[ntp:questions] Re: [Bug 177] Clock stepping messes up frequency. (fwd)

Roy roy at suespammers.org
Fri Oct 24 01:45:05 UTC 2003


"David L. Mills" <mills at udel.edu> wrote in message news:<3F976322.4B882AEA at udel.edu>...
>
> Would you be so kind as to send me
> both loopstats and peerstats for this or a similar interval?
>
Ok, here's the loopstats from these three days.

52851 768.147 -0.054226675 -119.835474 0.034450925 0.409222 15
52851 17151.152 -0.027192308 -119.630382 0.034108466 0.368934 15
52851 49918.149 0.038115401 -119.381501 0.052961734 0.342885 15
52851 82685.150 -0.051950561 -119.724717 0.069032111 0.342968 16
52852 29055.149 0.009548464 -119.490629 0.067511066 0.319248 16
52853 70790.149 -0.303959474 -121.936574 0.161662943 1.253835 4
52853 73715.141 -0.166563500 -178.880252 0.140650012 28.492537 4
52853 74620.152 -0.021400267 -129.140914 0.019528909 35.033826 4
52853 74684.148 -0.015529604 -129.200154 0.017238256 30.340198 6
52853 74748.147 -0.015106461 -129.257781 0.015280701 26.275398 6
52853 74813.147 -0.014391243 -129.312679 0.013630854 22.755178 6
52853 74878.152 -0.010771746 -129.353770 0.012139873 19.706573 6
52853 74942.151 -0.011129591 -129.396226 0.010724381 17.066406 7
52853 75008.151 -0.010681756 -129.406360 0.009718156 14.779942 7
52853 75136.157 -0.007718793 -129.416321 0.008871063 12.799806 7
52853 75264.146 -0.007991359 -129.432726 0.008537074 11.084961 7
52853 75392.151 -0.004842993 -129.436624 0.008122577 9.599858 7
52853 75521.154 -0.003119083 -129.439691 0.007543647 8.313721 8
52853 75651.147 -0.001898361 -129.436141 0.007013159 7.199894 8
52853 75909.153 0.001967335 -129.419743 0.007395149 6.235296 8
52853 76167.151 0.003796793 -129.408911 0.007654624 5.399928 8
52853 76424.150 0.005462253 -129.396901 0.007390579 4.676478 9
52853 76682.148 0.006797370 -129.384616 0.006811429 4.049954 9
52853 77195.154 0.010110565 -129.353370 0.006770189 3.507398 9
52853 77709.151 0.013124436 -129.322408 0.006971442 3.037535 9
52853 78222.144 0.017215118 -129.280775 0.007296489 2.630665 10
52853 78734.150 0.020684043 -129.223384 0.007145897 2.278403 10
52853 79760.153 0.027531992 -129.107757 0.007757711 1.974002 10
52853 80785.154 0.034818587 -128.982024 0.008388410 1.710691 10
52853 81810.146 0.040290626 -128.880965 0.008654262 1.482364 10
52853 82835.148 0.047717007 -128.747081 0.009348258 1.285509 9
52853 83858.151 0.054923981 -128.650026 0.009838066 1.114340 9
52853 84369.145 0.057206015 -128.596159 0.009654494 0.965423 8
52853 84880.145 0.057998716 -128.524626 0.009415305 0.836845 8
52853 85137.155 0.059681797 -128.454455 0.010824529 0.725578 7
52853 85394.147 0.054365670 -128.351139 0.010476401 0.630489 7
52853 85521.154 0.053737129 -128.246149 0.010177492 0.548537 7
52853 85648.157 0.052231611 -128.145734 0.009986880 0.477693 6
52853 85776.149 0.048759984 -127.959729 0.010799590 0.424019 6
52853 85840.153 0.045014569 -127.788012 0.010647189 0.377115 6
52853 85906.148 0.043458960 -127.622230 0.010819117 0.336946 6
52853 85972.153 0.040755553 -127.466759 0.010386624 0.301981 6
52853 86037.146 0.038455340 -127.320064 0.010393794 0.271614 6
52853 86100.170 0.044037579 -127.154699 0.009878994 0.249333 6
52853 86163.147 0.035357511 -127.021928 0.011230620 0.225903 6
52853 86226.151 0.032898390 -126.898392 0.010751614 0.205157 6
52853 86291.143 0.030822100 -126.780815 0.010498014 0.187145 6
52853 86354.149 0.029957424 -126.668322 0.010116154 0.171555 6

And also the peerstats covering the same time.

