Client signal fail (CSF) is a method that allows for the propagation of a fault condition to a MEP peer, without requiring ETH-CC or ETH-AIS. The message is sent when a MEP detects an issue with the entity in the direction the MEP to its peer MEP. A typical deployment model is an UP MEP configured on the entity that is not executing ETH-CC with its peer. When the entity over which the MEP is configured fails, the MEP can send the ETH-CSF fault message.
To process the reception of the ETH-CSF message, the csf-enable function must be enabled under the MEP. When processing of the received CSF message is enabled, the CSF is used as another method to trigger fault propagation, assuming fault propagation is enabled. If CSF is enabled but fault propagation is not enabled, the MEP shows the state of CSF being received from the peer. And lastly, when there is no fault condition, the CSF Rx State displays DCI (Client defect clear) indicating there are no existing failures, even if no CSF has been received. The CSF Rx State indicates the various fault and clear conditions received from the peer during the event.
CSF carries the type of defect that has been detected by the local MEP generating the CSF message.
000 – LOS – Client Loss of Signal
001 – FDI/AIS – Client forward defect indication
010 – RDI – Client reverse defect indication
Clearing the CSF state can be either implicit, time out, or explicit, requiring the client to send the PDU with the clear indicator (011 – DCI – Client defect clear indication). The receiving node uses the multiplier option to determine how to clear the CSF condition. When the multiplier is configured as non-zero (in increments of half seconds between 2 and 30) the CSF is cleared when CSF PDUs have not been received for that duration. A multiplier value of 0 means that the peer that has generated the CSF must send the 011 – DCI flags. There is no timeout condition.
Service-based MEP supports the reception of the ETH-CSF as an additional trigger for the fault propagation process. Primary VLAN and Virtual MEPs do not support the processing of the CSF PDU. CSF is transparent to MIPs. There is no support for the transmission of ETH-CSF packets on any MEP.