Posts by: Richard N Williams

Killing Time and the Importance of Time Synchronisation in Criminal Cases

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On occasion, we all need to know the time and we have a multitude of different devices to tell us it, from our mobile phones and wrist watches to the office wall clock or the chimes on the radio news. But how accurate are all these clocks and does it matter if they are all telling different times?

For our day-to-day business it probably doesn’t matter too much. If the office wall clock is a faster than your wrist-watch your boss probably won’t fire you for being a minute late but when it comes to solving criminal cases, timing is everything!

Take the case of Joan Beddeson, a 71-year-old found murdered in her home in Macclesfield. The chief suspect, her former lover who owed the victim over a quarter of a million pounds, 64-year-old John Crittenden, denied the killing, claiming he was at home in bed with his wife at the time of the murder.

However, police had discovered a credit card statement that showed that Crittenden had bought fuel in Worcester just hours before the killing and was then spotted on a camera 12 minutes later travelling up the motorway towards Macclesfield. Later that night the same car was recorded coming back down the motorway leaving Crittenden with a 45 minute window to commit his crime.

However, during his trial Crittenden, who admitted buying the fuel, denied travelling up the motorway and claimed the cameras were not accurate. However, the cameras were all synchronised using a NTP time server (Network Time Protocol) to Universal Coordinated Time (UTC) and was so accurate that Crittenden’s lawyers had no defence and he was convicted of the murder and sent to prison for life.

Time synchronisation is not just important in securing convictions it can also prove somebody’s innocence! When a woman was found murdered in Maryland US, the police thought they had found the perpetrators when the victim’s bank card was being used at an ATM. A check at a local CCTV camera provided footage of the three suspects using the machine and although the quality was quite grainy, once aired on America’s Most Wanted the three suspects were soon rounded up.

However, it emerged that the time recorded by the camera was three minutes off the time recorded by the ATM and the three people held were an entirely innocent family, not connected with he murder at all.

The investigators conceded that if the camera had been synchronised to a reliable source like the ATM machine, then the wrongful arrest would not have been made.

The cases above underline the importance of reliable time synchronisation. Even if a business is not involved in the detection of crime, failing to synchronise a computer network can leave a system vulnerable to fraud, data loss and even legal exposure and without it, organizations can be vulnerable and lose credibility.

Specialist NTP time servers (Network Time Protocol) are available and can synchronise a computer network and all its devices to an accurate clock source such as an atomic clock using either  the GPS or a specialist radio transmission, allowing networks to be accurately synchronized to Universal Coordinated Time (UTC).

History of Horology from Sundials to Atomic Clocks

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Mankind has always been preoccupied with measuring and recording the passage of time. Timekeeping has been essential for the development of civilisations; from knowing when to plant or harvest crops to identifying important events in the year.

Time has historically been measured in relation to the movement of the Earth; a day, is one revolution of the planet; while a year is an entire orbit of the Sun. Calendars were developed from as far back as 20,000 years ago when hunter-gatherers scratched lines and gouged holes in sticks and bones to possibly count the days between phases of the moon.

Civilizations from the Ancient Egyptians to the Roman Empire have used differing methods to discover what day of the year it is. However, measuring time as it passed throughout the day had always proved difficult to early mankind. Sundials were perhaps the first time pieces and they can trace their origin back over five thousand years; when obelisks were built, possibly to allow the telling of time by the cast of their shadows.

However, the time told on a sundial was based on the movement of the sun in the sky, which would differ throughout the seasons and of course would not work on cloudy days or at night. Other methods such as water clocks or the hourglass would simply act as crude timers. Telling the time of day would prove difficult with people relying on comparisons as time references such as: “As long as it would take a man to walk a quarter mile.”

People were reliant on these methods and others such as bell ringing to indicate important moments until the 14th century, when mechanical clocks first appeared which were driven by weight and regulated by a verge-and-foliot escapement (a gear system that advancing the gear train at regular intervals or ‘ticks’). These clocks were far more reliable than sundials or other methods allowing accurate and reliable telling of the time of day for the first time in human history.

