On a Layer 2 network running ERPS, if another fault detection protocol (for example, CFM) is enabled, the MEL field in RAPS PDUs determines whether the RAPS PDUs can be forwarded. If the MEL value in an ERPS ring is smaller than the MEL value of the fault detection protocol, the RAPS PDUs have a lower priority and are discarded. If the MEL value in an ERPS ring is larger than the MEL value of the fault detection protocol, the RAPS PDUs can be forwarded. In addition, the MEL value can also be used for interworking with other vendors' devices in an ERPS ring. The same MEL value ensures smooth communication between devices.