{
    "type" : "node",
    "name" : "gre",
    "layout" : [
        {
            "name" : "c",
            "size" : "1"
        },
        {
            "name" : "reserved",
            "size" : "1"
        },
        {
            "name" : "k",
            "size" : "1"
        },
        {
            "name" : "s",
            "size" : "1"
        },
        {
            "name" : "reserved",
            "size" : "9"
        },
        {
            "name" : "version",
            "size" : "3",
            "default" : "0",
            "readonly" : "true"
        },
        {
            "name" : "protocoltype",
            "size" : "16"
        },
        {
            "name" : "checksum",
            "size" : "16",
            "optional" : "c=1"
        },
        {
            "name" : "reserved",
            "size" : "16",
            "optional" : "c=1"
        },
        {
            "name" : "key",
            "size" : "32",
            "optional" : "k=1"
        },
        {
            "name" : "sequencenumber",
            "size" : "32",
            "optional" : "s=1"
        }
    ]
}