[ntp:questions] Re: Windows timekeeping - sudden degradation - why?

David J Taylor david-taylor at blueyonder.co.not-this-bit.nor-this-part.uk.invalid
Sun Dec 4 12:41:40 UTC 2005


Tom Smith wrote:
> The high jitter numbers may just be because of that system's
> own instability.
>
> Have you checked the current drift rate? That might have gotten
> disrupted, especially if there was network activity involved in your
> experiment. Try the ntpq command "rv 0" or "ntpdc -c loopinfo" and
> look for the frequency. It should have an absolute value of under 100. 
> If
> it's several hundred, you may need to re-initialize NTP by stopping
> it, deleting the drift file, and then restarting it. In any case,
> sample it periodically and see if it is oscillating.
>
> Any network related changes at that time, for example, on a switch?
> If it's fast ethernet, maybe you've renegotiated or otherwise
> acquired a mismatched speed/mode and you're now suffering packet
> losses. You might want to look at "netstat -e -s" and see if you have
> a significant number of errors or see if the "reach" output from
> "ntpq -p" looks different on this system than on others.
> -Tom


Tom,

Many thanks for your thoughtful suggestions.

It looks as if the drift is OK, at -64.911, but I will keep an eye on it. 
Here is the full output just in case there's something else glaringly 
obvious:

E:\>ntpq -c "rv 0" odin
status=46b4 leap_add_sec, sync_ntp, 11 events, event_peer/strat_chg,
version="ntpd 4.2.0 fr Oct 17 8:49:33 2003 (1)", processor="unknown",
system="WINDOWS/NT", leap=01, stratum=3, precision=-19,
rootdelay=62.583, rootdispersion=125.847, peer=62645, refid=192.168.0.1,
reftime=c73d5d1a.a4d239b4  Sun, Dec  4 2005 12:18:34.643, poll=7,
clock=c73d5f43.da3d1265  Sun, Dec  4 2005 12:27:47.852, state=4,
offset=18.583, frequency=-64.911, jitter=10.097, stability=0.028

There were no network changes I am aware of (it's just a small internal 
network, run by me....), and I don't recognise anything significant in the 
way of errors from the netstat command.  I do wonder about:

IPv4 Statistics, Received Address Errors = 2683

UDP Statistics for IPv4, No Ports = 6006

The system had been up for about 40 minutes.

Any comments?


E:\>netstat -e -s
Interface Statistics

                           Received            Sent

Bytes                     651081749        37472592
Unicast packets              484130          282526
Non-unicast packets            3741             999
Discards                          0               0
Errors                            0               0
Unknown protocols                 0

IPv4 Statistics

  Packets Received                   = 487302
  Received Header Errors             = 0
  Received Address Errors            = 2683
  Datagrams Forwarded                = 0
  Unknown Protocols Received         = 0
  Received Packets Discarded         = 14
  Received Packets Delivered         = 487288
  Output Requests                    = 283475
  Routing Discards                   = 0
  Discarded Output Packets           = 0
  Output Packet No Route             = 0
  Reassembly Required                = 0
  Reassembly Successful              = 0
  Reassembly Failures                = 0
  Datagrams Successfully Fragmented  = 0
  Datagrams Failing Fragmentation    = 0
  Fragments Created                  = 0

ICMPv4 Statistics

                            Received    Sent
  Messages                  12          9
  Errors                    0           0
  Destination Unreachable   0           1
  Time Exceeded             0           0
  Parameter Problems        0           0
  Source Quenches           0           0
  Redirects                 0           0
  Echos                     0           8
  Echo Replies              12          0
  Timestamps                0           0
  Timestamp Replies         0           0
  Address Masks             0           0
  Address Mask Replies      0           0

TCP Statistics for IPv4

  Active Opens                        = 153
  Passive Opens                       = 72
  Failed Connection Attempts          = 2
  Reset Connections                   = 127
  Current Connections                 = 20
  Segments Received                   = 482918
  Segments Sent                       = 281457
  Segments Retransmitted              = 5

UDP Statistics for IPv4

  Datagrams Received    = 1910
  No Ports              = 6006
  Receive Errors        = 0
  Datagrams Sent        = 1867

E:\>

Thanks,
David 





More information about the questions mailing list