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Robust Timing Over the Internet

kdawson posted more than 3 years ago | from the no-present-like-the-time dept.

The Internet 178

ChelleChelle writes "The NTP (Network Time Protocol) system for synchronizing computer clocks has been around for decades and has worked well for most general-purpose timing uses. However, new developments, such as the increasingly precise timing demands of the finance industry, are driving the need for a more precise and reliable network timing system. Julien Ridoux and Darryl Veitch from the University of Melbourne are working on such a system as part of the Radclock Project. In this article they share some of their expertise on synchronizing network clocks. The authors tackle the key challenge — taming delay variability — and provide useful guidelines for designing robust network timing algorithms."

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178 comments

make all wall street traders own stock for 1 day (4, Insightful)

Anonymous Coward | more than 3 years ago | (#32061884)

let's do away with the arbitrage, gambling, and bullshit from wall street. make them own a stock for ONE WHOLE DAY. No more of this low-latency trading bullshit. They're just skimming money off the top of the financial markets--away from the regular folks. EVERY PENNY THESE GUYS MAKE COMES OUT OF OUR POCKET.

Re:make all wall street traders own stock for 1 da (0)

Gordo_1 (256312) | more than 3 years ago | (#32062054)

EVERY PENNY THESE GUYS MAKE COMES OUT OF OUR POCKET.

That's only partially true -- it only comes out of the pockets of those who regularly buy and sell. Choose an asset allocation and diversify your investments in market-wide indexes and you can bypass the vast majority of that skimming.

Re:make all wall street traders own stock for 1 da (2, Insightful)

Anonymous Coward | more than 3 years ago | (#32062164)

Phew that's OK then, it's only everyone with a fucking superannuation.

Re:make all wall street traders own stock for 1 da (1)

MrNaz (730548) | more than 3 years ago | (#32062894)

Even if you diversify, you're still hit by the day-trading scumbags, just to a lesser extent.

Besides, your post boils down to "just don't live in a high crime neighborhood and you'll be fine, no need to make burglary a crime".

Re:make all wall street traders own stock for 1 da (2, Insightful)

IorDMUX (870522) | more than 3 years ago | (#32062086)

EVERY PENNY THESE GUYS MAKE COMES OUT OF OUR POCKET.

I see you have not the foggiest idea how "investments" and "fluidity" make the economy work.

Hint: When the Great Depression hit, the money lost by the traders on Wall Street did not suddenly spew forth into the hands of "us".

Re:make all wall street traders own stock for 1 da (2, Insightful)

1s44c (552956) | more than 3 years ago | (#32062408)

Hint: When the Great Depression hit, the money lost by the traders on Wall Street did not suddenly spew forth into the hands of "us".

Because the money you mention never really existed.

If I had a thousand dollars in paper money under my bed before the great depression it would have had a certain buying power. In the middle of the great depression it would have had a much greater buying power. The value lost on Wall Street spewed forth into paper money and real physical assets.

Re:make all wall street traders own stock for 1 da (2, Interesting)

drsmithy (35869) | more than 3 years ago | (#32062116)

let's do away with the arbitrage, gambling, and bullshit from wall street. make them own a stock for ONE WHOLE DAY. No more of this low-latency trading bullshit.

A Capital Gains Tax that started at 95% and decreased ~2.5% per month would go a long way towards fixing many problems (/avoiding them in the first place).

Re:make all wall street traders own stock for 1 da (1, Insightful)

Anonymous Coward | more than 3 years ago | (#32062202)

That's a really interesting (and stupid) idea. I guess the short term effect would be all Americans pulling all of their money out of any investment that had the slightest risk (stocks and bonds). Sounds like a great recipe for the next great depression!

Re:make all wall street traders own stock for 1 da (1)

Hognoxious (631665) | more than 3 years ago | (#32062328)

Or they'd come up with a workaround where X holds the stock forever, and traders swap "X points".

Re:make all wall street traders own stock for 1 da (0)

MrNaz (730548) | more than 3 years ago | (#32062910)

Actually no. That's a great idea. People would leave stocks where the risk of needing to evacuate the holding within the timeframe at which capital gains tax made the return sub-optimal. This idea would not place arbitrary rules on minimum holding time, so if you needed your cash back within 24 hours for some reason, you could get it, just without much of any profits you made. No need for the tax to stay high for a long time, it could drop to normal rates within a week, to ensure that the idiots who make money by buying and selling on the same fucking day are forced out of business like they should be. Their actions add nothing to the productive output of the economy.

Re:make all wall street traders own stock for 1 da (3, Insightful)

Sycraft-fu (314770) | more than 3 years ago | (#32062502)

While I think that's a bit extreme, I think you and the GP are both on to the right track. I think stocks should have a fairly short minimum hold time. A day would probably be fine, just something such that you aren't trying to gamble with them more or less, because that's why high speed day trading really is. It is gambling in every way that Vegas is.

