[ntp:questions] NIST vs. pool.ntp.org ?

Robert Scott no-one at notreal.invalid
Wed Mar 27 19:20:00 UTC 2013

I am confused about the proper usage of pool.ntp.org and NIST.
pool.ntp.org seems to be a collection of private sector time servers
offered for all to use, but with registration expected for regular
users.  And NIST has a government run set of time servers.  Neither
group (NIST or pool.ntp.org) seems to include or referece the other.
Are they in competition?  Who normally uses the NIST servers and who
uses pool.ntp.org?

I posted here several months ago about my specific application.  I
want to use SNTP, not to synchronize a system clock but to make a
frequency measurement on the audio sampling rate in a smartphone.  My
use of time servers will be very occasional - typically a user of my
app would only use the time servers once when the app is first
installed to do a calibration of the audio sampling rate in that
phone.  And my app will have very limited circulation.  So I won't be
hitting the servers very often at all.

Today I found the last bug that prevented me from getting response
from the time servers in my socket code.  I had neglected to set the
port number (123) using htons(123) to put the port number in network
byte order.  When I fixed that I finally started getting responses.

I have gotten responses from pool.ntp.org as well as several of the
NIST time servers listed on their website.  However the round-robin
address of time.nist.gov does not seem to return anything.  The recv()
function just times out.  And I sure don't want to hard-code any of
the other NIST server URLs in my app.  I was going to go with
pool.ntp.org until I saw the NIST servers that did not seem to be part
of the pool.

So I guess my main question is which servers should I use for my very
limited application?

Robert Scott
Hopkins, MN

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