{
    "hosts": [
        "h1",
        "h2",
        "h3"
    ],
    "switches": {
        "s1": {},
        "s2": {},
        "s3": {}
    },
    "links": [
        ["h1", "s1"], ["s1", "s2"], ["s1", "s3"],
        ["s3", "s2"], ["s2", "h2"], ["s3", "h3"]
    ]
}