[ntp:questions] Fudge time offset on client/peer?

Danny Mayer mayer at ntp.org
Sun Nov 8 01:08:24 UTC 2009


Good, as the resolver issue is in my plans but I'm not clear how this
relates to the fudging. The parse tree is there but why is that an
issue? Oh, because you need the address before you can create the
association. Once 4.2.6 is out we can start to move forward on the
resolver issue.


David Mills wrote:
> Danny,
> Sure you can in a couple of lines of code. However, where are you going
> to put the result? The proto_config() call has a fixed number of fields
> all tied up with data structures used for name resolution and for remote
> configuration. The original plan, now only part way completed, was to
> save everything in the parse ttree while the resolver is out to lunch,
> then pick up where it left off when lunch is over. That would completely
> resolve (no pun) the issue and allow an indefinate expansion in
> configuration options.
> Dave
> Danny Mayer wrote:
>> Dave,
>> Can we not just introduce an option on the server line for this? That
>> would effectively give you the association. The caviat here is how do
>> you know what to put in the argument?
>> Danny
>> David Mills wrote:
>>> Rich,
>>> I have the same situation you have, but a dedicated ISDN line and
>>> routers that have a mostly symmetric delays. A per-association fudge
>>> is not possilbe unless the peer mobilization code is overhauled.
>>> There is in fact a calibration mechanism designed to compensate for
>>> small inconsistencies using the PPS signal as the ultimate reference.
>>> That is controlled by the enable/disable calibrate command and
>>> applies to all associations. A command might be introduced that could
>>> affect a specified association, but it would have to be given via
>>> ntpq after mobilization.
>>> Dave
>>> Rich Wales wrote:
>>>>> I suggest you don't want that.  What you need is a fudge on the
>>>>> interface, not the association.
>>>> In this situation, I think I really do want a fudge on the association.
>>>> Consider the issue from the POV of my work desktop.  My work desktop
>>>> has a single network interface, connected to a conventional 100BASE-TX
>>>> ethernet network.  It has fast (and, for my purposes, sufficiently
>>>> symmetric) connectivity over my school's campus network to stratum-1
>>>> and stratum-2 servers run by the campus IT services.
>>>> In order for my work desktop to see the stratum-1 server I'm running at
>>>> my home, however, it has to go over the campus network to the
>>>> cable-modem
>>>> network servicing the townhouse complex where I live.  As I previously
>>>> mentioned, this cable modem network appears to have an asymmetry, which
>>>> I would like to fudge away for the benefit of my work desktop (but
>>>> *not*
>>>> for my home LAN).
>>>> If I were to fudge the network interface of my work desktop, this would
>>>> presumably affect not only its view of my home stratum-1 server, but
>>>> also
>>>> my work desktop's view of the campus tickers.
>>>> What I think I want/need is a way to fudge my work desktop's view of
>>>> one
>>>> peer/server, but not another peer/server.  That's why I wanted to be
>>>> able to fudge an association.
>>>> Rich Wales  /  richw at richw.org
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