Method and apparatus for supporting mismatch detection

A network node for use in a communication network, the network node comprising a number of Operation, Administration and Management, OAM, entities configured to monitor a plurality of bidirectional and distinct network paths for carrying a number of service instances from the network node to another network node, wherein a number of said network paths form a protection group associated with a respective service instance or group of service instances, wherein said number of OAM entities are further configured to

• continuously and periodically send Continuity Check Messages, CCMs, on a monitored network path to the other network node;
• in response to occurrence of a predetermined event, include an indication bit in the CCMs, which are sent on said monitored network path for a predetermined first period of time after the occurrence of said predetermined event, wherein the indication bit indicates presence of a mismatch information element in the CCM that includes the indication bit, wherein the mismatch information element includes information that specifies, for each protection group that said monitored network path is a member of, traffic status of a working network path and of a protection network path of the protection group.