Articles and resources
Articles and resources
In many applications, including time synchronisation, GNSS is now commonplace. The best known constellation is GPS. However, all these GNSS systems share a common vulnerability: the signals transmitted by these satellites are very weak. GNSS satellites operate from the Earth’s orbit. The transmitted signal is extremely weak when it reaches the earth’s surface. This low signal strength at the receivers makes GNSS use susceptible to intentional (malicious) or unintentional interference.
With the rise of the Internet and IT networks, many solutions today work over IP. Whether video surveillance, access control, or attendance time management, all this equipment uses IP technologies to communicate and operate. As with any network, time synchronisation is essential, not only to ensure the proper functioning of monitoring systems, but also to ensure accurate and chronological timestamping of events.
To work, your network infrastructure needs a single accurate time reference. All IT equipment has an embedded hardware or software clock which is used by the equipment to timestamp files, transactions, events, images, etc. This internal clock drifts like any ordinary watch. It becomes an issue when these devices are connected to a network and share common resources such as file systems.
Using an Internet service to retrieve and distribute the time is a common practice in many businesses. It doesn’t require any special equipment – just an Internet connection. Up to now, this practice has seemed simple and safe in principle. And yet...
The integrity of any file system depends on the names and dates of the files, including information on the date of creation, last access, last archive and last modification. In a distributed file sharing system, a master file is kept by an NFS (Network File System) server, for use by remote clients.
