Re: Clock Accuracy (was: no subject)

["Steve Bonds" <pow7yec02 () sneakemail com>]

Kenny:

This really isn't a tcpdump question per se, but a question about the
precision of your system's local clock.

You can find out more than you ever wanted to know about system time by
following some links from the NTP (Network Time Protocol) website:

http://www.ntp.org

I also found this useful:

http://www.tldp.org/HOWTO/mini/Clock.html

And google is always helpful:

http://www.google.com/search?hl=en&q=linux+clock+precision
http://www.google.com/search?hl=en&q=linux+time+precision

The answer is-- there is no one answer.  It will depend on who made your
motherboard, the patches applied to Linux, and possibly on what programs
are running at the time.  The tcpdump warning is just that-- a warning
that even though your timestamps are recorded to the microsecond
(millionths of a second), they may only be accurate to some level higher
than that.

Most modern PCs can be expected to be precise to a level of 10
milliseconds (thousandths of a second) for time measurements made in quick
succession, and some do much better.

  -- Steve

On Tue, 29 Apr 2003, qshao-at-sfu.ca |TCPdump Workers| wrote:

> Hi, there:
> I am fresh man here.
> I have collected some data from a PIII machine, under Redhat 7.0 ,kernel
> 2.2.16-22 tcpdump version: 3.7.1. 
> I was wondering if someone can tell me the granularity of the timestamps. I
> read some description about tcpdump file which said " Timestamps have
> millisecond precision, even though they are reported using six digits past
> the decimal. "
>
> Is it true? I thought it should be depend on the machine, if I am right, can
> anyone give me a feeling about the time granularity my data? millisecond? or
> serval microseconds?
> Many thanks!
>
> Kenny

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