gPTP Time Synchronization Test: Packet Transmission Delay

zyz — Fri, 07 Mar 2025 12:08:12 GMT

Recently, during our GPTP time synchronization testing, we observed a delay issue with Follow_Up/Sync messages (based on the receiver's captured data):

A message that should have been received at 53 seconds was actually received at 54 seconds, and the Follow_Up message carried a timestamp of 53 seconds.
A message that should have been received at 54 seconds was actually received at 55 seconds, and the Follow_Up message carried a timestamp of 54 seconds.
Please refer to the attachment for detailed information.

Could you help analyze the possible causes of this issue? Additionally, I have a question: In the GPTP protocol, is T1 recorded at the exact moment when the Sync message leaves the MAC layer and enters the PHY layer, or is it recorded when the Sync message is placed into the MAC internal transmit buffer?
If T1 is recorded when the Sync message leaves the MAC layer and enters the PHY layer, does this mean the issue is unrelated to the Master device?

Re: gPTP Time Synchronization Test: Packet Transmission Delay

chenyin_h — Wed, 12 Mar 2025 01:53:58 GMT

Hello, @zyz

Thanks for the post.

Let's discuss it together in your alternative thread.

Chenyin

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gPTP Time Synchronization Test: Packet Transmission Delay

Re: gPTP Time Synchronization Test: Packet Transmission Delay