Transparent clock for precision timing distribution
First Claim
1. A method comprising:
- receiving, by an optical network unit (ONU) of a network having asymmetric delay, a precision time protocol (PTP) packet including an indication of a time at which the PTP packet was received by an optical line terminal (OLT) of the network, wherein a first clock in the ONU and a second clock in the OLT are synchronized;
determining, by the ONU and based at least in part on a current time, the asymmetric delay, and one or more pre-forwarding packet processing calculations, a time at which the PTP packet is to be forwarded to a client device;
determining, by the ONU, a residence time of the PTP packet in the network as the difference between the time at which the PTP packet is to be forwarded and the time at which the PTP packet was received by the OLT;
adding, by the ONU, the residence time to a time stamp correction field of the PTP packet; and
forwarding, by the ONU, the PTP packet to the client device.
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Accused Products
Abstract
One or more devices of a network having asymmetric delay are configured to participate in time synchronization protocol sessions in which a client device synchronizes its local clock to a master device. In one example, a system includes an optical line terminal configured to receive a time synchronization protocol packet from a grandmaster clock and an optical network unit (ONU) configured to calculate a residence time of the time synchronization protocol packet, encode the residence time into the packet, and to forward the packet to a client device. Moreover, the system may participate in a plurality of time synchronization protocol sessions with a plurality of client devices, such that the client devices become synchronized in frequency and phase.
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Citations
29 Claims
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1. A method comprising:
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receiving, by an optical network unit (ONU) of a network having asymmetric delay, a precision time protocol (PTP) packet including an indication of a time at which the PTP packet was received by an optical line terminal (OLT) of the network, wherein a first clock in the ONU and a second clock in the OLT are synchronized; determining, by the ONU and based at least in part on a current time, the asymmetric delay, and one or more pre-forwarding packet processing calculations, a time at which the PTP packet is to be forwarded to a client device; determining, by the ONU, a residence time of the PTP packet in the network as the difference between the time at which the PTP packet is to be forwarded and the time at which the PTP packet was received by the OLT; adding, by the ONU, the residence time to a time stamp correction field of the PTP packet; and forwarding, by the ONU, the PTP packet to the client device. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A system in a network having asymmetric delay, the system comprising:
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an optical line terminal (OLT) configured to receive a precision time protocol (PTP) packet, and add an indication of a time at which the PTP packet was received to the PTP packet, wherein the PTP packet originates at a client device; and an optical network unit (ONU) configured to receive the PTP packet when forwarded by the OLT, determine a time at which the PTP packet is to be forwarded, determine a residence time of the PTP packet as the difference between the time at which the PTP packet is to be forwarded and the time at which the PTP packet was received by the OLT, add the residence time to a time stamp correction field of the PTP packet, and forward the PTP packet, wherein a first clock in the ONU and a second clock in the OLT are synchronized. - View Dependent Claims (8, 9, 10, 11, 12)
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13. A non-transitory computer-readable storage medium encoded with instruction for causing one or more programmable processors of an optical network unit (ONU) of a network having asymmetric delay to:
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receive a precision time protocol (PTP) packet including an indication of a time at which the PTP packet was received by an optical line terminal (OLT) of the network, wherein a first clock in the ONU and a second clock in the OLT are synchronized; determine, based at least in part on a current time, the asymmetric delay, and one or more pre-forwarding packet processing calculations, a time at which the PTP packet is to be forwarded to a client device; determine a residence time of the PTP packet in the network as the difference between the time at which the PTP packet is to be forwarded and the time at which the PTP packet was received by the OLT; add the residence time to a time stamp correction field of the PTP packet; and forward the PTP packet to the client device. - View Dependent Claims (14, 15)
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16. A method comprising:
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receiving, by an optical line terminal (OLT) of a network having asymmetric delay, a precision time protocol (PTP) packet, wherein the PTP packet originates at a grandmaster clock; determining, by the OLT, a time at which the PTP packet was received; adding, by the OLT, an indication of the time to the PTP packet; determining, by the OLT, an upstream residence time value and a downstream residence time value for the PTP packet; adding, by the OLT, the upstream residence time value and the downstream residence time value to a time stamp correction field of the PTP packet; and forwarding, by the OLT, the PTP packet to an optical network unit (ONU) of the network, wherein a first clock in the ONU and a second clock in the OLT are synchronized. - View Dependent Claims (17, 18, 19, 20)
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21. A non-transitory computer-readable storage medium encoded with instruction for causing one or more programmable processors of an optical line terminal (OLT) of a network having asymmetric delay to:
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receive a precision time protocol (PTP) packet, wherein the PTP packet originates at a grandmaster clock; determine a time at which the PTP packet was received; add an indication of the time to the PTP packet; determine an upstream residence time value and a downstream residence time value for the PTP packet; add the upstream residence time value and the downstream residence time value to a time stamp correction field of the PTP packet; and forward the PTP packet to an optical network unit (ONU) of the network, wherein a first clock in the ONU and a second clock in the OLT are synchronized. - View Dependent Claims (22, 23)
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24. An optical network unit (ONU) device in a network having asymmetric delay configured to:
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receive a precision time protocol (PTP) packet including an indication of a time at which the PTP packet was received by an optical line terminal (OLT) of the network, wherein a first clock in the ONU and a second clock in the OLT are synchronized; determine, based at least in part on a current time, the asymmetric delay, and one or more pre-forwarding packet processing calculations, a time at which the PTP packet is to be forwarded to a client device; determine a residence time of the PTP packet in the network as the difference between the time at which the PTP packet is to be forwarded and the time at which the PTP packet was received by the OLT; add the residence time to a time stamp correction field of the PTP packet; and forward the PTP packet to the client device. - View Dependent Claims (25, 26, 27)
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28. An optical line terminal (OLT) device in a network having asymmetric delay configured to:
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receive a precision time protocol (PTP) packet, wherein the PTP packet originates at a grandmaster clock; determine a time at which the PTP packet was received; add an indication of the time to the PTP packet; determine an upstream residence time value and a downstream residence time value for the PTP packet; add the upstream residence time value and the downstream residence time value to a time stamp correction field of the PTP packet; and forward the PTP packet to an optical network unit (ONU) of the network, wherein a first clock in the ONU and a second clock in the OLT are synchronized. - View Dependent Claims (29)
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Specification