digraph G {
    rankdir = LR;
    BTS -> BSC [label="Abis"];
    BSC -> OsmoMSC [label="3GPP AoIP"];
    OsmoMSC -> OsmoMGW [label="MGCP"];
    BSC -> OsmoMGW [label="RTP",dir=both];
    OsmoMSC -> OsmoSIP [label="MNCC"];
    OsmoSIP -> PBX [label="SIP Trunk"];
    OsmoMGW -> PBX [label="RTP",dir=both];
    {rank=same OsmoMSC OsmoMGW}
    OsmoSIP [label="osmo-sip-connector"];
    OsmoMGW [color=red];

    hNodeB -> OsmoHNBGW [label="Iuh"];
    OsmoHNBGW -> OsmoMSC [label="IuCS"];
    hNodeB -> OsmoMGW [label="RTP",dir=both];
}