[ntp:questions] Re: Asymmetric lines
Richard B. Gilbert
rgilbert88 at comcast.net
Sat Feb 5 02:07:40 UTC 2005
John Pettitt wrote:
>
> Hi all
> I just put up a stratum 1 server (FreeBSD using the GPS18 with PPS)
> on the end of a very asymmetric line (6000 kbps down 608 kbps up).
> When I look on the local machine (gatekeeper.no-such-agency.net) I see
> this:
>
> ntpq> pe
> remote refid st t when poll reach delay offset
> jitter
> ==============================================================================
>
> *GPS_NMEA(0) .GPS. 0 l 8 16 377 0.000
> 0.003 0.002
> LOCAL(0) 73.78.73.84 5 l 1 64 377 0.000
> 0.000 0.002
> +[stratum1-a] .GPS. 1 u 29 64 377 21.147
> 2.068 9.112
> +[stratum2-b] .CDMA. 1 u 51 64 377 17.442
> 2.019 6.896
> +time.sr.sonic.n 63.192.96.10 2 u 37 64 377 10.896
> 0.891 0.579
>
>
> note: names of the stratum 1 servers edited
>
> However when I look from one of my other boxes
> (eschelon.no-such-agency.net in a server farm connected by multiple
> OC12's) I see
>
> ntpq> pe
> remote refid st t when poll reach delay offset
> jitter
> ==============================================================================
>
> LOCAL(0) 73.78.73.84 5 l 57 64 377 0.000
> 0.000 0.002
> *gatekeeper.no-s .GPS. 1 u 777 1024 377 21.392
> -1.933 0.098 <- my S1 server
> +[stratum1-a] .GPS. 1 u 791 1024 377 7.456
> -1.524 0.421
> +[stratum1-b] .CDMA. 1 u 789 1024 377 3.446
> -1.171 0.216
>
>
> Again the names of the stratum 1's edited but they are the same
> servers as above.
>
> So I'm seeing a 2ms offset on the box itself and about 600ms from the
> outside world. I probably wouldn't care about this except that the
> offset seems to be stopping ntpd on my S1 from backing off it's poll
> intervals (it's been stuck at 64 for 12 hours).
>
> I seem to recall an asymmetric fudge patch being discussed but I can't
> find it. Does anybody have a copy? (or other suggestions for
> tweaking the setup)
>
> John
> P.S. both gatekeeper and eschelon are part of pool.ntp.org
I don't see the 600ms! Gatekeeper differs from its reference clock by
3 microseconds and from its upstream network servers by 1 -- 2
milliseconds. Eschelon is seeing a -1.9 millisecond offset from
gatekeeper and -1 to -1.5 millisecond offsets from its upstream networks
servers. What am I missing?
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