Method, system and device for synchronizing clocks

• US 9,641,268 B2
• Filed: 03/27/2015
• Issued: 05/02/2017
• Est. Priority Date: 09/28/2012
• Status: Active Grant

• Current Assignee: Huawei Technologies Co., Ltd. (Huawei Investment & Holding Co., Ltd.)
• Original Assignee: Huawei Technologies Co., Ltd. (Huawei Investment & Holding Co., Ltd.)
• Inventors: Li, Hao, Xing, Jun, Tang, Xiaoyu, Zhong, Qixiang
• Primary Examiner(s): Hamza, Faruk
• Assistant Examiner(s): Haque, Abu-Sayeed
• Application Number:
  US14/671,975
• Publication Number:
  US 20150207580A1
• Time in Patent Office: 767 Days
• CPC Class Codes: H04J 3/0641 Change of the master or reference, e.g. take-over or failure of the master
• CPC Class Codes: H04J 3/0679 by determining clock distribution path in a network

Abstract

A method for synchronizing clocks, including: receiving at least two clock signals, where the at least two clock signals are sent by a bidirectional clock tracking link respectively corresponding thereto; setting two or more clock signals coming from a same network element into a same clock source group; selecting one clock signal in a same clock source group as a currently tracked clock signal; and if the currently tracked clock signal belongs to the clock source group, respectively sending a standby clock signal carrying quality-level do not use information by using the bidirectional clock tracking link respectively corresponding to each of the clock signals in the clock source group. The present invention achieves the effect that in the scenario where there are two or more bidirectional clock tracking links between two network elements, a clock tracking loop will not be generated.

Claims

1. A method for synchronizing clocks of network elements having bidirectional clock tracking links, comprising:

receiving, by a network element, a plurality of clock signals via respective bidirectional clock tracking links, wherein the plurality of clock signals comprise a first standby clock signal;

setting, by the network element, two or more clock signals of the plurality of clock signals into a clock source group, wherein the two or more clock signals come from another network element;

selecting, by the network element, a clock signal from the two or more clock signals as a currently tracked clock signal; and

sending, by the network element, a second standby clock signal carrying quality level do not use information (QL DNU) via bidirectional clock tracking links corresponding to each of the clock signals in the clock source group.

2. The method according to claim 1, wherein selecting the clock signal as the currently tracked clock signal is based on clock priority and/or clock quality level information corresponding to clock signals of the clock source group.

3. The method according to claim 1, further comprising:

determining that the currently tracked clock signal is lost or a clock quality level of the currently tracked clock signal is declined; and

re-selecting, in response to determining that the currently tracked clock signal is lost or the clock quality level of the currently tracked clock signal is declined, another clock signal in the clock source group as the currently tracked clock signal according to clock priority and/or clock quality level information corresponding to clock signals of the clock source group.

4. The method according to claim 1, further comprising:

determining that clock quality level information of all the clock signals in the clock source group is lower than clock quality level information of the first standby clock signal; and

sending, in response to determining that the clock quality level information of all the clock signals in the clock source group is lower than the clock quality level information of the first standby clock signal, a third standby clock signal carrying switched clock quality level information via the bidirectional clock tracking links corresponding to each of the clock signals in the clock source group.

5. A network element, comprising a processor and a non-transitory computer-readable medium having processor-executable instructions stored thereon, wherein the processor-executable instructions, when executed by the processor, facilitate:

receiving a plurality of clock signals via respective bidirectional clock tracking links, wherein the plurality of clock signals comprise a first standby clock signal;

setting two or more clock signals of the plurality of clock signals into a same clock source group, wherein the two or more clock signals come from another network element;

selecting a clock signal from the two or more clock signals as a currently tracked clock signal; and

sending a second standby clock signal carrying quality level do not use information (QL_DNU) via bidirectional clock tracking links corresponding to each of the clock signals in the clock source group.

6. The network element according to claim 5, wherein selection of the clock signal as the currently tracked clock signal is based on clock priority and/or clock quality level information corresponding to clock signals of the clock source group.

7. The network element according to claim 5, wherein the processor-executable instructions, when executed, further facilitate:

determining that the currently tracked clock signal is lost or a clock quality level of the currently tracked clock signal is declined, and re-select another clock signal in the clock source group as the currently tracked clock signal according to clock priority and/or clock quality level information corresponding to clock signals of the clock source group.

8. The network element according to claim 5, wherein the processor-executable instructions, when executed, further facilitate:

determining that clock quality level information of all clock signals in the clock source group is lower than a clock quality level information of the first standby clock signal, and sending a third standby clock signal carrying switched clock quality level information via bidirectional clock tracking links corresponding to each of the clock signals in the clock source group.

9. A system for synchronizing clocks, comprising:

at least one network element according to claim 5.

10. A network element, comprising:

a receiver, configured to receive a plurality of clock signals via respective bidirectional clock tracking links, wherein the plurality of clock signals comprise a first standby clock signal;

a processor, configured to set two or more clock signals of the plurality of clock signals into a same clock source group, wherein the two or more clock signals come from another network element, and to select a clock signal from the two or more clock signals as a currently tracked clock signal; and

a transmitter, configured to send a second standby clock signal carrying quality level do not use information (QL_DNU) via bidirectional clock tracking links corresponding to each of the clock signals in the clock source group.

11. The network element according to claim 10, wherein selection of the clock signal as the currently tracked clock signal is based on clock priority and/or clock quality level information corresponding to clock signals of the clock source group.

12. The network element according to claim 10, wherein the processor is further configured to determine that the currently tracked clock signal is lost or a clock quality level of the currently tracked clock signal is declined, and to re-select another clock signal in the clock source group as the currently tracked clock signal according to clock priority and/or clock quality level information corresponding to clock signals of the clock source group.

13. The network element according to claim 10, wherein the processor is further configured to determine that clock quality level information of all clock signals in the clock source group is lower than a clock quality level information of the first standby clock signal;

and

wherein the transmitter is further configured to send a third standby clock signal carrying switched clock quality level information via bidirectional clock tracking links corresponding to each of the clock signals in the clock source group.

14. A system for synchronizing clocks, comprising:

at least one network element according to claim 10.