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NTP Pool Project Reaches 500 Servers

CowboyNeal posted more than 8 years ago | from the about-time dept.

The Internet 165

flok writes "Finally after 3 years the NTP Pool project has reached 500 servers! The NTP pool project tries to be an accurate and free time-source to every internet-connected device. Everybody who's system has running an NTP daemon which can give an accurate time-indication can join the project. Not only is it handy to have accurate time on your workstation to be able to see when you need to leave the house to catch the train in time, it is also usefull to be able to accurately correlate events between your system and others in case one gets hacked."

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165 comments

I just use my watch (0)

Anonymous Coward | more than 8 years ago | (#14471247)

It syncs with the atomic clock every night. Speaking of that, why is there no USB type device to allow timesync that way?

Re:I just use my watch (1, Insightful)

Anonymous Coward | more than 8 years ago | (#14471363)

Because you have the internet...

Re:I just use my watch (1)

moonbender (547943) | more than 8 years ago | (#14471522)

There are devices that attach to a PC which sync the clock via radio - haven't seen one for USB yet, but I'm sure they exist. They're not very cheap, though, while internet syncing is free and easily accurate enough for most applications.

Re:I just use my watch (1)

tylernt (581794) | more than 8 years ago | (#14471921)

Researched this for work not too long ago. You can use a consumer-grade GPS receiver to get within 1 second accuracy, but there's a lot of jitter. More expensive PPS (Pulse-Per-Second) GPS receivers are extremely accurate but cost about $1,000. This is assuming you have a clear view of a large swath of sky. You can interface these with (GPL) NTPd with an RS232 serial cable or you can buy a $3,000 total hardware solution in an 19" 1U rackmount server.

There are also radio receivers that listen to WWV (same as the "atomic" clocks you buy at Wal-Mart). Again, you can buy a $3,000 total hardware solution, or you can use any handy shortwave receiver and patch the headphone jack into your sound card Line-in port and let NTPd do the same thing.

The third solution is to use a special modem that connects to a cellular network (Verizon was the one we looked at), I think that solution ran about $1,000.

This is all going by memory so I might be off on some of the prices.

Re:I just use my watch (0)

Anonymous Coward | more than 8 years ago | (#14472080)

Garmin GPS25 $20 on Ebay + $50 for 2nd hand computer to run NTP + Webserver. Debian Linux was free. The only real cost was the time spent learning how to configure it.

I am now a small part of the NTP pool. My local network time is good to 0.1mS, the offset errors (10mS usually) as seen by external users are caused by my ADSL line :-(

Re:I just use my watch (1)

Bishop (4500) | more than 8 years ago | (#14471586)

A USB gps device can be easily used to timesync that way. Older modems could be put into a mode to decode the time from a dialup server. A suspect that a few HAM groups have a circuit that will decode the time too. However anyone who has cared about time accuracy has had access to NTP for two decades, and access to GPS recievers for almost as long. The radio broadcast time is less accurate then NTP unless you are right next to the transmitter. The radio waves skip across the atmosphere causeing unpredictable jitter. GPS is ofcourse the most accurate short of having your own atomic clock.

oooo so exciting (4, Funny)

SpaceCadetTrav (641261) | more than 8 years ago | (#14471266)

Congratulations. If you are reading a Slashdot thread about 500 time servers, you really are a nerd.

Re:oooo so exciting (4, Funny)

Hatta (162192) | more than 8 years ago | (#14471313)

Congratulations. If you are reading a Slashdot thread about 500 time servers, you really are a nerd.

And what if you're posting in one?

Re:oooo so exciting (1)

Kjella (173770) | more than 8 years ago | (#14471723)

And what if you're posting in one?

Then you're really a ne... oh, wait this is a post to a discussion about 500 time servers, isn't it?

Re:oooo so exciting (0)

Anonymous Coward | more than 8 years ago | (#14471328)

Have you checked the slogan of this site lately? You know, the part before "stuff that matters"?

Re:oooo so exciting (2, Funny)

Anonymous Coward | more than 8 years ago | (#14471361)

You know, the part before "stuff that matters"?

I've always wondered about that phrase -- who is this "Matters", and why would I want to stuff him?

Even more puzzling: with what?

