lab: exercise sheet cut to two pages, three simple steps
One double-sided A4 sheet with 1in margins, still in the LNCS look. 1. Who announces the address you are using: find your current address and its prefix and origin AS, then whois it and your lab prefix. 2. Announce your prefix, read the bytes, find it from outside, ping it. 3. Announce with communities: only the SwissIX route servers, then only SWITCH, with reachability checkboxes, one discussion question, clean up. Sections 1 and 2 fill page one; section 3 has page two. Dropped the ETH lookup, the long registry comparison, NO_EXPORT, the byte-decoding task, the reference appendix and most of the bibliography. Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
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@@ -1,361 +1,191 @@
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% Exercise sheet for the "Hands-on BGP" lecture.
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% Exercise sheet for the "Hands-on BGP" lecture: two A4 pages, one sheet.
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% Springer LNCS class (llncs.cls ships with TeX Live). Build: latexmk -pdf handout.tex
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\documentclass[runningheads,a4paper]{llncs}
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\documentclass[a4paper]{llncs}
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\usepackage[a4paper,margin=1in]{geometry}
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\usepackage[T1]{fontenc}
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\usepackage[utf8]{inputenc}
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\usepackage{microtype}
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\usepackage{booktabs}
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\usepackage{enumitem}
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\usepackage{amssymb}
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\usepackage{xcolor}
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\usepackage{listings}
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\usepackage{tikz}
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\usetikzlibrary{positioning,arrows.meta,fit}
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\usetikzlibrary{positioning,arrows.meta}
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\PassOptionsToPackage{hyphens}{url}
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\usepackage[hidelinks]{hyperref}
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\renewcommand\UrlFont{\ttfamily\small}
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\pagestyle{empty}
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% Floats sit in the text here, so they need less air than in a paper.
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\setlength{\intextsep}{7pt}
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\setlength{\abovecaptionskip}{4pt}
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\setlength{\belowcaptionskip}{0pt}
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% ---- things to change per class -------------------------------------------
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\newcommand{\labhost}{bgplab.rayhaan.net}
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\newcommand{\laburl}{https://\labhost/statusz}
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\newcommand{\labspace}{2a0d:d741::/40}
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\newcommand{\laburl}{https://bgplab.rayhaan.net/statusz}
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\newcommand{\myprefix}{\texttt{2a0d:d741:}\underline{\texttt{\,n\,}}\texttt{::/48}}
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% ---- exercise machinery ------------------------------------------------------
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\lstset{basicstyle=\ttfamily\small,columns=fullflexible,keepspaces=true,
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frame=single,framerule=0.3pt,xleftmargin=1.2em,xrightmargin=0.4em,
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aboveskip=0.6em,belowskip=0.4em,breaklines=true}
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aboveskip=0.5em,belowskip=0.3em}
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\newcounter{task}[section]
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\renewcommand{\thetask}{\thesection.\arabic{task}}
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\newcommand{\task}[1]{\refstepcounter{task}\medskip\noindent
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\textbf{Task \thetask}\enspace\textit{#1}\par\nobreak\smallskip\noindent\ignorespaces}
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% Dotted lines to write on: \answer[3] gives three.
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\newcommand{\task}[1]{\refstepcounter{task}\smallskip\noindent
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\textbf{Task \thetask}\enspace\textit{#1}\enspace\ignorespaces}
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\newcommand{\answer}[1][1]{\par\nobreak
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\foreach \i in {1,...,#1}{\vspace{1.05em}\noindent\makebox[\linewidth]{\dotfill}\par}\smallskip}
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% Fill-in rows: the dots always run to the margin, never past it.
