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Do You Have The Time? 451

Posted by timothy
from the what's-the-time-mister-wolf dept.
RetroGeek writes: "This ZDNet article talks about the perils of the PC clock. And (something I did not know) that Windows XP and Mac OS X both automatically get a time stamp from MicroSoft and Apple respectively. At any rate, my home firewall gets the time every hour from the NIST servers, then each of the machines on my LAN query the time server daemon on the firewall. That way all my home network machines have the same time. And latency on the LAN is next to zero. Now if I can only get my VCR connected. Anyone else running a time server?" So how do you get the time?
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Do You Have The Time?

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  • by Ethelred Unraed (32954) on Thursday July 04, 2002 @06:09PM (#3823975) Journal

    I look at a clock. Or maybe my (wind-up) wristwatch.

    Sheesh. Geeks. If it ain't digital, it ain't.

    Cheers,

    Ethelred [grantham.de]

    • I look at the display on my dash, wrist, cell, or whatever happens to be available in line of sight. For my organic needs, "accurate within a few minutes" is accurate enough.

      For my LAN, I have two machines running ntpd, getting their sync from two different sets of time servers. The other machines on the LAN sync to the two local time servers.

      My digital needs require better than "within a few minutes" accuracy.

    • I look briefly at the time when I set up my computer, ensure that it's within the proper range of "It's light out" or "It's dark out" and leave it be.

      Late for a meeting? "Oh my god! The clock on my PC was wrong! Damned XP time-synch decided I was in Hungary.

      Seriously, though, I prefer setting the time myself from my watch or from the microwave in the lounge, or from calling out to a co-worker "Hey Sam! Got the time?"

      I just feel odd about letting *anything* remote change any setting on my computer, even if it's just the time. ESPECIALLY if I'm on Windows. I mean... How long before there's a clock-virus? :p

      -Sara
  • by shoppa (464619) on Thursday July 04, 2002 @06:10PM (#3823976)
    1. Roofmounted Trimble SVeeSix-CM3 GPS receiver with microsecond-accurate pulse-per-second output: $24.95 [bgmicro.com].
    2. Network Time Protocol synchronization software: Free [udel.edu]
    • by ceejayoz (567949) <cj@ceejayoz.com> on Thursday July 04, 2002 @06:24PM (#3824038) Homepage Journal
      3. Having the correct time, always: Priceless [mastercard.com].
    • That's probably alot better than the roofmounted sun-dial and array of lightsensors that I have.
    • I mean, geeze. I know some people who aren't the best with directions, but you're the only one I've ever heard of that needs to know the Latitude and Longitude of his house to get back... Or is this just in case the foundation shifts?
    • Radioshack has a wall clock that checks for (i forget the exact title) a radio signal that the Gov and NASA use to synchronize their time.

      Click here! [radioshack.com]

      noonch
      • Re:Atomic Wall Clock (Score:3, Interesting)

        by Phork (74706)
        It gets the signal from wwvb in colorado, which broadcasts the time on 60khz encoded in bcd using some odd modulation scheme. wwvb time is very accurate, at the trasmitter i think the accuracy is within a picosecond. If you know your location you can calculate the time it takes the signal to reach you from the transmitter, and get your time as accurate as the clock at the transmitter. WWVB is run by NIST. They also run two other radio stations, wwv and wwvh. WWV broadcasts from the same site in colorado that WWVB broadcasts from, but broadcasts a voice signal of the time, a pulse every second, as well as bcd and several other things. WWV broadacts on 2.5, 5, 10, 15, and 20 MHz. WWVH broadcasrs the same thing as WWV but is located in hawai, has a female voice instead of the male voice that WWV has, and doesnt broadcast on 20mhz. WWV rocks.
    • I see I'm not the only one, so details!

