How Computers Keep Abreast of Time

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Time governs our lives and keeping abreast of it is vital if we want to get to work on time, make it home for dinner or watch our favourite shows of an evening.

It is also crucial for computer systems. Computers use time as a point of reference, indeed, time is the only point of reference it can use to distinguish between two events and it is crucial that computers operating in networks are synchronized together.

Time synchronization is when all computers that are connected together run the same time. Time synchronization, however, is not simple to implement, primarily because computers are not good time keepers.

We are all used to the time being displayed on the bottom right hand of our computer desktops but this time is normally generated by the onboard crystal oscillator (normally quartz) on the motherboard.

Unfortunately these onboard clocks are prone to drift and a computer clock may lose or gain a second or so each day. While this may not sound like much, it can soon accumulate and with some networks consisting of hundreds and even thousands of machines, if they are all running different times its not hard to imagine the consequences; emails may arrive before they are sent, data may fails to backup, files will get lost and the networks will be amass of confusion and nearly impossible to debug.

To ensure synchronization throughout a network all devices must connect to a single time source. NTP (Network Time Protocol) has been devised for this very purpose and can distribute a time source to all devices and ensure that any drift is countered.

For true accuracy the single time source should be a source of UTC (Coordinated Universal Time) which is a global timescale that is used across continents and pays no heed to timezones, this allows networks on opposite sides of the Earth to be synchronized together.

A source of UTC should also be governed by an atomic clock as any drift in the time will mean that your network will be out of sync with UTC. By far the easiest, most efficient, secure, accurate and reliable method of receiving an atomic clock source of UTC is to use a dedicated NTP time server. NTP servers receive the UTC time from either the GPS network (Global Positioning System) or from radio transmission broadcast by national physics laboratories such as NIST or NPL.

Networking Secrets Synchronization

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An efficient and error free operation is the goal of any administrator that is setting up a computer network. Ensuring the smooth running and passing of data without errors or loss of connections is a prerequisite for any decent functioning network system.

There are some fundamental things that can be carried out to minimise risk of encountering problems further down the line. A decent network server is a must, as is an efficient router but there is one piece of technology often overlooked in computer networking – the network time server.

The importance of correct computer network time only becomes apparent when something goes wrong. When an error does occur (and without adequate time synchronization it is a matter of when not if) it can be next to impossible to pin down what caused in and where. Just imagine all the error logs on the different machines all with timestamps telling a different time, finding out where and when the error occurred can be near impossible – and that’s before you can even get round to fixing it.

Fortunately most network administrators appreciate the value of synchronization and most ensure the network receives a time signal from across the Internet. However, many administrators are unaware of the vulnerabilities this may cause throughout the network.

By using an online time server, a UDP port (123) needs be kept open which can be an open gate to malicious programs and users. Furthermore, there is no authentication of the online time server so the signal could be hijacked or just be inaccurate.

A dedicated network time server running the protocol NTP (Network Time Protocol) will operate externally to the network and receive the time from an atomic clock source directly (through radio or GPS) making NTP servers, secure, accurate and reliable.

Seven Reasons why your Network needs a Time Server

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Time servers, often referred to as NTP time servers after the protocol (Network Time Protocol) used to distribute time are an increasingly important part of any computer network. The NTP server receives a timing signal from an accurate source (such as an atomic clock) and then distributes it to all devices on the network.

However, despite the increasing importance of these time synchronisation devices, many network administrators still fail to accurately synchronise their networks and can leave their entire computer system vulnerable.

Here are seven reasons why a NTP time server is a crucial piece of equipment for YOUR network:

• Security: NTP servers use an external source of time and don’t rely on an open firewall port. An unsynchronized server will also be vulnerable to malicious users who can take advantage of time differences.

• Error logging: failing to adequately synchronize a computer network may mean that it is near impossible to trace errors or malicious attack, especially if the times on the log files from different machine do not match.

• Legal Protection: Not being able to prove the time can have legal implications if somebody has committed fraud or other illegal activity against your company.

