ntpperf simulates NTP clients or PTP slaves sending requests at an increasing
rate and prints how many responses were received and lost. If the computer
running ntpperf has an accurate clock and the network delay to the server/master
is constant and known (e.g. there is a direct connection), it can also show
how does the accuracy of the transmit timestamp change with increasing rate of
requests.

ntpperf generates and processes raw Ethernet frames using libpcap. Requests from
the simulated clients/slaves have source addresses from a specified private
IPv4 network. The server/master and/or network needs to be configured to route
the responses to the computer running ntpperf, which should drop them (ideally
in the raw table of iptables to minimize the time wasted in the networking stack).

Network Time Security (NTS) support using the gnutls library can be enabled by
setting the NTPPERF_NTS environment variable for the build.