Re:oooo so exciting (2, Insightful)

Xugumad (39311) | more than 8 years ago | (#14471388)

Or a sys-admin, maybe? I work with computer systems that need to be kept reasonably in sync, time wise, and NTP is a good way of doing that...

500 (1, Flamebait)

paulsgre (890463) | more than 8 years ago | (#14471267)

Why is 500 servers notable?

Re:500 (1, Funny)

Anonymous Coward | more than 8 years ago | (#14471274)

Because its 1 more than 499..

Re:500 (2, Insightful)

Heembo (916647) | more than 8 years ago | (#14471387)

Well, would 459 be a notable checkpint? Since most humans use base-10 math these days, 500 is a comfortable and familiar socio-mathematical number in terms of a good notable checkpoint. Now, since we are nerds, I believe that 512 would have been a much greater checkpoint. All praise binary!

Re:500 (1)

paulsgre (890463) | more than 8 years ago | (#14471498)

No, I think some functional measure or evidence of increased productivity/problem analysis using the system would be a better benchmark than any number of servers. Or if when a certain number of reliable servers were reached, some extended or vital functionality was attained.

Re:500 (1)

undeadly (941339) | more than 8 years ago | (#14471490)

Why is 500 servers notable?

A time service is a sensitive, but important, service to use. Having many reliable time servers to choose among will lessen the security risk of hacked servers, or servers just out of sync for some reason. A public timer server will see alot of traffic, so not everyone has the bandwidth nor the hardware.

The OpenBSD Network Time Protocol daemon [openbsd.org] selects randomly among various time servers, and is very easy to setup. However, if there are few time servers available, there is not much randomness to it...

Re:500 (3, Informative)

wayne (1579) | more than 8 years ago | (#14471505)

Why is 500 servers notable?

Last year, the pool was falling behind on servers. More clients were joining than servers, so the load on each server was growing. Since then, Ask Bjørn Hansen has created a bunch of automated scripts to handle all of the servers and the server growth has taken off. We still need more servers, and 500 is a nice round number to give as an excuse to say "Please join the NTP pool!".

Stratums (4, Insightful)

bsd4me (759597) | more than 8 years ago | (#14471662)

It would also be nice if ISPs would set up their own pools (and advertise them) so clients wouldn't have to go off network, and then if end-users would would set up their own pool for their networks. Not every machine that needs accurate time has to be at stratum-2 or stratum-3, especially workstations. The NTP Pool website makes it look like it is a good idea if every machine on a network syncs to the NTP Pool, instead of setting up internal servers, which is how NTP is really designed to work.

Re:Stratums (2, Informative)

Gerald (9696) | more than 8 years ago | (#14471700)

Try this:

    - Traceroute off your network, e.g. to cnn.com
    - For each hop in the route, run 'ntpdate -q '

9 times out of 10, you'll find an NTP server one or two hops away.

Re:Stratums (1)

Detritus (11846) | more than 8 years ago | (#14471987)

That's assuming that the ISP has a clue. I've run into too many local NTP servers that are grossly in error and the person responsible for the server no longer works there, doesn't understand NTP, never checks to see that the server is still working, or doesn't care that the server is broken.

Auto-configure ntp via dhcp (2, Interesting)

jrp2 (458093) | more than 8 years ago | (#14472075)

"It would also be nice if ISPs would set up their own pools (and advertise them) so clients wouldn't have to go off network"

Agreed. Most do, but as you mention, don't advertise them. I am not sure how many people would actually know what to do with them if they were advertised though.

It would be quite slick if they advertised them via DHCP, and clients used that info to auto-configure their ntp client. All quite possible and very easy to do by the ISP. NTP servers can be advertised via dhcp.

http://gentoo-wiki.com/HOWTO_NTP [gentoo-wiki.com]

http://www.greyware.com/software/domaintime/techni cal/architecture/dhcp.asp [greyware.com]

Trains aren't that reliable (3, Insightful)

Ithika (703697) | more than 8 years ago | (#14471286)

And what makes sure the trains are on time?

Re:Trains aren't that reliable (1)

TorKlingberg (599697) | more than 8 years ago | (#14471413)

You don't live in Japan, right? I have been going by train every weekday for four months, it's been late once. 2 minutes. And then I could smell the breaks at every station.

