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Gigabit Internet Disconnects and Speed Loss

Frequent Visitor

Gigabit Internet Disconnects and Speed Loss

Over the last week, I began noticing my connection would randomly disconnect for a few seconds, come back, but subsequently my download speed would go from its normal rock-solid 940 Mbps to around 600 Mbps and stay there until I rebooted my modem. When it first started happening, it seemed to occur more frequently when I was doing more bandwidth/packet heavy activities with a lot of FEC/codewords like gaming and streaming. However, I also found it would do this on its own over time, just at a slower pace while I was at work. I monitored the signals on the cable modem page and noticed a little bit of a signal power dip on the higher channels, but SNR was acceptable on all of them. Fast forward to today and now the signal power levels have dropped even more significantly on the higher channels, in some cases by about 2-2.5 dBmV. This also corresponds with a large number of uncorrectable codewords, progressively more as go down the list. The logs don't seem to indicate any T3 or T4 timeouts when I've checked, but they do indicate a lot of CM Status message sent notifications and the occassional MDD message timeout warning thrown in.

 

UPDATE: I did check the signal power levels an hour or so after posting this and they seem to have gone up a bit, but still appear to gradually degrade consistently towards the higher channels/frequencies. Also, there hasn't been any disconnects since a few days ago, but the signal power levels still concern me despite no T3 timeouts.

 

As far as my subscription and hardware goes, I am on the Gigabit Internet tier as referenced above and using a Netgear CM1000-1AZNAS modem with the latest firmware (v.3.01.06) along with a Netgear Nighthawk R6700v3 home router. I have tried it both with and without the router so this has no bearing on the situation. I use Cat6 cable for my local LAN and my modem is connected without a splitter directly to the coaxial that runs to the cable box outside. When the signal power degrades after a reboot and I start experiencing the issues, the modem lights stay completely normal.

 

Can I please have someone reach out to me in a DM so we can check the CMTS and my modem's historical RF signal reports along with my local node/plant as well? I haven't set up a tech visit yet as I wanted some feedback from this first and those items checked so they could be included in any case we might need to open.

 

Here are my cable modem signals (I haven't restarted it in about 2 days):

 

Downstream Bonded Channels
Channel Lock Status Modulation Channel ID Frequency Power SNR / MER Unerrored Codewords Correctable Codewords Uncorrectable Codewords
1 Locked QAM256 1 477000000 Hz 6.8 dBmV 41.4 dB 3388136489 60590 13541
2 Locked QAM256 2 483000000 Hz 6.5 dBmV 41.6 dB 3575095056 62340 20851
3 Locked QAM256 3 489000000 Hz 6.5 dBmV 41.6 dB 3575098843 62225 24995
4 Locked QAM256 4 495000000 Hz 6.4 dBmV 41.7 dB 3575061579 62349 22606
5 Locked QAM256 5 507000000 Hz 6.6 dBmV 41.5 dB 3575087071 63327 33289
6 Locked QAM256 6 513000000 Hz 6.6 dBmV 41.5 dB 3575083947 66896 41939
7 Locked QAM256 7 519000000 Hz 6.5 dBmV 41.5 dB 3575077944 72723 46711
8 Locked QAM256 8 525000000 Hz 6.6 dBmV 41.3 dB 3575068457 79018 50186
9 Locked QAM256 9 531000000 Hz 6.5 dBmV 41.5 dB 3575086441 86556 52988
10 Locked QAM256 10 537000000 Hz 6.6 dBmV 40.8 dB 3575073830 93908 54503
11 Locked QAM256 11 543000000 Hz 6.5 dBmV 41.3 dB 3575074986 101785 55776
12 Locked QAM256 12 549000000 Hz 6.3 dBmV 41.4 dB 3575069583 108410 56593
13 Locked QAM256 13 555000000 Hz 6.2 dBmV 41.2 dB 3575061685 116484 58049
14 Locked QAM256 14 561000000 Hz 6.2 dBmV 41.2 dB 3575058091 124438 58636
15 Locked QAM256 15 567000000 Hz 6.0 dBmV 40.8 dB 3575053838 132437 60150
16 Locked QAM256 16 573000000 Hz 5.8 dBmV 40.5 dB 3574959331 141281 61368
17 Locked QAM256 17 579000000 Hz 5.5 dBmV 39.9 dB 3575052988 152672 61772
18 Locked QAM256 18 585000000 Hz 5.6 dBmV 39.4 dB 3575087547 162256 63375
19 Locked QAM256 19 591000000 Hz 5.4 dBmV 39.3 dB 3575074232 175270 66116
20 Locked QAM256 20 597000000 Hz 5.4 dBmV 39.3 dB 3575070810 185757 66636
21 Locked QAM256 21 603000000 Hz 5.4 dBmV 39.7 dB 3575065155 194758 68945
22 Locked QAM256 22 609000000 Hz 5.2 dBmV 40.1 dB 3575047378 210354 69965
23 Locked QAM256 23 615000000 Hz 5.1 dBmV 40.2 dB 3575014337 244240 74593
24 Locked QAM256 24 621000000 Hz 5.0 dBmV 40.5 dB 3574973087 257423 65557
25 Locked QAM256 25 627000000 Hz 4.7 dBmV 40.5 dB 3574945430 284725 75483
26 Locked QAM256 26 633000000 Hz 4.4 dBmV 40.4 dB 3574895956 329041 85206
27 Locked QAM256 27 639000000 Hz 4.5 dBmV 39.5 dB 3574764117 418146 94963
28 Locked QAM256 28 645000000 Hz 4.4 dBmV 39.8 dB 3574623846 496277 114342
29 Locked QAM256 29 651000000 Hz 4.3 dBmV 40.3 dB 3574567835 562011 148065
30 Locked QAM256 30 657000000 Hz 4.1 dBmV 40.3 dB 3574388109 610732 153177
31 Locked QAM256 31 663000000 Hz 3.9 dBmV 40.2 dB 3574311408 730618 203563
32 Locked QAM256 32 669000000 Hz 3.8 dBmV 40.2 dB 3574144726 891650 236520

