Windows uses SNTP to fetch time which is more or less a one-shot deal, same with ntpdate on *nix. SNTP is just a stripped down version of a NTP packet. (You will notice in the internet time tab it says "next sync at...") Your clock will be most accurate right after it syncs, but will slowly drift without any correction. Depending on how good (or bad) the PCs crystal is, some clocks will drift more than others. NTP is a continually running daemon/service which will constantly be adjusting things to make sure your time is as accurate as it can be with the sources you provide.
Depending on your needs, you might just want to stick with window's SNTP (w32time) on the XP machines, but have them sync more often (you can change the parameter in the registry - Google is your friend on this one). The server machines you might want to switch over to NTP as their time accuracy can be more critical (especially for domains - if time is too far off people won't be able to login). There are lots of companies out there that offer NTP based GPS devices. Symmetricom, Zyfer, etc, etc (I'm sure there is a good list somewhere). But you will need access to your building's roof (or at minimum a very good window view in the right direction) for the GPS antenna. Once you hook them up and they are locked, the device has an IP address like anything else on your network and will respond to NTP, SNTP, and other time-related requests. Check out some of the brochures on the Symmetricom site, they will tell you how many thousands of requests per second each machine can handle while still maintaining a certain level of time accuracy across the network. Another alternative is to use a BSD or Solaris machine and hook a GPS (with PPS signal) up to it. I say those two OSes because they already have build in PPSAPI support. Linux will require kernel patching and you probably wouldn't want to do it on a production machine. If you really want to be a stickler for time on your servers you could build you own little "black box" to distribute a PPS signal to all the Solaris machines. With a GPS based PPS source you can get sub-millisecond accuracy on that device. However, over a local network you can still maintain time within a couple ms. IIRC, the 2003 time service is really just a SNTP only server (you can actually enable the SNTP server on an XP machine for people without a MS server product, but that's another story). If you installed a windows port of the NTP program you would get the full blown NTP client / server abilities, so those machines would be able to distribute more accurate time. I think I might have rambled some, but I hope it answers your questions or at least gets you thinking some. ;) Jason _______________________________________________ questions mailing list [email protected] https://lists.ntp.isc.org/mailman/listinfo/questions
