Category: chronology

Benefits of Accurate Network Time Synchronization

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Your computer probably does hundreds and thousands of tasks a day. If that is part of a network then the number of tasks could be millions. From sending emails to saving data, and everything else your computer is tasked to do, they are all logged by the computer or server.

Computers use timestamps to logo processes and indeed, timestamps are used as the only method a computer has to indicate when and if a task or application has been conducted. Timestamps are normally a 16 or 32 bit integer (one long number) that counts back the seconds from a prime epoch – normally 01 January 1970.

So for every task you computer does it will be stamped with the number of seconds from 1970 that the transaction was conducted. These timestamps are the only piece of information a computer system has to ascertain what tasks have been completed and what tasks have yet to be instigated.

The problem with computer networks of more than one machine is that the clocks on individual devices are not accurate enough for many modern time sensitive applications. Computer clocks are prone to drift they are typically based on inexpensive crystal oscillator circuits and can often drift by over a second a day.

This may not seem much but in today’s time sensitive world a second can be a long time indeed especially when you take into account the needs of industries like the stock exchange where a second can be the difference in price of several percent or online seat reservation, where a second can make the difference between an available seat and one that is sold.

This drift is also accumulative so within only a few months the computer systems could be over a minute out of sync and this can have dramatic effects on time sensitive transactions and can result in all sorts of unexpected problems from emails not arriving as a computer thinks they have arrived before they have been sent to data not being backed up or lost completely.

A NTP time server or network time server are increasingly becoming crucial pieces of equipment for the modern computer network. They receive an accurate source of time from an atomic clock and distribute it to all devices on the network. As atomic clocks are incredibly accurate (they won’t drift by a second even in a 100,000 years) and the protocol NTP (Network Time Protocol) continually checks the devices time against the master atomic clock time – it means the computer network will be able to run perfectly synchronised with each device within a few milliseconds of the atomic clock.

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.

Keeping Your Network Secure A Beginners Guide

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Network security is vitally important for most business systems. Whilst email viruses and denial-of-service attacks (DoS attack) may cause us headaches on our home systems, for businesses, these sorts of attacks can cripple a network for days – costing businesses hundreds of millions each year in lost revenue.

Keeping a network secure to prevent this type of malicious attack is usually of paramount importance for network administrators, and while most invest heavily in some forms of security measures there is often vulnerabilities inadvertently left exposed.

Firewalls are the best place to begin when you are trying to develop a secure network. A firewall can be implemented in either hardware or software, or most commonly a combination of both. Firewalls are used to prevent unauthorized users from accessing private networks connected to the Internet, especially local intranets. All traffic entering or leaving the intranet pass through the firewall, which examines each message and blocks those that do not meet the specified criteria.

Anti-virus software works in two ways. Firstly it acts similarly to a firewall by blocking anything that is identified in its database as possibly malicious (viruses, Trojans, spyware etc). Secondly Anti-virus software is used to detect, and remove existing malware on a network or workstation.

One of the most over-looked aspects of network security is time synchronization. Network administrators either fail to realise the importance of synchronization between all devices on a network. Failing to synchronize a network is often a common security issue. Not only can malicious users take advantage of computers running at different times but if a network is struck by an attack, identifying and rectifying the problem can be near impossible if every device is running on a different time.

Even when a network administrator is aware of the importance of time synchronization they often make a common security mistake when attempting to synchronize their network. Instead of investing in a dedicated time server that receives a secure source of UTC (Coordinated Universal Time) externally from their network using atomic clock sources like GPS, some network administrators opt to use a shortcut and use a source of Internet time.

There are two major security issues in using the Internet as a time server. Firstly, to allow the time code through the network a UDP port (123) has to be left open in the firewall. This can be taken advantage of by malicious users who can use this open port as an entrance to the network. Secondly, the inbuilt security measure used by the time protocol NTP, known as authentication, doesn’t work across the Internet which means that NTP has no guarantee the time signal is coming from where it is supposed to.

To ensure your network is secure isn’t it time you invested in an external dedicated NTP time server?

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 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.

Using NTP Networks

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Network Time Protocol is by far the most widely used application for synchronizing computer time across local area networks and wider areas networks (LANs and WANs). The principles behind NTP are fairly simple. It checks the time on a system clock and compares it with an authoritative, single source of time, making corrections to the devices to ensure they are all synchronized to the time source.

Selecting the time source to use is perhaps the fundamentally most important thing in setting up a NTP network. Most network administrators opt, quite rightly to use a source of UTC time (Coordinated Universal Time). This is a global timescale and means that a computer network synchronized to UTC is not only using the same timescale as every other UTC synchronized network but also there is no need to worry about different time zones around the globe.

NTP uses different layers, known as strata, to determine the closeness and therefore accuracy, to a time source. As UTC is governed by atomic clocks, any atomic clock giving out a time signal is referred to as stratum 0 and any device that receives the time directly from an atomic clock is stratum 1. Stratum 2 devices are devices that receive the time from stratum 1 and so on. NTP supports over 16 different stratum levels although accuracy and reliable decrease with each stratum layer further away you get.

Man network administrators opt to use an internet source of UTC time. Apart from the security risks of using a time source from the internet and allowing it access through your firewall. Internet time servers are also stratum 2 devices in that they are normally servers that receive the time from single stratum 1 device.

A dedicated NTP time server on the other had are stratum 1 devices in themselves. They receive the time directly from atomic clocks, either via GPS or long wave radio transmissions. This makes them far more secure than internet providers as the time source is external to the network (and firewall) but also it makes them more accurate.