Upstream Bonded Channels
Channel Lock Status Modulation Channel ID Frequency Power
1 Locked ATDMA 1 36500000 Hz 40.8 dBmV
2 Locked ATDMA 2 30100000 Hz 41.3 dBmV
3 Locked ATDMA 3 23700000 Hz 41.8 dBmV
4 Not Locked Unknown 0 0 Hz 0.0 dBmV
5 Not Locked Unknown 0 0 Hz 0.0 dBmV
6 Not Locked Unknown 0 0 Hz 0.0 dBmV
7 Not Locked Unknown 0 0 Hz 0.0 dBmV
8 Not Locked Unknown 0 0 Hz 0.0 dBmV

Downstream OFDM Channels
Channel Lock Status Modulation / Profile ID Channel ID Frequency Power SNR / MER Active Subcarrier Number Range Unerrored Codewords Correctable Codewords Uncorrectable Codewords
1 Locked 0, 255 159 678000000 Hz 4.3 dBmV 37.5 dB 1126 ~ 2969 20108747272 14745863307 6173200
2 Not Locked 0, 255 0 0 Hz 2.8 dBmV 0.0 dB 0 ~ 4095 0 0 0
Frequent Visitor

Re: Gigabit Internet Disconnects and Speed Loss

Just a quick update so I can keep my signal levels organized. I did end up rebooting the modem after the original post, but the signal power levels didn't start rebounding until about a half hour later. Once they did, I didn't experience any disconnects with online gaming and streaming and download speeds were rock solid at their normal 940 Mbps or so all night and even when I checked them at 8AM this morning. The signal levels on the higher channels/frequencies still appear to be a bit on the low side, but FEC uncorrectables are much better. I will check them again later after work, but here are the signal levels from this morning:

 

