[ntp:questions] A question about the NTP delay time formula

David Mills mills at udel.edu
Tue Jun 23 19:55:11 UTC 2009


Lei,

It's a bug. There are at least  40,000 angry timekeepers calling for my 
arrest.

You shouldn't be using 2030 anyway; it has been obsoleted by 4330 and 
that in turn by the NTPv4 specification when published.

Dave

.Lei wrote:

>In RFC 2030(written by Prof. D.Mills), we have roundtrip delay time
>formula as follows:
>
> d = (T4 - T1) - (T2 - T3) .................(1)
>
>However, IMHO, it should be
>
> d = (T4-T1) - (T3 - T2)....................(1)'
>
>using which we can get
>
>t = ((T2 - T1) + (T3 - T4)) / 2 ...........(2)
>
>successfully by inserting d into the following formula
>
>t = T3 + d/2 - T4. ...........................(3)
>
>But if we use d as in formula (1), we can not get (2).
>
>Anyone has an idea? :)
>
>Thanks.
>-Lei
>
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