[ntp:questions] Can NTP sync within 1ms

Charles Elliott charles.elliott316 at comcast.net
Sat Apr 26 12:26:50 UTC 2014

      I use Windows 8.1 and regularly see offsets of less than 1 ms.  

Right now the offset is -0.105 and the jitter is 0.028.  Twas not 

always thus; several factors contributed to these results:


1. Use of Gigabyte Ethernet on the LAN, and the LAN is lightly loaded.  


2. A high speed Internet connection; either 15 Mbps or about 28 

   Mbps will improve accuracy because the delays between your 

   LAN timer server and the Internet time servers are more consistent 

   and more than halved WRT to a 1-3 Mbps connection.


3.  The NTP client and LAN server is on a computer that runs FreeNAS, 

    which is lightly loaded.  FreeNAS runs on FreeBSD.  Anecdotally, 

    NTPD serves more accurate time on FreeBSD.


4. The ISP router to which you are connected really matters.  

   If that router is congested so that delays through it vary by time 

   of day, or increase greatly every time a neighbor downloads a movie 

   or other long file, then you will serve widely varying time to the LAN.


5. The Internet Stratum 2 or 1 time servers you choose should be close-by 

   (50-75 miles) and lightly loaded.  If your LAN time server accesses 

   time from a heavily loaded network and/or server, or the servers are 

   more than 50-75 miles away, there is little hope of serving time with

   low jitter.  You can find a list of U.S. Government time servers and 

   their status by searching for "NIST time servers," and of course 

   there is a complete list of servers on www.ntp.org.



Charles Elliott

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