Time Synchronization Source Failover

1

(% class="row" %)

2

(((

3

(% class="col-xs-12 col-sm-7 test-report-content" %)

(((

----

In real-world deployments, redundancy and recovery mechanisms are essential to ensure accurate time synchronization is maintained should one of the time synchronization sources fail.

8

This test aims to evaluate the time error measured at the output of each Telecom Boundary Clock after the primary time synchronization source/Grandmaster fails and a switch-over to the secondary Grandmaster is initiated.

9

10

For this test, all the Boundary Clocks were directly locked to both Grandmasters (GMs); GM-A served as the primary GM and GM-B as the backup GM; for this, all BCs had local priorities configured to prioritize and lock to GM-A on PTP and SyncE. Two different Microchip TimeProvider® 4500 were used as GM-A and GM-B.

11

We executed two different scenarios for this test, once with Microchip’s Sync-Only Redundancy feature enabled between both T-GMs. In the Sync-Only Redundancy feature, the two T-GMs are synchronized to each other and GNSS reference. We then simulated a “fiber cut” by disconnecting all the physical T-BC connections to T-GM-A to initiate the failover to T-GM-B; after a measurement period of 1000s including the failover, the measurement was restarted and all cables were reconnected to T-GM-A, initiating a switch back to T-GM-A from all T-BCs on PTP and SyncE.

12

13

[[Figure 121: Test run 1, Sync-Only Redundancy disabled with Cable pull - Setup>>image:434865443411066881_5.17-cable.png||alt="Figure 121" width="550"]]

14

15

For the second run, we disabled the Sync-Only Redundancy feature on the GMs and disconnected the GNSS from GM-A, causing the BCs to switch to GM-B; after measuring for 1000s including the failover, the measurement was restarted and the GNSS connection to GM-A was re-established, and all BCs locked back to GM-A on PTP and SyncE.

16

The Calnex Paragon-Neo PAM4 and the Keysight Time Sync Analyzer were used to measure the PTP and SyncE output of all the BCs.

17

18

[[Figure 122: Test run 2, Sync-Only Redundancy disabled with GNSS disconnection - Setup>>image:434865443411001345_5.17-GNSS.png||alt="Figure 122" width="550"]]

19

20

In both runs, a two-way time error threshold of the Class level of accuracy 6B was set, which is, as per ITU-T G.8271, +/- 130ns, but all BCs even passed 6C, which is defined as +/- 65ns.

21

For the MTIE, the ITU-T G.823 E1 SEC wander limit mask was applied as the threshold throughout all procedures and switchovers, which, once again, all BCs easily passed.

22

23

(% id="prev-next-links" %)

24

|[[< Previous>>doc:O-RAN Tests]]|[[Next ~>>>doc:Chain Ring of Class D Boundary Clocks]]

25

)))

26

27

(% class="col-xs-12 col-sm-5 test-report-sidebar" %)

28

(((