Transparent clock for precision timing distribution
First Claim
1. A method comprising:
- calculating, with a device of a network having asymmetric delay, a downstream residence time of a time synchronization protocol packet within the network;
adding an indication of the residence time into the packet;
forwarding the packet to a client device;
after forwarding the packet to the client device, receiving the packet from the client device;
calculating an upstream residence time of the packet;
adding the upstream residence time in the packet;
forwarding the packet to a grandmaster clock;
receiving, from the client device, a delay request packet;
adding an upstream residence time value to a time stamp correction field of the delay request packet;
forwarding the delay request packet to the grandmaster clock;
receiving the delay request packet back from the grandmaster clock;
adding a downstream residence time value to the time stamp correction field of the delay request packet after receiving the delay request packet back from the grandmaster clock; and
forwarding the delay request packet to the client device to cause the client device to synchronize a local clock of the client device to the grandmaster clock.
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0 Petitions
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.
112 Citations
28 Claims
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1. A method comprising:
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calculating, with a device of a network having asymmetric delay, a downstream residence time of a time synchronization protocol packet within the network; adding an indication of the residence time into the packet; forwarding the packet to a client device; after forwarding the packet to the client device, receiving the packet from the client device; calculating an upstream residence time of the packet; adding the upstream residence time in the packet; forwarding the packet to a grandmaster clock; receiving, from the client device, a delay request packet; adding an upstream residence time value to a time stamp correction field of the delay request packet; forwarding the delay request packet to the grandmaster clock; receiving the delay request packet back from the grandmaster clock; adding a downstream residence time value to the time stamp correction field of the delay request packet after receiving the delay request packet back from the grandmaster clock; and forwarding the delay request packet to the client device to cause the client device to synchronize a local clock of the client device to the grandmaster clock. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A system comprising:
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an optical line terminal (OLT) configured to receive a time synchronization protocol packet from a grandmaster clock, and to calculate a link delay from the grandmaster clock to the system; and an optical network unit (ONU) configured to calculate a residence time of the time synchronization protocol packet within a network including the OLT and the ONU, add the residence time into the packet, to forward the packet to a client device, and to add the link delay from the upstream network device, in addition to the residence time, into the packet, wherein the network has asymmetric delay such that a downstream delay from the OLT to the ONU is different than an upstream delay from the ONU to the OLT. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18, 19)
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20. A computer-readable storage medium encoded with instruction for causing one or more programmable processors of a network having asymmetric delay to:
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calculate a downstream residence time of a time synchronization protocol packet within the network; encode the residence time into the packet; forward the packet to a client device; receive the packet from the client device after forwarding the packet to the client device; calculate an upstream residence time of the packet; encode the upstream residence time in the packet; forward the packet to a grandmaster clock; receive, from the client device, a delay request packet; add an upstream residence time value to a time stamp correction field of the delay request packet; forward the delay request packet to the grandmaster clock; receive the delay request packet back from the grandmaster clock; add a downstream residence time value to the time stamp correction field of the delay request packet after receiving the delay request packet back from the grandmaster clock; and forward the delay request packet to the client device to cause the client device to synchronize a local clock of the client device to the grandmaster clock. - View Dependent Claims (21, 22, 23, 24, 25, 26, 27, 28)
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Specification