[Aavso-photometry] Internet Time Sync

[Wolfgang Renz]

Hi Tim

Primary (stratum 1) and secondary (stratum 2) NTP time servers have
an access policy and therefore usually have at least voluntary restrictions
to avoid overloading them (if this happens, they might tighten their
restrictions or even stop their service):
   http://ntp.isc.org/bin/view/Servers/RulesOfEngagement

Stratum servers are intended to be used to synchronize other time servers.
They are NOT intended to be queried by single computers say every 10 min !
tick.usno.navy.mil and tock.usno.navy.mil are such primary stratum 1 time
servers that have a restricted access:
   http://ntp.isc.org/bin/view/Servers/RestrictedAccess
   http://ntp.isc.org/bin/view/Servers/TickUsnoNavyMil
   http://ntp.isc.org/bin/view/Servers/TockUsnoNavyMil
So its better to not use them for ordinary NTP users.

Here you can find all time servers.
NTP Home - NTP.Servers Web:
   http://ntp.isc.org/bin/view/Servers/WebHome
Public NTP Primary (stratum 1) Time Servers (intended to synchronise secondary servers)
   http://ntp.isc.org/bin/view/Servers/StratumOneTimeServers
   http://www.eecis.udel.edu/~mills/ntp/clock1a.html
Public NTP Secondary (stratum 2) Time Servers (intended to synchronise LANs/WANs)
   http://ntp.isc.org/bin/view/Servers/StratumTwoTimeServers
   http://www.eecis.udel.edu/~mills/ntp/clock2a.html
Public NTP Pool Time Servers (intended to synchronise computer clocks)
   http://ntp.isc.org/bin/view/Servers/NTPPoolServers
   Area:          HostName:                   PoolServers:
   Worldwide      pool.ntp.org                http://www.pool.ntp.org/zone/@
   Africa         africa.pool.ntp.org         http://www.pool.ntp.org/zone/africa
   Asia           asia.pool.ntp.org           http://www.pool.ntp.org/zone/asia
   Europe         europe.pool.ntp.org         http://www.pool.ntp.org/zone/europe
   North America  north-america.pool.ntp.org  http://www.pool.ntp.org/zone/north-america
   Oceania        oceania.pool.ntp.org        http://www.pool.ntp.org/zone/oceania
   South America  south-america.pool.ntp.org  http://www.pool.ntp.org/zone/south-america

To synchronise computer clocks one should use pool servers.
For these there exist also sub-zones by country:
   For the US see:
   http://www.pool.ntp.org/zone/us
These might be closer to you computer and therefore even have a shorter
ping round trip time than some stratum servers. 

If you still feel the need to query stratum time servers, please restrict yourself
to use secondary stratum 2 time servers.


Clear skies
 Wolfgang

-- 
Wolfgang Renz, Karlsruhe, Germany
Rz.BAV = WRe.vsnet = RWG.AAVSO



----- Original Message ----- 
From: "Tim Crawford" <tcarchcape at yahoo.com>
To: <aavso-photometry at mira.aavso.org>
Sent: Tuesday, April 03, 2007 1:13 AM
Subject: [Aavso-photometry] Internet Time Sync

>I try to use one of the following two server sources,
> each time I observe:
>     tick.usno.navy.mil
>     tock.usno.navy.mil
> 
> These can be busy sources so if one is busy try the
> other; they are easy to add to your server list on the
> internet time tab of the date and time control panel.
> 
> Ad Astra
> 
> Tim Crawford  CTX
> Arch Cape Observatory