Posted by Richard N Williams on September 22nd, 2010
Ask anybody what the key to network timing is and you will probably get the response NTP (Network Time Protocol). NTP is a protocol that distributes and checks the time on all network devices to a reference clock – and it is this reference which is the true key to network time synchronisation.
Whilst a version of NTP is easy to obtain – it is normally installed on most operating systems, or is otherwise free to download – but getting a source of time is where the true key to network time synchronisation lies.
Atomic clocks govern the global timescale UTC (Coordinated Universal Time) and it is this timescale that is best for network timing as synchronising all devices on a network to UTC is equivalent of having you network synchronised with every other UTC synced network on Earth.
So getting a source of UTC time is the true key to accurate network time synchronisation, so what are the options?
Internet Time Sources
The obvious choice for most NTP users, but internet time suffers from two major flaws; firstly, internet time operates through the firewall and is therefore fraught with security risks – if the time can get through your firewall, then other things can too. Secondly, internet time sources can be hit and miss with their accuracy.
Due to the fact most internet time sources are stratum 2 devices (they connect to another device that receives the UTC source time) and the distance from client to host can never be truly ascertained or accounted for – it can make them inaccurate – with some internet time sources minutes, hours and even days away from true UTC time.
Radio Referenced Time Server
Another source of UTC time which doesn’t suffer from either security or accuracy flaws is receiving the time from long wave radio signals that some country’s national physics laboratories broadcast. While these signals are available throughout the USA (courtesy of NIST) the UK (NPL) and several other European countries and can be picked up witha basic radio referenced NTP server they are not available everywhere and the signals can be difficult to receive in some urban locations or anywhere where there is electrical interference.
For completely accurate, secure and a reliable source of UTC time there is no substitute for GPS time. GPS timing signals are beamed directly from atomic clocks onboard the GPS satellites (Global Positioning System) and received by GPS NTP time servers. These can then distribute the atomic clock time around the network.
GPS timing sources are accurate, secure and available literally anywhere on the planet 24 hours a day.