Securing time between nodes

Patent metadata

Field	Value
Publication number	US-10158441-B1
Application number	US-201715612525-A
Country	US
Kind code	B1
Filing date	Jun 2, 2017
Priority date	Jun 2, 2017
Publication date	Dec 18, 2018
Grant date	Dec 18, 2018

Abstract

Systems and methods are provided for validating time between a local clock included in the slave node of a network with a master clock included in the master node of the network. The master node determines a propagation delay between the master node and the slave node, sends a synchronization message to the slave node at a first time, determines an expected receipt time of the synchronization message at the slave node based on the first time, the determined propagation delay between the master node and the slave node, and a rate ratio of the master clock to the local clock, and sends a follow up message to the slave node, the follow up message including the first time and the expected receipt time.

First claim

What is claimed is:

1. A method of validating time between a local clock included in a slave node of a network with a master clock included in a master node of the network, the method comprising:
in the master node:
determining a propagation delay between the master node and the slave node;
sending a synchronization message to the slave node at a first time;
determining an expected receipt time of the synchronization message at the slave node, based on the first time, the determined propagation delay between the master node and the slave node, and a rate ratio of the master clock to the local clock; and
sending a follow up message to the slave node, the follow up message including the first time and the expected receipt time.

2. The method of claim 1 , the method further comprising:
in the slave node:
receiving the synchronization message at a second time;
receiving the follow up message including the first time and the expected receipt time; and
determining whether the second time is within a predetermined range of the expected receipt time.

3. The method of claim 1 wherein the expected receipt time is determined by converting the first time to a time domain of the slave node using the rate ratio and adding the converted first time to the propagation delay determined by the master node.

4. The method of claim 1 wherein the rate ratio is determined by the master node by a propagation delay transaction performed between the master node and the slave node.

5. The method of claim 1 , the method further comprising:
in the master node:
determining an expected propagation delay using the propagation delay determined by the master node and the rate ratio, wherein the follow up message further includes the expected propagation delay.

6. The method of claim 5 , the method further comprising:
in the slave node:
determining a propagation delay between the slave node and the master node; and
determining whether the propagation delay determined by the slave node is within a predetermined range of the expected propagation delay.

7. The method of claim 1 , the method further comprising:
in the master node:
determining an expected rate ratio, wherein the follow up message further includes the expected rate ratio.

8. The method of claim 7 , the method further comprising:
in the slave node:
determining a rate ratio of the local clock to the master clock; and
determining whether the rate ratio determined by the slave node is within a predetermined range of the expected rate ratio.

9. The method of claim 1 wherein synchronization of the local clock included in the slave node of the network with the master clock included in the master node of the network is performed according to generalized precision time protocol.

10. The method of claim 1 wherein synchronization of the local clock included in the slave node of the network with the master clock included in the master node of the network is performed over a single link of the network.

11. A master node interconnected to a slave node in a network, wherein time is validated between a local clock included in the slave node and a master clock included in a master node, the master node comprising:
a network interface constructed to send a synchronization message to the slave node at a first time;
a processor coupled to a memory and constructed to determine a propagation delay between the master node and the slave node, and to determine an expected receipt time of the synchronization message at the slave node, based on the first time, the determined propagation delay between the master node and the slave node, and a rate ratio of the master clock to the local clock,
wherein the network interface is further constructed to send a follow up message to the slave node, the follow up message including the first time and the expected receipt time.

12. The master node of claim 11 , wherein the slave node receives the synchronization message at a second time, receives the follow up message including the first time and the expected receipt time, and determines whether the second time is within a predetermined range of the expected receipt time.

13. The master node of claim 11 wherein the expected receipt time is determined by converting the first time to a time domain of the slave node using the rate ratio and adding the converted first time to the propagation delay determined by the master node.

14. The master node of claim 11 wherein the rate ratio is determined by the master node by a propagation delay transaction performed between the master node and the slave node.

15. The master node of claim 11 the processor being further constructed to determine an expected propagation delay using the propagation delay determined by the master node and the rate ratio, wherein the follow up message further includes the expected propagation delay.

16. The master node of claim 15 wherein the slave node determines a propagation delay between the slave node and the master node and determines whether the propagation delay determined by the slave node is within a predetermined range of the expected propagation delay.

17. The master node of claim 11 the processor being further constructed to determine an expected rate ratio, wherein the follow up message further includes the expected rate ratio.

18. The master node of claim 17 wherein the slave node determines a rate ratio of the local clock to the master clock and determines whether the rate ratio determined by the slave node is within a predetermined range of the expected rate ratio.

19. The master node of claim 11 wherein the synchronization of the local clock included in the slave node of the network with the master clock included in the master node of the network is performed according to generalized precision time protocol.

20. The master node of claim 11 wherein synchronization of the local clock included in the slave node of the network with the master clock included in the master node of the network is performed over a single link of the network.

21. A non-transitory computer-readable storage medium storing executable program instructions which when executed by a master node interconnected to a slave node perform a method for validating time between a local clock included in the slave node of a network with a master clock included in the master node of the network, the method comprising:
determining a propagation delay between the master node and the slave node;
sending a synchronization message to the slave node at a first time;
determining an expected receipt time of the synchronization message at the slave node, based on the first time, the determined propagation delay between the master node and the slave node, and a rate ratio of the master clock to the local clock; and
sending a follow up message to the slave node, the follow up message including the first time and the expected receipt time.

22. The non-transitory computer-readable storage medium of claim 21 , the method further comprising:
in the slave node:
receiving the synchronization message at a second time;
receiving the follow up message including the first time and the expected receipt time; and
determining whether the second time is within a predetermined range of the expected receipt time.

23. The non-transitory computer-readable storage medium of claim 21 wherein the expected receipt time is determined by converting the first time to a time domain of the slave node using the rat

Assignees

• Apple Inc

Inventors

• Butterworth Ashley I
• Mora Matthew X

Classifications

• H04J3/0667

  Bidirectional timestamps, e.g. NTP or PTP for compensation of clock drift and for compensation of propagation delays (arrangements for monitoring round trip delays in packet switching networks H04L43/0864) · CPC title

• H04W56/001

  Synchronization between nodes · CPC title

• H04W56/0015 Primary

  one node acting as a reference for the others · CPC title

• H04J3/0682

  by delay compensation, e.g. by compensation of propagation delay or variations thereof, by ranging · CPC title

• H04J3/0661

  using timestamps · CPC title