[ntp:questions] Odd reachability with local clock on XP

Philip Prindeville philipp_subx at redfish-solutions.com
Fri Oct 11 21:51:45 UTC 2013


[not sure why this was delayed but it was…reposting.]

On Oct 9, 2013, at 9:30 PM, unruh <unruh at invalid.ca> wrote:

> On 2013-10-10, Philip Prindeville <philipp_subx at redfish-solutions.com> wrote:
>> 
>> On Oct 9, 2013, at 6:26 PM, unruh <unruh at invalid.ca> wrote:
>> 
>>> On 2013-10-09, Philip Prindeville <philipp_subx at redfish-solutions.com> wrote:
>>>> Hi,
>>>> 
>>>> I'm running ntp-4.2.6p5 on Windows XP (SP3).  I have, amongst other things, the following in my config:
>>>> 
>>>> server 127.127.1.0 noselect minpoll 4 maxpoll 6
>>>> fudge 127.127.1.0 stratum 10
>>> 
>>> Why would you have that? It is really dumb in almost all cases. 
>> 
>> I have it for instrumentation purposes.  I'm trying to track the accuracy of an XP box as a local reference clock (it will not be peered with any other time servers nor have any external clocks) versus a reliable time source such as an appliance with a CDMA or GPS receiver.
>> 
>> A customer believes that PC time is "good enough" for their purposes, and I need to convince them otherwise.
>> 
> 
> The local clock ALWAYS has zero offset and zero delay--ie it always says
> your local clock is perfect. Ie, this tells you nothing. What you want
> to do is get rid of it and look at the offsset from the remote clocks to
> get an idea of how bad the system is as a clock. But of course even that
> would only be valid if you told ntp not to discipline your pc's clock. 

It's not the offset that worries me, it's the reach(ability) showing that only the first packet got through but no subsequent ones did.

-Philip




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