blockdiag {

    //orientation = portrait;

    // Blocks used
    SDN [label = "SDN\nController", width = 64];
    M [label = "PON\nManager", width = 64];
    V [label = "Voltha\nCore & NBI", width = 74];
    A [label = "OLT\nAdapter", width = 64];
    A2 [label = "ONU\nAdapter", width = 64];
    U [label = "Upstream\nNetwork", width = 64];
    L2 [label = "L2 Aggr.", width = 64, shape = cloud];
    OL [label = "OLT chip\n& firmware", width = 64];
    ON [label = ONU, width = 64];
    R [label = RG, width = 64];

    U <-> L2 [label = Pd];
    L2 <-> OL [label = Pu];
    OL <-> ON;
    ON <-> R [label = Pr];
    M <-> V;
    M <-> SDN;
    SDN <-> V [label = Pv];
    V <-> A [label = Pa];
    V <-> A2;
    A <-> OL [label = Pc];

    group {
        SDN; M; V; A; A2; U; L2; OL; ON; R;
        shape = line;
        color = "#FFFFFF";
        fontsize = 24;

        group {
            label = "PON Network";
            V; A; A2; OL; ON;

            group {
                label = "Voltha";
                color = "#AAAAFF"
                V; A; A2;
            }


        }
    }
}