I also thing a sliding tax would make sense. If you execute quick trades, you are subjected to a fairly high tax. 95% is a bit excessive, but something still fairly high. Then, as you say, the tax drops on a monthly basis until it hits zero. That would act to encourage investing, rather than gambling. It rewards people who put their money away for the future, and do so in a manner that allows it to help the economy grow. It would also still allow for quicker trades, but the government gets to take a cut in that case.

I really do think we need to start looking at something like this for three reasons:

1) Because there are companies that try to game the system. That's never a good thing. You game the system on a large scale, you'll break it. When you are talking about something highly important to the economy, that's not acceptable.

2) Because there are too many gamblers. There are plenty of traders who basically gamble on the market. They make day trades not based on anything about the company, but just to try and grab money from trends. This is not useful, and isn't what the stock market is for. It leads to unnecessary instability and thus should be discouraged.

3) To help combat people's fear response. A non-trivial part of the big drop in the stock market last year was people being fearful. They panicked because of the economic troubles and wanted all their money out. That means even if the fund managers thought it was a bad idea, they had no choice. You have to do what your client wants. That of course lead to more drops and more panic and so on. Perhaps tax incentives could help stave that off with people.

Re:make all wall street traders own stock for 1 da (1)

micheas (231635) | more than 3 years ago | (#32062510)

let's do away with the arbitrage, gambling, and bullshit from wall street. make them own a stock for ONE WHOLE DAY. No more of this low-latency trading bullshit.

A Capital Gains Tax that started at 95% and decreased ~2.5% per month would go a long way towards fixing many problems (/avoiding them in the first place).

So you short against the box. (buy N shares and sell N shares short collaterallizing the type two account (the account that buys the stock) with the cash in the type 3 account (the account that is short the stock)

Worst case, you have to deliver the borrowed stock before 38 months have passed, and get hit with a tax bill when you unwind the trade in a private transaction between your two accounts.

I am sure that there are other workarounds.

Re:make all wall street traders own stock for 1 da (2, Insightful)

swamp_ig (466489) | more than 3 years ago | (#32062868)

Easy Answer: (in most tax laws)

Any arangement who's primary purpose is to avoid taxation is illegal, and will be charged tax at the rate at which it would normally have been taxed.

Re:make all wall street traders own stock for 1 da (2, Insightful)

kerrbear (163235) | more than 3 years ago | (#32062368)

Agreed. When are some of these people going to realize that greed is bad. Trying to game a system is inherently wrong. Not just morally, but wrong systemically. It will always result in harm to the system. These people soothe their conscience with excuses- "We're spreading the risk and that's a good thing", "It's only fractions of pennies off of many people, nobody will notice." , etc. Until the whole thing comes crashing down because in reality the financial system is core dependent on actual investment and trust, not on gambling. To quote Chinatown:

Jake Gittes: How much are you worth?
Noah Cross: I have no idea. How much do you want?
Jake Gittes: I just wanna know what you're worth. More than 10 million?
Noah Cross: Oh my, yes!
Jake Gittes: Why are you doing it? How much better can you eat? What could you buy that you can't already afford?

Re:make all wall street traders own stock for 1 da (2, Interesting)

mgblst (80109) | more than 3 years ago | (#32062726)

Who the hell isn't greedy. If you were offered more money at work, would you turn it down. Most people wouldn't. And all your colleagues are going to get paid more.

This is all these people are doing, they are doing there jobs, and they get paid bonuses for doing it well.

It is ignorant and stupid to pretend that this situation is just that simple.

Re:make all wall street traders own stock for 1 da (2, Insightful)

1s44c (552956) | more than 3 years ago | (#32062384)

let's do away with the arbitrage, gambling, and bullshit from wall street. make them own a stock for ONE WHOLE DAY. No more of this low-latency trading bullshit. They're just skimming money off the top of the financial markets--away from the regular folks. EVERY PENNY THESE GUYS MAKE COMES OUT OF OUR POCKET.

You are absolutely, painfully right and it pains me deeply that I don't have any mod points.

These jokers want time more accurate than NTP can provide but I'll bet most of them still believe time is a universal invariant. They don't need time more accurate than NTP can provide, they need to be hit in the head with a hammer until they stop moving.

Re:make all wall street traders own stock for 1 da (-1, Troll)

nacturation (646836) | more than 3 years ago | (#32062696)

These jokers want time more accurate than NTP can provide but I'll bet most of them still believe time is a universal invariant. They don't need time more accurate than NTP can provide, they need to be hit in the head with a hammer until they stop moving.

Obligatory XKCD [goatkcd.com]

Re:make all wall street traders own stock for 1 da (0, Troll)

Bartab (233395) | more than 3 years ago | (#32062450)

No. Every penny gov't employees make comes out of "your pockets". The same gov't employees that, on average, make more than private employees. The same gov't employees agitating for tax increases so they can get pay raises.

