I am solving different time synchronization of PC.
Checked that NTP synchronizes to less than 1 millisecond using ntpq. I would like to ask for help on how to verify this without using ntpq, ntdate etc.
I used 'ssh' to see the approximate difference in time between computers on the screen. I'd like to know a slightly more accurate time error for everything I have to consider, such as the Netwick Transmission Delay.
I use several nvidia xavier in uuntu 18.04 and 'ROS melodic'
If you are looking to establish timings for networking calls then you would want microsecond accuracy between the servers since the latency between systems can often be sub-millisecond on individual network segments. The tools themselves are often the best place to check for the accuracy figures, since they will be using that figure themselves to calculate the "correct" time.
If you are able to send test packets between the servers you are interested in then a latency measurement between the servers using a ping-pong style of test will give a network latency. Assuming this is symmetric, i.e. each way is identical latency, you can then calculate the half-round-trip time. At this point, running another test where you send a timestamp from one system to another and compare the two (subtracting 1/2 RTT from the sender) should give you a good idea of the time difference.
You would need to run the above test for multiple packets since the first few packets are likely to be impacted by the server cache and won't be consistent.