52851 756.142 198.82.162.213 9414 -0.055626500 0.032689000 0.209285486
0.052890500
52851 768.256 208.184.49.9 9614 -0.060883000 0.039414000 0.208807072
0.051076500
52851 770.145 216.204.156.2 9414 -0.056121000 0.036930000 0.208826224
0.057415500
52851 14211.137 128.59.39.48 9314 -0.029517669 0.021739297 0.224430366
0.015677590
52851 17140.150 198.82.162.213 9314 -0.023504500 0.035221000
0.224887830 0.032122000
52851 17151.152 208.184.49.9 9614 -0.028271500 0.039613000 0.224399807
0.032611500
52851 21986.112 127.127.1.0 9014 0.000000000 0.000000000 0.000000000
0.000003815
52851 33537.172 216.204.156.2 9314 -0.004176000 0.066538000
0.346331224 0.051945000
52851 46980.153 128.59.39.48 9314 0.050824429 0.039540409 0.353792007
0.080342097
52851 49908.145 198.82.162.213 9314 0.048390500 0.033993000
0.354249002 0.071895000
52851 49918.168 208.184.49.9 9614 0.042877500 0.039385000 0.353756232
0.071149000
52851 54755.114 127.127.1.0 9014 0.000000000 0.000000000 0.000000000
0.000003815
52851 66304.142 216.204.156.2 9314 -0.015683000 0.036056000
0.414243724 0.011507000
52851 79747.140 128.59.39.48 9414 -0.041810244 0.029376104 0.417617944
0.092634673
52851 82676.146 198.82.162.213 9314 -0.054501000 0.033062000
0.418089646 0.102891500
52851 82685.151 208.184.49.9 9614 -0.059179000 0.038460000 0.417594475
0.102056500
52852 1124.111 127.127.1.0 9014 0.000000000 0.000000000 0.000000000
0.000003815
52852 12672.143 216.204.156.2 9414 -0.034667500 0.037477000
0.447367474 0.018984500
52852 26117.220 128.59.39.48 9314 0.020120368 0.106932919 0.448833296
0.061930612
52852 29044.145 198.82.162.213 9314 0.008252000 0.034320000
0.449289939 0.062753000
52852 29055.277 208.184.49.9 9614 0.001587000 0.039888000 0.448815920
0.060766000
52852 33892.113 127.127.1.0 9014 0.000000000 0.000000000 0.000000000
0.000003815
52852 66662.115 127.127.1.0 9014 0.000000000 0.000000000 0.000000000
0.000003815
52852 78208.182 216.204.156.2 9314 -0.136565500 0.075309000
0.707049349 0.101898000
52853 5252.135 128.59.39.48 9414 -0.187050797 0.023114231 0.707538647
0.207171165
52853 8179.151 198.82.162.213 9414 -0.193489000 0.036490000
0.708002615 0.201741000
52853 8191.153 208.184.49.9 9414 -0.199848500 0.040275000 0.707531760
0.201435500
52853 13029.106 127.127.1.0 9014 0.000000000 0.000000000 0.000000000
0.000003815
52853 45796.108 127.127.1.0 9014 0.000000000 0.000000000 0.000000000
0.000003815
52853 57343.197 216.204.156.2 9414 -0.353048000 0.086792000
0.835202903 0.216482500
52853 70790.281 128.59.39.48 9614 -0.385028033 0.033612444 0.835233647
0.197977236
52853 73715.141 198.82.162.213 9614 -0.166563500 0.033775000
0.835686424 0.026925500
52853 73727.149 208.184.49.9 9614 -0.168642500 0.039243000 0.835209709
0.031206000
52853 73781.147 198.82.162.213 9414 -0.150223500 0.034773000
0.410899490 0.016340000
52853 73791.147 208.184.49.9 9614 -0.155229500 0.038173000 0.410404963
0.013413000
52853 73845.145 198.82.162.213 9414 -0.138330000 0.033630000
0.198969178 0.011893500
52853 73854.149 208.184.49.9 9614 -0.141701500 0.039919000 0.198473244
0.013528000
52853 73911.144 198.82.162.213 9414 -0.125838500 0.033043000
0.093497029 0.012491500
52853 73917.149 208.184.49.9 9614 -0.129792500 0.039755000 0.092985510
