An invention provides a method for efficient utilization of a transport capacity provided by an Optical Transport Network, OTN, the method comprising the steps of: (a) mapping (S1) client signals comprising Lower Order, LO, Optical Data Units, LO ODUk, into Optical Data Tributary Units, ODTU, each requiring a number of Tributary Slots, TS, of an aggregate OPU_N payload area having a size corresponding to the available aggregated OPU payload areas of Nx independent Higher Order, HO, Optical Data Units, HO ODUk, to be transported; (b) multiplexing (S2) the Optical Data Tributary Units, ODTU, into the aggregate OPU_N payload area; (c) mapping (S3) the Tributary Slots, TS, of the aggregate OPU_N payload area into Tributary Slots, TS, provided by the OPU payload areas of the Nx independent Higher Order, HO, Optical Data Units, HO ODUk, according to a predefined mapping rule, MR; and (d) further multiplexing the Nx independent Optical Data Units, ODUk, containing the OPU payload areas or transmitting them as Optical Transport Units, OTUk