CLOCKDIFF 8 iputils clockdiff measure clock difference between hosts clockdiff -o -o1 destination clockdiff Measures clock difference between us and destination with 1 msec resolution using ICMP TIMESTAMP [2] packets or, optionally, IP TIMESTAMP option [3] option added to ICMP ECHO. [1] -o Use IP TIMESTAMP with ICMP ECHO instead of ICMP TIMESTAMP messages. It is useful with some destinations, which do not support ICMP TIMESTAMP (f.e. Solaris <2.4). -o1 Slightly different form of -o, namely it uses three-term IP TIMESTAMP with prespecified hop addresses instead of four term one. What flavor works better depends on target host. Particularly, -o is better for Linux. • Some nodes (Cisco) use non-standard timestamps, which is allowed by RFC, but makes timestamps mostly useless. • Some nodes generate messed timestamps (Solaris>2.4), when run xntpd. Seems, its IP stack uses a corrupted clock source, which is synchronized to time-of-day clock periodically and jumps randomly making timestamps mostly useless. Good news is that you can use NTP in this case, which is even better. • clockdiff shows difference in time modulo 24 days. ping8, arping8, tracepath8. [1] ICMP ECHO, RFC0792, page 14. [2] ICMP TIMESTAMP, RFC0792, page 16. [3] IP TIMESTAMP option, RFC0791, 3.1, page 16. clockdiff was compiled by Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>. It was based on code borrowed from BSD timed daemon. clockdiff requires CAP_NET_RAW capability to be executed. It is safe to be used as set-uid root. clockdiff is part of iputils package.