iperf -s -D --mss mss

def start_server(self, protocol='TCP', port=5001, mss=None, window=None):
        """iperf -s -D --mss mss
        """
        cmd = ['iperf', '-s', '-p', str(port)]
        if not cmp(protocol, 'UDP'):
            cmd.append('-u')
        if mss:
            cmd.extend(['-M', str(mss)])
        if window:
            cmd.extend(['-w', str(window)])
        pid = utils.create_deamon(cmd)
        data = dict()
        data['pid'] = pid
        return data