Measurements of errors in timestamps of NTP servers
This document compares accuracy and performance of a few
different stratum-1 NTP servers. An Intel I210 NIC with
hardware timestamping (using default RX/TX compensation in the
igb driver) and PPS input on one of its software-defined pins
(SDP) is used as a reference. The server and the I210 NIC were
directly connected with a short cable (no switches between
them) and synchronized to the same PPS signal, or synchronized
to other NICs over PCIe in a symmetric setup.
Except LeoNTP, all servers were running on Linux with
chrony, rsntp, or a DPDK NTP implementation. chrony was tested
in both basic and interleaved modes
Summary
| HW |
TX/RX timestamping |
Max pkt. rate |
Offset (idle) (us) |
Offset (loaded) (us) |
| AR9331 |
user/kernel (basic) |
2200 |
61.6 +/- 17.3 |
54.0 +/- 56.8 |
| AR9331 |
kernel/kernel (xleave) |
2000 |
-7.8 +/- 9.5 |
-17.8 +/- 29.3 |
| Raspberry Pi 3B+ (pps-gpio) |
user/kernel (basic) |
17000 |
-9.2 +/- 2.9 |
-2.3 +/- 9.4 |
| Raspberry Pi 3B+ (pps-gpio) |
kernel/kernel (xleave) |
17000 |
-15.2 +/- 2.9 |
-12.7 +/- 6.3 |
| Raspberry Pi 3B+ (pps-gpio-poll) |
user/kernel (basic) |
17000 |
-11.2 +/- 3.0 |
-6.1 +/- 9.2 |
| Raspberry Pi 3B+ (pps-gpio-poll) |
kernel/kernel (xleave) |
17000 |
-17.4 +/- 3.0 |
-17.8 +/- 6.0 |
| Orange Pi PC (pps-gpio-poll) |
user/kernel (basic) |
17000 |
5.0 +/- 3.0 |
6.2 +/- 8.4 |
| Orange Pi PC (pps-gpio-poll) |
kernel/kernel (xleave) |
17000 |
-10.2 +/- 2.8 |
-8.2 +/- 2.9 |
| LeoNTP v119 |
firmware (basic) |
110000 |
-0.2 +/- 0.02 |
-0.2 +/- 0.04 |
| E3-1220 + I350 |
user/kernel (basic) |
350000 |
-10.5 +/- 2.5 |
-9.2 +/- 7.5 |
| E3-1220 + I350 |
kernel/kernel (xleave) |
240000 |
-13.1 +/- 2.0 |
-10.3 +/- 7.4 |
| E3-1220 + I350 (rsntp) |
user/user (basic) |
1100000 |
-21.2 +/- 5.5 |
-18.8 +/- 13.6 |
| E3-1220 + I350 (PMD) |
user/user (basic) |
1100000 |
0.7 +/- 1.15 |
2.7 +/- 2.76 |
| E3-1220 + X550T (PMD) |
user/user (basic) |
11000000 |
1.7 +/- 1.07 |
1.6 +/- 0.95 |
| I210 @ 1Gb/s |
HW/HW (xleave) |
|
0.0 +/- 0.01 |
|
| I350 @ 1Gb/s |
HW/HW (xleave) |
|
-0.2 +/- 0.01 |
-0.2 +/- 0.01 |
| X550T @ 1Gb/s |
HW/HW (xleave) |
|
0.6 +/- 0.01 |
|
Measurements
Servers using software timestamping
Autoscaled graphs
Fixed-scale graphs
Servers using hardware timestamping
Autoscaled graphs
Fixed-scale graphs