Don't pretend its just the rich getting taxed either. That's not only silly classism, but inherently wrong. The first tax implemented by the Obama administration was a regressive sin tax. The Obamacare system contains seven seperate taxes that directly tax people making under $200k/yr, including increases to income tax.

The market, on the other hand, actually creates wealth.

Re:make all wall street traders own stock for 1 da (1, Interesting)

alexhard (778254) | more than 3 years ago | (#32062528)

That's a ridiculous idea. It would increase volatility tremendously, increase spreads tremendously, increase mispricing tremendously, and of course destroy any semblance of liquidity for half the securities out there. Saying that arbitrageurs are skimming is like saying market makers are skimming. Partly true, but it completely ignores the positive effects of their actions for the market.

Mod parent down. (5, Insightful)

Anonymous Coward | more than 3 years ago | (#32062556)

Actually this kind of trading (especially arbitrage) narrows the spread making it cheaper for ordinary people to enter the market.
So if you ban it you go back to only the big boys being able to afford to execute trades.

However, using any system, high frequency or otherwise, to deliberately manipulate the market is a different thing.

I'm sorry I'm posting as AC but it could affect my job.

Re:Mod parent down. (1, Informative)

Anonymous Coward | more than 3 years ago | (#32062790)

Arbitrage is only beneficial if the actions of arbitrageurs result in narrowing the spread (i.e. reducing the arbitrage opportunity), which in this case doesn't happen. The fast traders are exploiting a systemic information asymmetry which other market participants can't avoid, so their opportunity for arbitrage is not eliminated by their actions. This particular arbitrage opportunity is a result of a flawed market system and does not depend on outside information. Therefore it can only be (and must be) eliminated by correcting the way the market works.

Re:Mod parent down. (0)

Anonymous Coward | more than 3 years ago | (#32062958)

A trading environment relying on asymmetrical information requires asymmetrical timing. /ducks

Trust yourself... (1)

ls671 (1122017) | more than 3 years ago | (#32061888)

I like the trust yourself part. I actually implemented a dirty script to restrict how much ntp can change my clock speed and I call every minute from crond ;-))

Limits are hardcoded and depend on the machine ;-))

$ cat setclockfrequency
#!/bin/sh

# 251616 = 3.839
# 269120 = 4.106
# 280448 = 4.279
# 288544 = 4.403
# 9372208 = 143.009
# 10703936 = 163.329
# 11308784 = 172.558

###let LOWLIMIT=243520
###let HILIMIT=286496

let LOWLIMIT=10072208
let HILIMIT=10408784

let FREQ=`adjtimex -p | grep frequency | cut -d ":" -f 2 | cut -c 2-`
if [ ${FREQ} -gt ${HILIMIT} ]
then
adjtimex -f ${HILIMIT}
fi

if [ ${FREQ} -lt ${LOWLIMIT} ]
then
adjtimex -f ${LOWLIMIT}
fi

Re:Trust yourself... (0)

Anonymous Coward | more than 3 years ago | (#32062006)

Your smilies make me >:-(

Also, can't you just turn off ntp?

Re:Trust yourself... (1)

buchner.johannes (1139593) | more than 3 years ago | (#32062084)

Can you please explain what the issue is you are trying to solve with this?

Re:Trust yourself... (4, Interesting)

ls671 (1122017) | more than 3 years ago | (#32062158)

Network issues. If say, on average, once every 25 polls, ntpd doesn't get realistic data from higher stratum servers because of the network, don't let ntpd crank up the frequency to ridiculous values like it does when this occurs.

There are realistic values for the frequency on every machine with a good clock. It is ridiculous to set the frequency below or above these values.

Last time I checked, there is no way in ntpd to configure these values. The typical ntp guru reply will be: "Get a decent network connection". The author in TFA noted that such a "decent connection" is virtually impossible to achieve because of "variable delay". He also noted that it is sometime better to trust yourself, which is kind of what that script does.
 

Re:Trust yourself... (2, Interesting)

ls671 (1122017) | more than 3 years ago | (#32062314)

Author of TFA also mention:

"More generally, the algorithm should be designed never to overreact to anything. Remember, its view of the world is always approximate and may be wrong, so why try to be too clever when inaction works so well? Unfortunately, feedback algorithms such as ntpd have more reactive strategies that drive the clock more strongly in the direction of their opinions. This is a major source of their nonrobustness to disruptive events."

I fully agree with this and I realized it several years ago while testing ntpd in various configurations.

Re:Trust yourself... (0)

Anonymous Coward | more than 3 years ago | (#32062654)

meh, "computer scientists" playing at real engineering like always..

OK, but... (1)

Tenek (738297) | more than 3 years ago | (#32061900)

TFA already points out that there are existing solutions to this problem... sure, they're expensive, but when their example of the finance industry is involved, people will happily pay six, seven figures to get an edge over the competition anyways. If it's not worth the cost, you probably don't need that level of precision. Nice to improve the system, but how much benefit will anyone see from it?