      I've been looking for a cheap GPS time receiver that interfaces with standard ntpd nicely. I can see you're on to something with these referb units, and the serial converter you mention. I could probably figure this out given enough time, but a few more details of what you bought, and how you hooked it up would be really nice. If I can get this going for

  • IP spoofing target (Score:4, Insightful)

    by RichMan (8097) on Thursday July 04, 2002 @06:12PM (#3823981)
    Ok, this is bad. A somewhat critical state of the OS is dependant on a blindly connected service. Please tell me the time server is authenticated fully and unbreakably. Hah.
    Just wait for
    1) MS to implement expirable licenses on all software
    2) someone to break the authentication service
    3) IP spoofing of the time server to a clock set 100 years in the future when everyones time based license has expired

    The result is instant crippling of all MS licenses!
    • by FearUncertaintyDoubt (578295) on Thursday July 04, 2002 @06:48PM (#3824117)
      You forgot:

      4) ???
      5) Profit

    • by The Monster (227884) on Thursday July 04, 2002 @07:18PM (#3824220) Homepage
      The summary says that you have to get your sync from MS. Fortunately, this is untrue. I see two choices when I'm running XP:
      • time.windows.com
      • time.nist.gov
      Take a wild guess which one I chose...

      But if you want more choices than that:
      This article inspired me to do some dumpster-diving in the Registry... Import this key/value:

      [HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\ W32Time\TimeProviders\NtpServer]

      "InputProvider"=dword:00000001
      This allowed me to set my own choice of NTP server, and then synced from it. Like many other MS 'features', the
      default can be changed, if you know how...
      • by The Monster (227884) on Thursday July 04, 2002 @07:52PM (#3824301) Homepage
        A few more moments perusing the Registry reveals that you can also set the interval between syncs:
        [HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\ W32Time\TimeProviders\NtpClient]

        "SpecialPollInterval"=dword:00003840
        The value '3840' there is hex for 14400, the number of seconds in 4 hours. Note that setting
        the key won't affect the next, but the one after that will read this value to determine the time
        for the one after that.
    • I don't think so :) If you didn't want your subscription to expire you could set your computer to look at a local ntp server instead of MS, and have your subscription never expire. I'm guessing they do a little more than if (date expire_date) { on the computer to see if your license expired. And don't make bogus claims you can't back up, quit with the "all they have to do is..." attitude. You post is so subjective it sounds like you don't have the slightest clue what it takes to accomplish what you're saying.
  • by lakeland (218447) <lakeland@acm.org> on Thursday July 04, 2002 @06:12PM (#3823982) Homepage
    Personally I arbitarialy declare the firewall as having the same time and use cron to update everyone from that. Since latency between machines is almost equal, everybody is out by the same amount.

    Before anybody thinks it is silly to keep clocks tightly synchronised, try running NFS without it and you'll run into no end of problems. Even as little as one second will cause errors with make. The key is that all clocks must read the same, not that they need to be correct.

    Oh, and don't get fooled into thinking you can accurately synchronise against those atomic clocks. The algorithms they use to average results make a number of incorrect assumptions that will result in you being out by a small constant amount, about as much as if you'd synchronised off an ordinary clock.
    • Since latency between machines is almost equal, everybody is out by the same amount.

      NTP uses a nifty little algorithm to compensate for network latency. I forget the details but it makes little difference whether you sync from a LAN box or from one on the other side of the planet.
  • School server time (Score:2, Interesting)

    by agent oranje (169160)
    At my school, a time server is set up to keep the computers on the network within a certain range of time. I believe the purpose of this is for security, as we can't renew our kerberos tickets if our time is more than X minutes from the server's specified time.
  • around the clock (Score:2, Insightful)

    by jean-guy69 (445459)
    So how do you get the time?
    using one of these [udel.edu] ?
  • Time for my VCR (Score:5, Interesting)

    by the eric conspiracy (20178) on Thursday July 04, 2002 @06:14PM (#3823990)
    Some VCRs including my JVC can get a time signal that is broadcasted by PBS stations via cable. It's wonderful to never have to set that puppy.Combined with ntp for my computers, and WWV for my stand alone clocks (so called 'atomic alarm clocks' I am down to one clock that I have to set - my wristwatch.

    • Re:Time for my VCR (Score:5, Interesting)

      by Mr. Sketch (111112) <mister.sketch@gCOUGARmail.com minus cat> on Thursday July 04, 2002 @06:19PM (#3824017)
      I am down to one clock that I have to set - my wristwatch.

