Jan Hoevers <[EMAIL PROTECTED]> writes: > That's correct, it is a network issue. The monitoring system is in > California, for us here in europe there's an ocean and a continent in > between. > > I did some simple tests on this a few months ago; my conclusion was that > the monitoring system can be used to see if my server is reachable, > nothing more. The inaccuracies introduced by the network are in the > order of ten to fifty ms, with peaks far over 100 ms, while a carefully > run stratum 2 server doesn't have to be more than a millisecond off.
Yet it somehow never has any trouble with my server: http://www.pool.ntp.org/scores/194.63.250.121 Note that the offset is mostly within 2 ms, with occasional peaks approaching 10 ms. Assuming the measuring server correctly estimates and compensates for network latency (using the very simple algorithm described in the NTP and SNTP RFCs), it should not affect the offset it sees unless there is considerable asymmetry between the outbound and inbound leg. << To calculate the roundtrip delay d and system clock offset t relative to the server, the client sets the Transmit Timestamp field in the request to the time of day according to the client clock in NTP timestamp format. For this purpose, the clock need not be synchronized. The server copies this field to the Originate Timestamp in the reply and sets the Receive Timestamp and Transmit Timestamp fields to the time of day according to the server clock in NTP timestamp format. When the server reply is received, the client determines a Destination Timestamp variable as the time of arrival according to its clock in NTP timestamp format. The following table summarizes the four timestamps. Timestamp Name ID When Generated ------------------------------------------------------------ Originate Timestamp T1 time request sent by client Receive Timestamp T2 time request received by server Transmit Timestamp T3 time reply sent by server Destination Timestamp T4 time reply received by client The roundtrip delay d and system clock offset t are defined as: d = (T4 - T1) - (T3 - T2) t = ((T2 - T1) + (T3 - T4)) / 2. >> DES -- Dag-Erling Smørgrav - [EMAIL PROTECTED] _______________________________________________ timekeepers mailing list [email protected] https://fortytwo.ch/mailman/cgi-bin/listinfo/timekeepers
