Computer system clocks are a valuable aid to anyone who needs to know what time it is and does not have a wristwatch or smartphone handy. However, very few people know that the time set by the system is not only relevant for the user, but also for the computers themselves, indeed, if the time goes wrong, it would happen that you cannot access your browser and that is how essential it is the NTP protocol.
This time protocol or NTP is the result of development work by David L. Mills, professor at the University of Delaware in the United States. The first official specification of the protocol, which is part of the Internet protocol family, was published in September 1985 in RFC 985. NTP is described in this document as a protocol for synchronizing multiple network clocks using a set of clients. and distributed servers. As predecessors, mention is made of the ICMP Timestamp message and the Time Protocol, since their functions were included in the Network Time Protocol.
The way NTP works basically differs from most other protocols. NTP does not synchronize all connected clocks, it establishes a hierarchy of time servers and clients. Each level of this hierarchy is called stratum, and Stratum 1 constitutes the highest level which synchronizes the servers with a reference time source, such as a radio controlled clock, GPS receiver or modem. The Stratum 1 servers distribute the time to different clients on the network, which are called Stratum 2.
This gives a possible high precision synchronization thanks to the different time references. Each computer is synchronized with up to three reliable time sources. NTP allows comparison of machine hours and clock setting. A precision of 128 ms can be achieved, often greater than 50 ms.
This protocol remained for a long time as the most widespread solution when implementing NTP in Linux distributions. The latest versions are increasingly turning to the timesyncd client application, which is part of the systemd management system, for clock synchronization. Also macOS and Windows operating systems currently use the Network time protocol to obtain UTC through simple system processes that work via the Internet and do not require additional software.
Something that should be emphasized is that as in everything nothing is 100% protected and is that it is based on the UDP connectionless protocol, which could allow an attacker to send packets to an NTP server with a false sender address through IP spoofing and by that should take some security measures as in everything.
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