      Not if you had one of these [thinkgeek.com].
      • Check your local mass merchant. On the West Coast we have Fred Meyer. They carry a line in the $50 range. The casio brand is high enough volume to provide economy of volume while providing a quality product. They have the usual utility watch features including water resistant.
        A list of the watches can be seen here in the $50 price range. It includes LaCross and Casio brands.
        http://www.gadgets4sure.com/cgi-bin/ePage s.filerea der?3d24dd6b001506400000c0a8013a0569+EN/catalogs/1 23581

        However if you are looking for pure geek appeal, check out the solar powered ceramic case model for over a grand here..
        http://www.shoplifestyle.com/store/product .asp?dep t%5Fid=26%5Fid=4158=0VK0N50BE5XM8GVTV55B2GRBB1W2DP RC
      • by MrCreosote (34188) on Thursday July 04, 2002 @08:49PM (#3824489)
        'My watch is accurate to 1 second in 1 million years'

        'So what time is it now?'

        'Uhh, about quarter past.'
  • by krez (75916) on Thursday July 04, 2002 @06:14PM (#3823991) Homepage
    There's a nice open-source utility at Sourceforge (http://sourceforge.net/projects/nettime/) that I use at work on my Windows machine.

    I like it because it's simple, unobtrusive, and invisible once it's installed.
  • apple's time stamp (Score:4, Informative)

    by Juanvaldes (544895) on Thursday July 04, 2002 @06:14PM (#3823992)
    Well, you can turn it off if you want...
    System Pref's ->Date & Time -> Network Time
    • Win XP's time stamp (Score:2, Informative)

      by NaDrew (561847)
      You can turn off Win XP's time stamp easily too:

      Control Panel -> Date and Time -> Internet Time -> [x] Automatically Synchronize With An Internet Time Server.

      You can also have it use time.nist.gov instead of the default time.windows.com (if you don't want your machine checking in with MS once a week).
    • by foniksonik (573572)
      Or you can do what I do and set your NTP server to ntp.nasa.gov !!! Does anyone think that NASA is going to fool around with their time?

      OS X at least allows you to choose where youget your time setting from, i don't know about XP.

      OS 9 did the same. I've always used NASA's NTP server for time synch.
  • Simple (Score:3, Informative)

    by Mr. Sketch (111112) <mister.sketch@gCOUGARmail.com minus cat> on Thursday July 04, 2002 @06:15PM (#3823995)
    time.org [time.org].

    I can even get the date too :)
  • http://www.ntp.org (Score:4, Informative)

    by MavEtJu (241979) <slashdotNO@SPAMmavetju.org> on Thursday July 04, 2002 @06:16PM (#3824000) Homepage
    Go to http://www.ntp.org [ntp.org] to get all your time-synchronisation questions answered.

    Also for in- or near-Germany living people: http://www.dcf77.de [dcf77.de]. Wish I knew it was a german-specific service before I came to .au and found out that my DCF77 receiver didn't work here...
  • Some newer VCRs (and therefore probably DVD players) have this feature that allows them to set their time to a time signal on a certain channel, usually public television in the US. The station transmits the time via XDS (extended data services). Maybe you could set up something with a TV card on your time server...

    oh dear... too... much... hacking... ;-)
  • by halftrack (454203)
    Look at my left wrist, and see if it checks with my pc-clock. If not I set it - that is; the pc-clock.
  • by angio (33504) on Thursday July 04, 2002 @06:18PM (#3824014) Homepage
    As part of the Resilient Overlay Networks [mit.edu] project at MIT, I maintain a testbed of about 20 nodes, most of which have GPS-based time synchronization. We've started using a really fun little box from EndRun Technologies [endruntechnologies.com] called the Praecis Ct. It gets GPS time that's being rebroadcast by cellular CDMA base stations. They provide accuracy to about 10 microseconds, and don't require a roof antenna -- anywhere you can get CDMA cellular service, you can use these things. They're kind of pricey (about $1k), but they're completely easy to use and set up. For more general information about NTP and things, see ntp.org [ntp.org], which mtaintains a nice FAQ about things-ntp.

    For a few of the european hosts, we use GPS time receivers, primarily the Motorolla Oncore UT+ kits. You can get eval units of these, google around. They're nearly as easy to use, but do require a kernel config change.

    It's really kind of addictive playing with time. :-) And you get spoiled by never having any clock weirdness on any of your machines...

  • I found... (Score:5, Interesting)

    by IanBevan (213109) on Thursday July 04, 2002 @06:18PM (#3824016) Homepage
    ..that the Microsoft time server was 3 minutes slow ! This was about 2 weeks ago. I checked it against both another time server, and then the UK speaking clock (dial 123 in the UK) which is synchronised with Greenwich. As a result, I disabled the time synch (right click on the time in the system tray, Adjust Date Time, Internet tab, uncheck the box). I now use the time synchronisation feature that comes with the Dynip [dynip.com] client.
    Since the MS time synch is enabled by default, they really should make sure their server farm has the correct time :(
  • I run ntpd on my firewall machine and set it to broadcast over the local network once a minute.