The next step forward in horology came in the 17th century when the pendulum was developed to help clocks maintain their accuracy. Clock making soon became widespread and it was not for another three hundred years that the next revolutionary step in horology would take place; with the development of electronic clocks. These were based on the movement of a vibrating crystal (usually quartz) to create an electric signal with an exact frequency.

While electronic clocks were far more accurate than mechanical clocks it wasn’t until the development of Atomic Clocks and around fifty years ago that modern technologies such as communication satellites, GPS and global computer networks became possible.

Most atomic clocks use the resonance of the atom caesium-133 which vibrates exactly at a frequency of 9,192,631,770 every second. Since 1967 the International System of Units (SI) has defined the second as that number of cycles from this atom which makes atomic clocks (sometimes called caesium oscillators) the standard for time measurements.

Atomic clocks are accurate to less than 2 nanoseconds per day, which equates to about one second in 1.4 million years. Because of this accuracy, a universal time scale UTC (Coordinated Universal Time or Temps Universel Coordonné) has been developed that maintains a continuous and stable time scale and supports such features as leap seconds – added to compensate for the slowing of the Earth’s rotation.

However, atomic clocks are extremely expensive and are generally only to be found in large-scale physics laboratories. However, NTP servers (Network Time Protocol), the standard means for achieving time synchronisation on computer networks,  can synchronise networks to an atomic clock by using either the Global Positioning System (GPS) network or specialist radio transmissions.

The development of atomic clocks, GPS and NTP time servers has been vital for modern technologies, allowing computer networks all over the world to be synchronized to UTC.

Use of GPS for Computer Timing Applications

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The Global Positioning System (GPS) is now a familiar tool in helping motorists to navigate but GPS has more uses than merely triangulating a position for direction finding, it can be utilized to provide time and frequency information worldwide.

Developed by the United States military, GPS incorporates at least 24 communication satellites in high orbit, all of which contain precise timing equipment to enable the satellite to triangulate positions with accuracy.

However, each satellite’s highly accurate atomic clock timing reference can also be used by NTP (Network Time Protocol) servers to synchronise computer networks using the highly accurate GPS time signal as an external reference.

GPS is an ideal time and frequency source because it can provide highly accurate time anywhere in the world using relatively cheap components. Each GPS satellite transmits in two frequencies L2 for the military use and L1 for use by civilians transmitted at 1575 MHz, Low-cost GPS antennas and receivers are now widely available.

The radio signal transmitted by the satellite can pass through windows but can be blocked by buildings so the ideal location for a GPS antenna is on a rooftop with a good view of the sky. The more satellites it can receive from the better the signal. However, roof-mounted antennas can be prone to lighting strikes or other voltage surges so a suppressor is recommend; installed inline on the GPS cable.

The cable between the GPS antenna and receiver is also critical. The maximum distance that a cable can run is normally only 20-30 metres but a high quality coax cable combined with a GPS amplifier placed in-line to boost the gain of the antenna can allow in excess of 100 metre cable runs.

A GPS receiver then decodes the signal sent from the antenna to a computer readable protocol which can be utilised by most time servers and operating systems including, Windows, LINUX and UNIX.

The GPS receiver also outputs a precise pulse every second that GPS NTP servers and computer time servers may utilise to provide ultra-precise timing. The pulse-per-second timing on most receivers is accurate to within 0.001 of a second of UTC (Coordinated Universal Time)

GPS is ideal in providing NTP time servers or stand-alone computers with a highly accurate external reference for synchronisation.

Even with relatively low cost equipment, accuracy of a hundred nanoseconds (a nanosecond = a billionth of a second) can be reasonably achieved using GPS as an external reference.

How to Configure an NTP Network Time Server in Windows XP

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Summary: This article describes how to configure Windows XP to act as an authoritative time server using NTP (Network Time Protocol).

Computer time synchronisation is highly important in modern computer networks, precision and time synchronization is critical in many applications, particularly time sensitive transactions. Just imagine buying an airline seat only to be told at the airport that the ticket was sold twice because it was purchased afterwards on a computer that had a slower clock!

Modern computers do have internal clocks called Real Time Clock chips (RTC) that provide time and date information. These chips are battery backed so that even during power outages, they can maintain time but personal computers are not designed to be perfect clocks. Their design has been optimized for mass production and low-cost rather than maintaining accurate time.