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\newcommand{\fillin}[1]{\par\nopagebreak\noindent #1~\dotfill\par\vspace{0.5em}}
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\newcommand{\fillintwo}[2]{\par\nopagebreak\noindent
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\parbox[t]{0.485\linewidth}{#1~\dotfill}\hfill\parbox[t]{0.485\linewidth}{#2~\dotfill}\par\vspace{0.5em}}
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\newcommand{\fillinthree}[3]{\par\nopagebreak\noindent
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\parbox[t]{0.42\linewidth}{#1~\dotfill}\hfill\parbox[t]{0.27\linewidth}{#2~\dotfill}\hfill\parbox[t]{0.27\linewidth}{#3~\dotfill}\par\vspace{0.5em}}
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\foreach \i in {1,...,#1}{\vspace{1.0em}\noindent\makebox[\linewidth]{\dotfill}\par}\smallskip}
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\newcommand{\fillintwo}[2]{\par\nopagebreak\smallskip\noindent
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\parbox[t]{0.485\linewidth}{#1~\dotfill}\hfill\parbox[t]{0.485\linewidth}{#2~\dotfill}\par\vspace{0.4em}}
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\newcommand{\fillinthree}[3]{\par\nopagebreak\smallskip\noindent
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\parbox[t]{0.32\linewidth}{#1~\dotfill}\hfill\parbox[t]{0.32\linewidth}{#2~\dotfill}\hfill\parbox[t]{0.32\linewidth}{#3~\dotfill}\par\vspace{0.4em}}
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\newcommand{\cbox}{$\square$\;}
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% The reachability check that recurs through the sheet.
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\newcommand{\reach}{\par\nopagebreak\smallskip\noindent
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\begin{tabular}{@{}l@{\hspace{2em}}l@{}}
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\cbox laptop, university network: reachable & \cbox phone, mobile data: reachable
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\end{tabular}\par\smallskip}
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Reachable from:\hspace{1.2em}\cbox laptop on the university network\hspace{2em}\cbox phone on mobile data\par\smallskip}
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\begin{document}
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\title{Hands-on BGP:\\Announcing and Steering a Prefix on the Internet}
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\subtitle{Exercise sheet}
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\titlerunning{Hands-on BGP: exercise sheet}
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\title{Hands-on BGP: Announcing and Steering a Prefix}
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\author{Rayhaan Jaufeerally}
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\authorrunning{Network Security, 2026}
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\institute{Network Security, ETH Z\"urich\\
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\email{Lab page: \url{\laburl}}}
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\institute{Network Security, ETH Z\"urich \qquad Lab page: \url{\laburl}}
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\maketitle
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\begin{abstract}
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In this exercise you take an IPv6 prefix that is registered for you, find out
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what the Internet's registries say about it, announce it to the real Internet
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with BGP, and then use BGP communities to decide which networks may learn it.
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By the end your prefix should be reachable from the university network and
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from nowhere else. Work through the tasks in order and write your answers on
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this sheet; the questions marked \emph{Think} are for discussion.
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\keywords{BGP \and IPv6 \and RIPE database \and route servers \and BGP communities}
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You look up who announces the address you are using right now, announce an
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IPv6 prefix of your own to the real Internet with BGP, and then use BGP
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communities to decide which networks may learn it. By the end your prefix
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should be reachable from the university network and from nowhere else.
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\end{abstract}
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\noindent
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\begin{tabular}{@{}p{0.47\linewidth}@{\hspace{0.06\linewidth}}p{0.47\linewidth}@{}}
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Name: \dotfill & Student number $n$ (decimal): \dotfill \\[0.9em]
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$n$ in hexadecimal: \dotfill & Your prefix: \myprefix
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\end{tabular}
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\medskip\noindent
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Every student has one \texttt{/48} out of the lab's \texttt{\labspace}. The
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third group of your prefix is your student number \emph{written in
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hexadecimal}: student 10 has \texttt{2a0d:d741:a::/48}, student 16 has
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\texttt{2a0d:d741:10::/48}. Fill in the fields above before you continue.
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\parbox[t]{0.44\linewidth}{Name:~\dotfill}\hfill
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\parbox[t]{0.24\linewidth}{Student no.\ $n$:~\dotfill}\hfill
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\parbox[t]{0.27\linewidth}{Prefix: \myprefix}
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\smallskip\noindent
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Your prefix is \myprefix, where \texttt{n} is your student number \emph{in
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hexadecimal}: student 10 has \texttt{2a0d:d741:a::/48}, student 26 has
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\texttt{2a0d:d741:1a::/48}.