0.011909000
52853 73977.148 198.82.162.213 9414 -0.111173000 0.037126000
0.041719021 0.014665500
52853 73980.150 208.184.49.9 9614 -0.118269000 0.039620000 0.041199768
0.011523500
52853 74043.145 198.82.162.213 9414 -0.101576000 0.033564000
0.016788084 0.009597000
52853 74043.155 208.184.49.9 9614 -0.105633000 0.043342000 0.016265021
0.012636000
52853 74108.152 208.184.49.9 9614 -0.097107500 0.038699000 0.004770744
0.008525500
52853 74109.145 198.82.162.213 9414 -0.091306500 0.032669000
0.005280682 0.010269500
52853 74173.148 198.82.162.213 9414 -0.080084000 0.032860000
0.001430135 0.011222500
52853 74174.153 208.184.49.9 9614 -0.085870500 0.038677000 0.000949143
0.011237000
52853 74237.145 208.184.49.9 9614 -0.076191000 0.038302000 0.000934084
0.009679500
52853 74238.139 198.82.162.213 9414 -0.070468500 0.030933000
0.001430428 0.009615500
52853 74301.150 208.184.49.9 9614 -0.065981500 0.039681000 0.000934025
0.010209500
52853 74302.143 198.82.162.213 9414 -0.060504000 0.033652000
0.001423162 0.009964500
52853 74365.146 198.82.162.213 9414 -0.051178000 0.033124000
0.001412088 0.009326000
52853 74366.152 208.184.49.9 9614 -0.057210000 0.038752000 0.000941408
0.008771500
52853 74428.149 198.82.162.213 9414 -0.039557000 0.042330000
0.001406639 0.011621000
52853 74430.145 208.184.49.9 9614 -0.048855000 0.038596000 0.000937600
0.008355000
52853 74491.144 198.82.162.213 9414 -0.034167500 0.031715000
0.001404002 0.005389500
52853 74494.150 208.184.49.9 9614 -0.039506000 0.039704000 0.000935666
0.009349000
52853 74554.137 198.82.162.213 9414 -0.026207500 0.032075000
0.001402771 0.007960000
52853 74557.154 208.184.49.9 9614 -0.031190000 0.039160000 0.000927228
0.008316000
52853 74619.149 198.82.162.213 9414 -0.020911500 0.039931000
0.001417127 0.005296000
52853 74620.152 208.184.49.9 9614 -0.021598000 0.042884000 0.000923068
0.009592000
52853 74684.138 198.82.162.213 9414 -0.012175500 0.032189000
0.001424275 0.008736000
52853 74684.149 208.184.49.9 9614 -0.016659500 0.041849000 0.000928518
0.004938500
52853 74747.141 198.82.162.213 9414 -0.010011000 0.033884000
0.001412967 0.002164500
52853 74748.147 208.184.49.9 9614 -0.016531000 0.039680000 0.000931213
0.000128500
52853 74812.141 198.82.162.213 9414 -0.009338000 0.032432000
0.001422224 0.000673000
52853 74813.147 208.184.49.9 9614 -0.015835500 0.038757000 0.000940002
0.000695500
52853 74878.142 198.82.162.213 9414 -0.007822500 0.032935000
0.001434236 0.001515500
52853 74878.152 208.184.49.9 9614 -0.011802000 0.042868000 0.000944396
0.004033500
52853 74942.151 208.184.49.9 9614 -0.012048500 0.040179000 0.000939123
0.000246500
52853 75005.144 198.82.162.213 9414 -0.006167500 0.031991000
0.001894080 0.001655000
52853 75008.151 208.184.49.9 9614 -0.011886500 0.039239000 0.000951369
0.000162000
52853 75133.138 198.82.162.213 9414 -0.004133000 0.032890000
0.002129568 0.002034500
52853 75136.157 208.184.49.9 9614 -0.008845500 0.041769000 0.001418771
0.003041000
52853 75260.142 198.82.162.213 9414 -0.002094500 0.033461000
0.002237967 0.002038500
52853 75264.147 208.184.49.9 9614 -0.009510500 0.038123000 0.001650568
0.000665000
52853 75389.146 198.82.162.213 9414 -0.000322500 0.033515000
0.002305232 0.001772000
