=\mylength+\tcbpostercolspacing}{Wi-Fi}
\posterbox[width=\mylength]{name=92, column=1, row=9, xshift=2*\mylength+2*\tcbpostercolspacing}{PPP}
\posterbox[width=\mylength]{name=92, column=1, row=9, xshift=3*\mylength+3*\tcbpostercolspacing}{USB/RNDIS}
\posterbox[width=\mylength]{column*=6, row=9}{G3-PLC}

%Right column
\posterbox[colback=gray, colframe=gray, colupper=black]{column=7, row=1, span=2, rowspan=3}{7 - Application}
\posterbox[colback=gray!80, colframe=gray!80, colupper=black]{column=7, row=4, span=2}{5 - Session}
\posterbox[colback=gray!60, colframe=gray!60, colupper=black]{column=7, row=5, span=2}{4 - Transport}
\posterbox[colback=gray!40, colframe=gray!40, colupper=black]{column=7, row=6, span=2, rowspan=3}{3 - Network}
\posterbox[colback=gray!20, colframe=gray!20, colupper=black]{column=7, row=9, span=2}{2 - Data Link}

\end{tcbposter}

\end{document}