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% ==============================================================================
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\section{Who Holds Which Addresses?}
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\section{Who Announces the Address You Are Using?}
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Address space and AS numbers are handed down from IANA to five regional
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registries and on to their members. For Europe the registry is the RIPE NCC,
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and its database is public~\cite{ripedb}.
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\task{Find your address.}
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Open \texttt{bgp.tools} in a browser: the top of the page shows the address
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you are connecting from, the prefix it belongs to, and the network that
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announces that prefix.
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\fillinthree{Your address:}{its prefix:}{announced by AS:}
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\task{Look up your own prefix.}
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Query the RIPE database, with your prefix in place of the example:
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\task{Ask the registry.}
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The RIPE database~\cite{ripedb} records who holds address space
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(\texttt{inet6num}, or \texttt{inetnum} for IPv4) and who may announce it
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(\texttt{route6}, \texttt{route}). Look up your address, then your lab prefix:
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\begin{lstlisting}
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whois -h whois.ripe.net 2a0d:d741:1::/48
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whois -h whois.ripe.net <your address> whois -h whois.ripe.net 2a0d:d741:<n>::/48
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\end{lstlisting}
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(No \texttt{whois} on your machine? The same query works in a
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browser~\cite{ripedb}.) You get an \texttt{inet6num} object describing a block of addresses and a
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\texttt{route6} object saying who may announce a prefix.
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\enlargethispage{2\baselineskip}
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\fillintwo{\texttt{inet6num} block:}{its \texttt{status}:}
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\fillintwo{\texttt{route6} \texttt{origin} AS:}{maintained by (\texttt{mnt-by}):}
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\task{Look up a prefix you use every day.}
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Find an address of \texttt{ethz.ch} and look it up the same way:
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\begin{lstlisting}
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dig +short ethz.ch AAAA
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whois -h whois.ripe.net <the address you got>
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\end{lstlisting}
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\fillinthree{\texttt{inet6num} block:}{\texttt{status}:}{\texttt{origin}:}
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\task{Compare the database with the routing table.}
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The database says who \emph{may} announce a prefix. Whether anybody \emph{does}
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is a different question. Look up both prefixes on RIPEstat
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(\texttt{stat.ripe.net}) or on \texttt{bgp.tools}.
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\fillin{Is ETH's prefix announced, and by which AS?}
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\fillintwo{Is yours?}{That AS belongs to:}
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\medskip\noindent\textbf{Think.}
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ETH's prefix is originated by an AS that is not called ETH. Whose is it, and
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what does that tell you about how the university reaches the Internet? Your
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\texttt{route6} object exists although nobody announces the prefix: what is
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such an object good for?