    The local machines run a small (64k) utility called K9 which listens for the broadcast and sets the time accordingly. I found most time clients for windows were very large and much to bloated for what I wanted to do. K9 works perfectly. There is even source code available for your favorite flavour of *NIX
  • I have the time (Score:2, Informative)

    by billsf (34378)
    If you use UNIX, just set up ntpd. You are often
    requested to inform the providers of stratum one
    servers that you use them. Since most NTP
    servers discriminate against end-user DSL and
    cablemodem services, i offer a "stratum 2" service
    for these people.

    All told, all my friends have the time to a few
    milli-seconds, a vast improvement over what the
    local telco can offer.

    As for Windoze, i know nothing, but believe
    NTPD is somewhat functional.Time is very
    important for UNIX and all secure services.

  • by burnsy (563104) on Thursday July 04, 2002 @06:23PM (#3824035)

    UNFORTUNATELY, the clients in Windows and Mac OS aren't ideal. They share two problems: First, they may not synchronize often enough.

    That Coursey sure is a whinner and clearly he does little research. I took me 15 seconnds to find this at Google.

    To control the number of seconds to wait between attempts to synchronize the system clock to an time source on the Internet using the following Windows XP...

    Hive: HKEY_LOCAL_MACHINE
    Key: SYSTEM\CurrentControlSet\Services\W32Time\TimeProv iders\NtpClient
    Name: SpecialPollInterval
    Type: REG_DWORD
    Value: #secondsdesired default

  • by Dr. Ion (169741) on Thursday July 04, 2002 @06:24PM (#3824039)
    If you're on cable or DSL, most of the upstream routers run proper NTP servers, and they're just a hop away. The bandwidth for running an NTP client is minimal.

    To find the nearest NTP server, to a traceroute to a few non-local hosts. Then start at your nearest router and ping each one for a time server using something like 'ntptrace'.

    Near-perfect accuracy, just a trickle of data, and your provider will thank you for using nearby machinery.
  • by Dr. Awktagon (233360) on Thursday July 04, 2002 @06:24PM (#3824045) Homepage
    On your Red Hat Linux server/firewall/whatever (easily adapted to any NTP setup, really):

    ntp.conf:
    server time.apple.com
    server tick.usno.navy.mil
    server tock.usno.navy.mil
    # In case the network is down
    server 127.127.1.0
    fudge 127.127.1.0 stratum 10

    broadcastdelay 0.008
    authenticate no

    driftfile /etc/ntp/drift
    pidfile /var/run/ntpd.pid
    logfile /var/log/ntpd

    and /etc/ntp/step-tickers has the IP addresses for those hosts, all one line (the Red Hat startup script uses these to set the clock at boot, in case it's WAY out of sync.):

    17.254.0.27 192.5.41.40 192.5.41.41 17.254.0.26 17.254.0.31

    Then on your LAN, have all your other machines use this machine as the time server. That's it! Never set a clock again.

    It's important to have accurate time for many protocols, including HTTP, and also to timestamp your logs accurately for forensics and evidence.

    For even more accurate and secure local timeservers, run a GPS antenna to your roof and buy one of these products [truetime.net].
    • Don't use the master clocks unless you need that kind of accuracy (then ask them and they will give the the names of better servers).

      Do a traceroute out out of your net and see if you can find a few other servers.
      $ ntpdate -v -u 64.39.2.65
      will tell you if its running ntp or not. Pick a few of your upstream and go with that. If you have several upstream routes/providers then ntp will make sure you get the correct time if one of them gets way out of sync.

