[ntp:questions] looking for public NTP servers

Richard B. gilbert rgilbert88 at comcast.net
Thu Mar 1 18:30:15 UTC 2007

oquinones at commercebankfl.com wrote:
> I am located on Miami Florida , 33172. At the moment I am syncronized with 
> I would like to setup a secundary NTP 
> server for redundancy. Any sujestions?
> Osvaldo Quinones


You will find lists of public stratum 1 and stratum 2 servers at:

Try to select servers that are close to you; e.g. in Florida, Georgia, 
Alabama, South Carolina, etc.  Other things being equal, closer is 
better.  If your internet gateway is located in, say, New Jersey then 
the best you can do is to choose servers in New Jersey, Pennsylvania, 
Delaware, New York, etc.

For reliability you should have a minimum of four servers.  Two servers 
is the worst possible configuration; when they differ, as they 
inevitably will, which one do you believe???  A configuration with four 
servers can survive the failure of any one server.  A five server 
configuration can survive the loss of two servers.  Seven servers 
protects against three failing servers.  If four or more of your servers 
fail, you have probably made poor choices of servers! :-)

Look for servers with low values of round trip delay.  Delays of up to 
twenty-five or thirty milliseconds are okay.  The delay is important 
because it limits the maximum error in transmitting time from server to 
client to one half the round trip value.  The error will usually be much 
less but can't possibly be more.

If you have a single path to the internet, that path is a single point 
of failure!

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