This ITU-T Recommendation specifies the operational procedures that two international maintenance organizations have to follow in case of failure or degradation of the transport network: paths, section or synchronization. These procedures are required in order to: localize and clear the fault, permit protection/reversibility and facilitate restoration and return to the original configuration. The maintenance procedures in this ITU-T Recommendation defines reference points requiring information to be exchanged between maintenance organizations of involved Network Operators/Service Providers.