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\answer[3]
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\fillintwo{Your address: held by (\texttt{netname})}{\texttt{origin} AS:}
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\fillintwo{Your lab prefix: \texttt{origin} AS}{is it announced right now?}
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% ==============================================================================
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\section{Announcing Your Prefix}
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\begin{figure}[t]
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\begin{figure}[h]
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\centering
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\begin{tikzpicture}[font=\footnotesize, node distance=6mm and 8.5mm,
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box/.style={draw, rounded corners=1.5pt, minimum height=8mm, inner xsep=3pt, align=center},
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\begin{tikzpicture}[font=\footnotesize, node distance=5mm and 11mm,
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box/.style={draw, rounded corners=1.5pt, minimum height=7.5mm, inner xsep=4pt, align=center},
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bgp/.style={-{Stealth[length=2mm]}, dashed}, web/.style={-{Stealth[length=2mm]}}]
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\node[box] (you) {you\\[-1pt]\scriptsize browser};
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\node[box, right=of you] (ferrix) {lab daemon\\[-1pt]\scriptsize AS4200000001};
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\node[box, right=of ferrix] (pr) {\texttt{pr01.rue}\\[-1pt]\scriptsize AS210036};
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\node[box, right=of pr] (rs) {SwissIX\\[-1pt]\scriptsize route servers\\[-1pt]\scriptsize AS42476};
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\node[box, right=of rs] (sw) {SWITCH\\[-1pt]\scriptsize AS559\\[-1pt]\scriptsize (ETH Z\"urich)};
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\node[box, below=5mm of rs] (other) {other exchanges,\\[-1pt]transit};
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\node[box, right=of pr] (rs) {SwissIX route servers\\[-1pt]\scriptsize AS42476};
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\node[box, right=of rs] (sw) {SWITCH (ETH)\\[-1pt]\scriptsize AS559};
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\node[box, below=4mm of rs] (other) {other exchanges, transit};
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\draw[web] (you) -- node[above, inner sep=1.5pt]{\tiny HTTPS} (ferrix);
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\draw[bgp] (ferrix) -- node[above, inner sep=1.5pt]{\tiny BGP} (pr);
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\draw[bgp] (pr) -- (rs);
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\draw[bgp] (rs) -- (sw);
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\draw[bgp] (pr) |- (other);
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\end{tikzpicture}
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\caption{The lab. Your browser talks to a small BGP daemon, which announces
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your prefix to the router \texttt{pr01.rue}. That router peers at several
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Internet exchanges and buys transit. Dashed arrows are BGP sessions.}
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\caption{The lab. Dashed arrows are BGP sessions~\cite{rfc4271}; everything right of
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\texttt{pr01.rue} is the real Internet.}
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\label{fig:lab}
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\end{figure}
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Open \url{\laburl} and log in with the credentials given in class. The page
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belongs to the lab daemon of Fig.~\ref{fig:lab}. It speaks
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BGP~\cite{rfc4271} to \texttt{pr01.rue}, and whatever you announce here
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reaches the real Internet within a minute or two. Use the \emph{auto-refresh}
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link at the top right to keep the tables current.
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\task{Look before you touch.}
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\noindent\begin{minipage}{\linewidth}
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Read the \emph{Peers} table, then open the \emph{Configuration} line under
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the header.
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\fillintwo{Neighbour's AS number:}{session state:}
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\fillintwo{The daemon's own AS number:}{it only accepts prefixes in:}
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\end{minipage}
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\task{Announce.}
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Enter your name as \emph{owner} and your prefix, leave everything else
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untouched, and press \emph{Announce}. Only the owner can withdraw a route, so
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spell your name the same way each time.
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Open \url{\laburl} (credentials are given in class). Enter your name as
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\emph{owner} and your prefix, leave everything else untouched, and press
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\emph{Announce}. Only the owner can withdraw a route, so spell your name the
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same way each time.
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\task{Read the message you just sent.}
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\task{Read what you sent.}
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Click \emph{bytes} next to your route and hover over the coloured segments.
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An UPDATE is a header, two length fields, a list of path attributes, and a
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list of IPv4 prefixes.
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\fillintwo{AS number(s) in \texttt{AS\_PATH}:}{attribute carrying your prefix:}
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\fillintwo{Length of the message, in bytes:}{AS number(s) in \texttt{AS\_PATH}:}
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\fillin{Your prefix is carried in the attribute named}
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\noindent It is not in the prefix list at the end of the message. Why?
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\answer[2]
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\task{See it from the outside.}
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Wait two minutes, then look your prefix up again on RIPEstat or
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\texttt{bgp.tools}.
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\fillintwo{Origin AS seen by the world:}{an AS path you found:}
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\noindent The daemon's AS4200000001 is missing from that path. Where did it go, and why
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is that necessary? (Hint: RFC~6996~\cite{rfc6996}.)
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\answer[2]
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\task{See it from outside.}
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Wait two minutes, then look your prefix up on \texttt{bgp.tools}.
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\fillintwo{Origin AS the world sees:}{an AS path you found:}
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\noindent The lab daemon's AS4200000001 is missing from that path. Where did it go, and why?
