CLOCKDIFF(8)						 System Manager's Manual: iputils					      CLOCKDIFF(8)

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

       o Some nodes (Cisco) use non-standard timestamps, which is allowed by RFC, but makes timestamps mostly useless.

       o Some nodes generate messed timestamps (Solaris>2.4), when run xntpd. Seems, its IP stack uses a corrupted clock source, which is synchro-
	 nized	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.

       o 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.

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 for anonymous  ftp  ftp://ftp.inr.ac.ru/ip-rout-
       ing/iputils-current.tar.gz.

iputils-020927							 27 September 2002						      CLOCKDIFF(8)