[-,thick,%
		  every node/.style={shape=rectangle,inner sep=1pt,thick}, level distance=1.2cm]
		\node {VPN} [edge from parent fork down]
		  [sibling distance=8cm]
		  child {node {overlay}
		    [sibling distance=4cm]
		    child {node {livello 2}
		    [sibling distance=2cm]
		     child {node[align=center] {connection\\oriented}
		     [sibling distance=1cm]
		      child {node[align=center] {Frame\\Relay}}
		      child {node {ATM}}}
		     child {node {MPLS}}}
		    child {node {livello 3}
		    [sibling distance=2cm]
		     child {node {site-to-site}
		     [sibling distance=1cm]
		      child {node {IPsec}}
		      child {node {GRE}}}
		     child {node {di accesso}}
		     [sibling distance=1cm]
		      child {node {PPTP}}
		      child {node {L2TP}}}
		    child {node {livello 4}
		     child {node {SSL}}}}
		  child {node {peer}
		    child {node {livello 3}}
		    [sibling distance=4cm]
		     child {node[align=center] {senza\\MPLS}
		     [sibling distance=2cm]
		      child {node[align=center] {router\\dedicato}}
		      child {node[align=center] {router\\condiviso}}}
		     child {node {MPLS}
		     [sibling distance=2cm]
		      child {node {BGP}}
		      child {node[align=center] {virtual\\router}}}};