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04-PTP Troubleshooting Guide

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Troubleshooting network management & monitoring

PTP issues

PTP time synchronization failure

Symptom

The device has been configured to synchronize time via PTP. However, the system time of the device is not synchronized with the PTP clock source. The system time displayed in the display clock command output on the device, and the timestamp in the logs generated on the device are inconsistent with the time of the PTP clock source.

Common causes

The following are the common causes of this type of issue:

· System time configuration error.

· The current grandmaster (GM) is not the planned PTP clock source.

· PTP module configuration error.

· PTP message transmit and receive anomaly on the PTP port.

· The PTP time synchronization accuracy is beyond the normal range.

Troubleshooting flow

Figure 1 shows the troubleshooting flowchart.

Figure 1 Flowchart for troubleshooting PTP time synchronization failure

Solution

To resolve the issue:

1. Identify if errors exist in the system time configuration.

Execute the display current-configuration | include clock command on the device to view the effective system time configuration.

a. If the clock protocol ptp command is not displayed in the command output, execute the clock protocol ptp command to specify PTP for obtaining the system time.

b. The device obtains Coordinated Universal Time (UTC) via PTP. If a time zone and daylight saving time have been configured on the PTP clock source, execute the clock timezone command and clock summer-time command in system view on the device to specify the time zone and daylight saving time. Ensure that the time zone and daylight saving time configured on the device are consistent with those on the PTP clock source.

c. Execute the display clock command on the device. If the displayed system time is consistent with the PTP clock source, the issue has been resolved, and no further processing is required. If the displayed system time is inconsistent with the PTP clock source, proceed to the next step.

2. If the PTP time is in synchronized state, identify if the current GM is the PTP clock source planned for the network.

Execute the display ptp clock command on the device. If the value of the Lock status field is Locked, the PTP time is in synchronized state. Then execute the display ptp parent command and view the information of the PTP clock source in the Grandmaster clock section. If the displayed PTP clock source is not the clock source planned for the network, perform the following steps:

a. Identify if the PTP clock source planned for the network is faulty. If the planned PTP clock source is faulty, recover the PTP clock source first.

b. Execute the ptp clock-source on the device to specify the clock precision and class for the clock source to enable the planned PTP clock source to be elected as the GM of the entire PTP clock synchronization network.

c. Check the PTP sync link between the device and the planned PTP clock source. If a PTP sync link fault causes the network to use the backup PTP clock source, fix the link fault issue.

d. Execute the display clock command on the device. If the displayed system time is consistent with the PTP clock source, the issue has been resolved, and no further processing is required. If the displayed system time is inconsistent with the PTP clock source, proceed to the next step.

3. If the PTP time is in unsynchronized state, identify whether any errors exist in the PTP configuration.

a. Execute the display ptp clock command on the device to identify if any errors exist in the PTP configuration of the device. Devices in the same PTP clock synchronization network must meet the following requirements:

- Run the same PTP profile. If the PTP profiles are different, execute the ptp profile command in system view to change their PTP profiles to be the same.

- Be assigned to the same PTP domain. If they are assigned to different PTP domains, execute the ptp domain command in system view to assign them to the same PTP domain.

- Have PTP modes (clock node types) matching their locations in the network topology. If their PTP modes do not meet the networking requirements, execute the ptp mode command in system view to specify correct PTP modes for them. For example, when the IEEE 1588v2 protocol is used, if the device is connected to PTP upstream and downstream nodes, you cannot configure the PTP mode of the device as OC.

<Sysname> display ptp clock

PTP global state : Enabled

PTP profile : IEEE 1588 Version 2

PTP mode : BC

Slave only : No

Lock status : Unlocked

Clock ID : 08B61B-FFFE-6B0200

Clock type : Local

Clock domain : 1

Number of PTP ports : 2

Priority1 : 128

Priority2 : 128

Clock quality :

Class : 248

Accuracy : 254

Offset (log variance) : 65535

Offset from master : 78500000 (ns)

Mean path delay : 500000 (ns)

Steps removed : 1

Local clock time : Sun Apr 9 17:19:09 2023

b. Execute the display ptp interface command on the device, and identify if any errors exist in the PTP configuration of the PTP interfaces. The configuration of the PTP interfaces in the same PTP clock synchronization network must meet the following requirements:

- PTP is enabled on the interfaces involved in PTP clock synchronization. If PTP is not enabled on such an interface, execute the ptp enable command in interface view to enable PTP on that interface. Make sure the PTP state of the interface connected to the PTP clock source is Slave, and the PTP state of the interface connected to the downstream PTP node is Master.

Interfaces on a T-BC clock node running the ITU-T G.8275.1 protocol and a T-BC or T-BC-P clock node running the ITU-T G.8275.2 protocol are master-only ports. For these interfaces to act as subordinate ports, execute the ptp notslave disable command on the interfaces.

- The local and peer interfaces are configured with the same delay measurement mechanism. If they use different delay measurement mechanism, execute the ptp delay-mechanism command in interface view to configure the same delay measurement mechanism for them.

- The local and peer interfaces are configured with the same PTP transport protocol. If they use different PTP transport protocol, execute the ptp transport-protocol command in interface view to configure the same PTP transport protocol for the peer interfaces.

- The local and peer interfaces are configured with PTP message transmission intervals based on the mean path delay to ensure that the PTP message timeout timer is greater than the mean path delay. If the average path delay is large, the device might fail to receive the PTP messages within the timeout timer, which ultimately affects PTP time synchronization. You can execute the ptp announce-interval, ptp announce-timeout, ptp delay-resp-interval, ptp pdelay-req-interval, and ptp syn-interval commands in Ethernet interface view to modify the transmission parameters of PTP messages. Configure the PTP message transmission parameters of the device and the upstream and downstream nodes according to the allowable value range of the device, to avoid mismatches in the PTP message transmission parameters, leading to PTP synchronization failure.

<Sysname> display ptp interface brief

<Sysname> display ptp interface ten-gigabitethernet 0/0/6

Clock ID : 08B61B-FFFE-6B0200

Port number : 2

PTP version : 2

PTP state : Enabled

Transport protocol of PTP : IEEE 802.3/Ethernet

Port state : Slave

Force state : No

Clock step : Two

Asymmetry correction : 0

Delay mechanism : End to End

Unicast negotiate port role : Disabled

Announce interval (log mean) : 1

Announce receipt time out : 3

Sync interval (log mean) : 0

Delay request interval (log mean) : 0

Peer delay request interval (log mean) : 0

Mean path delay : 500000 (ns)

4. If the PTP time is in unsynchronized state, identify whether exceptions have occurred on the PTP message transmit and receive.

Execute the reset ptp statistics command in user view on the local device, upstream PTP device, and downstream PTP device to clear PTP statistics. Then, execute the display ptp statistics command to display PTP statistics. The PTP packets received on the local device must be of the same type and quantity as the PTP packets transmitted from the upstream device, or the count differs by 1 to 2 packets (because of transmission delay). The PTP packets transmitted from the local device must be of the same type and quantity as those received on the downstream device, or the count differs by 1 to 2 packets (because of transmission delay). If the PTP packet statistics does not align with this condition, an exception occurs with the PTP packets transmit and receive.

<Sysname> display ptp statistics

Interface : GigabitEthernet1/0/6

Received packets

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Announce :50 Sync :100 Signaling :0

DelayReq :0 DelayResp :96 FollowUp :100