A method for transmitting data in an Optical Transport Network, OTN, the method comprising: obtaining at least one pair of Optical Channel Data Units-0, ODU0's; mapping the at least one pair of ODU0's to an Optical Channel Data Tributary Unit, ODTU, to form an ODTUvkt, wherein k is greater than or equal to 1, t is 2 or 3, v does not represent any essential meaning but makes the ODTUvkt different from the ODTUkt, and an external structure of the ODTUvkt is the same as an external structure of an Optical Channel Data Tributary Unit-kt, ODTUkt, wherein the external structure of the ODTUvkt refers to the number of rows and columns of the ODTUvkt, the position of the fixed filler column, and the structure and indication rules of the overall Justification Control, JC, indication; and mapping the ODTUvkt to timeslot i and timeslot i+n of a timeslot cycle of a 1.25G Optical Channel Data Unit-t, ODUt, indicating the at least one pair of ODU0's carried in the timeslot i as Optical Channel Data Unit-k, ODUk, and transmitting the ODUk to a destination node, wherein n is the number of timeslots in a timeslot cycle of a 2.5G ODUt; wherein: the mapping of the at least one pair of ODU0's to the ODTU to form the ODTUvkt comprises: mapping data streams in the at least one pair of ODU0's to the ODTU to form the ODTUvkt; adding a Justification Control, JC, indication of one ODU0 in the pair of ODU0's, a corresponding Justification Opportunity, JO, indication, and an Frame Alignment, FA, indication into the ODTUvkt whose n multi-frame cycle is an odd cycle; and adding a JC indication of the other ODU0 in the pair of ODU0's, a corresponding JO indication, and an FA indication into the ODTUvkt whose n multi-frame cycle is an even cycle. obtaining at least one pair of Optical Channel Data Units-0, ODU0's; mapping the at least one pair of ODU0's to an Optical Channel Data Tributary Unit, ODTU, to form an ODTUvkt, wherein k is greater than or equal to 1, t is 2 or 3, v does not represent any essential meaning but makes the ODTUvkt different from the ODTUkt, and an external structure of the ODTUvkt is the same as an external structure of an Optical Channel Data Tributary Unit-kt, ODTUkt, wherein the external structure of the ODTUvkt refers to the number of rows and columns of the ODTUvkt, the position of the fixed filler column, and the structure and indication rules of the overall Justification Control, JC, indication; and mapping the ODTUvkt to timeslot i and timeslot i+n of a timeslot cycle of a 1.25G Optical Channel Data Unit-t, ODUt, indicating the at least one pair of ODU0's carried in the timeslot i as Optical Channel Data Unit-k, ODUk, and transmitting the ODUk to a destination node, wherein n is the number of timeslots in a timeslot cycle of a 2.5G ODUt; wherein: the mapping of the at least one pair of ODU0's to the ODTU to form the ODTUvkt comprises: mapping data streams in the at least one pair of ODU0's to the ODTU to form the ODTUvkt; adding a Justification Control, JC, indication of one ODU0 in the pair of ODU0's, a corresponding Justification Opportunity, JO, indication, and an Frame Alignment, FA, indication into the ODTUvkt whose n multi-frame cycle is an odd cycle; and adding a JC indication of the other ODU0 in the pair of ODU0's, a corresponding JO indication, and an FA indication into the ODTUvkt whose n multi-frame cycle is an even cycle. mapping data streams in the at least one pair of ODU0's to the ODTU to form the ODTUvkt; adding a Justification Control, JC, indication of one ODU0 in the pair of ODU0's, a corresponding Justification Opportunity, JO, indication, and an Frame Alignment, FA, indication into the ODTUvkt whose n multi-frame cycle is an odd cycle; and adding a JC indication of the other ODU0 in the pair of ODU0's, a corresponding JO indication, and an FA indication into the ODTUvkt whose n multi-frame cycle is an even cycle.