Re:OK, but... (1)

Reik (101256) | more than 3 years ago | (#32062008)

I didn't see them mention IEEE1588. I don't know how many switches(if any.. hehe well, I know one..) implement it yet..and I only know of the one National Semi phy that does, but it's a solution and not really expensive just poorly implemented as of yet.

Re:OK, but... (1)

Z00L00K (682162) | more than 3 years ago | (#32062236)

In my opinion the finance industry have to live with some minor differences in timing.

What this has really done now is to provide an idea of an opening for fraudulent behavior in the finance industry. Just imagine what would happen if someone was able to inject timing faults into the servers when their favorite transaction was executed.

Re:OK, but... (1)

Hognoxious (631665) | more than 3 years ago | (#32062344)

Are you talking of the situation where the stock goes up and I buy it, but I frig it so it looks like I bought it at the old (lower) price?

The time doesn't matter, as long as the sequence is known. But I don't think the system works like that; quantity and price are always included, AFAIK, plus it wouldn't match the counterparty's books.

Re:OK, but... (1)

compro01 (777531) | more than 3 years ago | (#32062432)

One example goes kinda like this

1. News breaks overnight that will make people want to buy company FOO stock.
2. The instant (as determined by the very accurate clocks on their servers) the market opens, trading firm BAR buys up all the available FOO stock and then instantly puts it back up for sale for a little bit more.
3. The rush of people buying the stock buy it from firm BAR.

Rinse and repeat every day and you're talking about billions of dollars made by firm BAR that people without ultra accurate clocks and time distribution can't make, thus you get an arms race to get more and more accurate timing.

Re:OK, but... (1)

KDR_11k (778916) | more than 3 years ago | (#32062468)

Expensive? Our freaking wall clock can sync to an atomic clock via RF. Sure, there's maybe a bit of signal travel delay involved but the distance from sender to receiver shouldn't change much so you could calculate it and automatically compensate.

Re:OK, but... (1)

Rockoon (1252108) | more than 3 years ago | (#32062916)

Those clocks receive a signal thats transmitted at a ridiculously low rate, like 1 bit per second or some such. I'm going to go ahead and assume that hardware thats designed to receive it isnt designed for low or consistent latency.

GPS (3, Interesting)

dracocat (554744) | more than 3 years ago | (#32061918)

How about GPS receiver + exact known location?

I would think just eliminating an unknown latency and replacing it with a known one (radio waves generally travel at a consistent rate) would get you a pretty accurate time. If you add one more known variable which is the exact location of the device, then you should be able to get an even more accurate time.

Re:GPS (1)

at10u8 (179705) | more than 3 years ago | (#32061938)

to get what accuracy? the ionosphere can mess up GPS signals by about 100 nanoseconds

Re:GPS (0, Troll)

Tumbleweed (3706) | more than 3 years ago | (#32062284)

to get what accuracy? the ionosphere can mess up GPS signals by about 100 nanoseconds

What?! That sounds like terrorism! Let's do away with this 'ionosphere' once and for all!

Re:GPS (1)

dkf (304284) | more than 3 years ago | (#32062924)

the ionosphere can mess up GPS signals by about 100 nanoseconds

That's variable. You use the GPS time signal over a long period of time (days) to calculate the rate at which your clock drifts, at which point you can do a reasonably good correction for things and get your clock pretty accurate. Asking for perfect timing a second or two after switching the device on is just unfair!

Re:GPS (0)

Anonymous Coward | more than 3 years ago | (#32061958)

And how do you calculate location? Time maybe?

Re:GPS (1)

paul248 (536459) | more than 3 years ago | (#32062218)

The GPS satellites all have synchronized atomic clocks on board. If your GPS receiver also had an atomic clock, then the distance to each satellite could be computed by subtracting the times and multiplying by the speed of light. So, with 3 satellites, you could calculate your location.

However, GPS receivers are cheap, and don't have atomic clocks. But if you get a signal from *four* satellites, then you can use the redundant information to deduce the correct time, and then use that time to find your location.

Re:GPS (0, Flamebait)

Anonymous Coward | more than 3 years ago | (#32062264)

You keep it in a fixed place, you spastic.

Re:GPS (1)

Bios_Hakr (68586) | more than 3 years ago | (#32061976)

GPS is okay. But I would think that a financial institution would prefer to invest in a good cesium-beam frequency standard. These units are calibrated at the factory and drift something like one second every few thousand years. Plus, there is no need to have an external antenna to pick up GPS signals. If you *absolutely* need stable and accurate clocking, cesium is the only way to go.

Re:GPS (0)

paul248 (536459) | more than 3 years ago | (#32062678)

But what if you have a fancy cesium clock, and one day your datacenter accelerates to near the speed of light and returns to its original location? With GPS, you at least know that your time is synchronized with all the other systems using GPS.

