[time-nuts] Re: NIST NTP servers way off for anyone else?

[Magnus Danielson]

Hi,

Expect network routes to be more dispersed these days, as it is needed.

While the wedge plot is a classic for NTP, it may be interesting to plot 
forward and backward path histograms independently.

Cheers,
Magnus

On 2021-12-15 16:25, Adam Space wrote:
> Yeah I think it is localized. Network paths have been quite variable for
> me. Every once in a while I start getting massive delays from the NIST
> servers to my system, resulting in results like yours.
>
> Interestingly though, time-e-g was one of the only servers that didn't have
> this problem for me. This is a recent wedge plot for it. seems to be
> working fine for me now, just with a variable outgoing delay causing
> positive offsets, which seems to be more of a problem with my connection
> than anything else.
>
> On Tue, Dec 14, 2021 at 9:04 PM K5ROE Mike <K5ROE at roetto.org> wrote:
>
>> On 12/14/21 5:23 PM, Hal Murray wrote:
>>>> Out of curiosity, since you monitor NIST Gaithersburg, if you were to
>> average
>>>> over the offsets for a whole month, what kind of value would you get?
>> Surely
>>>> it is close to zero but I am curious how close. Within 1ms?
>>> It depends.  Mostly on the routing between you and NIST.  If you are
>> closer,
>>> the routing is more likely to be symmetric.
>>>
>>>   From my experience, routing is generally stable on the scale of
>> months.  There
>>> are short (hours) changes when a fiber gets cut or a router gets busted.
>>> There are long term changes as people add fibers and/or change business
>> deals.
>>> There are some cases where a stable routing will produce 2 answers: x%
>> of the
>>> packets will be slightly faster/slower than most of them.  I think what's
>>> going on is that the routers are doing load sharing on multiple paths,
>> hashing
>>> on the address+port.  Or something like that.  So it's a roll of the dice
>>> which path you get.
>>>
>>> --------
>>>
>>> I'm in California.
>>>
>>> NIST has NTP servers at 3 locations in the Boulder CO area: NIST, WWV,
>> and
>>> Univ of Colorado.  (Google maps says WWV is 60 miles north of Bouler.
>> Univ of
>>> Colorado is a few miles from NIST.)
>>>
>>>   From a cheap cloud server (Digital Ocean) in San Francisco, the RTT to
>> NIST is
>>> 31.5 ms, to WWV is 32.1 ms, to Univ of Colorado is 54.5 ms.  The time
>> offsets
>>> are about 1 ms for NIST and WWV and 12 ms for Univ of Colorado.
>>>
>>>   From my home (AT&T via Sonic), 30 miles south of San Francisco, the
>> RTTs are
>>> 61 ms for NIST and WWV and 81-82 for Univ of Colorado.  Offsets are 6-7
>> ms for
>>> NIST and WWV and 4-5 ms in the other direction for Univ of Colorado.
>>>
>>>
>> Might be a localized routing phenomenon.  Using my verizon connection from
>> Northern Virginia the results are awful for time-e-g.nist.gov:
>>
>>        remote           refid      st t when poll reach   delay   offset
>> jitter
>>
>> ==============================================================================
>> -192.168.1.219   68.69.221.61     2 u   56   64  377    0.400   -0.290
>>   0.035
>> *192.168.1.224   .PPS.            1 u    1   16  377    0.184    0.087
>>   0.017
>> -129.6.15.26     .NIST.           1 u   32   64  377   93.087  -37.940
>>   7.867
>>
>> However from my AWS machine in Oregon:
>>
>> MS Name/IP address         Stratum Poll Reach LastRx Last sample
>>
>> ===============================================================================
>> ^- 152.63.13.177                 3   6   377    63  -2011us[-2011us] +/-
>> 128ms
>> ^+ 209.182.153.6                 2   7   377    65   -959us[ -959us] +/-
>>   86ms
>> ^- 64.139.66.105                 3   6   377   128  -5838us[-5838us] +/-
>> 134ms
>> ^+ 129.6.15.26                   1   6   377    64  -2075us[-2075us] +/-
>>   37ms
>> ^* 173.66.105.50                 1   8   377   438   -448us[ -870us] +/-
>>   38ms
>>
>>
>> -mike
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