def set_max_fragment_size(self, send_fragment_size):
        # -1 is default fragment size: 0 (don't fragment)
        #  0 is don't fragment
        #    other values are max fragment size
        if send_fragment_size == -1:
            self.set_default_max_fragment_size()
        else:
            self._max_send_frag = send_fragment_size