[ntp:questions] Compensating for asymmetric delay on a per-peer/server basis?

Charles Elliott elliott.ch at comcast.net
Wed Sep 10 12:36:20 UTC 2014


You can do it in broadcast mode, but I am not sure it works,
or has even been tried on a WAN.  Broadcast mode was solid
as a rock on my LAN for more than a year, especially after 
I started using GB Ethernet.

I don't use broadcast mode now after switching to using FreeNAS
as a time server, it addition to its other duties.  

Charles Elliott

> -----Original Message-----
> From: questions-bounces+elliott.ch=comcast.net at lists.ntp.org
> [mailto:questions-bounces+elliott.ch=comcast.net at lists.ntp.org] On
> Behalf Of Rob
> Sent: Wednesday, September 10, 2014 3:34 AM
> To: questions at lists.ntp.org
> Subject: Re: [ntp:questions] Compensating for asymmetric delay on a
> per-peer/server basis?
> 
> Rich Wales <richw at richw.org> wrote:
> > Replying to "Rob":
> >
> >> Yes, you can use:  fudge 1.2.3.4 time1 -0.002  or similar.
> >> see the manual.
> >
> > This didn't work.  And the following error message appeared in my
> syslog:
> >
> >     inappropriate address 10.0.229.163 for the fudge command,
> >     line ignored
> >
> > As best I can tell from the online manual, the "fudge" command is
> > defined only for local reference clocks and has no effect on peers or
> > servers.
> 
> Ok you are right.  In fact I filed bug #2598 myself for a similar
> situation...   In my case I wanted to compensate for the delay
> asymmetry
> for external users using my GPS reference via my ADSL line.  So I would
> like to apply such a fudge command to a network interface, not to a
> peer server.
> 
> I forgot that it is not even possible to apply it to a server, what you
> would like to do.  I think the only thing you can do is apply an offset
> to your GPS and live with the fact that you are always 2ms off.  At
> least then you don't have a time wander when you switch to your backup
> and the external users of your system get the correct time.  That is
> what I did as a workaround until someone fixes this in ntpd.
> 
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