Clock synchronizaton using codeword marker

Patent metadata

Field	Value
Publication number	US-2018205477-A1
Application number	US-201715406350-A
Country	US
Kind code	A1
Filing date	Jan 13, 2017
Priority date	Jan 13, 2017
Publication date	Jul 19, 2018
Grant date	—

Abstract

Aspects of the present disclosure includes a method and program product for clock synchronization of a networked computer system. The method records a time (t1) when a first codeword marker in a datastream is sent from a master computer to a slave computer and records a second time (t2) when the slave computer receives the first codeword marker. The method includes recording a third time (t3) when a third codeword marker in a datastream is sent from the slave computer to the master computer. The method includes recording a fourth time t4 when the master receives the third codeword marker from the slave. The method calculates a time offset θ, according to;

θ
=

(

t



2

-

t



1

)

+

(

t



4

-

t



3

)

2

,

and a roundtrip delay δ, according to δ=(t4−t1)−(t3−t2). The clock in the slave computer is synchronized with a clock in the master computer using θ and δ.

First claim

We claim:

1 . A method for clock synchronization of a networked computer system comprising, the method comprising:
recording a time (t1) when a first codeword marker in a datastream is sent from a master computer to a slave computer; recording a second time (t2) when the slave computer receives the first codeword marker; sending a second codeword marker in the datastream from the master computer to the slave computer, the second codeword marker containing the first time (t1); recording a third time (t3) when a third codeword marker in the datastream is sent from the slave computer to the master computer, wherein the third codeword marker is a first available codeword marker after receipt of slave computer of the second codeword marker; recording a fourth time t4 when master receives the third codeword marker from the slave; sending a fourth codeword marker in the datastream from the master computer to the slave computer, the fourth codeword marker containing the fourth time t4; calculating a time offset θ, according to

θ
=

(

t



2

-

t



1

)

+

(

t



4

-

t



3

)

2

;

calculating a roundtrip delay δ, according to δ=(t4−t1)−(t3−t2); and
synchronizing a clock in the slave computer with a clock in the master computer using θ and δ.

2 . The method of claim 1 , wherein the slave computer determines an elapsed time (T mm ) from receipt of the first codeword worker from the master computer to receipt of the second codeword marker from the master computer and if T mm is less than a predetermined value, clock synchronization is not initiated.

3 . The method of claim 2 , wherein the predetermined value is twice a time between two consecutive codeword markers.

4 . The method of claim 1 , wherein the master computer determines an elapsed time (T ms ) from sending of the second codeword worker to the slave computer to receipt of the third codeword marker from the slave computer and if T ms is less than a predetermined value, clock synchronization is not initiated.

5 . The method of claim 4 , wherein the predetermined value is triple a time between two consecutive codeword markers.

6 . The method of claim 1 , wherein the slave computer determines an elapsed time (T sm ) from sending of the third codeword worker to the master computer to receipt of the fourth codeword marker from the master computer and if T sm is less than a predetermined value, clock synchronization is not initiated.

7 . The method of claim 6 , wherein the predetermined value is triple a time between two consecutive codeword markers.

8 . A program product stored on a computer readable storage medium, the program product operative to synchronize clocks within a computer network containing a master computer and a slave computer, the computer readable storage medium comprising program code for:
recording a time (t1) when a first codeword marker in a datastream is sent from the master computer to the slave computer; recording a second time (t2) when the slave computer receives the first codeword marker; sending a second codeword marker in the datastream from the master computer to the slave computer, the second codeword marker containing the first time (t1); recording a third time (t3) when a third codeword marker in the datastream is sent from the slave computer to the master computer, wherein the third codeword marker is a first available codeword marker after receipt of slave computer of the second codeword marker; recording a fourth time t4 when master receives the third codeword marker from the slave; sending a fourth codeword marker in the datastream from the master computer to the slave computer, the fourth codeword marker containing the fourth time t4; calculating a time offset θ, according to

θ
=

(

t



2

-

t



1

)

+

(

t



4

-

t



3

)

2

;

calculating a roundtrip delay δ, according to δ=(t4−t1)−(t3−t2); and
synchronizing a clock in the slave computer with a clock in the master computer using θ and δ.

9 . The program product of claim 8 , wherein the slave computer determines an elapsed time (T mm ) from receipt of the first codeword worker from the master computer to receipt of the second codeword marker from the master computer and if T mm is less than a predetermined value, clock synchronization, is not initiated.

10 . The program product of claim 9 , wherein the predetermined value is twice a time between two consecutive codeword markers.

11 . The program product of cl

Assignees

• Globalfoundries Inc

Inventors

• Yang Kai
• Sun Bin
• Yao Yuan
• Han Zhen

Classifications

• H04J3/0667 Primary

  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

• H04J3/0644

  External master-clock · CPC title

• H04J3/0658 Primary

  Clock or time synchronisation among packet nodes · CPC title