= rsntp

+rsntp+ is an experimental high-performance NTP server written in Rust. It does
not implement a full NTP client and relies on another NTP client and server to
be running on the system instead. It periodically updates its state to mirror
the real NTP client/server and uses multiple threads to serve the current
system time.

By default, +rsntp+ uses one thread for IPv4 and another for IPv6. In order to
get the best performance, it's necessary to increase the number of threads
using the +--ipv4-threads+ and +--ipv6-threads+ options to correspond to the
number of CPU cores available on the system.

The real NTP client/server needs to be configured to listen on 127.0.0.1 on
port 11123 (or another port if specified with the +--server-addr+ option). For
instance, the following configuration should work with +chronyd+:

----
allow 127.0.0.1
port 11123
bindaddress 127.0.0.1
----

The following table shows the maximum number of NTP requests handled per second
measured on a Linux (4.16) machine with an Intel E5-1220 CPU (4 cores) and an
Intel I350 network card (1 Gb/s).

|==========================================================
| 1 thread	| 430 kpps
| 2 threads	| 750 kpps
| 3 threads	| 1030 kpps
| 4 threads	| 1100 kpps (maximum for 1 Gb/s)
|==========================================================