Patent claim: The method of any one of claims 1 to 8 wherein the building step when building a transmission schedule table TS for an output port scheduler OPS takes into account any transmission delay occurring from said output port scheduler OPS to its adjacent downstream output port scheduler OPS.

Related passage: The purpose of the GATE message is to grant transmission windows to ONUs for both discovery messages and normal transmission cycles.A single MPCP GATE can convey up to four individual grants from which the first one is used in the current cycle and the following are scheduled by the OLT into the future indicated by the value of the appropriate Grant n Start time fields.The number of grants conveyed within a single GATE can also be set to 0 when the GATE is simply used to keep the connection between the OLT and ONU alive in order to prevent ONUs automatic deregistration under very light traffic conditions.The MPCP GATE 0002 is an instance of a generic MPCPDU message and has the following data fields see FIG 8Destination Address DA.The DA in a MPCPDU is the MAC Control Multicast address as specified in the annexes to IEEE 802.3 ah clause 31 or the individual MAC address associated with the port to which the MPCPDU is destined Source Address SA.The SA in a MPCPDU is the individual MAC address associated with the port through which the MPCPDU is transmitted.For MPCPDUs originating at the OLT end this can be the address of any of the individual MAC ports.These MAC ports may all share a single unicast address as explained in IEEE 802.3 ah clause 64.1.2 LengthType.MPCPDUs are always Type encoded and carry the MACControlType field value as specified in IEEE 802.3 ah clause 31.4.1.3 Opcode.The opcode identifies the specific MPCPDU being encapsulated.Values are defined in IEEE 802.3 ah Table 31A1 Timestamp.The timestamp field conveys the content of the localTime register at the time of transmission of the MPCPDUs.This field is 32 bits long and counts 16bit transmissions.The timestamp counts time with a 16 bit time granularity 1 TQ16 ns2 B1 Gbps Flags.This is an 8 bit register that holds the following flags Table 1o The Number of grants field contains the number of grants composed of valid Length Start Time pairs in the MPCPDU.This is a number between 0 and 4.If Number of grants is set to 0 the sole purpose of the message is conveying a timestamp to an ONU o The Discovery flag field indicates that the signaled grants would be used for the discovery process in which case a single grant shall be issued in the gate message o The Force Report flag fields ask the ONU to issue a REPORT message related to each corresponding grant number at each corresponding transmission opportunity indicated in this GATEGrant n Length.Length of the signaled grant this is a 16 bit unsigned field.The length is counted in 16 bit time increments.There are 4 Grants that are possibly packed into the GATE MPCPDU.The laserOnTime syncTime and laserOffTime are included in and thus consume part of the Grant n Length Grant n Start Time.Start time of the grant this is a 32 bit unsigned field.The start time is compared to the local ONU clock to correlate the start of the grant with the predefined moment of time estimated by the OLT scheduler relative to the OLT clock.Transmitted values shall satisfy the condition Grant n Start Time lt Grant n1 Start Time for consecutive grants within the same GATE MPCPDUSync Time.This is an unsigned 16 bit value indicating the required synchronization time of the OLT receiver.During the synchronization time the ONU shall send IDLE codepairs.The value is counted in 16 bit time increments.The advertised value takes into account the synchronization requirements for all receiver elements including PMD1 PMA2 and PCS3.This field is present only when the gate is a discovery gate as signaled by the Discovery flag and is not present otherwise PadReserved.This is an empty field that is transmitted as zeros and ignored on reception when constructing a complying MPCP protocol implementation.The size of this field depends on the used Grant n LengthStart Time entrypairs and accordingly varies in length from 13 to 39.