Linux and ICMP timestamp requests. Post: 41317

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clockdiff

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.	It  is	now  main-
       tained by YOSHIFUJI Hideaki <yoshfuji@skbuff.net>.

SECURITY

       clockdiff requires CAP_NET_RAW 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-cur-
       rent.tar.bz2.

iputils-121221							   10 June 2014 						      CLOCKDIFF(8)

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