• Accuracy: NTP Time Servers ensure that all networked computers are synchronized automatically to the exact time throughout your network so everybody in your company can have access to the exact time.

• Global Harmony: A global timescale known as UTC (Coordinated Universal Time) has been developed to ensure that systems across the globe can run the exact same time. By utilising a NTP server not only will every device on you network be synchronised together but your network will be synchronised with every other network on Earth that is hooked up to UTC.

• Control: With a NTP server you have control of the configuration. You can allow automatic changes each spring and autumn for daylight saving time or set your server time to be locked to UTC time only – or indeed, any time zone you choose.

• Automatic update of time. No user intervention required, a NTP time server will account for leap seconds and time zones ensuring trouble free synchronisation.

Life Without the Atomic Clock

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When we consider the most important inventions of the last 100 years, very few people will think of an atomic clock. In fact, if you ask somebody to come up with a top ten of inventions and innovations its doubtful if the atomic clock would figure at all.

Its probably not hard to imagine what people think of as the most life-changing inventions: the Internet, mobile phones, satellite navigation systems, media players etc.

However, nearly all theses technologies rely on accurate and precise time and they would not function without it. The atomic clocks lies at the heart of many of the modern innovations, technologies and applications associated with them.

Let’s take the Internet as an example. The Internet is, in its simplest form, a global network of computers, and this network spans time zones and countries. Now consider some of the things we use the Internet for: online auctions, Internet banking or seat reservation for example. These transactions could not be possible with precise and accurate time and synchronisation.

Imagine booking a seat on an airline at 10am and then another customer tries to book the same seat after you on a computer with a slower clock. The computer only has the time to go on so will consider the person who booked after you to have been the first customer because the clock says so! This is the reason any Internet network that requires time sensitive transactions is connected to a NTP server to receive and distribute an atomic clock time signal.

And for other technologies the atomic clock is even more crucial. Satellite navigation (GPS) is a prime example. GPS (Global Positioning System) works by triangulating atomic clock signals from satellites. Because of the high velocity of radio waves an inaccuracy of 1 second could see a sat-nav device out by 100,000 km.

Other technologies too from mobile phone networks to air traffic control systems are completely reliable on atomic clocks demonstrating how underrated this technology is.

Closed Circuit Cameras are Useless Without a Network Time Server

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For those of us that live in Britain, the CCTV camera (closed circuit TV) will be a familiar site on the high streets. Over four million cameras are in operation throughout the British Isles with every major city being monitored by state funded cameras which has cost the British taxpayer over £200 million ($400 million).

The reasons for use of such widespread surveillance have always been declared as to prevent and detect crime. However, critics argue that there is little evidence that CCTV cameras have done anything to dent the rising street crime on the UK’s streets and that the money could be better well spent.

One of the problems of CCTV is that many cities have both cameras controlled by local councils and privately controlled cameras. When it comes to crime detection the police often have to obtain as much evidence as possible which often means combining the different local authority controlled CCTV cameras with the privately controlled systems.

Many local authorities synchronise their CCTV cameras together, however, if the police have to obtain images from a neighbouring borough or from a private camera these may not be synchronised at all, of if so, synchronised to a different time completely.

This is where CCTV falls down in the fight against crime. Just imagine a suspected criminal is spotted on one CCTV camera committing a criminal act. The time on the camera could say 11.05pm but what if the police follow the suspects movements across a city and use footage from a privately owned camera or from other boroughs and while the CCTV camera that caught the suspect in the act may say 11.05, the other camera could spot the suspect minutes later only for the time to be even earlier. You could imagine a good defence lawyer taking full advantage of this.

To ensure their worth in the fight against crime, it is imperative that CCTV cameras are time synchronized using a network time server. These times servers ensure every device (in this case camera) is running the exact same time. But how do we ensure all cameras are synchronised to the same time source. Well fortunately, a global time source known as UTC (coordinated Universal Time) has been developed for this exact purpose. UTC is what governs computer networks, air traffic control and other time sensitive technologies.