Re:Trains aren't that reliable (1)

Ethan Allison (904983) | more than 8 years ago | (#14471559)

Well, Japanese trains are notorious for their punctuality. Remember the time when that one train derailed itself, crashed into a building, and killed a bunch of people just because it was trying to make up for the fact that it was a minute and a half late?
Where I live (Twin Cities, MN, USA), up to 10 minutes late is pretty normal for almost every single bus route, and our train line.

Re:Trains aren't that reliable (1)

Stween (322349) | more than 8 years ago | (#14471871)

Wow. 10 minutes. You should come to the UK, we're much better at laterunning. In fact, quite often we like just to cancel trains.

My favourite announcements at stations are the ones where they announce that the train is on time. Oh yes.

Re:Trains aren't that reliable (1, Funny)

Anonymous Coward | more than 8 years ago | (#14471418)

Stalin!

Re:Trains aren't that reliable (0)

Anonymous Coward | more than 8 years ago | (#14472088)

In soviet russia the train makes you run on time!!!!

Re:Trains aren't that reliable (1)

Greg Koenig (92609) | more than 8 years ago | (#14471703)

And what makes sure the trains are on time?

Germans!

Re:Trains aren't that reliable (1)

LuckyStarr (12445) | more than 8 years ago | (#14471965)

In fact... no. :) The Deutsche Bundesbahn (German National Railways) is known (or better, infamous) for many things, but punctuality is not one of them. I almost have a feeling that trains are more on time if YOU are late.

But... (2, Informative)

joey_knisch (804995) | more than 8 years ago | (#14471306)

I live in an area with buses and a DOT that doesn't give a shit about being 12 seconds early. Oh well. I will continue to use my watch set 5 minutes fast.

However, congrats. I will continue to use your NTP servers for computer related crap well into the future.

Re:But... (0)

Anonymous Coward | more than 8 years ago | (#14471542)

Why 5 minutes fast? Isn't barbarian time good enough for you?

Confused (3, Funny)

Alarash (746254) | more than 8 years ago | (#14471312)

I'm confused. They are supposed to be a reliable time source, and their home page doesn't even show the current time!

Re:Confused (1, Interesting)

Da3vid (926771) | more than 8 years ago | (#14471344)

I find this website a bit perplexing. Sure, I can appreciate the value of having an accurately sync'd computer, but I set my CPU a year to my atomic clock, and it still is within 15 seconds. That goes for my laptop, too. Maybe I'm a fluke, maybe this program could win me back that 15 seconds, but how important are they? I don't think its going to help me with my day, business, or any other daily tasks. I can only see this potentially useful in tracking movement of viruses across multiple networks, but I doubt that 500 servers provides anything very meaningful. If there were thousands, maybe. My mental picture is like the movie Twister with their stupid gadget at the end, putting the little metal sensors into the tornado. Imagine a few thousand computers all swirling around in a mess of viruses, so you could collect all the information to watch.

If you thought you were a nerd just for reading about 500 time servers, you'd really be a nerd for being interested in that kind of information.

-Da3vid-

Re:Confused (4, Informative)

bsd4me (759597) | more than 8 years ago | (#14471408)

Accurate time is important when you are sharing resources with other computers. One example is running a build on an NFS share. If the file timestamps are wrong, then make may do unnecessary compiles, or skip files. Other protocols, like rsync, use timestamps to try to figure out whether updates are needed.

Re:Confused (0)

Anonymous Coward | more than 8 years ago | (#14471683)

is your sig unlambda?

i've only seen it with lower case operators before.

Re:Confused (1)

bsd4me (759597) | more than 8 years ago | (#14471787)

It is the lamba term

(\x.x x)(\x.x x)

expressed with combinators. Unlamba is basically an implementation of combinatory logic, but combinators are usually written in capitals.

Re:Confused (1)

jcaldwel (935913) | more than 8 years ago | (#14471732)

I started losing count of the number of times there were "bugs" in time-of-day-sensitive applications I wrote, schedulers and such. 100% of these bugs were due to one or more of these machines with an incorrect time.

I finally had to make it a formal requirement on production machines that we run ntpdate followed by a "hwclock --systohc" (to save us after a boot) in a cron job.