Re:GPS (1)

SEWilco (27983) | more than 3 years ago | (#32061998)

You don't need to worry about the radio wave propagation, just wait for the GPS device to lock on and start querying its time. Much of the effort of the GPS device is in synchronizing its clock with the GPS clocks, resulting in probably less than 1 microsecond of error.

Re:GPS (1)

Matrix14 (135171) | more than 3 years ago | (#32062046)

It turns out that GPS doesn't actually send the time. That's just a convenient simplification for explaining how it works. Instead, it sends a long bitstring with minimal repetition, with each satellite sending the same bit in the sequence simultaneously. Receivers compute how far out of sync the bitstrings are with each other to find their location.

Re:GPS (1)

dracocat (554744) | more than 3 years ago | (#32062070)

I thought the Data Signal, repeated every 15 minutes roughly contained date/time and clock corrections? You might be drifting for 15 minutes at a time I guess...

Re:GPS (1)

Matrix14 (135171) | more than 3 years ago | (#32062082)

Hmm, yeah, I am reading the WP page on GPS now, and it looks like it does send out time info. A lot of things are sent, and it is not clear to me from the article how often this time is sent out.

Re:GPS (0)

Anonymous Coward | more than 3 years ago | (#32062130)

I think is is every couple of seconds. NTP currently uses GPS and other time sources as stratum 0 devices, and the computer that they are connected to as stratum 1 devices.

Re:GPS (1)

DerekLyons (302214) | more than 3 years ago | (#32062378)

How about GPS receiver + exact known location?
 
I would think just eliminating an unknown latency and replacing it with a known one (radio waves generally travel at a consistent rate) would get you a pretty accurate time.

While radio waves do travel a constant speed, what they don't do is travel a consistent path between the satellite and the receiver. Some of this is due to the satellite's orbital motion, and the timing errors resulting from that can be eliminated. However, the path is also altered by changing ionospheric conditions which are difficult to model and predict. (Which is why WAAS and other workarounds have been implemented.)

Would make sense (4, Informative)

Sycraft-fu (314770) | more than 3 years ago | (#32062472)

GPS is accurate to about 50 nanoseconds. All kinds of devices that need precision time get it from GPS. You don't need much more than a standard receiver, just one that is designed to place a high priority on time updates. The GPS system itself keeps very accurate time since each satellite has an atomic clock, and they all sync to the master clock.

To me that would seem the best way, if accuracy is really important and the systems are high end. Have each device have its own receiver and just have them sync to that. Don't sync them to each other, since you aren't going to get anything more accurate.

Re:If only I knew where I was (0)

Anonymous Coward | more than 3 years ago | (#32062542)

If only I knew what time it was, I wouldn't be so lost!

can't trust self if microsoft (4, Interesting)

at10u8 (179705) | more than 3 years ago | (#32061926)

Microsoft refuses to consider the notion [microsoft.com] of clocks accurate to within 2 seconds.

Re:can't trust self if microsoft (3, Funny)

Bios_Hakr (68586) | more than 3 years ago | (#32062000)

I don't really see a problem with that. You wouldn't use Notepad for a mission-critical editing, why would you use W32Time for mission-critical timing?

That being said, I don't know what 3rd-party system you would use for sub-second timing.

Re:can't trust self if microsoft (-1, Troll)

at10u8 (179705) | more than 3 years ago | (#32062038)

It's not W32Time. It is not possible to regulate the Windows system clock that well no matter what is used to try to do it.

Re:can't trust self if microsoft (4, Informative)

Rockoon (1252108) | more than 3 years ago | (#32062982)

He was modded troll, but hes right.. sort of.

The problem isnt "windows" .. the problem is "x86 computers."

Accurate timing on the modern PC is ridiculously difficult due to the hardware situation. The original IBM PC and its clones came with Intel's 8253 or 8254 Programmable Interval Timer (PIT) chip and back then it was pretty good. This timer chip had an internal frequency matching the CPU's of the time of 4.77mhz, and ticks were evenly distributed between 4 internal counters, so each counter had 1193181.81818181.... ticks per second. Pretty damn good.

Many of the old-school people might be familiar with the 18.2 ticks per second of the DOS clock. This rate was a direct consequence of configuring one of those counters to emit an interrupt every 65536 ticks, the longest possible interrupt interval due to these chips using 16-bit words.

Anyways, over time many manufacturers stopped using Intel's PIT's and started emulating them with other hardware (such as PMT.) None of these emulations can be configured to tick at exactly the same rate as the Intel PIT, and even among these emulated timers there wasn't any consistency.

To counter the serious problem of accurate timing on the PC, Microsoft and a few other large companies moved to define a new standard named HPET. Many new motherboards will have an HPET timer, but not all of them, and there are some problems with some HPET implementations as well (such as appearing to tick backwards sometimes.)

The issue of accurate timing on PC's has considerable effect on multi-player game developers.

