[ntp:questions] Asymmetric lines

John Pettitt jpp at cloudview.com
Fri Feb 4 20:06:25 UTC 2005


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



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