  • nexus:~# ntpdate time.nist.gov
    4 Jul 15:17:34 ntpdate[26989]: adjust time server 192.43.244.18 offset 0.000626 sec
    nexus:~# date
    Thu Jul 4 15:17:22 MST 2002


    It's 3:17 PM right now. So yes, I know what time it is. Debian users can apt-get install ntp or ntpdate... it should be part of the base system in freebsd, and the NTP homepage is http://www.eecis.udel.edu/~ntp/ [udel.edu]

    Sh
  • Ya, With multiple PC's in the house, my windows boxs always had the correct time(sa.windows.com i think is the time server). On my unix boxes I just use rdate, "rdate -s time-nw.nist.gov" and everything is set. Was thinking about setting up a ntp server, but it would use time-nw.nist.gov also, might as well cut that step out.
    -
    Verizon uses thin copper on city streets... = no dsl.
    • The benefit with running a server like ntpd is that its always running. It'll run a query once every 5 minutes or so, and rather than just simply resetting your clock, it'll statistically derive the real time accounting for network lag and randomness and all of that. It'll reliably get better-than-a-millisecond accuracy, given a few days of this. Plus, it can use the same mechanism to detect drifts and inaccuracies in your PC's own clock, and tweak the kernel to compensate. Plus, if you have a pool of peer machines, they can help eachother detect drift more quickly (without having to resort to longterm statistical analysis).

      For these reasons, I run ntpd on most of my machines, rather than some set-and-exit cron job.
  • Pre-Internet I used a program that would make a quick long distance call to the naval observatory over the modem to set the clock. When I first got Internet access I started using a program called Atomic Clock, but over the years fewer and fewer time servers seemed to support the protocol it used, and eventually the very few I could find were obviously in need of some attention to their clocks themselves, they were drastically off. I'm currently using a little program for the PC called NTPC. I've had to occasionally track down a new time server when the predefined ones became unavailable, but otherwise it works fine.

    Can the M$ time sync for XP be disabled, or is this just another way for them to impose Bill's vision on us all?

    • Re:clock setting (Score:5, Insightful)

      by danheskett (178529) <danheskett AT gmail DOT com> on Thursday July 04, 2002 @07:43PM (#3824280)
      Can the M$ time sync for XP be disabled, or is this just another way for them to impose Bill's vision on us all?

      For the love of christ man, listen to yourself! Its the god-damned time man! The TIME. Everything isnt a big conspiracy you know!

      For the love of mercy, its just the friggin TIME OF DAY. Its not alient deathrays come to take away your MP3's or pr0n collection!

      Seriously, man, get a clue!

      And, all your little utilities are pretty silly these days. If you are using a mdoern version of Windows - NT, 2k, or XP I can confirm support this, simply use the "net time" command. Run it with /? for parameters. And yes, it can be disabled!
  • ...it should be good enough for me!

    US Naval Observatory Time Servers [navy.mil]
  • Lunch (Score:2, Funny)

    by quantaman (517394)
    I set my watch about 5 min fast so I won't be late and the clock of my work station is about 10-15 min slow. I leave for lunch when my work station reads 12 and we hang around and talk till about 1:15 by my watch. I feel like I get 15 min extra every day!
  • I know several people that set their clocks ahead of time so as to make themselves think that they're running late, when in actuality, they're on time. If MS or Apple changes this time to the 'correct' time, this could cause people to actually -be- late. Imagine the dilema: you come in late, and lose your job. Is that MS's or Apple's fault for changing your time on you w/o your permission? Or your's for using their OS?
    • by stripes (3681)
      Is that MS's or Apple's fault for changing your time on you w/o your permission?

      Well in Apple's case at least it might be your fault for not going to "Date and Time" panel and either unchecking "Use a network time server", or pointing at a NTP server that keeps your kinda time (yes OSX uses real NTP, and yes, they let you choose any NTP server you like).

      Or much better...for not changing the timezone files so you live 7 hours and 50 minutes ahead of GMT not 8 hours...

      • For me, maybe. I'm talking about the type of people that's mentality requires the clock be set 10 minutes fast or such - they're also generally the type that don't know what their computer does, in my experience.

    • My SO is like this and it drives me fucking nuts having all the clocks set anywhere from 5 to 20 minutes in advance. She has it all set up so that she "gains time" from when she gets out of bed to when she gets in her car, ie. the bedroom clock is 20 minutes ahead, the kitchen 15, and the car clock 10.

