def METHOD_NAME(
    toggle_all_simulator_ports_to_upper_tor, upper_tor_host, lower_tor_host,    # noqa F811
    send_t1_to_server_with_action, shutdown_tor_heartbeat):                     # noqa F811
    """
    Send downstream traffic from T1 to the standby ToR and stop the LinkProber module on the active ToR.
    Confirm switchover and disruption lasts < 1 second.
    """
    send_t1_to_server_with_action(
        lower_tor_host, verify=True, delay=MUX_SIM_ALLOWED_DISRUPTION_SEC,
        action=lambda: shutdown_tor_heartbeat(upper_tor_host)
    )
    verify_tor_states(
        expected_active_host=lower_tor_host,
        expected_standby_host=upper_tor_host
    )