For many applications, this is can be quite adequate, although, quite often machines need time to be synchronised with other PC’s on a network and when computers are out of sync with each other problems can arise such as sharing network files or in some environments even fraud!

Microsoft Windows XP has a time synchronisation utility built into the operating system called Windows Time (w32time.exe) which can be configured to operate as a network time server. It can be configured to both synchronise a network using the internal clock or an external time source.

Note: Microsoft strongly recommends that you configure a time server with a hardware source rather than from the internet where there is no authentication.

To configure Windows Time service to use the internal hardware clock, first check that w32time is located in the system services list in the registry, to check:
Click Start, Run then type regedit then click ok.
Locate and then click the following registry entry:

It is highly recommended that you back up the registry as serious problems may occur if you modify the registry incorrectly, modifications to the registry are done at your own risk.

To begin configuration for an internal clock, click on Config in the w32Time folder.

In the right pane, right-click AnnounceFlags, then click modify.

The ‘AnnounceFlags’ registry entry indicates whether the server is a trusted time reference, 5 indicates a trusted source so in the Edit DWord Value box, under Value Data, type 5, then click OK.

Network Time Protocol (NTP) is an Internet protocol used for the transfer of accurate time, providing time information along so that a precise time can be obtained

To enable the Network Time Protocol; NTPserver, locate and click:
In the right pane, right-click Enabled, then click Modify
In the Edit DWord Value box, type 1 under Value data, then click OK.

Exit Registry Editor

Click Start, then Run then type the following and press Enter:
Net stop w32time && net start w32time

To reset the local computers’ time, type the following on all computers except for the time server which must not be synchronised with itself:

To configure Windows Time to use an external time source
Run Registry Edit and locate the following:

In the right pane, right-click Type, then click Modify
In the Edit Value box, under Value Data, type NTP and then click OK.

Now as before in the Config folder, right-click AnnounceFlags, Modify and in the Edit DWORD Value box, under Value Data, type 5, then click OK.

Locate and click the following

In the right pane, right-click SpecialPollInterval, then click Modify.
In the Edit DWORD Value box, under Value Data, type the number of seconds you want for each poll, ie 900 will poll every 15 minutes, then click OK.

Now enable the NtpServer:

In the right pane, right-click Enabled, then click Modify
In the Edit DWord Value box, type 1 under Value data, then click OK.
Now in the right pane, right-click NtpServer, then Modify and in the Edit DWORD Value under Value Data type Peers, then click OK.

To configure the time correction settings, locate:
In the right pane, right-click MaxPosPhaseCorrection, then Modify, in the Edit DWORD Value box, under Base, click Decimal, under Value Data, type a time in seconds such as 3600 (an hour) then click OK.

Now go back and click:

In the right pane, right-click MaxNegPhaseCorrection, then Modify.
In the Edit DWORD box under base, click Decimal, under value data type the time in seconds you want to poll such as 3600 (polls in one hour)

Exit Registry

Now to restart windows time service, click Start, Run and type:
net stop w32time && net start w32time

And on each computer, other than the domain controller, type:
And that’s it your time server should be now up and running.

Setting Time on your Computer

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An accurate time source is needed for many computer applications. Every Personal Computer comprises of an internal Clock, it is beneficial to check the date and time settings on your PC daily. For critical application, you should synchronise the time base with a highly accurate external time source.

Personal Computers are not designed to be perfect clocks. Their design has been optimised for mass production and low-cost rather than maintaining accurate time. Where time is crucial to the application, there are a number of precise external references available that enable computers to maintain accurate system time. This article looks at the various sources of time references to show how they can be utilised to maintain synchronised time on your computer.

Working to a synchronised time base is essential in computer networks. Without any external reference, individual computers will start to drift, anything from a few seconds to a few minutes each day. Clearly such a situation would not be acceptable when processing transactions or performing time critical tasks.

On the Internet this problem has been solved by introducing the Network Time Protocol (NTP). The NTP protocol supports the distribution of accurate time from a highly precise time server to network time clients. Most modern operating systems have the ability to synchronise time with an NTP server. Generally all that is required is the IP address or domain name of Stratum 1 or Stratum 2 NTP servers.

