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

[Brad WF7T]

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
>
>