def bandwidth(bandwidth):
    """
    Bandwidth is in gigabytes per day.
    -1 is "unlimited".
    0 means no bandwidth. Only valid if ipv4 and ipv6 are False.
    """
    if isinstance(bandwidth, int):
        if bandwidth >= -1:
            return True
        else:
            raise ValueError('bandwidth can be no lower than -1.')
    else:
        raise TypeError('bandwidth must be integer.')