Re:Confused (1)

pitc (557530) | more than 8 years ago | (#14471913)

rsync only uses the timestamp if you tell it to. Otherwise it checksums each file.

Re:Confused (1)

elconde (779753) | more than 8 years ago | (#14472178)

15 seconds a year isn't bad. My laptop was drifting 15 seconds a day before I started using ntp.

Your machine is going to party like it's 1999 .... (2, Insightful)

TallMatthew (919136) | more than 8 years ago | (#14471323)

What keeps someone from joining the pool and giving out the wrong time?

There are some nifty bits of nastiness that can be delivered when a machine is privy to having its clock changed from afar.

Re:Your machine is going to party like it's 1999 . (2, Insightful)

bsd4me (759597) | more than 8 years ago | (#14471376)

A proper NTP implemetation for a computer gathers information from several clock sources. The NTP protocol also has provisions to determine whether a clock is accurate or not based on the responses from other clocks. IIRC, this is called a "false ticker" in the spec.

Re:Your machine is going to party like it's 1999 . (4, Informative)

isj (453011) | more than 8 years ago | (#14471380)

What keeps someone from joining the pool and giving out the wrong time?

Nothing.

However, NTP clients uses multiple servers and uses some fairly advanced correlation algorithms to detect outlyers and bad servers. The client configuration is your responsibility. So configure it to use a set of servers that you believe you can trust.

There are some nifty bits of nastiness that can be delivered when a machine is privy to having its clock changed from afar.

Then use the secure protocols.

Re:Your machine is going to party like it's 1999 . (2, Informative)

wayne (1579) | more than 8 years ago | (#14471476)

What keeps someone from joining the pool and giving out the wrong time?

All machines in the NTP pool are monitored for quality and if they are bad enough, they won't be put into the pool.

Also, it is recommended that you have at least 3, maybe up to 5, NTP servers so that you can detect a bad NTP server. (If you have one time server, you won't know that anything is wrong. If you have two, you will know something is wrong, but you won't know which NTP server is bad. If you have three or more, you can pick the best one.)

Re:Your machine is going to party like it's 1999 . (2, Insightful)

OneSmartFellow (716217) | more than 8 years ago | (#14471806)

Two main design decisions preclude this from causing disaster.


1.) A proper NTP implementation will only normally change the skew of your clock, so it speeds up or slows down, but does not jump around.


2.) A proper NTP implementation will assume that a clock with a large variance compared to other sources is unreliable, and so it will try not to use it. Of course this assumes you have more than one time source available (and configured).

PCs keep lousy time. (2, Interesting)

Anonymous Coward | more than 8 years ago | (#14471346)

What is it with PCs? I've owned several over the last 15 years, and without exception
the clocks simply could not keep accurate time. I've bought 5 buck watches at wal-mart that
kept better time than my PCs. In some cases, they lose (or gain) several (somtimes tens of)
seconds per day.

Is it those Dallas chips that can't keep time? or is it the clock frequency division that
most PCs use?

Re:PCs keep lousy time. (4, Informative)

LuckyStarr (12445) | more than 8 years ago | (#14471935)

Try warming your 5 buck watch to 50C (don't know how much that is in F) hold it there for a few hours and then cool it down again to room temperature. Do this every day for a few months.

You will see your 5 buck watch will track the time as good as the Dallas chips.

Temperature affects the speed of clocks.

more useful for nfs, clustering (1)

Colin Smith (2679) | more than 8 years ago | (#14471351)

other than that I don't think I'd bother. a couple of minutes here or there hardly matters.

 

Re:more useful for nfs, clustering (1)

Ed Random (27877) | more than 8 years ago | (#14471433)

other than that I don't think I'd bother. a couple of minutes here or there hardly matters.

Well, it does matter for Kerberos / MS Active Directory authentication.

In any shared software development environment, time needs to be accurate or your builds will fail in strange ways.

And I'd like to be able to correllate our syslog output, too...

Re:more useful for nfs, clustering (1)

Pop69 (700500) | more than 8 years ago | (#14471677)

Try running the computer systems for an insurance company where a couple of minutes can be very important to when a client is "on risk". On my systems time has to be accurate and synchronised across the whole network.

Re:more useful for nfs, clustering (0)

Anonymous Coward | more than 8 years ago | (#14471766)

That's funny. My insurance company doesn't seem to understand time constants shorter than a month.