With a stratum 1 time server a network can be synchronized to within a few milliseconds of UTC without risk of compromising your security.

Using Atomic Clocks to Synchronize a Network

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Most computer networks have to be synchronized to some degree. Allowing the clocks on computers across a network to all be telling different times is really asking for trouble. All sorts of errors can occur such as emails not arriving, data getting lost, and errors get unnoticed as the machines struggle to makes sense of the paradoxes that unsynchronized time can cause.

The problem is computers use time in the form of timestamps as the only point of reference between different events. If these don’t match then computers struggle to establish not only the order of events but also if the events took place at all.

Synchronizing a computer network together is extremely simple, thanks largely to the protocol NTP (Network Time Protocol). NTP is installed on most computer operating systems including Windows and most versions of Linux.

NTP uses a single time source and ensures that every device on the network is synchronized to that time. For many networks this single time source can be anything from the IT manager’s wrist watch to the clock on one of the desktop machines.

However, for networks that have to communicate with other networks, have to deal with time sensitive transactions or where high levels of security are required then synchronization to a UTC source is a must.

Coordinated Universal Time (UTC) is a global timescale used by industry all over the world. It is governed by a constellation of atomic clocks making it highly accurate (modern atomic clocks can keep time for 100 million years without losing a second).

For secure synchronization to UTC there is really only one method and that is to use a dedicated NTP time server. Online NTP servers are used by some network administrators but they are taking a risk not only with the accuracy of the synchronization but also with security as malicious users can imitate the NTP time signal and penetrate the firewall.

As dedicated NTP servers are external to the firewall, relying instead on the GPS satellite signal or specialist radio transmissions they are far more secure.

Differences in Time

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We are all aware of the differences in time zones. Anybody that has travelled across the Atlantic or Pacific will feel the effects of jet lag caused by having to adjust our own internal body clocks. In some countries, such as the USA, several different time zones exist in the one country meaning there are several hours difference in time from the East Coast to the West.

This difference in time zones can cause confusion although for residents of countries that straddle more than one time zone they soon adapt to the situation. However, there are more timescales and differences in time than just time zones.

Different time standards have been developed for decades to cope with time zone differences and to allow for a single time standard that the whole world can synchronize too. Unfortunately since the first time standards were developed such as British Railway Time and Greenwich Mean Time, other standards have had to be developed to cope with different applications.

One of the problem of developing a time standard is choosing what to base it on. Traditionally, all systems of time have been developed on the rotation of the Earth (24 hours). However, following the development of atomic clocks, it was soon discovered that no two days are exactly the same length and quite often they can fall short of the expected 24 hours.

New time standards where then developed based on Atomic clocks as they proved to be far more reliable and accurate than using the Earth’s rotation as a starting point. Here is a list of some of the most common time standards in use. They are divided into two types, those that are based on Earth’s rotation and those that are based on atomic clocks:

Time standards based on Earth’s rotation
True solar time is based on the solar day – is the period between one solar noon and the next.

Sidereal time is based on the stars. A sidereal day is the time it takes Earth to make one revolution with respect to the stars (not the sun).

Greenwich Mean Time (GMT) based upon when the sun is highest (noon) above the prime meridian (often called the Greenwich meridian). GMT used to be an international time standard before the advent of precise atomic clocks.

Time standards based on atomic clocks

International Atomic Time (TAI) is the international time standard from which the time standards below, including UTC, are calculated. TAI is based on a constellation of atomic clocks from all over the world.

GPS Time Also based on TAI, GPS time is the time told by atomic clocks aboard GPS satellites. Originally the same as UTC, GPS time is currently 17 seconds (precisely) behind as 17 leap seconds have been added to UTC since the satellites were launched.
Coordinated Universal Time (UTC) is based on both atomic time and GMT. Additional Leap seconds are added to UTC to counter the imprecision of Earth’s rotation but the time is derived from TAI making it as accurate.

UTC is the true commercial timescale. Computer systems all over the world synchronize to UTC using NTP time servers. These dedicated devices receive the time from an atomic clock (either by GPS or specialist radio transmissions from organisations like NIST or NPL).

Time Synchronization Using the GPS Network

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The GPS (Global Positioning System) systems has revolutionized navigation for pilots, mariners and drivers a like. Nearly every brand new car is sold with an inbuilt satellite navigation system already installed and similar detachable devices continue to sell in their millions.

Yet the GPS system is a multi purpose tool thanks mainly to the technology it employs to provide navigational information. Each GPS satellite contains an atomic clock which signal is used to triangulate positioning information.

GPS has been around since the late 1970’s but it was only in 1983 that is stopped from being purely a tool of the military and was opened up to allow free commercial access following an accidental shooting down of a passenger airliner.

To utilise the GPS system as a timing reference, a GPS clock or GPS time server is required. These devices usually rely on the time protocol NTP (Network Time Protocol) to distribute the GPS time signal that arrives via the GPS antenna.

GPS time is not the same as UTC (Coordinated Universal Time) which is normally used  NTP for time synchronization via radio transmissions or the internet. GPS time did originally match UTC in 1980 during its inception but sine that time there have been leap seconds added to UTC to counteract the variations of the earth’s rotation, however the on-board satellite clocks are corrected to compensate for the difference between GPS time and UTC, which is 17seconds, as of 2009.

By utilising a GPS time server an entire computer network can be synchronized to within a few milliseconds of UTC ensuring that all computers are safe, secure and able to deal effectively with time sensitive transactions.