Hi Bob, Lots of good general info here: http://ntp.org/
More specific info here: http://support.ntp.org/bin/view/Servers/WebHome In general, if your need is very important, and you're serving time to a bunch of other computers, you can access some stratum 1 time servers. They are connected directly to an official "source" of time, such as an atomic clock or a GPS or a radio clock. Use these only if you have to, as they are very heavily loaded. If your needs are less severe, you can use some stratum 2 time servers. They use stratum 1 servers as their source. Stratum 1 list: http://support.ntp.org/bin/view/Servers/StratumOneTimeServers Stratum 2 list: http://support.ntp.org/bin/view/Servers/StratumTwoTimeServers In either case, scroll down the list until you see location US or US TX. You should find some good options there. Click on each server entry to find more details about it. You should also consider the NTP Pool project. With those servers, the routers choose one or more servers for you at random. Info here: http://www.pool.ntp.org/en/ http://www.pool.ntp.org/en/use.html http://www.pool.ntp.org/zone/north-america http://www.pool.ntp.org/zone/us In your case, you probably want to use US specific pool servers. You can do this by putting the following in your ntp.conf file. server 0.us.pool.ntp.org server 1.us.pool.ntp.org server 2.us.pool.ntp.org server 3.us.pool.ntp.org In my case, I have 4 servers specifically chosen from the stratum 2 list, and 4 US pool servers as indicated above. I'm located in Georgia. As someone else said, you can set up your own stratum 1 time server by attaching a GPS to your PC and getting time from there. You can get different levels of accuracy depending on how you attach it. The GPS itself will generally have an accuracy of 1 us or better. Getting the data into the computer is the trick. From my experience, you may expect the following at the computer in Windows. Linux is better.: Attach with USB: ~ + / - 10 ms accuracy Warning, using this method, you are reading time data from the GPS in the form of ASCII strings, referred to as NMEA data. This data varies in it's timing on some GPS's over time by about 70 ms or so in either direction. So, overall, the solution is not very accurate and not much better than you get from the internet. However, if + / - 100 ms is good enough for you, you could use this. This still has the advantage of being able to run without internet access. Attach with USB with PPS (pulse per second) signal to the DCD pin (pin 1) running through a USB - Serial converter: ~ + / - 1 ms accuracy Attach with SERIAL connection with PPS to signal to the DCD pin (pin 1): ~ + / - 40 us accuracy Once you have your own stratum 1 server running, it can serve time to other computers on your personal LAN. You want to make sure you have security restrictions in ntp.conf. I'll be glad to share mine if needed, but I'm not at that computer right now. You also want to set your software firewalls to allow ntp communication within your LAN, but not incoming from the internet without you first requesting it. In my case, the network latencies on my wifi LAN vary widely, from a few ms when idle, to hundreds of ms when heavily used. My approximate results for other computers not connected directly to the GPS are as follows: Poll a local stratum 1 server on my LAN: ~ + / - 10 ms accuracy Poll a remote internet server: ~ + / - 50 ms accuracy As I said, Linux generally performs better than Windows. These results are from Windows. Some people get much better results from internet polling, depending on their network configuration. I'm certainly not an expert on NTP, but I'd be glad to answer any questions about how I got my stratum 1 server running. It is, by the way, cross platform. So, I can boot into Windows or Linux and it still works. Sincerely, Ron -- Sent from my Android Acer A500 tablet with bluetooth keyboard and K-9 Mail. Please excuse my potential brevity. (To whom it may concern. My email address has changed. Replying to former messages prior to 03/31/12 with my personal address will go to the wrong address. Please send all personal correspondence to the new address.) (PS - If you email me and don't get a quick response, don't be concerned. I get about 300 emails per day from alternate energy mailing lists and such. I don't always see new email messages very quickly. If you need a reply and haven't heard from me in 1 - 2 weeks, send your message again.) Ron Frazier timekeepingdude AT techstarship.com [email protected] wrote: Can someone help me figure out a really good NTP server near Houston? Thank you. _____________________________________________ questions mailing list [email protected] http://lists.ntp.org/listinfo/questions _______________________________________________ questions mailing list [email protected] http://lists.ntp.org/listinfo/questions
