[ntp:questions] Re: role of the root delay and dispersion in NTP header

David L. Mills mills at udel.edu
Thu Sep 4 02:46:23 UTC 2003


Drk,

Your mission, should you choose to accept it, is in the architecture
briefing at the NTP project page linked from www.ntp.org. The briefing
(and others on that page) includes a error budget/explanation including
root quantities, precision, distance, dispersion and everything else a
lad could need. Note how the root quantities accumulate by stratum and
consider the formal correctness of the maximum error and expected error
statistics.

Dave

Drk Ryan wrote:
> 
> In the NTP header (NTP Data Format)..what exactly is the role of the
> ROOT delay and dispersion and how are they recalculated for each host
> i.e. offset/rtt and dispersion as detected by NTP has 2 components,
> host to peer and host to root via peer. The offset values as returned
> by the ntpq query is I presume offset from host to peer...you then
> need to look at peer to root (from NTP header) to determine what the
> offset for host to root i.e. UTC should be which is the ultimate
> correction of interest...is this right??
> 
> Also, how is the precision field of the NTP header determined?



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