\centering
\begin{pspicture}(8,3)
%    \showgrid
    \psset{nodesep=2pt, arrows=<->}

    \cnodeput(4,2.5){PR}{Prov.}
    \cnodeput(4,1.25){AS}{AS}
    \cnodeput(1.5,1.25){PE1}{Peer 1}
    \cnodeput(6.5,1.25){PE2}{Peer 2}
    \cnodeput(4,0){C1}{Cust.}

    \ncline{AS}{PR}
    \ncline{C1}{AS}
    \ncline{PE1}{AS}
    \ncline{PE2}{AS}


    \psset{nodesep=2pt, linestyle=dotted, arrows=<->}

\end{pspicture}