Add an image of network types

PDF/A compliant!

en/chap02.tex

@@ -29,7 +29,7 @@ exchanged messages. First, each network elects a \emph{designated router} (or
 DR) which coordinates exchange of the messages in that network segment.
 Second, the system can be partitioned into \emph{areas}. That way, the frequent
 LSAs are only flooded throughout a limited set of networks; the \emph{area
-border routers} send accumulated LSAs into other areas.\footnote{These
+border routers} (ABRs) send accumulated LSAs into other areas.\footnote{These
 inter-area LSAs are called \uv{Summary LSAs}, but there is no requirement that
 the routing information is actually aggregated.} These LSAs do not describe the
 topology of the originating area.
@@ -48,6 +48,14 @@ originating from or destinated to that network. For representing routes outside
 of the area and the whole system, OSPF recognises \emph{extra-area} and
 \emph{external} networks respectively. It is also possible for a router to be
 adjacent to an extra-area router through a point-to-point link.
+Figure.~\ref{fig:nettypes} shows the same classification visually.
+
+\begin{figure}[h]
+	\centering
+	\includegraphics[width=12cm]{../img/types-of-networks.pdf}
+	\caption{Types of networks as seen from the cyan area.}
+	\label{fig:nettypes}
+\end{figure}
 
 Once the router has complete information about the topology of an area, it
 constructs a graph representation of the network and calculates the shortest path