digraph G {
  node [shape=rect];
  rankdir=LR;

  eUE;

  subgraph cluster1 {
    label="osmo-epdg (combined ePDG/AAA)";

    { rank=same; strongswan; osmoepdg;}
    osmoepdg [label="osmo-epdg/erlang"; color="blue"];
  }

  subgraph cluster2 {
    rankdir=LR;
    label="epc";

    { rank=same; HSS; PGW; PCRF; }
    PCRF -> PGW [dir="both"];
  }

  eUE -> strongswan [label="SWu (ePDG)", dir="both"];
  strongswan -> osmoepdg [label="CEIA/GSUP", dir="both"];
  osmoepdg -> HSS [label="SWx (AAA)", dir="both"];
  osmoepdg -> PGW [label="S2b (ePDG)", dir="both", weight=100];
  PGW -> ims [label="IPv4/IPv6", dir="both"];
  PGW -> osmoepdg [label="S6b (AAA)", dir="both"];

  eUE -> ims [label="IPv4/IPv6 (tunnel)", style=dotted, weight=-1];
}