Re:more useful for nfs, clustering (0)

Anonymous Coward | more than 8 years ago | (#14471919)

It is usefull for other things too. An example of where having correct time is usefull is with a pc that records tv or talk radio shows.

--
pc

Re:more useful for nfs, clustering (2, Funny)

ThaFooz (900535) | more than 8 years ago | (#14472144)

other than that I don't think I'd bother. a couple of minutes here or there hardly matters.

Yeah, I didn't think it mattered too much on non-critical systems either. Then I ran MythTV and missed the last couple minutes on my Futurama episodes. Never again.

Why we removed our servers from the pool... (5, Interesting)

jafo (11982) | more than 8 years ago | (#14471356)

We've run public NTP servers for the better part of a decade now, mostly for the convenience of geographically local folks like the various LUGs. When I found out about the pool, I had our servers added there. Everything was fine for a few months, then over a month we started getting phone calls from firewall admins about how our time servers were attacking their networks. Every time a machine in their network would ask our servers for the time, our servers responded with 10 packets spaced at 1 second intervals, so these improperly configured firewalls were logging a lot of packets from us.

I finally shut it down after one particular call, the third that week, where the caller was rude and abusive when I suggested that he should be doing more investigation about the traffic before calling someone else to complain about it. Being a public service, it's just not something that scales well to have to field these calls. I hated to do it, but it was just too much of a distraction.

I'm not saying that you shouldn't add your servers to the pool... I just thought it was an amusing story.

Sean

Re:Why we removed our servers from the pool... (2, Interesting)

wayne (1579) | more than 8 years ago | (#14471462)

Every time a machine in their network would ask our servers for the time, our servers responded with 10 packets spaced at 1 second intervals

Uh, your servers are supposed to only reply with *ONE* packet.

That said, I have also had a few people complain to me about my machine attacking them because they have configured their machine to use the NTP pool. Over the last 2 years, it has totalled around 3, so you must have had really bad luck.

Overall, I have been very happy with my involvement with the NTP pool. It has been working very well and I like being to help others out. I have also created a bunch of NTP monitoring scripts [schlitt.net] to help NTP pool members make sure things are running smoothly. These scripts confirm that being in the pool really doesn't generate that much traffic, so even people with cable modems/DSL (with static IP addresses) can easily participate.

Re:Why we removed our servers from the pool... (1)

jafo (11982) | more than 8 years ago | (#14471621)

>Uh, your servers are supposed to only reply with *ONE* packet.

Be that as it may, tcpdump of that particular remote address showed one
request coming in and 10 responses going back, spaced at 1 second
intervals. This may be because the remote was making a request that
resulted in the 10 responses. I'd doubt it was a but in ntpd, but that
may be as well.

Sean

Re:Why we removed our servers from the pool... (3, Informative)

Detritus (11846) | more than 8 years ago | (#14471686)

Uh, your servers are supposed to only reply with *ONE* packet.

See the "iburst" keyword in ntp.conf. This results in a burst of ntp packets at startup.

New Way uses HW (4, Informative)

putko (753330) | more than 8 years ago | (#14471362)

Supposedly, if you need an accurate timebase, you are supposed to just use GPS (which gives the exact time) instead of relying on a complicated clock protocol.

It is great that NTP is so widely distributed. It is typical that at the moment the old technology is finally working, there is an altogether better solution.

Re:New Way uses HW (3, Insightful)

Anonymous Coward | more than 8 years ago | (#14471399)

What do you mean by "finally working"? It's been working for ages, I've been using public NTP servers much before I found about pool.ntp.org.

Besides, what a GPS receiver gives you is a stratum 1 host. What are you going to do, get a receiver per machine? Of course not, you connect it to one box with a NTP server, and make the rest synchronize with it.

Perhaps the usefulness of public NTP servers is somewhat less now, but they're still good to have. I'm sure at many companies buying a GPS receiver could be complicated, even though accurate time is a very, very nice thing to have these days.

Re:New Way uses HW (1)

putko (753330) | more than 8 years ago | (#14471455)

"Finally working" was imprecise. Please try: "finally working enough to satisfy all users".

If time really matters, you'll have one per machine. I wouldn't say "of course not," as you did. They only cost about $75 (US) now.

