<p>Disclosed is a link state detection method. It comprises the steps of : a switch element receiving link state information from the switch element to a lower level unit and accessibility information from the lower level unit to a destination unit, which is detected by the lower level unit; according to the link state information from the switch element to the lower level unit and the accessibility information from the lower level unit to the destination unit, accessibility information from the switch element to the destination unit is acquired. A link state detection system is also provided.</p>