A CCTV camera using a NTP server that receives a UTC time source from an atomic clock will not only be accurate but the time told on the devices will be provable in court and accurate to a thousandth of a second (millisecond).

2038 The Next Computer Time Bug

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Remember the turn of the millennium. Whilst many of us were counting down the seconds until midnight, there were network administrators across the globe with their fingers crossed hoping their computer systems will still be working after the new millennium kicked in.

The millennium bug was the result of early computer pioneers designing systems with only two digits to represent the time as computer memory was very scarce at the time. The problem didn’t arise because of the turn of the millennium, it arose because it was the end of the century and two digit year flicked around to 00 (which the machines assume was 1900)

Fortunately by the turn of the millennium most computers were updated and enough precautions were taken that meant that the Y2K bug, as it became known, didn’t cause the widespread havoc it was first feared.

However, the Y2K bug is not the only time related problem that computer systems can be expected to face, another problem with the way computers tell the time has been realised and many more machines will be affected in 2038.

The Unix Millennium Bug (or Y2K38) is similar to the original bug in that it is a problem connected with the way computers tell the time. The 2038 problem will occur because most machines use a 32 bit integer to calculate the time. This 32 bit number is set from the number of seconds from 1 January 1970, but because the number is limited to 32 digits by 2038 there will be no more digits left to deal with the advance of time.

To solve this problem, many systems and languages have switched to a 64-bit version, or supplied alternatives which are 64-bit and as the problem will not occur for nearly three decades there is plenty of time to ensure all computer systems can be protected.

However, these problems with timestamps are not the only time related errors that can occur on a computer network. One of the most common causes of computer network errors is lack of time synchronization. Failing to ensure each machine is running at an identical time using a NTP time server can result in data being lost, the network being vulnerable to attack from malicious users and can cause all sorts of errors such as emails arriving before they have been sent.

To ensure your computer network is adequately synchronized an external NTP time server is recommended.

Parking Tickets and the NTP Server

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There is nothing worse than returning to your car only to discover that your parking meter time limit has expired and you’ve got a parking ticket slapped on to your windscreen.

More-often-than-not it’s only a matter of being a couple of minutes late before an over eager parking attendant spots your expired meter or ticket and issues you a fine.

However, as the people of Chicago are discovering, whilst a minute may be the difference between getting back to the car in time or receiving a ticket, a minute may also be the difference between different parking meters.

It seems the clocks on the 3000 new parking meter pay boxes in Cale, Chicago have been discovered to be unsynchronized. In fact, of the nearly 60 pay boxes observed, most are off at least a minute and in some cases, nearly 2 minutes from what is “actual” time.

This has posed a headache to the firm in charge of parking in the Cale district and they could face legal challenges from the thousands of motorists that have been given tickets from these machine.

The problem with the Cale parking system is that while they claim they regularly calibrate their machine there is no accurate synchronization to a common time reference. In most modern applications UTC (Coordinated Universal Time) is used as a base timescale and to synchronize devices, like Cale’s parking meters, a NTP server, linked to an atomic clock will receive UTC time and ensure every device has the exact time.

NTP servers are used in the calibration of not just parking meters but also traffic lights, air traffic control and the entire banking system to name but a few applications and can synchronize every device connected to it to within a few milliseconds of UTC.

It’s a shame Cale’s parking attendants didn’t see the value of of a dedicated NTP time server – I’m sure they are regretting not having one now.

Which time signal? GPS or WWVB and MSF

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Dedicated NTP time server devices are the easiest, most accurate, reliable and secure method of receiving a source of UTC time (Coordinated Universal Time) for synchronizing a computer network.

NTP servers (Network Time Protocol) operate outside the firewall and are not reliant on the Internet which means they are highly secure and not vulnerable to malicious users who, in the case of Internet time sources can use the NTP client signals as a method of accessing the network or penetrating the firewall.

