digraph G {
    rankdir="TB";

    v4host [ shape="box" label="IPv4 Host" rank="min" ];
    v6host [ shape="box" label="IPv6 Host" ];

    parser  [ label="Parser"];
    deparser  [ label="Deparser"];
    translation  [ label="Translation"];
    v4packet  [ label="IPv4 Packet"];
    v6packet  [ label="IPv6 Packet"];

    subgraph cluster_nat64 {
        label="P4 Switch";
        parser->v4packet->translation->v6packet->deparser;
    }

    deparser->v6host;
    v4host->parser;

}