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December 2016

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From:
Curtis Schroeder <[log in to unmask]>
Reply To:
SAC-PSG-CIGI <[log in to unmask]>
Date:
Fri, 30 Dec 2016 15:40:09 -0500
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More Windows NTP background material (http://dataturbine.org/documentation/technical-articles/network-time-sync-and-dataturbine/):

Windows also uses NTP for clock synchronization. Unfortunately, it uses SNTP (Simple NTP) instead of the full protocol. (According to this page, Windows 2003 does use NTP, the rest use SNTP. Microsoft confirms this.) SNTP has a number of limitations that make it problematic:

    * NTP adjusts the clock on the fly, so that the time changes gradually. SNTP does single corrections and simply resets the clock. For software, this means that the system clock time may suddenly change.
    * The native time synchronization was designed for the Kerberos ‘loose sync’ specification, which only requires that PC clocks only be within 20 seconds of each other. (Reference: this MS (Word format) document on their time implementation).
    * By default, SNTP is only run once every eight days. It runs daily on an Active Domain.
    * SNTP does not account for local clock inaccuracy, so between syncs the clock will drift uncorrected.

There are several ways to get better synchronization on Windows:

    * Run SNTP more often. This can be done by a free Java program, the NetTime (open source pascal) program or by editing the registry to use NTP.
    * Run a full NTP client. Although it started as a Unix program, NTP has been ported to Windows. Meinburg hasthis page of clients, including installers and GUIs.

So, testing on Windows with a full NTP client, instead of the built-in SNTP client, could definitely make a difference in NTP timing accuracy between the CIGI host & IG.

Curt

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