A dedicated NTP server will also receive it’s time code direct from an atomic clock, this makes it a stratum 1 time server as opposed to online time servers which are stratum 2 time servers, that is they get the time from a stratum 1 server and so are not as accurate.

In using a NTP time server there is only really one decision to make and that is how the time signal is to be received and for this there is only two choices:

The first is to make use of the time standard radio transmissions broadcast by national physics laboratories such as NIST in the USA or the UK’s NPL. These signals (WWVB in the US, MSF in the UK) are limited in range although the USA signal is available in most parts of Canada and Alaska. However, they are vulnerable to local interference and topography as other long wave radio signals are.

The alternative to the WWVB/MSF signal is to utilise the GPS satellite network (Global Positioning System). Atomic clocks are used by GPS satellites as the basis for navigational information used by satellite receivers. These atomic clocks can be used by using a NTP time server fitted with a GPS antenna.

Whilst the GPS time signal is strictly speaking not UTC- it is 17 seconds behind as leap seconds have never been added to GPS time (as the satellites are unreachable) but NTP can account for this (by simply adding 17 whole seconds). The advantage of GPS is that it is available anywhere on the planet just as long as the GPS antenna has a clear view of the sky.

Duel systems that can utilise both types of signal are also available.

Configuring a Network to use a NTP Server Part two: Distributing the Time

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NTP (Network Time Protocol) is the protocol designed for time distribution amongst a network. NTP is hierarchical. It organises a network into strata, which are the distance from a clock source and the device.

A dedicated NTP server that receives the time from a UTC source such as GPS or the national time and frequency signals is regarded as a stratum 1 device. Any device that is connected to a NTP server becomes a stratum 2 device and devices farther down the chain become stratum 2, 3 and so on.

Stratum layers exist to prevent cyclical dependencies in the hierarchy. But the stratum level is not an indication of quality or reliability.

NTP checks the time on all devices on the network it then adjusts the time according to how much drift it discovers. Yet NTP goes further than just checking the time on a the reference clock, the NTP program exchanges time information by packets (blocks of data) but refuses to believe the time it is told until several exchanges have taken place, each passing a set of tests known asprotocol specifications. It often takes about five good samples until a NTP server is accepted as a timing source.

NTP uses timestamps to represent the current time the day. As time is linear, each timestamp is always greater than the previous one. NTP timestamps are in two formats but they relay the seconds from a set point in time (known as the prime epoch, set at 00:00 1 January 1900 for UTC) The NTP algorithm then uses this timestamp to determine the amount to advance or retreat the system or network clock.

NTP analyses the timestamp values including the frequency of errors and the stability. A NTP server will maintain an estimate of the quality of both its reference clocks and itself.

Configuring a Network to use a NTP Server Part one: Finding a Time Source

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Keeping your network synchronized with the correct time is crucial for modern networking. Because of the value of timestamps in communciating globally and across multi-networks, it is imperative that every machine is running a source of UTC (Coordinated Universal Time).

UTC was developed to allow the entire global community to use the same time no matter where they are on the globe as UTC doesn’t use time-zones so it allows accurate communication regardless of location.

However, finding a source of UTC is often where some network administrators fall down when they are attempting to synchronize a network. There are many areas that a source of UTC can be received from but very few that will provide both accurate and secure reference to the time.

The internet is full of purported sources of UTC, however, many of them offer no where near their acclaimed accuracy. Furthermore, resorting to the internet can lead to security vulnerabilities.

Internet time sources are external to the firewall and therefore a hole has to be left open which can be taken advantage of by malicious users. Furthermore, NTP, the protocol used to distribute and receive time sources, cannot instigate its authentication security measure across the internet so it is not possible to ensure the time is coming from where it is supposed to.

External sources of UTC time are far more secure. There are two methods used by most administrators. Long wave radio signals as broadcast by national physics laboratories and the GPS signal which is available everywhere on the globe.

The external sources of UTC ensure your NTP network is receiving not just an accurate source of UTC but also a secure one.