Re:New Way uses HW (0)

Anonymous Coward | more than 8 years ago | (#14471546)

That assumes all your machines can get a good signal for the GPS. Besides $75/machine adds up pretty quick when you have a roomful of computers.

Re:New Way uses HW (2, Insightful)

pe1chl (90186) | more than 8 years ago | (#14472240)

Even ONE receiver (GPS) can be a problem in an office building with metalized glass windows and no access to the roof.
Also, not everyone wants to setup an antenna on the roof and wire it into the computer room.

For typical computer network purposes (where relative time accuracy is more important than absolute accuracy), NTP is a very good solution. It will get all systems on your lan within milliseconds or better, and the whole network within tens of milliseconds. It will be better than a message-based (non-PPS) GPS receiver connected to all your systems!

When you require nanosecond accuracy, you probably don't need it on all systems in your network.

Re:New Way uses HW (5, Insightful)

cswiger2005 (905744) | more than 8 years ago | (#14471473)

GPS does indeed make a wonderful external time reference, and many stratum-1 NTP timeservers are using it.

Of course, most machines locked in a rack in a hosting facility don't have even the slightest chance of seeing enough sky to lock onto GPS, so it's safe to say that NTP's death or obsolesence is premature to announce just yet. :-)

--
-Chuck

PS: O Slashdot wizards, why does Slashdot's posting filter claim ntpq output is lame?
It's a conspiracy, I tell you, to force me to write more text!
Bah, that doesn't work, the lameness filter doesn't like a line filled with "=" signs at all, even if I use an <ecode> tag.

Re:New Way uses HW (3, Insightful)

tpgp (48001) | more than 8 years ago | (#14471518)

Supposedly, if you need an accurate timebase, you are supposed to just use GPS (which gives the exact time) instead of relying on a complicated clock protocol.

Unless your data center is inside a shielded room / underground / in the center of your building.

It is great that NTP is so widely distributed. It is typical that at the moment the old technology is finally working, there is an altogether better solution.

Its not a better solution - its a better solution in some cases.

NTP has the massive advantage of working anywhere you have a network connection and not requiring expensive hardware (GPS hardware you can attach to a PC & match the reliability of NTP is not your yum-cha $75 GPS unit)

Re:New Way uses HW (2, Informative)

Myself (57572) | more than 8 years ago | (#14471584)

Of course, the CDMA cellular network derives its timing directly from a GPS-stabilized clock, and local clock standards that reference a CDMA receiver are available. These work in almost any building short of a full faraday cage. (And some of them can hook directly to a network and serve NTP!)

Also, the 1pps output of a $75 GPS unit is considerably more accurate than NTP if your network is subject to *any* sort of variable delay, which of course packet-based networks are.

Not that NTP isn't useful, just don't expect submillisecond accuracy out of it.

Re:New Way uses HW (1)

tylernt (581794) | more than 8 years ago | (#14471956)

"Also, the 1pps output of a $75 GPS unit"

None of the $75 GPS units I've looked at have had PPS. I thought PPS-enabled receivers were a lot more expensive than your run-of-the-mill GPS receiver?

Re:New Way uses HW (1)

pe1chl (90186) | more than 8 years ago | (#14472211)

The GPS receiver used internal to these units often has a PPS signal. It is the USB interface that provides only a serial message interface to the system.
When you find an RS232-interfaced receiver, chances are that it provides PPS on the DCD pin.

I am using OEM module GPS receivers here (bare printed circuit boards that are/were used by system integrators to build systems) and the three different types I have all provide a PPS signal.
These are sometimes available as surplus components.

Re:New Way uses HW (1)

tylernt (581794) | more than 8 years ago | (#14472370)

I didn't actually test any for PPS, I just assumed that if they didn't advertise PPS, they didn't have it. Obviously this assumption was incorrect -- undocumented features hadn't occurred to me. D'oh!

Re:New Way uses HW (1)

pe1chl (90186) | more than 8 years ago | (#14472096)

GSM does not seem to have these time transmissions. If it does, the typical GSM handset does not take advantage of it.

On a LAN, you can expect submillisecond accuracy out of NTP. At least when your OS clock can be phaselocked to an external reference.
Of course it will be difficult when you are syncing over an asymetrically loaded Internet link.

