More intro

en/intro.tex

@@ -1,19 +1,116 @@
 \chapter*{Introduction}
 \addcontentsline{toc}{chapter}{Introduction}
 
-\section{Terminology}
+Network administrators need to be aware of the
+current state of their networks. While routing protocols like OSPF often need
+to have complete information about the state of the networks, we did not find
+an existing project that would visualise this data easily. We have therefore
+created a rather simple program called Birdvisu, which aims to fill this hole.
 
-\section{Notation}
+Apart from visualising the topology, we provide the user with basic analysis
+tools like showing the shortest path DAGs for routers. Furthermore, the
+architecture of Birdvisu will allow enhancing the data from the routing
+protocol with additional data, e.g. the utilization of particular links.
 
-% Also note the use of Cisco icons
+\X{mov?}While the primary motivation for implementing Birdvisu was the need of the
+author, we believe that it might be useful for various OSPF deployments like
+community wireless networks or homelabs\X{2x glos}.
 
-\section{Structure of the thesis}
+\section*{Terminology}
+\addcontentsline{toc}{section}{Terminology}
+
+In this thesis, we use the word \emph{host} to mean a device connected to a
+network and capable of processing (sending, receiving, forwarding, \dots) IP packets.
+
+An \emph{administrator} is a person or a group of people, who provide the
+routers with configuration and who make sure that the routers (and other
+infrastructure) functions correctly.
+
+The word \emph{network} will always denote a set of hosts, that can exchange
+packets \uv{directly}, without forwarding, under normal circumstances. While
+this is somewhat synonymous with the term \emph{network segment}, when the
+network splits, there may be multiple link-layer segments belonging to the same
+network.
+
+We say that a router is said to be \emph{incident} to a network when it has an
+interface into it. For simplicity, we also say that that network is incident to
+that router (that is, the incidence relation is symmetrical). We say that
+a router is a \emph{neighbour} of another router, when they are incident to a
+shared network, and conversely, that two networks are neighbours when they
+share a router.
+
+We will use the word \emph{network system} (or just \emph{system}) to describe a
+set of network managed by a single administrator, which is intended to forward
+packets across it. This can mean the whole autonomous system\footnote{This is
+where we borrowed the word \uv{system} from.}, but often this is a much smaller
+part. When we speak about routing using OSPF, a system is only the set of
+networks that run a single instance of OSPF.
+
+By the term \emph{IP} we mean the Internet Protocol of either version 4 or 6.
+When it is important to distinguish, we explicitly write \emph{IPv4} or
+\emph{IPv6}. IP may also denote an IP address, as in \uv{a router has an IP},
+but this usage should be clear from the context.
+
+We distinguish between \emph{routing} as the act of finding next hops\X{glos},
+and \emph{forwarding}, the act of sending a received packet through an
+interface according to a \emph{routing table}. (Whether the routing table is
+distinct from the network-layer forwarding table is an implementation detail.)
+
+A \emph{topology} describes the connections in the network system, i.e. which
+router is connected to which networks, with what costs etc. We use the term
+\emph{graph} only when talking about visualisation of the network to
+distinguish between the real state and a virtual one. Moreover, in
+section~\ref{s:net-idiosyncracies} we will see that a topology is in fact not a
+graph (as understood by graph theory).
+
+\medskip
+
+We will be using many other networking terms, which we hope are well-known, but
+for the sake of completeness, we provide a \hyperref[ch:glossary]{glossary} and
+a \hyperref[ch:abbrs]{list of abbreviations} at the end of this thesis.
+
+\section*{Notation}
+\addcontentsline{toc}{section}{Notation}
+
+We write filenames and commands in monospace font, like in \texttt{rm -rf
+/bin}. Snippets of code are also written in monospace, but when we speak of a
+particular class in text, it is only capitalised, as in \uv{The keys of the
+dictionary are VertexIDs}.
+
+For network diagrams, we use the Network topology icons from
+Cisco\cite{cisco-icons}. The basic icons are shown on
+Figure~\ref{fig:basic-icons}.
+
+\begin{figure}[h]
+	\centering
+	\begin{subfigure}[b]{0.3\textwidth}
+		\centering
+		\X{Router}
+		\caption*{Router}
+	\end{subfigure}
+	\begin{subfigure}[b]{0.3\textwidth}
+		\centering
+		\X{Network}
+		\caption*{Network}
+	\end{subfigure}
+	\begin{subfigure}[b]{0.3\textwidth}
+		\centering
+		\X{Switch}
+		\caption*{Switch}
+	\end{subfigure}
+	\caption{Basic Cisco network icons}
+	\label{fig:basic-icons}
+\end{figure}
+
+\section*{Structure of the thesis}
+\addcontentsline{toc}{section}{Structure of the thesis}
 
 %- motivation
 %	-tgt audience of birdvisu
 %	- previous work / other approaches to network monitoring
+%		- And why we do not like them
 %	- Problem statement / project goals
-%		- Non-goals
+%		- Non-goals and future goals
 %- Analysis / Survey (behaviour of computer networks)
 %	- gennet as a method of testing behaviour
 %	- OSPF
@@ -24,6 +121,7 @@
 %	- Project structure / overview
 %	- Annotators
 %	- handles
+%	- Handling expected expansion
 %- Usage
 %- Evaluation?
 %	- Home