A network node (3, 4) comprising at least one client interface port (40) and a database (46, 48) storing data allowing to retrieve for a given client interface, a service associated therewith, for a given service, a client interface associated therewith. A Maintenance End Point (MEP) (50, 52) is established on the network node and is associated with an end-to-end service between a client device (10, 12) connected with said client interface port and a remote client device connected to a remote network node (3, 4). Said MEP is configured to exchange connectivity messages with a corresponding MEP (50, 52) established on said remote network node and to detect a client interface fault and a service fault based on connectivity messages received from said corresponding MEP, or based on missing connectivity messages from said corresponding MEP. Said network node is configured to determine which service(s) is (are) related to said client interface and to inform the MEP related to this service about said client interface fault, and is configured to determine which client interface(s) is (are) associated with said service and to carry out a predetermined action associated with said client interface(s).