This Recommendation specifies the interfaces for the Transport MPLS (T-MPLS) hierarchy@ in particular the: ? encapsulation of T-MPLS client signals into the T-MPLS characteristic information that will be present on T-MPLS NNI links in the transport network; ? encapsulation of T-MPLS characteristic information into the T-MPLS link frames that will be present on T-MPLS NNI links in the transport network; ? T-MPLS link frame format interworking when T-MPLS subnetworks with different link frame formats are interconnected; ? T-MPLS hierarchy within the transport network and associated T-MPLS multiplexing; ? T-MPLS nested connection monitoring per hierarchy level within the transport network; ? T-MPLS OAM associated with nested connection monitoring in the transport network; ? encapsulation of in-band T-MPLS control plane information into the T-MPLS link frames that will be present on T-MPLS NNI links in the transport network. The T-MPLS network uses various server layer networks like OTH@ SDH@ PDH@ ETH and RPR. The detailed requirements are specified in a number of ITU-T Recommendations@ ANSI Standards@ IEEE Standards and IETF RFC@ which are referred to. This Recommendation specifies unicast LSPs; multicast LSPs are for further study. This Recommendation does not cover inter-operator control plane aspects of the T-MPLS NNI.