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Zeitsynchronisation über das Internet

• NTP entwickelt 1981 von David L. Mills an der University of Delaware (http://www.ntp.org)
• SNTP: Simple Network Time Protocol ist eine vereinfachte Teilmenge von NTP

NTP Network Time Protocol

NTP has the ability to synchronize computers across multiple time servers while compensating for network jitter and other statistical errors. Because of this ability, it is generally suitable for the synchronization of a corporate time server to an atomic clock on the global internet to within tens of milliseconds. This protocol is defined in the Internet standard RFC 1305. (Port 123)

SNTP Simple Network Time Protocol

SNTP is a subset of the Network Time Protocol. SNTP is able to compensate for network round trip delay and take account of nominal dispersion to the root time source, but normally depends on a single time server at any given time. Because of this, it is generally suitable for synchronization of clients to a known time source on a corporate intranet.

Accurate synchronization between client and server to the order of microseconds is attainable on local area networks using SNTP. The SNTPv4 protocol is defined in the internet standard RFC 2030. (obsoletes SNTPv3 RFC 1769)

Zeitquelle NTP Time Server im Internet

• Uni Osnabrück (DCF77)
  • ntps1-1.rz.uni-osnabrueck.de
• TU Berlin
  • ntps1-0.cs.tu-berlin.de
  • ntps1-1.cs.tu-berlin.de
• Physikalisch Technische Bundesanstalt, Braunschweig (PTB)
  • ntp1.ptb.de
  • ntp2.ptb.de
• Deutsche Telekom
  • ntp1.sda.t-online.de
• Uni Erlangen
  • ntps1-1.uni-erlangen.de

Welche Software benötigen wir?

• Auf dem Server
• Auf den Clients: Tardis95 oder http://sourceforge.net/projects/nettime/

Stratum 1 und Stratum 2

Stratum 1: primary reference (NTP sites using an atomic clock for timing) Stratum 2-15: secondary reference (Stratum 2: NTP sites with slightly less accurate time sources) Public Servers: Sites that allow the general public to synchronize with them.

Welche Software benötigen wir?

• Auf dem Server
• Auf den Clients: Tardis95

Time-Service als Bestandteil des Betriebssystems

See: Windows Services Die Betriebssysteme Windows2000 und WindowsXP enthalten einen Time-Service, genannt w32time. Dieser kann so konfiguriert werden, dass direkt gegen einen public NTP-Server im Internet synchronisiert wird.

• net stop w32time
• net start w32time
• net time /setsntp:servername
• net time /querysntp
• w32tm -once (Test der Verbindung)

Windows2000 polls every 8 hours ("SpecialSkew"), WindowsXP once a week..... (Knowledgebase Q223184)

• HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\W32Time\Parameters

Namen von Windows-Services herausfinden: sc query

-- Main.DietrichKracht - 06 Jun 2004