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\answer[1]
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\task{Reach it.}
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The router answers for every address in the lab space, so your prefix is
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reachable exactly when your announcement got out. From your laptop, and from
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your phone \emph{on mobile data}:
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\begin{lstlisting}
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ping -6 2a0d:d741:<n>::1 traceroute -6 2a0d:d741:<n>::1
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\end{lstlisting}
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reachable exactly when your announcement got out:\quad
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\texttt{ping -6 2a0d:d741:<n>::1}
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\reach
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% ==============================================================================
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\section{Steering Your Prefix with Communities}
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% Let the opening paragraph finish on this page; the table then opens the next.
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\enlargethispage{4\baselineskip}
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{\interlinepenalty=10000
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A community is a tag on a route. It means whatever the network that reads it
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has decided it means~\cite{rfc1997,rfc8092}. Table~\ref{tab:communities}
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lists the ones you need. Two networks act on them in turn: first our router
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\texttt{pr01.rue}, then the SwissIX route servers~\cite{swissix}, which pass
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routes between the members of the exchange.\par}
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A community is a tag on a route; it means whatever the network reading it has
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decided it means~\cite{rfc8092}. Two networks act on yours in turn: first our
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router \texttt{pr01.rue}, then the SwissIX route servers~\cite{swissix}, which
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pass routes between the members of the exchange. The page's preset menu has
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all of the communities below.
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\begin{table}[!htb]
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\begin{table}[h]
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\centering
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\caption{Large communities for this exercise, written
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\texttt{who:function:target}. Within one network, \emph{never} beats
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\emph{announce}, which beats \emph{nowhere}. The page's preset menu has all of
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them.}
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\label{tab:communities}
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\begin{tabular}{@{}l@{\hspace{1.4em}}l@{\hspace{1.4em}}l@{}}
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\begin{tabular}{@{}l@{\hspace{1.6em}}l@{\hspace{1.6em}}l@{}}
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\toprule
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Community & Read by & Effect \\
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Large community & Read by & Effect \\
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\midrule
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\texttt{210036:0:0} & \texttt{pr01.rue} & announce nowhere \ldots \\
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\texttt{210036:1:42476} & \texttt{pr01.rue} & \ldots except to AS42476 (SwissIX route servers) \\
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\texttt{210036:0:}\textit{as} & \texttt{pr01.rue} & never announce to neighbour \textit{as} \\
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\texttt{210036:1:42476} & \texttt{pr01.rue} & \ldots except to AS42476, the SwissIX route servers \\
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\midrule
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\texttt{42476:0:0} & SwissIX & send to no member \ldots \\
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\texttt{42476:1:559} & SwissIX & \ldots except AS559, SWITCH \\
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\texttt{42476:0:}\textit{as} & SwissIX & never send to member \textit{as} \\
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\midrule
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\texttt{NO\_EXPORT} & everyone & keep the route, pass it to no other AS \\
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\texttt{42476:1:559} & SwissIX & \ldots except AS559, SWITCH, the network ETH is part of \\
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\bottomrule
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\end{tabular}
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\end{table}
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\task{One exchange only.}
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Announce your prefix again, now with the large communities
|
||||
\texttt{210036:0:0} and \texttt{210036:1:42476}. Announcing a prefix you
|
||||
already own replaces it. \emph{Before} you look: who do you expect to still
|
||||
see it?
|
||||
Announce your prefix again with \texttt{210036:0:0} and
|
||||
\texttt{210036:1:42476}; announcing a prefix you own replaces it. Before you
|
||||
look: who do you expect to still see it?
|
||||
\answer[1]
|
||||
\noindent Wait two minutes and check.
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||||
\fillin{Origin and path now:}
|
||||
\noindent Wait two minutes, then check on \texttt{bgp.tools} and with \texttt{ping}.
|
||||
\reach
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||||
|
||||
\task{The university only.}
|
||||
Add \texttt{42476:0:0} and \texttt{42476:1:559} to the two you already have,
|
||||
and announce again. Our router now tells only the route servers, and the route
|
||||
servers tell only SWITCH, the network ETH is part of.
|
||||
|
||||
Add \texttt{42476:0:0} and \texttt{42476:1:559} to the two you already have and
|
||||
announce again. Our router now tells only the route servers, and they tell
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||||
only SWITCH.