A reference to some of the issues, and some of the attempts to fix them (source code) [gamedev.net]

Re:can't trust self if microsoft (1)

sl149q (1537343) | more than 3 years ago | (#32062048)

Well I like my iPhone, but it appears to sync time from the nearest cell tower... And in my neighborhood I see variations from what I would expect (using NTP to compare) for anywhere up to 1.5 seconds. More annoyingly the time will jump between various offsets. E.g. go from +500msec fast to -900msec slow and then back. I think switching between cells.

It would be better if they just synced with NTP, or gave you the option of using NTP or cell.

Re:can't trust self if microsoft (-1, Flamebait)

Anonymous Coward | more than 3 years ago | (#32062104)

Ohmygod! I don't even want to think about how many problems I could have if the clock on my phone was out by 500ms...

Anal, much?

Re:can't trust self if microsoft (0)

Anonymous Coward | more than 3 years ago | (#32062602)

iPhone

gave you the option

Yeah, right

crypto now! (-1, Flamebait)

Anonymous Coward | more than 3 years ago | (#32061960)

Unsecured protocols are foolish. NTP over some secured tunneling protocol like TLS would maybe be be a solution if the server could use anything else than simple cleartext.

PTPd? (5, Interesting)

Jeremi (14640) | more than 3 years ago | (#32061996)

I'm surprised the article didn't mention PTPd [wikipedia.org] , which is an implementation of the IEEE 1588 precision time-synchronization standard. I was under the impression that was the standard way to solve this sort of problem when NTP wasn't enough.

Re:PTPd? (5, Informative)

apharov (598871) | more than 3 years ago | (#32062416)

(disclaimer: just finished my Master's thesis on a related subject) PTPd is ok, but not in itself up-to-date at the moment. It doesn't implement the most recent IEEE 1588-2008 standard, which has significant improvements compared to the 1588-2002. About the 1588 in general: its main selling point is the ability to do hardware timestamping (when using hardware with support!) of the two-way timing messages between master and slave. This eliminates the very significant timing jitter that happens in the software stack before the messages are timestamped. For reference, commercially available master-slave implementations using IEEE 1588 achieve synchronisation within tens of nanoseconds within LAN, and microseconds to tens of microseconds within WAN, depending on network conditions. So overall I think that while RADclock might be ok as an alternative between NTP and IEEE 1588, it doesn't really bring anything new to the table. Some of the stuff in the Rideaux/Veitch paper has also been used with IEEE 1588 for quite some time, for instance the filtering for fast timing packets is a necessity for accurate synchronisation with IEEE 1588.

Re:PTPd? (1)

iritant (156271) | more than 3 years ago | (#32063002)

Thanks for the informative post that was on topic. One question: with 1588 what sort of hierarchy do you set up? Does everyone have a rubidium or cesium clock attached?

Wants vs. needs vs. design (2, Interesting)

Anonymous Coward | more than 3 years ago | (#32062026)

It's not clear to me the financial system needs such high precision timing.

My cynicism tells me they need it now to implement fraudulent micro-second trading, where see what you're buying, correlate with other people's buys and then buy a fraction of a second ahead of you.

At any rate, it's not clear they need it, or that giving it to them won't lead to instability.

Maybe someone should actually design a financial system, and design one that can use imprecise, or precision timing.

Re:Wants vs. needs vs. design (1)

Hognoxious (631665) | more than 3 years ago | (#32062350)

If you're talking about "front running", you don't need accurate timing for that. You (the broker) just slip your order in front of the customer's.

Ridiculous (2, Interesting)

GNUALMAFUERTE (697061) | more than 3 years ago | (#32062036)

NTP is accurate to within 10 milliseconds in any decent connection. Get a really good, stable, low latency connection and hook yourself up to a stratum 1 server and you can cut that number down tenfold ...

Can anyone explain what kind of financial application would require bigger accuracy?

I understand that certain scientific experiments require more accuracy than that, but those guys are probably already hooked up to stratum 0 servers directly.

Why on earth would any financial system (yes, even the stock market) require 10ms time accuracy? They were able to rip us off with fucking sand clocks. NTP should be enough for them.

Re:Ridiculous (5, Informative)

Anonymous Coward | more than 3 years ago | (#32062080)

This sort of thing probably has something to do with it:

http://www.nytimes.com/2009/07/24/business/24trading.html [nytimes.com]

Re:Ridiculous (0)

Anonymous Coward | more than 3 years ago | (#32062200)

mod parent up, very interesting

Re:Ridiculous (2, Insightful)

MichaelSmith (789609) | more than 3 years ago | (#32062222)

Its old fashioned day trading accelerated by a factor of a few million. Of course, you need to back it up with a good AI because humans can't react fast enough and a flatline with his ass in a can will react in a predictable way.

Re:Ridiculous (0, Troll)

Hognoxious (631665) | more than 3 years ago | (#32062476)

Any article that refers to software as "codes" should be ignored.