Downstream Bonded Channels
Channel Lock Status Modulation Channel ID Frequency Power SNR / MER Unerrored Codewords Correctable Codewords Uncorrectable Codewords
1 Locked QAM256 1 477000000 Hz 8.3 dBmV 41.3 dB 1858608748 16 77
2 Locked QAM256 2 483000000 Hz 8.1 dBmV 41.9 dB 1946260864 168 988
3 Locked QAM256 3 489000000 Hz 8.0 dBmV 41.7 dB 1946303094 185 972
4 Locked QAM256 4 495000000 Hz 8.0 dBmV 41.5 dB 1946261653 172 985
5 Locked QAM256 5 507000000 Hz 8.2 dBmV 41.7 dB 1946310694 177 984
6 Locked QAM256 6 513000000 Hz 8.2 dBmV 41.7 dB 1946265682 177 981
7 Locked QAM256 7 519000000 Hz 8.1 dBmV 41.6 dB 1946323095 178 980
8 Locked QAM256 8 525000000 Hz 8.2 dBmV 41.5 dB 1946228400 183 976
9 Locked QAM256 9 531000000 Hz 8.1 dBmV 41.5 dB 1946292489 193 931
10 Locked QAM256 10 537000000 Hz 8.2 dBmV 40.8 dB 1946335591 204 920
11 Locked QAM256 11 543000000 Hz 8.1 dBmV 41.4 dB 1946341518 199 924
12 Locked QAM256 12 549000000 Hz 8.0 dBmV 41.5 dB 1946301347 184 937
13 Locked QAM256 13 555000000 Hz 7.8 dBmV 41.4 dB 1946349878 170 951
14 Locked QAM256 14 561000000 Hz 7.8 dBmV 41.4 dB 1946294591 174 947
15 Locked QAM256 15 567000000 Hz 7.6 dBmV 41.3 dB 1946364076 181 941
16 Locked QAM256 16 573000000 Hz 7.4 dBmV 41.2 dB 1946365900 169 953
17 Locked QAM256 17 579000000 Hz 7.2 dBmV 41.0 dB 1946321504 158 939
18 Locked QAM256 18 585000000 Hz 7.3 dBmV 40.8 dB 1946380845 187 907
19 Locked QAM256 19 591000000 Hz 7.0 dBmV 40.9 dB 1946315156 173 923
20 Locked QAM256 20 597000000 Hz 7.0 dBmV 40.7 dB 1946312765 177 920
21 Locked QAM256 21 603000000 Hz 7.0 dBmV 40.7 dB 1946397824 167 931
22 Locked QAM256 22 609000000 Hz 6.8 dBmV 40.9 dB 1946399425 192 911
23 Locked QAM256 23 615000000 Hz 6.6 dBmV 40.9 dB 1946321465 170 931
24 Locked QAM256 24 621000000 Hz 6.6 dBmV 40.8 dB 1946408914 179 923
25 Locked QAM256 25 627000000 Hz 6.3 dBmV 40.6 dB 1946318843 171 910
26 Locked QAM256 26 633000000 Hz 6.0 dBmV 40.7 dB 1946304978 168 912
27 Locked QAM256 27 639000000 Hz 6.0 dBmV 39.7 dB 1946412490 202 880
28 Locked QAM256 28 645000000 Hz 6.0 dBmV 40.0 dB 1946420561 145 934
29 Locked QAM256 29 651000000 Hz 5.9 dBmV 40.5 dB 1946427010 171 907
30 Locked QAM256 30 657000000 Hz 5.7 dBmV 40.5 dB 1946383304 186 892
31 Locked QAM256 31 663000000 Hz 5.5 dBmV 40.3 dB 1946433317 179 900
32 Locked QAM256 32 669000000 Hz 5.4 dBmV 40.3 dB 1946428277 169

 

909

 

Upstream Bonded Channels
Channel Lock Status Modulation Channel ID Frequency Power
1 Locked ATDMA 1 36500000 Hz 40.0 dBmV
2 Locked ATDMA 2 30100000 Hz 40.5 dBmV
3 Locked ATDMA 3 23700000 Hz 41.5 dBmV

 

Downstream OFDM Channels
Channel Lock Status Modulation / Profile ID Channel ID Frequency Power SNR / MER Active Subcarrier Number Range Unerrored Codewords Correctable Codewords Uncorrectable Codewords
1 Locked 0, 255 159 678000000 Hz 5.8 dBmV 37.8 dB 1126 ~ 2969 5454548485 3977134226 205741

 

 

Frequent Visitor

Re: Gigabit Internet Disconnects and Speed Loss

So fast forward to today and after a week of no issues and solid performance, the sudden signal power drops resumed and started causing temporary disconnects again. I did notice something interesting though in that the last two occurrences were on warm days (75+ F).