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||||
\reach
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||||
\noindent Is your prefix still visible on RIPEstat or bgp.tools? Explain what you see.
|
||||
\noindent Is your prefix still visible on \texttt{bgp.tools}? Explain what you see.
|
||||
\answer[2]
|
||||
|
||||
\task{Find the communities in the bytes.}
|
||||
Open \emph{bytes} again and find \texttt{LARGE\_COMMUNITIES}. Each community
|
||||
is three 32-bit numbers. $42476$ is \texttt{a5ec} in hexadecimal; write down
|
||||
the twelve bytes of \texttt{42476:1:559}:
|
||||
\answer[1]
|
||||
\noindent Now compare with what the rest of the world received: the
|
||||
\texttt{210036:\ldots} communities are gone but the \texttt{42476:\ldots} ones
|
||||
are still there. Who removed them, and why only those?
|
||||
\answer[2]
|
||||
|
||||
\task{A well-known community.}
|
||||
Remove all large communities and set the (standard) community
|
||||
\texttt{NO\_EXPORT} instead. Predict who will learn the route, then check.
|
||||
\answer[2]
|
||||
|
||||
\task{Clean up.}
|
||||
Withdraw your prefix. How long does it take to disappear from the looking
|
||||
glass, and what did the withdrawal look like compared to the announcement?
|
||||
\answer[2]
|
||||
|
||||
\medskip\noindent\textbf{Think.}
|
||||
\task{Think.}
|
||||
You steered routing in two networks you do not operate, using nothing but
|
||||
numbers attached to a route. What would happen if you attached a community
|
||||
that one of \emph{their} upstreams acts on? Look at the \emph{Configuration}
|
||||
on the lab page and at Table~\ref{tab:communities}: which communities were you
|
||||
\emph{not} allowed to send, and who decided that?
|
||||
\answer[3]
|
||||
numbers attached to a route. What stops you from attaching a community that
|
||||
one of \emph{their} upstreams acts on?
|
||||
\answer[2]
|
||||
|
||||
\begin{thebibliography}{8}
|
||||
\task{Clean up.} Withdraw your prefix and watch it disappear.
|
||||
|
||||
\begin{thebibliography}{4}
|
||||
\small
|
||||
\bibitem{rfc4271} Rekhter, Y., Li, T., Hares, S.: A Border Gateway Protocol 4 (BGP-4). RFC 4271 (2006)
|
||||
\bibitem{rfc1997} Chandra, R., Traina, P., Li, T.: BGP Communities Attribute. RFC 1997 (1996)
|
||||
\bibitem{rfc8092} Heitz, J., Snijders, J., Patel, K., Bagdonas, I., Hilliard, N.: BGP Large Communities Attribute. RFC 8092 (2017)
|
||||
\bibitem{rfc6996} Mitchell, J.: Autonomous System (AS) Reservation for Private Use. RFC 6996 (2013)
|
||||
\bibitem{ripedb} RIPE NCC: RIPE Database Query, \url{https://apps.db.ripe.net/db-web-ui/query}
|
||||
\bibitem{swissix} SwissIX: Action BGP Communities, \url{https://www.swissix.ch/resources/action-bgp-communities/}
|
||||
\end{thebibliography}
|
||||
|
||||
\clearpage
|
||||
\appendix
|
||||
\section{Reference}
|
||||
\small
|
||||
|
||||
\noindent\textbf{IPv6 notation.} An address is 128 bits, written as eight
|
||||
groups of four hexadecimal digits. Leading zeros in a group may be dropped,
|
||||
and one run of all-zero groups may be written \texttt{::}. A prefix
|
||||
\texttt{2a0d:d741:1::/48} fixes the first 48 bits and leaves the rest free.
