perfSONAR User Q&A and Other Discussion

[Brian Candler <>]

On 05/12/2014 18:32, Eli Dart wrote:

Just out of curiosity, why would you trust ping to measure latency if you're not satisfied with OWAMP?

Because the round-trip latency measurement doesn't depend on clock skew.

If NTP clock skew is causing you problems, I'm guessing you're measuring latency over very short distances, but I'd like to ask before I assume.  What sort of network are you trying to measure?  I apologize if I've missed it in earlier threads.

Yes, it's short distances - right now it's in the office for test, and when deployed it will be over a few hops of fibre.

However I've just discovered that the office ISP appears to be blocking NTP responses - probably a misguided attempt to protect against NTP DoS attacks - so maybe NTP should be able to achieve better than I have been seeing once the boxes go into the field. I'll also try to give the ISP some clue.

Regards,

Brian.