Time service (NTP)
The time service ensures synchronized time on distributed computer systems. Various other services require a synchronized time.
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Time Service (NTP)
The Network Time Protocol (NTP) is used to synchronize the time of a computer with other computers or with an external clock via the internet. The primary NTP server should be synchronized as precisely as possible via external timers to the Coordinated Universal Time (UTC). Other servers synchronize depending on their configuration directly or indirectly, via intermediate servers, with the primary server. So the servers form a hierarchy, the hierarchy level is called stratum: Primary servers are stratum 1 servers, and server that synchronize directly with the primary servers are stratum 2 servers. Clients synchronize their time on different operating systems via different programs, which use the network time protocol (RFC 1305) or the simple network Time Protocol (RFC 1769) as protocol to communicate with the servers.
Configuration of the NTP Clients
Within the KITnet the following time servers should be used for time synchronization:
To get the most accurate time possible and a good redundancy it is necessary to enter always all four hosts.
In case only one server can be specified in the NTP client configuration, the name ntp.scc.kit.edu should be used, which alternately refers to one of the aforementioned servers for reasons of load distribution. If only IP addresses and no host names can be entered, the IP addresses of the host names mentioned above should be used.
Development of the NTP infrastructure at KIT
The NTP infrastructure at SCC is distributed across two locations on CN and CS. This guarantees high availability, if clients use all four time servers. Time servers from Meinberg are used. The time sources used are DCF77 at one site and GNSS (Galileo, GPS, GLONASS, Baidu) at the other three sites. In case of failures, the SCC NTP servers fall back to the following external stratum 1 sources:
- Physikalisch-Technische Bundesanstalt
- BelWü (DCF77, GNSS)
- University of Stuttgart (DCF77)
- FAU Erlangen (DCF77, GNSS)
- TU Berlin (GNSS)
- FU Berlin (GNSS)
More information about NTP can be found at www.ntp.org