NTP Server

Mon Oct 25 14:56:29 UTC 2010

> On Sun, 24 Oct 2010, George Bonser wrote:
> > The main reason for that is that the "free" servers won't remain "free"
> > if every single individual host on the Internet is hitting them.  By
> > running your own internal servers a stratum down you offload that
> > traffic from the public servers and preserve that resource.  NTP is a
> > great candidate for v4 anycast, too, so you can have a common
> > configuration at all your locations if you want.
> 
>   It sure would be nice if datacenter facilities offered an independent NTP
>   time source as a benefit for hosting with them.  It would also be great if
>   ISPs would offer this on the local network as well for their customers, as
>   likely they are already have one in several regions.
> 
>   time.windows.com and time.apple.com are also fine, though I'm not sure
>   either has published their NTP source, whether it is a device or they are
>   simply using the same ntp.org pool as many of us.
> 
>   I've never had a problem with the public NTP sources, but as George said,
>   "free" may not always be "free."

That's particularly true given what some of the free servers have been
made to endure.  For example, Netgear caused UW Madison a ton of trouble
with a defective product that caused a traffic flood:

http://pages.cs.wisc.edu/~plonka/netgear-sntp/

NTP is not that hard to provide.  Set up four servers.  If you only care
about relatively stable time, they probably need only be stratum two, this
is easy, just go and sync each one with two different stratum one servers,
monitor them, and tell customers that it's a free service you make a
reasonable attempt to keep running accurate to the second, and that your
goal is to keep three operational at any time.

Your internal servers can then run NTP to sync with those servers; the use
of four will make the failure of up to two (one offline, one with the wrong
time, for example) fairly tolerable.  Some customers will not care to
listen to instructions to sync to four clocks.  You have to consider how to
make their failure to listen to you to be their own problem.

Four is, IMHO, the best number of servers to have.  They do not need to be
fast or modern machines.  You can use something cheap like a pile of old
Intel ISP1100's (~40-50 watts each) which might even be doing something
else like DNS, monitoring, etc. if you have to.

Speaking of which, if anyone is in need of some nice Intel ISP1100's, we
are retiring some.  Great low power platform for basic services like NTP,
proc speeds up to 1GHz, memory up to 1GB, two PCI slots, serial console
capable, etc.  Available fairly cheap.  Great for things like NTP, DNS,
we've got one for our FTP archive, Asterisk PBX, etc.

... JG
-- 
Joe Greco - sol.net Network Services - Milwaukee, WI - http://www.sol.net
"We call it the 'one bite at the apple' rule. Give me one chance [and] then I
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With 24 million small businesses in the US alone, that's way too many apples.