|
||||
Hexadecimal digits: \texttt{a}\,=\,10, \texttt{b}\,=\,11, \texttt{c}\,=\,12,
|
||||
\texttt{d}\,=\,13, \texttt{e}\,=\,14, \texttt{f}\,=\,15; for a two-digit value,
|
||||
$n = 16 \cdot \mathit{first} + \mathit{second}$, so $26 = \texttt{1a}$.
|
||||
|
||||
\begin{table}[!htb]
|
||||
\centering
|
||||
\caption{Anatomy of a BGP UPDATE message~\cite{rfc4271}.}
|
||||
\begin{tabular}{@{}l@{\hspace{1.4em}}l@{\hspace{1.4em}}l@{}}
|
||||
\toprule
|
||||
Bytes & Field & Contents \\
|
||||
\midrule
|
||||
16 & marker & all ones; marks a message boundary \\
|
||||
2 & length & of the whole message, 19 to 4096 bytes \\
|
||||
1 & type & 1 OPEN, 2 UPDATE, \\
|
||||
& & 3 NOTIFICATION, 4 KEEPALIVE \\
|
||||
\midrule
|
||||
2 + $w$ & withdrawn routes & IPv4 prefixes no longer reachable \\
|
||||
2 + $a$ & path attributes & everything about the route \\
|
||||
rest & NLRI & IPv4 prefixes being announced \\
|
||||
\bottomrule
|
||||
\end{tabular}
|
||||
\end{table}
|
||||
|
||||
\begin{table}[!htb]
|
||||
\centering
|
||||
\caption{Path attributes you will meet. Each is sent as flags, type, length,
|
||||
value. Flag bits: \texttt{0x80} optional, \texttt{0x40} transitive (passed on
|
||||
even by routers that do not understand it), \texttt{0x10} two-byte length.}
|
||||
\begin{tabular}{@{}r@{\hspace{1.2em}}l@{\hspace{1.4em}}l@{}}
|
||||
\toprule
|
||||
Type & Name & Meaning \\
|
||||
\midrule
|
||||
1 & \texttt{ORIGIN} & how the route entered BGP \\
|
||||
2 & \texttt{AS\_PATH} & networks crossed: nearest first, origin last \\
|
||||
3 & \texttt{NEXT\_HOP} & where to send the packets (IPv4) \\
|
||||
4 & \texttt{MULTI\_EXIT\_DISC} & hint to the neighbour; lower is preferred \\
|
||||
8 & \texttt{COMMUNITIES} & 32-bit tags, written \texttt{a:b}~\cite{rfc1997} \\
|
||||
14 & \texttt{MP\_REACH\_NLRI} & IPv6 (and other) prefixes, with their next hop \\
|
||||
32 & \texttt{LARGE\_COMMUNITIES} & three 32-bit numbers, written \texttt{a:b:c}~\cite{rfc8092} \\
|
||||
\bottomrule
|
||||
\end{tabular}
|
||||
\end{table}
|
||||
|
||||
\noindent\textbf{Glossary.}
|
||||
\begin{description}[leftmargin=2.4cm,style=sameline,itemsep=0pt,topsep=2pt,parsep=0pt]
|
||||
\item[AS] Autonomous system: a network under one administration, identified
|
||||
by a number. Numbers from 4200000000 upwards are for private use~\cite{rfc6996}.
|
||||
\item[Prefix] Addresses sharing their leading bits. The longest matching prefix wins.
|
||||
\item[Transit] Paying a provider to carry your traffic to and from the whole Internet.
|
||||
\item[Peering] Two networks exchanging their own and their customers' routes, usually for free.
|
||||
\item[Exchange] An IX: a shared Ethernet network where many networks meet to peer.
|
||||
\item[Route server] Passes routes between members of an exchange; carries no traffic.
|
||||
\item[\texttt{route6}] A database object stating that an AS may originate an IPv6 prefix.
|
||||
\end{description}
|
||||
|
||||
|
||||
|
||||
\end{document}
|
||||
Reference in new issue
Block a user