Re:New Way uses HW (1, Informative)

Anonymous Coward | more than 8 years ago | (#14471635)

It is great that NTP is so widely distributed. It is typical that at the moment the old technology is finally working, there is an altogether better solution.

So, you're going to connect a GPS receiver to every single workstation and server?

The way NTP works is that the primary ("Stratum 1") servers get their time from GPS (and other places). The next level (stratum two) would sync of off these and would serve time to clients (so that the primary time servers wouldn't be over burdened).

You would setup your servers and desktops (and routers, switches, etc.) to sync with the stratum two servers. These clients would in essence become "stratum three". You can go down the stratum numbers as you need for the scalability / redundancy needs that you may have. While technically a stratum x+1 server may not be as accurate as an x server, we're talking about differences of tenths of a second over the Internet.

This way you get accurate time (error of tens of milliseconds or less on a LAN), without having to add a GPS reciever on every machine. Most people only need their time sync'd to a couple of seconds, so public NTP servers are good enough.

Time sync protocol that Windows uses is a form of NTP (it goes to time.windows.com), and OS X uses the standard NTP software underneath the hood (you can edit /etc/ntp.conf on OS X).

Re:New Way uses HW (0)

Anonymous Coward | more than 8 years ago | (#14471682)

"if you need an accurate timebase, you are supposed to just use GPS"

NTP has a useful feature where there are lots of servers on lots of networks, few of which can be shutdown by the US government. GPS doesn't share that feature.

Re:New Way uses HW (1)

Detritus (11846) | more than 8 years ago | (#14471946)

There is much more to a time and frequency distribution system than a GPS receiver producing 1 PPS, unless your requirements are very minimal. You still need a very stable local oscillator, time code generators, etc. You also have to consider redundancy and single points of failure.

NTP is a cheap and effective way of distributing time to systems that do not need high-quality time.

Re:New Way uses HW (0)

Anonymous Coward | more than 8 years ago | (#14472224)

The problem with GPS as a time device is that most new consumer GPS devices can no longer easily hook up to desktop computers. The GPS vendors are going proprietary, making it hard for the GPSs to be used for anything other than their intended commercial purpose. The only mechanism to extend these new GPS devices is to use very expensive, low quality, proprietary software.

Re:New Way uses HW (1)

standards (461431) | more than 8 years ago | (#14472321)

It is true that vendors are going more propietary - just see the article by this cowboy: http://www.oreillynet.com/pub/wlg/5745 [oreillynet.com]

For Linux and Macintosh, there are ways you can get at least the proprietary Garmin GPS's to work. See http://lancej.blogspot.com/2005/10/using-garmin-et rex-vistac-with.html [blogspot.com]

I've had no problems using GPS with Linux, but I bet it'll get worse over time, as I believe the vendors will continue to try harder to lock customers into their own software packages.

Chicago said it best... (1)

BigCheese (47608) | more than 8 years ago | (#14471485)

Does anybody really know what time it is
I don't
Does anybody really care
care
If so I can't imagine why
about time
We've all got time enough to die
Oh no, no

Recommended NTP clients (2, Informative)

ZorroXXX (610877) | more than 8 years ago | (#14471533)

Since nobody has mentioned anything about clients yet, here are my suggestions:

  • Linux: Chrony [sunsite.dk] . Works very well for dial-up when you not are connected all the time.
  • Windows: NetTime [sourceforge.net] . Although no longer an active project, this program still works perfectly and is in my opinion better than the "official" windows service.

I run a pool server: some interesting bits (4, Informative)

Nelson Minar (7732) | more than 8 years ago | (#14471537)

Debian's default NTP configuration is to get time from pool.ntp.org. This is a significant contribution to the Linux world, similar to how Microsoft and Apple provide NTP service to their customers. Yay for us!

There is modest protection against bad servers in the pool. The time from pool servers is monitored and if a server seems insane it's taken out of the rotation.

My pool server gets about 14 requests a second from about 100,000 different IP addresses a day. Sadly, a lot of those requests are junk; 100 IP addresses account for 1/3 of all the requests I get. Fortunately NTP is a very lightweight protocol, so you can mostly ignore the spammy clients.