52853 75392.151 208.184.49.9 9614 -0.006151500 0.038805000 0.001764592
0.003359000
52853 75516.138 198.82.162.213 9414 0.000745500 0.032681000
0.002322107 0.001068000
52853 75521.154 208.184.49.9 9614 -0.004422500 0.038685000 0.001827170
0.001729000
52853 75644.143 198.82.162.213 9414 0.001834000 0.033770000
0.002336111 0.001088500
52853 75651.147 208.184.49.9 9614 -0.003089500 0.038547000 0.001864025
0.001333000
52853 75901.144 198.82.162.213 9414 0.007932000 0.038392000
0.003301209 0.006098000
52853 75909.153 208.184.49.9 9614 0.000134000 0.038646000 0.002833049
0.003223500
52853 76158.152 198.82.162.213 9414 0.010116500 0.038373000
0.003778162 0.002184500
52853 76167.152 208.184.49.9 9614 0.001925000 0.038952000 0.003311877
0.001791000
52853 76415.147 198.82.162.213 9414 0.010207500 0.035773000
0.004012830 0.000091000
52853 76424.150 208.184.49.9 9614 0.004016500 0.039735000 0.003538225
0.002091500
52853 76672.141 198.82.162.213 9414 0.010111000 0.031864000
0.004126385 0.000096500
52853 76682.148 208.184.49.9 9614 0.005809000 0.040236000 0.003655061
0.001792500
52853 77185.149 198.82.162.213 9414 0.014730000 0.034196000
0.006084353 0.004619000
52853 77195.155 208.184.49.9 9614 0.008792500 0.040483000 0.005607228
0.002983500
52853 77698.144 198.82.162.213 9414 0.018354500 0.033517000
0.007052088 0.003624500
52853 77709.151 208.184.49.9 9614 0.011209000 0.041024000 0.006579475
0.002416500
52853 78212.142 198.82.162.213 9414 0.022451500 0.035313000
0.007532088 0.004097000
52853 78222.145 208.184.49.9 9614 0.015424000 0.039112000 0.007046877
0.004215000
52853 78564.113 127.127.1.0 9014 0.000000000 0.000000000 0.000000000
0.000003815
52853 78725.145 198.82.162.213 9414 0.024648000 0.032520000
0.007753338 0.002196500
52853 78734.151 208.184.49.9 9614 0.019036500 0.039097000 0.007261916
0.003612500
52853 79749.148 198.82.162.213 9414 0.032257500 0.033147000
0.011659021 0.007609500
52853 79760.153 208.184.49.9 9614 0.025383000 0.039498000 0.011186877
0.006346500
52853 80772.141 198.82.162.213 9414 0.039589500 0.033951000
0.013581951 0.007332000
52853 80785.154 208.184.49.9 9614 0.032526000 0.038656000 0.013119416
0.007143000
52853 81796.141 198.82.162.213 9414 0.045679000 0.032494000
0.014528416 0.006089500
52853 81810.146 208.184.49.9 9614 0.038105500 0.039167000 0.014063186
0.005579500
52853 82819.144 198.82.162.213 9414 0.053742000 0.033562000
0.014971736 0.008063000
52853 82835.148 208.184.49.9 9614 0.044779000 0.038830000 0.014512600
0.006673500
52853 83843.147 198.82.162.213 9414 0.060541500 0.034011000
0.015185896 0.006799500
52853 83858.151 208.184.49.9 9614 0.052047000 0.039722000 0.014707424
0.007268000
52853 84354.142 198.82.162.213 9414 0.063384000 0.032620000
0.011460564 0.002842500
52853 84369.146 208.184.49.9 9614 0.054698000 0.038480000 0.010979924
0.002651000
52853 84865.141 198.82.162.213 9414 0.064365500 0.033331000
0.009597986 0.000981500
52853 84880.145 208.184.49.9 9614 0.055774500 0.039187000 0.009116232
0.001076500
52853 85120.152 198.82.162.213 9414 0.070809000 0.044932000
0.006761756 0.006443500
52853 85137.155 208.184.49.9 9614 0.056594000 0.039912000 0.006294299
0.000819500
52853 85376.142 198.82.162.213 9414 0.060866500 0.032425000
0.005373611 0.009942500
