A spate of Network Time Protocol DDoS attacks have hit the headlines recently with the BBC and PC World all reporting an increase in such incidents. Has your business suffered? Then read on…
Network time server manufacturers and suppliers, Galleon Systems, understand Network Time Protocol and provide numerous technologies capable of combatting the recent outbreak of Network Time Protocol DDoS attacks. Recently, the BBC made reference to online security specialists Cloudfare, which reported the ‘biggest’ attack of its kind and warned that a key vulnerability of internet infrastructure had been exploited. … Continue reading
To keep precise time, computer networks have to find a source of accurate, precise and secure time, which enables all devices to be synchronised together. One of the most common used devices for achieving this are radio time synchronisation receivers.
Users of the National Physical Laboratory’s (NPL) MSF time and frequency signal are probably aware that the signal is occasionally taken off-air for scheduled maintenance.
NPL have published there scheduled maintenance for 2010 where the signal will be temporarily taken off-air. Usually the scheduled downtimes lasts for less than four hours but users need to be aware that while NPL and VT Communications, who service the antenna, make every effort to ensure the transmitter is off for a brief amount of time as possible, there can be delays.
And while NPL like to ensure all users of the MSF signal have advanced warning of possible outages, emergency repairs and other issues may lead to unscheduled outages. Any user receiving problems receiving the MSF signal should check the NPL website in case of unscheduled maintenance before contacting your time server vendor.
The dates and times of the scheduled maintenance periods for 2010 are as follows:
* 11 March 2010 from 10:00 UTC to 14:00 UTC
* 10 June 2010 from 10:00 BST to 14:00 BST (UTC + 1 hr)
* 9 September 2010 from 10:00 BST to 14:00 BST (UTC + 1 hr)
* 9 December 2010 from 10:00 UTC to 14:00 UTC
As these scheduled outages should take no longer than four hours, users of MSF referenced time servers should not notice any drop off in accuracy of their network as their shouldn’t be enough time for any device to drift.
GPS time servers receive the time from the orbiting navigational satellites. As these are available anywhere on the globe and the signals are never down for outages they can provide a constant accurate time signal (GPS time is not the same as UTC but is easily converted by NTP as it is exactly 17 seconds behind due to leap seconds being added to UTC and not GPS).
The DCF 77 signal is a long wave transmission broadcast at 77 KHz from Frankfurt in Germany. DCF -77 is transmitted by Physikalisch-Technische Bundesanstalt, the German national physics laboratory.
DCF-77 is an accurate source of UTC time and is generated by atomic clocks that ensure its precision. DCF-77 is a useful source of time that can be adopted all over Europe by technologies needing an accurate time reference.
Radio controlled clocks and network time servers receive the time signal and in the case of time servers distribute this time signal across a computer network. Most computer network use NTP to distribute the DCF 77 time signal.
There are advantages of using a signal like DCF for time synchronisation. DCF is long wave and is therefore susceptible to interference from other electrical devices but they can penetrate buildings that give the DCF signal an advantage over that other source of UTC time generally available – GPS (Global Positioning System) – which requires a open view of the sky to receive satellite transmissions.
Other long wave radio signals are available in other countries that are similar to DCF-77. In the UK the MSF -60 signal is broadcast by NPL (National Physical Laboratory) from Cumbria while in the USA, NIST (National Institute of Standards and Time) transmit the WVBB signal from Boulder, Colorado.
NTP time servers are an efficient method of receiving these long wave transmissions and then using the time code as a synchronisation source. NTP servers can receive DCF, MSF and WVBB as well as many of them also being able to receive the GPS signal too.
Accurate time using Atomic Clocks is available across Great Britain and parts of northern Europe using the MSF Atomic Clock time signal transmitted from Cumbria, UK; it provides the ability to synchronize the time on computers and other electrical equipment.
The UK MSF signal is operated by NPL – the National Physical Laboratory. MSF has high transmitter power (50,000 watts), a very efficient antenna and an extremely low frequency (60,000 Hz). For comparison, a typical AM radio station broadcasts at a frequency of 1,000,000 Hz. The combination of high power and low frequency gives the radio waves from MSF a lot of bounce, and this single station can therefore cover most of Britain and some of continental Europe.
The time codes are sent from MSF using one of the simplest systems possible, and at a very low data rate of one bit per second. The 60,000 Hz signal is always transmitted, but every second it is significantly reduced in power for a period of 0.2, 0.5 or 0.8 seconds: • 0.2 seconds of reduced power means a binary zero • 0.5 seconds of reduced power is a binary one. • 0.8 seconds of reduced power is a separator. The time code is sent in BCD (Binary Coded Decimal) and indicates minutes, hours, day of the year and year, along with information about daylight savings time and leap years.
The time is transmitted using 53 bits and 7 separators, and therefore takes 60 seconds to transmit. A clock or watch can contain an extremely small and relatively simple antenna and receiver to decode the information in the signal and set the clock’s time accurately. All that you have to do is set the time zone, and the atomic clock will display the correct time.
Dedicated time servers that are tuned to receive the MSF time signal are available. These devices connect o a computer network like any other server only these receive the timing signal and distribute it to other machines on the network using NTP (Network Time Protocol).