[ntp:questions] Re: Asymmetric Network and Delay Questions.

Helmut Wollmersdorfer helmut at wollmersdorfer.at
Thu Jul 14 14:43:10 UTC 2005


Brad Knowles wrote:

>     Clock drift is a serious problem in most applications that are time 
> sensitive, but military and aerospace applications are the ones I know 
> of that are most sensitive to even the smallest errors.

One solution is, to avoid time dependency by design as far as possible.

In commercial applications it is a common mistake by developers, to 
query the system clock instead of a 'logical date'. For testers 'time 
travelling testing' is a nice and cheap way to find 'show stoppers'.

BTW I am writing this just one hour after patching a bug in script, 
which calculated the date of yesterday via a complex formula using 
Julian Date. This hit an overrun on 2005-07-08 but works on other dates. 
Time travelling testing would allow dedection of such a bug earlier.

A lot of application could be redesigned not to depend on accurate real 
time. E.g. sychronization between systems can use generation counters 
instead of time stamps.

Helmut Wollmersdorfer




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