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; (e) wherein the Lower Order, LO, Optical Data Units, LO ODUk, are mapped into the Optical Data Tributary Units, ODTU, by an asynchronous mapping procedure; and (f) wherein the predefined mapping rule, MR, indicates a mapping between Tributary Slots, TS, of the aggregate OPU_N payload area and Tributary Slots, TS, provided by the OPU payload area of Nx independent Optical Data Units, ODUk; and (g) wherein the predefined mapping rule, MR, indicates a mapping as follows: TS(A,B) ↔ TS(B) @ OTUk(A) wherein A is an OPU payload identifier, OID, identifying the OPU payload of an individual Optical Data Unit, ODUk, from a set of available Optical Data Units, ODUk, and B is a Tributary Slot, TS, number of an available Tributary Slot, TS, provided by the OPU payload of the individual Optical Data Unit, ODUk. (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; (e) wherein the Lower Order, LO, Optical Data Units, LO ODUk, are mapped into the Optical Data Tributary Units, ODTU, by an asynchronous mapping procedure; and (f) wherein the predefined mapping rule, MR, indicates a mapping between Tributary Slots, TS, of the aggregate OPU_N payload area and Tributary Slots, TS, provided by the OPU payload area of Nx independent Optical Data Units, ODUk; and (g) wherein the predefined mapping rule, MR, indicates a mapping as follows: TS(A,B) ↔ TS(B) @ OTUk(A) <EOS>