52853 85394.147 208.184.49.9 9614 0.052470000 0.038658000 0.004905861
0.004124000
52853 85506.139 198.82.162.213 9414 0.060984500 0.033797000
0.003764392 0.000118000
52853 85521.154 208.184.49.9 9614 0.051787000 0.039672000 0.003266760
0.000683000
52853 85636.145 198.82.162.213 9414 0.059607000 0.033524000
0.002985974 0.001377500
52853 85648.157 208.184.49.9 9614 0.050329000 0.038906000 0.002473518
0.001458000
52853 85765.148 198.82.162.213 9414 0.057184500 0.037605000
0.002615486 0.002422500
52853 85776.150 208.184.49.9 9614 0.045277000 0.039344000 0.002110646
0.005052000
52853 85829.139 198.82.162.213 9414 0.052198000 0.032848000
0.001972771 0.004986500
52853 85840.154 208.184.49.9 9614 0.042428500 0.038441000 0.001479182
0.002848500
52853 85894.147 198.82.162.213 9414 0.051696500 0.036287000
0.001671951 0.000501500
52853 85906.148 208.184.49.9 9614 0.040536500 0.038773000 0.001191428
0.001892000
52853 85959.148 198.82.162.213 9414 0.047268000 0.032898000
0.001534607 0.004428500
52853 85972.153 208.184.49.9 9614 0.038530500 0.039255000 0.001060588
0.002006000
52853 86024.143 198.82.162.213 9414 0.045900500 0.033385000
0.001471502 0.001367500
52853 86037.146 208.184.49.9 9614 0.035839000 0.037976000 0.000993322
0.002691500
52853 86087.147 198.82.162.213 9414 0.044139000 0.033216000
0.001430662 0.001761500
52853 86100.170 208.184.49.9 9614 0.043979000 0.057752000 0.000950432
0.008140000
52853 86150.141 198.82.162.213 9414 0.041383500 0.032755000
0.001412205 0.002755500
52853 86163.147 208.184.49.9 9614 0.032474500 0.039645000 0.000930861
0.011504500
52853 86213.145 198.82.162.213 9414 0.039643000 0.032436000
0.001404939 0.001740500
52853 86226.151 208.184.49.9 9614 0.030659000 0.039140000 0.000922951
0.001815500
52853 86279.140 198.82.162.213 9414 0.037980500 0.033213000
0.001425564 0.001662500
52853 86291.143 208.184.49.9 9614 0.028521500 0.037881000 0.000935783
0.002137500
52853 86345.143 198.82.162.213 9414 0.036710500 0.033321000
0.001435818 0.001270000
52853 86354.149 208.184.49.9 9614 0.027862500 0.039709000 0.000927287
0.000659000

I'll venture to try a little amateur analysis on this issue.  As you
pointed out, the jitter is pretty high.  It look to me like this is
caused in part because the samples used to calculate the offset are
taken at very different times.  But the calculations appear to treat
those samples as if they were just taken, rather than hours old.  This
isn't a significant issue at small poll intervals, but it makes a
significant difference as the poll ramps up above 9 hours.

Between 52851 82685.150 and 52852 29055.149 the time has been adjusted
by an apparent 61 ms.  At the next poll, 2^16 seconds later, the time
offset is now about 201 ms. in the opposite direction.  Since all the
time sources show an offset of more than 128 ms. this seems to invoke
the popcorn spike suppressor.  So it continues another 62599 seconds
before it decides that the offset is real.  By this time the offset is
probably -358 ms., but the old samples from the other time sources
make the calculated offset only -304 ms.

I'll see if I can find / generate some more examples...

Have a great time,


roy
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