Re:Ridiculous (0)

Anonymous Coward | more than 3 years ago | (#32062536)

It is unfortunately widespread within scientific circles. You can expect a "code" to do something extremely complex that takes a few years worth of study to understand, to do it within acceptable accuracy in the common cases, and to break down horribly if you violate one of a thousand undocumented assumptions. It will also follow CS best practices only as far as absolutely necessary to get it to work on the university servers, i.e. mostly not at all.

Re:Ridiculous (3, Informative)

IWannaBeAnAC (653701) | more than 3 years ago | (#32062964)

"Codes" is a common and long-standing jargon word in several significant sub-fields of CS, notably high performance and scientific computing. If you are unfamiliar with it, then you are simply betraying your own ignorance.

Re:Ridiculous (0)

Anonymous Coward | more than 3 years ago | (#32062090)

Goldman recently moved its server farm (or part of it) closer to the physical computer network they access for trading to cut latency. When you are trying to arbitrage the market, every pico second counts!

Re:Ridiculous (2, Informative)

Todd Knarr (15451) | more than 3 years ago | (#32062156)

These guys are probably trying to do sub-millisecond trading. They need to keep their clocks sync'd to the microsecond to keep different machines coordinated.

Me, I wonder why they're bothering. Run GPS-based stratum-1 servers at each site, and sync directly to them across the LAN. Or get a cesium-beam primary time source. End of problem. Or take heed of the current financial meltdown and acknowledge that if you try to create money out of thin air, sooner or later you're going to pay the piper and it's going to hurt so maybe it'd be better to not go there.

Re:Ridiculous (0)

Anonymous Coward | more than 3 years ago | (#32062394)

As long as everybody pays when the system crashes but you are among the few who profit as long as it works, why stop doing what you're doing? I fully support the rule that you can't sell stock when you bought the same stock less than a day earlier, unless the current stock price is more than 10% lower than when you last bought.

Re:Ridiculous (1)

nacturation (646836) | more than 3 years ago | (#32062630)

I fully support the rule that you can't sell stock when you bought the same stock less than a day earlier, unless the current stock price is more than 10% lower than when you last bought.

Let's have the government regulate everything. You can't return a product to the store that you bought less than 1 day earlier. You can't delete a file on your computer that you created less than 1 day earlier.

Re:Ridiculous (1, Insightful)

Anonymous Coward | more than 3 years ago | (#32062690)

Is there a problem with rampant abuse of deleting fresh files? Is there a problem with rampant abuse of returning products shortly after buying them (as opposed to one day later)?

There is a problem with algorithmic stock trading in millisecond intervals, which allows a few traders to game the market instead of participating on even ground. Even a most die-hard market liberal must agree that the market should work to eliminate arbitrage, not create it.

Re:Ridiculous (0)

Anonymous Coward | more than 3 years ago | (#32062180)

Can anyone explain what kind of financial application would require bigger accuracy?

You're thinking like a human. 10ms in computer terms is like a month in human terms. It's all about getting the edge. Get a jump on somebody and make an extra $0.00001 on the $. Now multiply it by a billion dollars.

Re:Ridiculous (1)

funkboy (71672) | more than 3 years ago | (#32062656)

10ms is not enough.

The same cocaine-addled financial industry that brought you the mortgage crisis is busy fighting a little undeclared network latency war as each trading house tries to get the lowest-latency network path to various financial exchanges around the world. Carriers with shorter fibre optic paths have been able to command price premiums upwards of $500/month per millisecond of decreased latency vs. their competition. Eventually the exchanges will just host trading houses' servers locally, everyone will be on a level playing field, and this fiasco will end.

Incidentally, the RIPE's RIS [ripe.net] routing information & network latency measurement project also requires precision beyond what NTP can provide. Each of the 200 or so RIS servers has a physically attached GPS receiver in order to provide accurate sub-millisecond network latency measurements.

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Off topic I know but.... (1)

erroneus (253617) | more than 3 years ago | (#32062230)

... is there a patch or driver hack for Windows that will allow the hardware clock to be set to GMT/UTC while the time zone offset is handled by the OS as it should be? It is such a pain in my ass that I run Linux with the occasional boot to Windows and having the time wrong for Windows. And of course if I set it, the time becomes wrong for Linux. Linux is doing it "right" and Windows is doing it wrong in my opinion. But what is the fix? I'd prefer Windows change its ways, not Linux.

Re:Off topic I know but.... (0)

Anonymous Coward | more than 3 years ago | (#32062278)

Set/Create HKLM\SYSTEM\CurrentControlSet\Control\TimeZoneInformation\RealTimeIsUniversal to DWORD 1. Works fine on my Windows 7 box but its supposedly really buggy on anything pre Windows 7.

Re:Off topic I know but.... (1)

jonadab (583620) | more than 3 years ago | (#32062820)

> I'd prefer Windows change its ways, not Linux.

The thing is, Linux is configurable. You *can* change its behavior, easily. Windows, not so much.

How bad do you need the time to be right in Windows? If that's really a requirement, then you should probably set the hardware clock to local time, because that's how Windows does it.