 

Here are the levels from a little while ago during one of the temporary disconnects. SNR continues to be good, but the power levels are extremely out of spec:

Downstream Bonded Channels  
Channel Lock Status Modulation Channel ID Frequency Power SNR / MER Unerrored Codewords Correctable Codewords Uncorrectable Codewords  
1 Locked QAM256 21 603000000 Hz 4.0 dBmV 40.4 dB 1.74E+09 15801 2000  
2 Locked QAM256 1 477000000 Hz 5.3 dBmV 41.0 dB 1.77E+09 4826 422  
3 Locked QAM256 2 483000000 Hz 5.1 dBmV 41.6 dB 1.77E+09 5512 460  
4 Locked QAM256 3 489000000 Hz 5.0 dBmV 41.5 dB 1.77E+09 5751 478  
5 Locked QAM256 4 495000000 Hz 4.9 dBmV 41.5 dB 1.77E+09 5701 447  
6 Locked QAM256 5 507000000 Hz 5.0 dBmV 41.0 dB 1.77E+09 6408 546  
7 Locked QAM256 6 513000000 Hz 5.0 dBmV 41.3 dB 1.77E+09 7464 656  
8 Locked QAM256 7 519000000 Hz 5.0 dBmV 41.2 dB 1.77E+09 8284 754  
9 Locked QAM256 8 525000000 Hz 5.0 dBmV 41.3 dB 1.77E+09 8631 831  
10 Locked QAM256 9 531000000 Hz 5.0 dBmV 41.3 dB 1.77E+09 9299 907  
11 Locked QAM256 10 537000000 Hz 5.1 dBmV 41.0 dB 1.77E+09 9985 1111  
12 Locked QAM256 11 543000000 Hz 5.0 dBmV 41.0 dB 1.77E+09 10650 1149  
13 Locked QAM256 12 549000000 Hz 4.9 dBmV 40.9 dB 1.77E+09 11184 1144  
14 Locked QAM256 13 555000000 Hz 4.7 dBmV 40.7 dB 1.77E+09 11504 1233  
15 Locked QAM256 14 561000000 Hz 4.7 dBmV 41.0 dB 1.77E+09 11878 1360  
16 Locked QAM256 15 567000000 Hz 4.5 dBmV 40.9 dB 1.77E+09 12433 1414  
17 Locked QAM256 16 573000000 Hz 4.3 dBmV 40.7 dB 1.77E+09 13176 1541  
18 Locked QAM256 17 579000000 Hz 4.1 dBmV 40.7 dB 1.77E+09 13735 1632  
19 Locked QAM256 18 585000000 Hz 4.2 dBmV 40.4 dB 1.77E+09 14040 1751  
20 Locked QAM256 19 591000000 Hz 4.0 dBmV 40.5 dB 1.77E+09 14608 1793  
21 Locked QAM256 20 597000000 Hz 4.0 dBmV 40.3 dB 1.77E+09 15422 1996  
22 Locked QAM256 29 651000000 Hz 3.2 dBmV 40.2 dB 1.73E+09 39615 6916  
23 Locked QAM256 22 609000000 Hz 3.8 dBmV 40.4 dB 1.77E+09 16286 2240  
24 Locked QAM256 23 615000000 Hz 3.7 dBmV 40.5 dB 1.77E+09 16798 2450  
25 Locked QAM256 24 621000000 Hz 3.6 dBmV 40.4 dB 1.77E+09 17831 2582  
26 Locked QAM256 25 627000000 Hz 3.4 dBmV 40.4 dB 1.77E+09 18919 2845  
27 Locked QAM256 26 633000000 Hz 3.1 dBmV 40.3 dB 1.77E+09 20233 3234  
28 Locked QAM256 27 639000000 Hz 3.2 dBmV 39.6 dB 1.77E+09 29615 4220  
29 Locked QAM256 28 645000000 Hz 3.3 dBmV 39.9 dB 1.77E+09 32487 5775  
30 Locked QAM256 30 657000000 Hz 3.2 dBmV 40.1 dB 1.77E+09 36433 7335  
31 Locked QAM256 31 663000000 Hz 3.2 dBmV 40.1 dB 1.77E+09 40351 8225  
32 Locked QAM256 32 669000000 Hz 3.4 dBmV 40.0 dB 1.77E+09 43543 9118  
                     
Upstream Bonded Channels          
Channel Lock Status Modulation Channel ID Frequency Power          
1 Locked ATDMA 1 36500000 Hz 40.8 dBmV          
2 Locked ATDMA 2 30100000 Hz 41.5 dBmV          
3 Locked ATDMA 3 23700000 Hz 41.8 dBmV          
                     
Downstream OFDM Channels
Channel Lock Status Modulation / Profile ID Channel ID Frequency Power SNR / MER Active Subcarrier Number Range Unerrored Codewords Correctable Codewords Uncorrectable Codewords
1 Locked 0, 255 159 678000000 Hz 4.7 dBmV 38.3 dB 1126 ~ 2969 2.87E+10 2.18E+10 1317735