+
+ \draw [fill=white]
+ ([xshift=1em,yshift=-2em]1.south west)
+ -- ([xshift=1em,yshift=-1em]1.south west)
+ -- ([yshift=-1em,xshift=1em]1.south east)
+ -- ([xshift=1em]1.north east)
+ -- ([xshift=3em]1.north east)
+ -- node [draw=none,midway,sloped,below,yshift=-2pt] {network} ([xshift=3em]3.south east)
+ -- ([xshift=1em]3.south east)
+ -- ([yshift=1em,xshift=1em]3.north east)
+ -- ([xshift=1em,yshift=1em]3.north west)
+ -- ([xshift=1em,yshift=2em]3.north west)
+ -- ([yshift=2em,xshift=1em]3.north east)
+ -- ([yshift=-2em,xshift=1em]1.south east)
+ -- cycle;
+
+ \draw [densely dotted] (1.south) -- (2.north);
+ \draw [densely dotted] (2.south) -- (3.north);