NTP Server load/stress testing

I am testing an NTP server and need tools/recommendations/ideas of how to do it. I want to load and/or stress test the server, also want to test DDoS. Please guide

Not ntpperf.

Probably a packet generator and sink combo.

Thanks for your support. I am using ntpperf but it doesn’t seem to work as I expected. Do you recommend any packet generator/sink combo?

What problem do you see with ntpperf?

You could use tcpdump to capture a request and replay it at a specific rate with tcpreplay. The server will see that as a single client and the performance can be different than with a larger number of clients as simulated by ntpperf.

If you need test faster rates (tens of gigabits), there are DPDK-based packet generators.

ntpperf is good…but I can’t seem to control how many clients can send requests at a time. There is the rate option but at default my test fails when rate is 1000 and clients show as 100. I would like to have an option like control the rate based on number of clients.