On the other hand, my experience suggests that the longer you've been running Linux, the less often you'll be inclined to boot into Windows. *shrug*. Give it a couple more years, and you'll probably forget all about caring whether the time is right in Windows. Heck, eventually you'll forget why you even have Windows installed.

Re:Off topic I know but.... (1)

erroneus (253617) | more than 3 years ago | (#32062966)

I run Linux often enough that I don't want to change it and regard its behavior as correct. I regard windows as incorrect. And you're right. I don't run the Windows that much -- just when I VPN into the office which is somewhat rare.

I don't usually "need" the time to be right... it's just annoying when it's not.

This is just piffle. (1)

DrNoNo (976214) | more than 3 years ago | (#32062246)

NTP has its limitations and to me the miracle is that it is as good as it is, given the lack of promises concerning packet delivery in a TCP/IP network [No guarantee on route, latency or even delivery]. If you need something more accurate, then use GPS as already suggested or one of the atomic clock backed radio services around the world and calibrate for transmission distances, which is a consistent correction for any location. This will take accuracy close to the theoretical limits and is potentially available cheaply enough that the cost should not be a bar to any application where this sort of accuracy really is justified. I just cannot see any point whatsoever in trying to do this over the internet when you cannot hope to meet the accuracy of existing means.

Speed of light and relativity (1)

Zaffle (13798) | more than 3 years ago | (#32062286)

I don't understand the need for wide-area highly accurate (less than 1ms accurate) timing. Once you get beyond a reasonable distance, the speed of light starts playing into the equation.

Re:Speed of light and relativity (4, Insightful)

1s44c (552956) | more than 3 years ago | (#32062426)

I don't understand the need for wide-area highly accurate (less than 1ms accurate) timing. Once you get beyond a reasonable distance, the speed of light starts playing into the equation.

Like most smart people you are forgetting how dumb most people are.

Wall street traders don't understand much about time. They only understand how to obfuscate financial transactions like a high speed shell game. To them more speed means more chances to skim off a percentage and the laws of physics don't even get considered.

Re:Speed of light and relativity (1)

renoX (11677) | more than 3 years ago | (#32062954)

Uh? I've read here that some traders are paying to put their hardware the closest they can to the trading servers so that they can have low latency..
So I'd guess that this is more a case of an article with a flawed example than anything else..

Re:Speed of light and relativity (2, Insightful)

Linker3000 (626634) | more than 3 years ago | (#32062658)

I vote that all traders - and lawyers and estate agents for that matter - are sent such a reasonable distance from the planet that the speed of light indeed starts playing into the equation.

ALl in the name of research, of course.

Works fine in telecommunications (2, Interesting)

s52d (1049172) | more than 3 years ago | (#32062422)

Hi!

Last few years, most cellular operators are rolling out IP to the base stations.
For HSPA/LTE speeds, E1/T1 PDH/ATM is out of the question,
and as IP is rolled out, GSM gets there as well.

Accurate timing is essential: even transmitter frequency is synchronized over IP,
and keeping 2 GHz accurate to 100 Hz is not simple.
Local oscillator can do it short term, but external correction is needed as well.

Beside GPS (used in IS-95), several systems are used.
IEEE 1588v2 is obvious one. Works.

Some vendors do it with modified NTP: generate a lot of requests, and do some statistic processing.
Thus, most of the jitter can be compensated, and accuracy can be kept.
Normally, it works over intranets, with NTP having high priority, but it is used over internet as well
(femto and pico base stations).

Real life tests indicate it works, just do not put it over ADSL ;-)

73
Iztok

Isn't the internet the wrong medium for this? (1)

KDR_11k (778916) | more than 3 years ago | (#32062436)

It seems to me that with all the intermediate systems and variable delays the internet isn't the right medium for clock synchronization, you'd be better off following the RF time signals broadcast by stations running atomic clocks. Much easier to synchronize those and the signal travels a known time to the receiver instead of going through a heterogeneous wire network.

Re:Isn't the internet the wrong medium for this? (1)

amorsen (7485) | more than 3 years ago | (#32062718)

Running antenna cable to the servers requiring synchronization is often a problem.

djb worked on this (1)

Ice Station Zebra (18124) | more than 3 years ago | (#32062802)

http://cr.yp.to/clockspeed.html [cr.yp.to]

clockspeed uses a hardware tick counter to compensate for a persistently fast or slow system clock. Given a few time measurements from a reliable source, it computes and then eliminates the clock skew.

sntpclock checks another system's NTP clock, and prints the results in a format suitable for input to clockspeed. sntpclock is the simplest available NTP/SNTP client.

taiclock and taiclockd form an even simpler alternative to SNTP. They are suitable for precise time synchronization over a local area network, without the hassles and potential security problems of an NTP server.

This version of clockspeed can use the Pentium RDTSC tick counter or the Solaris gethrtime() nanosecond counter.

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