[gull] Contrôle de ntp

[Daniel Cordey]

On Monday 05 June 2006 15:28, Jacques-André Eberhard wrote:
> Bonjour,
>
> Nous avons un Windows 2000 server SP4, puis un VmWare server et une SLES9
> avec le .rpm de ntp installé.

Bon, j'ai relu un bout du manuel de ntpd. Il y a pas mal d'explication et le 
mieux serait de lire ce manuel en detail. Je n'en mets qu'un petit bout dasns 
ce mail. 

Ma conclusion est :

executer ntpdate avant de demarer xntp, puis s'assurer que l'interval 
mentionne ci-dessous reste a 64 secondes.

dc

POLL INTERVAL CONTROL
 This version of NTP includes an intricate state machine to reduce the network 
load while maintaining a quality of synchronization consistent with the 
observed jitter and wander. There are a number of ways to tailor the 
operation in order enhance accuracy by reducing the interval or to reduce 
network overhead by increasing it. However, the user is advised to carefully 
consider the consequenses of changing the poll adjustment range from the 
default minimum of 64 s to the default maximum of 1,024 s. The default 
minimum can be changed with the tinker minpoll command to a value not less 
than 16 s. This value is used for all configured associations, unless 
overriden by the minpoll option on the configuration command. Note that most 
device drivers will not operate properly if the poll interval is less than 64 
s and that the broadcast server and manycast client associations will also 
use the default, unless overriden. 
 In some cases involving dial up or toll services, it may be useful to 
increase the minimum interval to a few tens of minutes and maximum interval 
to a day or so. Under normal operation conditions, once the clock discipline 
loop has stabilized the interval will be increased in steps from the minumum 
to the maximum. However, this assumes the intrinsic clock frequency error is 
small enough for the discipline loop correct it. The capture range of the 
loop is 500 PPM at an interval of 64s decreasing by a factor of two for each 
doubling of interval. At a minimum of 1,024 s, for example, the capture range 
is only 31 PPM. If the intrinsic error is greater than this, the drift file 
ntp.drift will have to be specially tailored to reduce the residual error 
below this limit. Once this is done, the drift file is automatically updated 
once per hour and is available to initialize the frequency on subsequent 
daemon restarts.