Re:I run a pool server: some interesting bits (1)

cide1 (126814) | more than 8 years ago | (#14471557)

similar to how Microsoft and Apple provide NTP service to their customers

I didn't realize Microsoft did this, but I know when I started buying Apple, I sure noticed it, and thought it was a very nice touch. Small things like this can give a lot of polish to a product.

Re:I run a pool server: some interesting bits (1, Informative)

Anonymous Coward | more than 8 years ago | (#14471820)

Apple has been running their NTP server for a long time now, even before starting to add builtin NTP support in their OS.

UIC's "unofficial" time server (5, Funny)

jms (11418) | more than 8 years ago | (#14471630)

Back when I was a university system programmer, I had an officemate named Tim. One day, Tim was poking around and discovered that hundreds of computers all across campus were synchronizing their clocks to his desktop workstation. He quickly figured out why.

The naming standard for desktop machines was to take the employee's first name and concatinate it with the first letter of their last name. So my desktop machine was named "johns.cc.uic.edu". Tim's machine was named "time.cc.uic.edu" because his last name began with "E". (cc meaning a "computer center" machine.)

Apparently many many university departments and users poked around and discovered what was obviously an official time server and configured their computers to synchronize to Tim's desktop machine. Tim, of course, had set his computer's clock by the office clock and never given it a second thought.

101 other uses for NTP (1)

packethead (322873) | more than 8 years ago | (#14471759)

accurately correlate events between your system and others in case one gets hacked."..... Of course, syncing database transactions is of no concern..

Public NTP server? (1)

mcrbids (148650) | more than 8 years ago | (#14471862)

For years, I've kept my own NTP server. It has references to like a dozen other NTP servers, and then all my other servers reference my own NTP server. I'm not as interested in having time 100% spot perfect, as in having all the servers together, so that cross-examining log files is possible. (BTW, setting up an NTP server takes all of about 10 minutes, with basically zero administration, other than making sure that NTPd is running)

I don't do any address restriction on the NTP server. Anybody doing a UDP sweep could find this time server easily. Is this a "Public" NTP server?

Now, at the moment, this particular time server sits on a DSL line, (NTP is pretty lightweight) so I don't go publishing it, but what constitutes a "public" NTP server - the DNS name, or its inclusion on a particular published list?

Re:Public NTP server? (2, Informative)

htmlboy (31265) | more than 8 years ago | (#14472101)

what constitutes a "public" NTP server - the DNS name, or its inclusion on a particular published list?

in this context, public probably means that the server's listed by pool.ntp.org [ntp.org] . isc also maintains a list of stratum 1 and 2 servers [isc.org] , some of which are publicly-accessible.

Re:Public NTP server? (1)

pe1chl (90186) | more than 8 years ago | (#14472151)

It is considered abusive to scan for an NTP server and then use it as a reference. A "public" NTP server is one that is explicitly listed as public and available for external users.

Listing it on pool.ntp.org of course is an explicit permission to use it.

NTP servers as distro usage trackers (1)

schwaang (667808) | more than 8 years ago | (#14472162)

I noticed that Fedora (at least early releases) sets the default ntp server to a .redhat.com server, and I believe Ubuntu sets the default to an ubuntu project server.

Does anyone know if these distros use traffic to their servers to track installed base? Or are they just being extra friendly?

Why I stopped participating (1)

Just Some Guy (3352) | more than 8 years ago | (#14472291)

I added my server to the pool for a while, but quit after a couple of months. The problem I had was the number of wildly misconfigured clients that were killing my system by polling every second. ISC's ntpd has options that sound like they would limit these abuses, but they never had any effect at all; tcpdump would show that I was cheerfully answering request after request after request from the same group of idiot machines.

Some people went as far as to write scripts that would add bad clients to the server's firewall rules. However, given that every other service I run has some mechanism or another to limit abuse, I didn't want to enable such a system for just this one relatively minor daemon.

ISC: please give ntpd a working way to automatically ignore broken clients! I'm more than happy to offer my little machine to provide a worthy public service, but watching my server grind down as it answers 600 packets per second - 99% (literally) from the same small pool of machines - was enough to make me withdraw.

By the way, I quit by simply removing my server from the DNS pool. Machines still synced to my server are welcome to remain there as long as they follow reasonable etiquette, but I won't be advertising for new clients in the near future.

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