      It's not worth a serious argument though because I don't usually use clocks anyway. It's just annoying as hell when one of my buds asks me the time and I'm like, "Uh, well that clock is 10 minutes ahead, I think. Er, wait, that one's fifteen, it's the other one that's ten. Well, it's like 3:15 plus or minus 10 plus or minus 5."
    • by bnenning (58349)
      In Mac OS X, you have to turn automatic NTP synchronization off before you can manually adjust the time. At least when using the Date & Time preference pane; you can also run "date" from a command line but in that case you should know what you're doing.
  • my setup (Score:2, Informative)

    by deviator (92787)
    Netware 5.1 server gets time from several NTP servers (i.e. tick.usno.navy.mil, tock.usno.navy.mil, etc.) and triangulates "correct" time from averaging out the sources. (Netware actually has the most intricate and cool time synchronization system built-in because NDS depends heavily on accurate timestamps)

    Windows-based workstations automatically set clock to time on Netware server using Novell-supplied file client software (Client32) when they login.

    Linux boxes get time from Netware server using NTP.

    MacOSX laptop gets time from Apple using NTP (it's mobile & physically travels to many different networks. :)

    btw, Microsoft has no concept of time synchronization. Throwing an NTP client into Win2K & WinXP isn't exactly what I'd call "enterprise-class time synchronization." I've struggled for years using a variety of techniques to keep clocks accurate on mid-sized Windows-based networks. Novell by _default_ synchronizes the local PC clock with the main login server. You actually have to override this feature if you want to do it yourself. It saves so much effort...
  • by AntiNorm (155641)
    My VCR is able to auto-set its clock based on XDS data that is sent along with closed caption information.
  • MacOS 8.6.x already had this feature.
  • "The default--and unchangeable-- synchronization interval for Windows XP is one week."

    This isn't entirely true: while there is no way to change the synch setting in Windows using the UI, but a simple change of a number in the Registry will give the desired results:

    To change the interval that Windows updates the time using the internet time servers via regedit, navigate to:

    1. HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services \W32Time\TimeProviders\NtpClient
    2. Select "SpecialPollInterval"
    3. Change decimal value from 604800 to a different value in seconds. i.e.: 172800 (2 Days) or 86400 (1 Day) and so on.
  • by John Hasler (414242) on Thursday July 04, 2002 @06:55PM (#3824140) Homepage
    The default configuration works with a dialup.
  • Coincidence (Score:3, Interesting)

    by Large Green Mallard (31462) <lgm@theducks.org> on Thursday July 04, 2002 @07:00PM (#3824157) Homepage
    Just yesterday at work I was talking with a researcher about this.. he was showing me an NTP server he made, using two DGPS units and some embedded ethernet controllers.. he said the accuracy on it was about 40 nanoseconds from UTC..

    That should probably be suitable I think :)

    http://truetime.net sells some rack GPS-based NTP Servers too.. but I don' know the price.
  • My older Mac runs AutoClock [mac.org], which computes the mean deviation between logins to NIST, then automatically adjusts the clock whenever it drifts out of sync. Neat.
  • "The people who use NIST's Internet Time Service range from Windows XP and Mac System X users"

    If they're not informed enough to call it Mac OS X (and the last time apple used "System" was before Mac OS 8 came along... which was a longggggggggg time ago), then I don't trust the rest of the article, either. So I don't care, and I'm going to use Network Time to set my clock right now, just to spite that stupid Microsoft Windowed TP-user.
  • My firewall config had a Linux box on the outside with a crossover cable into a Linksys. The perimeter firewall has now come inside. I run NTP on 6 Linux boxes and used to run w32time on an NT Server.

    Only problem is, I could never get the firewall (or any single NTP client) to become a server for the rest of the network, so my boxes are not very polite right now. I've read tons of docs and google hits, and they all seem to indicate that once an NTP client syncs, it will also become a server. Not so here.

    What, if anything needs to be done to make a sync'ed NTP client also act as a server? Thanks..
  • Easy:

    [root@aragorn /]# cat /etc/cron.hourly/timesync
    rdate -s ns.coop.net&


    Just search google for "Stratum 1" servers and look for your timezone in the list.
  • I use NASA's ntp server. ntp.nasa.gov

    OS X Date/Time has an option to use ntp and you can set which server. ntp.apple.com is the default but I prefer to use a server where time is very important for everything they do. NASA seems to fit the bill.

    Other ntp servers like any military server are probably similarly effective. I wouldn't necessarily trust a commercially owned and run ntp server though.

  • My firewall runs ntpd [udel.edu] to sync its time with one of the public time servers in Canada. All of my Unix-ish machines run ntpd to synchronize with that; Windows machines run Tardis [demon.co.uk] on startup to sync.