LINUX and UNIX operating systems can download the full NTP implementation from the NTP website at NTP is freely available, open source software, available under the GNU public license.

Mirosoft Windows XP/2000/2003 and Vista system software use a standart SNTP client for Simple Network Time Protocol. This is based on a sub-set of the Network Time Protocol, using a simplified NTP algorithm with many of the more complex high precision routines removed.

The Windows operating systems provide facilities for an IP address or domain name of an Internet or Intranet NTP server to be entered in the time properties tab. The SNTP client will then contact the NTP server periodically in order to update and synchronise system time.

Alternative methods will be required for standalone computers and systems which do not have access to the Internet. These can be provided with a local access to national radio time references which are transmitted free-to-air.

All that is required is a small RS232 serial or USB radio receiver, and the PC can obtain continuous accurate time. The Computer Time synchronises to the received time and frequency radio source.

Radio broadcasts are identified by their ‘call sign’ The UK time transmitter call sign, MSF, is located at Anthorn, Cumbria. Similar arrangements exist in Noth America – call sign WWVB from Colarado. Germany is covered by DCF broadcast from Mineflingen, near Frankfurt. National broadcasts are also available in France, Switzerland, Japan and Canada.

The only shortcoming with national radio time and frequency solutions is that they have a finite transmission range. In general they are limited to geographic boundaries also. Such issues do not apply to the Global Position System (GPS) a satellite based universal navigation system.

Each GPS satellite carries a highly accurate synchronised atomic clock. This enables GPS to provide precise timing information anywhere on the face of the planet. All that is required to receive the transmission is a low cost-cost GPS receiver and antenna with a clear view of the sky. PC connections are similar to the radio transmissions configuration, using a serial or USB port, enabling accurate timing information to be available continuously.

The Meaning of an Accurate Time Server

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This article is about the Importance of network time synchronisation and how significant it is to have an accurate network time server resource in the business.

Every Computer has a clock that sustains the internal system time. PC clocks have low- cost crystal oscillators that are notoriously prone to drift. Each Computer can drift at different rates.

The time difference can become bigger and bigger over a period of time. This can lead to huge problems within the company. This article conveys the value of network time synchronization and having an accurate network time server source in an organization.

Computer Time: Computer system time is maintained by low cost real time clock and crystal oscillator components. Crystal oscillators are built with very low tolerance, each oscillates at a slightly different rate. The temperature variation make the crystal change its frequency. This is one of the reason why computers are weak in keeping up an accurate time. A Companies Computers need to be synchronized otherwise each computer will drift at a slightly different quantity.

Each computer need a network time that is correctly synchronized otherwise it can cause huge problems, especially in transaction-processing surroundings. Unsynchronized PCs can lead to fraud and other problems that can be caused in an environment where synchronized time is needed. Problems can arise with shared network files, the reason is because the unsynchronized computers are using the same resource.

Network Time Servers: Network Time servers gain precise time from an external time reference and offer (presents) an accurate time source to network time clients. Time server use the Network Time Protocol (NTP), which is a UDP based protection over TCP/IP. There is a number of options that can be used to get an accurate time. GPS (Global Positioning Systems) offers a highly accurate time; all that is needed is a clear view to the sky. Another alternative would be radio frequency. The main countries that provide radio frequency are England (MSF); Germany (DCF-77) and the US (WWVB). Other countries are France (TDF); Canada (CHU); Japan (JJY) and Switzerland (HBG) and it is possible to obtain time from mobile phone network.

Internet Time Servers: There are a lot of Internet based NTP time server resources offered that can be used for network time synchronization. The Internet Time Server can cause Problem for the Company’s Computers. The time server is located outside the firewall, so a port must be left open to access the time server. This does not just lead to Security implications, but also to problems with the time server accuracy, reliability and provision.

Local Dedicated Network Time Server: A local devoted network time server overcome many problems related to Internet based references. The time server is located inside the security firewall and does not need any external access. Also, a local time server can improve accuracy due to reliable network paths between clients and server.

To resume, the network time synchronization is an important factor in Computer network installations. Unlike the internet based network time servers, which are known for they security problems, local dedicated network time servers overcome the security problems by offering secure, accurate and reliable network time synchronisation resolution.