Hi, The slave sends the delay_Req to the master. The slave should transmit a delay_Req at a regular interval depending on the configuration or negotiation of the inter-message interval (the desired time between each message). In IEEE 1588-2019, the requirement for regular messages is outlined in “9.5.11.2 Timing requirements” – generally they should be transmitted at an interval above 90% of the desired inter-message interval. So, for example, if you configured 32 packets per second (1/32 second interval), you would expect an average inter-message time value around that configured value (roughly +/- 10%) So, if the two delay_Req and sent are on top of each other, then the slave is misbehaving, although the master should tolerate short excursions from the inter-message interval.
In response to the delay_Req, the delay_Resp from the master “should be transmitted as soon as possible after the receipt of the associated Delay_Req message” (9.5.12 Transmission of a Delay_Resp message) If it’s taking its time, then the master is probably not being strictly adherent to the standards (seeing the timestamps on the tcpdump would help determine who is at fault). But there is some flexibility in the implementation whereby a significant number of outliers should be tolerated (30% in some cases), so the odd delay in messages should not be a big deal. Regards Dennis From: artst...@gmail.com <artst...@gmail.com> Sent: Sunday, September 4, 2022 21:25 To: linuxptp-users@lists.sourceforge.net Subject: [Linuxptp-users] Two Delay_req message Hi Please advise how linuxptp works As I understand it from the documents I found, ptp works in the following way: Announce message Sync message Follow_up message Delay_req message Delay_resp message I understand that depending on the mod ptp can work without Follow_up. But sometimes I see the following things in tcpdump: Announce message Sync message Follow_up message Delay_req message Delay_resp message Delay_req message Delay_resp message Announce message Sync message Follow_up message Delay_req message Delay_resp message or Sync message Follow_up message Delay_req message Delay_req message Delay_resp message Delay_resp message So it looks like the master sends two Delay_req. I just need to understand if it's expected ptp work or it's a bug with the driver Best regards, Vyacheslav
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