This notification is generated in the following cases:
          
- when a remote MEP first comes up, that is when we receive 
a CC message from that MEP for the first time.
          
- when the device receives a CC message from a MEP for which 
it has an expired CCDB entry.
          
- when a CC message is received for a remote MEP for which
the device already has a CCDB entry and the port-state in
the received CC message is different from the cached 
previous state.

This notification is generated when a remote MEP goes down; 
i.e. the entry in CCDB corresponding to this MEP times out 
or the device receives a CC message with zero hold-time.

This notification is generated when a device receives a CC
message with the service ID not matching the one locally 
configured for the VLAN in question.

This notification is generated when a device receives a CC
message with the same MEPID and MAC address as those of
the device itself, indicating that there is a forwarding
loop and that the device is receiving its own CC messages.

This notification is generated when a device receives a CC
message with the same MEPID but different MAC address as 
those of the device itself, indicating that there is a  
mis-configuration in the network where a remote device
has the same MEPID configured.

This notification is generated when an expected 
(configured) MEP does not come up during the cross-check
start timeout interval.

This notification is generated when an unexpected MEP
comes up.

This notification is generated when all the MEPs belonging
to a customer service instance come up before the expiration of
the cross-check start timeout interval.