[amsat-bb] Fwd: Polluted time server causing issues with digital modes

[Frank]

I looked at my log since 2009, my copy of Dimension 4 has never used 
this time sever.  The notes on this time server states closed and only 
for use by networks of 10 or more computers.  Matter of fact my 
Dimension 4 has only connected to the same time server since 2009.  I 
don't know what controls Dimension 4 and which time server it uses, but 
it does not seem to be random.  I agree that if a station is using a 
time server that is not accurate then the modes that rely on precise 
time syncing will not work.

Frank
K6FW

On 3/31/18 10:37 PM, Brad WF7T wrote:
> I am forwarding this for anyone interested. I think my discovery is correct
> and invite additional review/scrutiny.
>
> 73 Brad WF7T
>
> On Sunday, April 1, 2018 at 12:21:36 AM UTC-5, Brad WF7T wrote:
>> *I have discovered a polluted time server that is wreaking havoc with
>> time-synced digital modes, and worse. For everyone using round-robin style
>> time synchronization like Dimension 4, please remove the following time
>> server: rackety.udel.edu <http://rackety.udel.edu>.* It is consistently
>> sending time sync corrections that are between 10 and 41 seconds different
>> than every other SNTP server in the world. This will cause your PC clocks
>> to skip this amount and stay that way until another time sync occurs, e.g.
>> 5 to 15 minutes later, causing another massive time correction by another
>> accurate time NTP server. Please pass this information along to all
>> digital-active hams.
>>
>> While this amount of time is not of any consequence for RTTY, PSK and the
>> like, this behavior is detrimental to WSJT and QRSS modes. Terrestrial WSJT
>> modes like FT8, WSPR, Meteor scatter MSK144, and EME modes fail to decode
>> and will cause out of sequence transmissions.
>>
>> I also noticed a number of out-of-sequence FT8 tranmissions on 40M this
>> afternoon (BTW, open early to EU), which clued me into the situation. This
>> messed up time server could have been a contributor.
>>
>> *Remove or disable the following server: rackety.udel.edu
>> <http://rackety.udel.edu>.* Apparently it has been getting increasingly
>> worse since 3/8/2018 or so. I only discovered this tonight while I was
>> decoding WSPR on 474.2KHz (630M) and saw a huge time jump and lack of
>> decodes of some fairly strong signals.
>>
>> And yes, this is also an InfoSec problem. Time bases are important for
>> MANY Information Security purposes, but beyond the scope of this discussion.
>>
>> Excerpts of my Dimension4 time-base logs below. Please contact me with
>> questions/comments.
>>
>> 73 Brad WF7T
>> Nashville, TN
>>
>> ---
>>
>> ... First noted occurrence in my time-base logs
>>
>> 2018-03-07 10:36:44.461 -7.962988e+000 rackety.udel.edu SNTP <-- 7 second
>> correction
>> 2018-03-07 10:39:52.480 7.980464e+000 clock-1.cs.cmu.edu SNTP <-- fixed
>> on next round-robin sync
>>
>> ... Persists for a second day, appearing to get worse
>>
>> 2018-03-08 09:17:25.217 -1.015543e+001 rackety.udel.edu SNTP <-- 10
>> second correction
>> 2018-03-08 09:20:35.240 9.963055e+000 clock-1.cs.cmu.edu SNTP <-- Fixed
>> on next round-robin sync
>>
>> ... Jump ahead a week; yup, getting worse
>>
>> 2018-03-15 05:34:10.880 -1.761963e+001 rackety.udel.edu SNTP <--  17
>> second correction
>> 2018-03-15 05:37:29.176 1.812267e+001 ntp.cais.rnp.br         SNTP <--
>> Fixed on next round-robin sync
>>
>> ... Skipping ahead to tonight; SNAFU
>>
>> 2018-03-31 23:29:34.849 -4.165045e+001 rackety.udel.edu SNTP <-- 41.6
>> second correction!
>> 2018-03-31 23:33:35.421 4.192192e+001 ntp2.kansas.net SNTP <-- fixed on
>> next round-robin sync
>>
>>
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