NAME¶
clockdiff - measure clock difference between hosts
SYNOPSIS¶
clockdiff [
-o] [
-o1]
destination
DESCRIPTION¶
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]
OPTIONS¶
- -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.
WARNINGS¶
- •
- 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.
SEE ALSO¶
ping(8),
arping(8),
tracepath(8).
REFERENCES¶
[1] ICMP ECHO, RFC0792, page 14.
[2] ICMP TIMESTAMP, RFC0792, page 16.
[3] IP TIMESTAMP option, RFC0791, 3.1, page 16.
AUTHOR¶
clockdiff was compiled by Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>.
It was based on code borrowed from BSD
timed daemon. It is now
maintained by YOSHIFUJI Hideaki <yoshfuji@skbuff.net>.
SECURITY¶
clockdiff requires CAP_NET_RAWIO capability to be executed. It is safe to
be used as set-uid root.
AVAILABILITY¶
clockdiff is part of
iputils package and the latest versions are
available in source form at
http://www.skbuff.net/iputils/iputils-current.tar.bz2.