    A trick to find nearby time servers (other than looking at a list [udel.edu]): run ntptrace on a nearby, well-administered Unix machine. Find the last machine that's inside the organization--that will be the one they sync with the outside world. Run ntpq on that machine and type peers. You'll see a list of the NTP servers that it queries. Put some of those in your /etc/ntp.conf and you're good.

  • Don't Do That (Score:5, Informative)

    by John Hasler (414242) on Thursday July 04, 2002 @07:16PM (#3824213) Homepage
    "...my home firewall gets the time every hour from the NIST servers,..."

    Don't use stratum one servers for your home network. It's wasteful and unnecessary. Use a stratum 2 or higher server or your ISP's server.
    • by coyote-san (38515)
      Another point is that it's unnecessary to update more often than daily except for the most exacting situations. Do you really need to keep your clocks synchronized to within milliseconds? I've found daily updates against a time server (which is sync'd to my ISP's NTP source) via a cron job running 'rdate' is good enough to keep my systems synced to within a second.

      The other nice thing about this aproach is that it's easy to toss the Windows equivalence of 'rdate' into the startup scripts managed by Samba, so whenever a Windows box comes onto the network it's also synced.
  • Connecting to NIST using SNTP.
    Resolved address for NIST (192.43.244.18).
    Received time (ping 63 ms), error -1 ms.
    New time: Thursday, July 04, 2002 19:34:15.


    AboutTime [arachnoid.com]
    (win32)

  • After trying many time utilities for Windows which failed either in terms of simply getting the time sometimes or by being resource hogs (how hard can it be?), I found a great small footrprint freeware util called cmdtime.

    It's highly configurable by batch file or commandline (it's a commandline tool in a windows world - which is much better for something you want to be unobtrusive) and just plain works.
    cmdtime (and some other stuff) [softshape.com]

  • by jelson (144412) on Thursday July 04, 2002 @07:59PM (#3824318) Homepage
    Wow, who would have thought that the topic of my PhD thesis would be on the front page?

    Right now I'm doing research in very high precision time synchronization for very large numbers of very small things. My lab [ucla.edu] does work in sensor networks -- get a tiny little computer with a few sensors and a radio, sprinkle thousands of them out over a building or a battlefield or a forest. Have the network tell you where the fire started, where the enemy is lurking, which light bulb needs to be replaced, or a thousand other things.

    You need very time sync to do lots of this stuff -- to track motion, for example. Our current testbed times the flight of sound to tell how far apart things are, and for that we need accuracy on the order of 10 microseconds between clocks.

    My research right now centers around a new time sync scheme, called Reference Broadcast Synchronization, which in a recent study [ucla.edu] I showed is almost an order of magnitude more precise than NTP under the same conditions -- 5 microseconds between a group of nodes with a userspace implementation, and down to 1 microsecond in the in-kernel implementation (which is the resolution of the clock! I'll do better when I have a clock that ticks more than once a microsecond.)

    NTP, even under "optimal" conditions -- very high query rate to a stratum 1 GPS-steered clock in our lab--- did no better than 50 microseconds. When we introduced high levels of congestion on the network, NTP degraded by a factor of 30 while RBS was almost unchanged.

    Of course, NTP is still a fantastic protocol, and much better than trying to apply RBS to the Internet (which is basically impossible). But for tiny nodes that need very tight time sync, I say, we can do better :-).

    Some recent papers you might like are here [ucla.edu], including
    • "Fine Grained Network Time Sync using Reference Broadcasts" -- the original RBS paper
    • "Wireless Sensor Networks: A New Regime for time synchronization" -- my argument as to why NTP shouldn't be used for sensor networks
    • "Locating nodes in time and space: A case study" -- description of our testbed that is capable of localizing objects down to 1cm by measuring time of flight of sound, combined with RBS time sync.
    It's funny, I'm sitting in the lab right now, tinkering with the testbed when this article should come up.

  • man rdate

    - grunby
  • On OSX... (Score:3, Informative)

    by banky (9941) <gregg AT neurobashing DOT com> on Thursday July 04, 2002 @11:49PM (#3825119) Homepage Journal
    Just load netinfo manager and look for /config/ntp. From there you can use whatever server you want.

"The pyramid is opening!" "Which one?" "The one with the ever-widening hole in it!" -- The Firesign Theatre

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