Posted by Moe Trin on 07/01/07 23:42

On Sat, 30 Jun 2007, in the Usenet newsgroup comp.os.linux, in article
<dZxhi.4257$Io4.646@edtnps89>, Unruh wrote:

>ibuprofin@painkiller.example.tld (Moe Trin) writes:

>>I'd change network providers too. In the thirty-four years I've been
>>in networking, the longest we've been disconnected is six hours - the
>>classic 'backhoe fade' thanks to the city water department.

>Look, if you are really that desperate for accurate times, get a gps
>receiver with pps capability.

I'm not desperate for accurate times - we've been setting our servers
to a time standard for decades. We started by using the time ticks from
WWVB back in the 1970s, before we had IP. We've had GPS time receivers
for at least seven years, but that's in addition to the use of NTP pool
servers and company peers (which - surprise, surprise - also have GPS
receivers and use NTP pool servers).

>That will keep your system accurate to microseconds . And it will not
>go off when your network disconnects.

Actually, that wake-up call from the city occurred back in ~1992, and
prompted us to get redundant network connections in the same year. The
fun is verifying that your connections are indeed redundant, and not
running in the same conduit as leased pairs from your primary provider.

>And they are cheap ( the one I bought was less than $100) Use ntp to
>sync to it, not to th enetwork ( which is certainly not good to even
>msec, never mind microseconds).

Maybe you want to read the NTP documentation. If all you have is one
time source, you are indeed unable to correct for propagation delays.
But if you have more than that (can you say "redundancy" Bill? I
though you could), you can deduce and eliminate nearly all of the
delays.

>Then slave your other computers to that one as a stratum 1 server.

-rw-rw-r-- 1 gferg ldp 43295 Nov 18 2005 TimePrecision-HOWTO

>> Thus, there are three time servers here, each monitoring _separate_
>> time sources, and averaging that to 'tweak' their own concept of
>> correct time, and we're not even subject to those regulations - they
>> are only serving time to 2500+ users in this facility, and acting as
>> a stratum 4 reference to other time servers in other company locations.
>
>Why not get a gps clock with the network as backup?

Read the docs from Dave Mills at UofDelaware. He writes pretty well.

Old guy

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