[ntp:questions] NTPd is not sync for some poll interval values

Gaurav Narain Mathur narainmg at hotmail.com
Wed Feb 18 18:13:16 UTC 2009




> From: unruh-spam at physics.ubc.ca
> To: questions at lists.ntp.org
> Date: Fri, 6 Feb 2009 14:18:09 +0000
> Subject: Re: [ntp:questions] NTPd is not sync for some poll interval values
> 
> narainmg at hotmail.com (Gaurav Narain Mathur) writes:
> 
> >I have a problem where the NTPd would not sync the time with the
> >timeserver (10.0.0.1) if minpoll value is 7 and maxpoll is 8. It works
> >if the  minpoll is 4 maxpoll is 5. Can anybody please help me out in
> >identifying what the problem could be? The "flash" never becomes
> >"0" I think. Also another host on the same subnet sync with the same
> >poll values and with the same server (10.0.0.1).
> 
> Your offset its too large. Use ntpd -g to have it get rid of the large
> offset initially.
> 
> 

Thanks,. I'll try that. What puzzled me most was that a machine on the  
same subnet, syncing with the same time server and with the same initial
time as the one I am working with syncs ok. The machine I am interested
in does not. 

Digging in a little deeper, I have found that this might have something
to do with the routine precision values calculated on the two machines.
In the one where the minpoll and maxpoll of 7 and 8 work, the precision
is almost always calculated between 1-5 usec. The one I am working with
calculates the precision between 70-80 usec. I think this skews the 
peer_unfit calculation to always be above the threshold value and the 
peer is never deemed fit in my machine. 


> 
> >Any help is much appreciated. Debug output is attached below.
> 
> >Thanks.
> 
> >[...]
> 
> >~ $ ntpq -c "pe"
> >     remote           refid      st t when poll reach   delay   offset
> >jitter
> >=============================================================================
> >=
> > 10.0.0.1        64.247.17.254    3 u  117  128  377    1.125  -6423.0
> >1427.38
> >~ $ ntpq -c "pe"
> >     remote           refid      st t when poll reach   delay   offset
> >jitter
> >=============================================================================
> >=
> > 10.0.0.1        64.247.17.254    3 u   14  128  377    1.160  -8010.8
> >1420.48
> >~ $
> >~ $
> >~ $
> >~ $ ntpq -c "as"
> 
> >ind assID status  conf reach auth condition  last_event cnt
> >===========================================================
> >  1 63473  9014   yes   yes  none    reject   reachable  1
> >~ $
> >~ $
> >~ $ ntpq -c "rv"
> >assID=0 status=c011 sync_alarm, sync_unspec, 1 event, event_restart,
> >version="ntpd 4.2.4p4 at 1.1520-o Wed Feb  4 21:58:44 UTC 2009 (1)",
> >processor="mips", system="Linux/2.6.26.6", leap=11, stratum=16,
> >precision=-13, rootdelay=0.000, rootdispersion=27.375, peer=0,
> >refid=INIT, reftime=00000000.00000000  Thu, Feb  7 2036  6:28:16.000,
> >poll=6, clock=cd34a655.87cf0951  Wed, Feb  4 2009 23:42:13.530, state=0,
> >offset=0.000, frequency=0.000, jitter=0.122, noise=0.122,
> >stability=0.000, tai=0
> >~ $
> >~ $
> >~ $ ntpq -c "rv 63473"
> >assID=63473 status=9014 reach, conf, 1 event, event_reach,
> >srcadr=10.0.0.1, srcport=123, dstadr=10.0.0.9, dstport=123, leap=00,
> >stratum=3, precision=-20, rootdelay=93.857, rootdispersion=86.807,
> >refid=64.247.17.254, reach=377, unreach=0, hmode=3, pmode=4, hpoll=7,
> >ppoll=7, flash=400 peer_dist, keyid=0, ttl=0, offset=-8010.843,
> >delay=1.160, dispersion=1.989, jitter=1420.485,
> >reftime=cd34a51d.a5c4c862  Wed, Feb  4 2009 23:37:01.647,
> >org=cd34a636.e772df74  Wed, Feb  4 2009 23:41:42.904,
> >rec=cd34a63e.ea5f7fc8  Wed, Feb  4 2009 23:41:50.915,
> >xmt=cd34a63e.ea105e5d  Wed, Feb  4 2009 23:41:50.914,
> >filtdelay=     1.16    6.87    5.52    1.29    1.03    1.12    5.75    1.10,
> >filtoffset= -8010.8 -7691.1 -7368.6 -7053.1 -6738.2 -6423.0 -6110.4 -5788.1,
> >filtdisp=      0.12    2.07    3.99    5.91    7.82    9.72   11.63   13.56
> >~ $
> >~ $
> 
> >[...]
> 
> 
> >[...]
> 
> >~ $ cat /etc/ntp.conf
> 
> >###########################################################################
> >#
> ># Permit time synchronization with our time source, but do not
> ># permit the source to query or modify the service on this system.
> >restrict default kod nomodify notrap noquery
> 
> ># Permit all access over the loopback interface.  This could
> ># be tightened as well, but to do so would effect some of
> ># the administrative functions.
> >restrict 127.0.0.1
> 
> ># Hosts on local network are less restricted.
> >#restrict 192.168.1.0 mask 255.255.255.0 nomodify notrap
> 
> ># Undisciplined Local Clock. This is a fake driver intended for backup
> ># and when no outside source of synchronized time is available.
> >fudge   127.127.1.0 stratum 10
> 
> ># Drift file.  Put this in a directory which the daemon can write to.
> ># No symbolic links allowed, either, since the daemon updates the file
> ># by creating a temporary in the same directory and then rename()'ing
> ># it to the file.
> >driftfile /tmp/etc/ntp/drift
> 
> ># This command specifies the default directory path for cryptographic keys,
> ># parameters and certificates. The default is /usr/local/etc/.
> >keysdir /tmp/etc/ntp/
> 
> ># Key file containing the keys and key identifiers used when operating
> ># with symmetric key cryptography.
> >keys /tmp/etc/ntp/keys
> 
> ># Specify the key identifier to use with the ntpdc utility.
> >#requestkey 8
> 
> ># Specify the key identifier to use with the ntpq utility.
> >#controlkey 8
> 
> >###########################################################################
> ># Specify the key identifiers which are trusted.
> ># trustedkey 4 8 42
> >###########################################################################
> >#trustedkey
> 
> 
> >###########################################################################
> ># Add time servers here
> ># broadcast 192.168.1.255 key 42                # broadcast server
> ># broadcastclient                       # broadcast client
> ># broadcast 224.0.1.1 key 42            # multicast server
> ># multicastclient 224.0.1.1             # multicast client
> ># manycastserver 239.255.254.254                # manycast server
> ># manycastclient 239.255.254.254 key 42 # manycast client
> >###########################################################################
> >server 10.0.0.1 minpoll 7 maxpoll 8
> 
> >[...]
> >_________________________________________________________________
> >Windows Live™: Keep your life in sync.
> >http://windowslive.com/howitworks?ocid=TXT_TAGLM_WL_t1_allup_howitworks_02200
> >9
> 

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