[ntp:questions] Re: Tiime Sync solution

Adrian 'Dagurashibanipal' von Bidder grazdan at fortytwo.ch
Tue May 31 18:08:54 UTC 2005


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Clinging to sanity, Richard B. Gilbert mumbled in his beard:

> Eric Liu wrote:
[need 1ms accuracy in LAN]


> For 1 millisecond accuracy you will probably need to install a
> hardware reference clock on your master server.  Getting such accuracy
> from  servers on a WAN is chancy at best.

While I agree that anything better than 10ms over regular Internet
connections is pure luck, note that if you only need 1ms accuracy
*relative* between the machines on the LAN, instead of 1ms accuracy to
'real' UTC (as determined by whatever reference source you use), you
may be able to go without a hardware reference.

When you design your time infrastructure, pay attention that the LAN is
fast enough and has only little load - if in doubt, use a dedicated
'time network' in parallel to your regular data network.  You didn't
say what operating system you're using - it is said that Windows is
horrible at timekeeping, Linux is ok, FreeBSD is best (not sure if the
latter only applies for hardware reference clock performance or for
general ntpd use.)  I don't know about others - though I remember it
being discussed in this group.

My two old 350MHz machines here at home, connected over 10Mb LAN,
half-duplex, has something in the range 1 to 2ms offset usually, with a
quite small network load.  So I guess faster hardware and especially a
faster network should easily drive that down to where you want it.


cheers
- -- vbi

- -- 
work, n.:
        The blessed respite from screaming kids and
        soap operas for which you actually get paid.

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