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Daily speed and connectivity issues on Gigabit internet

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Daily speed and connectivity issues on Gigabit internet

I'll apologize in advance for how long this post is going to be. I've been dealing with this without a resolution for about a month now and the only way I could get my point across was in detail.

 

For about the last month on my Gigabit internet service, I've been noticing substantial speed drops and complete loss of connectivity at random times throughout the day. It seems to occur in two scenarios. One scenario being that it will suddenly drop out for anywhere from a few seconds to a few minutes at a time then return to normal. I've seen this happen off and on for a good 20 minutes at a time to a few hours. The other is that the speed will drop significantly for an undetermined amount of time, but not to the point the connection crashed like in the first scenario. I have to reboot the modem itself and hope the issue isn't happening anymore to get my download speed back to normal. The first scenario has been happening almost daily since this all started back in April at any given time without warning. The same goes for the second scenario, but less frequently because it normally jumps into full disconnect territory more often than just losing speed. In both scenarios, the logs show no timeouts and the modem status lights act as if everything is completely normal.

 

Equipment wise I am currently using a Comcast approved Arris SB8200 that was properly activated and provisioned with the correct boot file for my Gigabit service by Xfinity Tech Support a few days ago. When it first started happening in April, I was using a Netgear CM1000-1AZNAS that had been activated and provisioned since September of last year without an issue up to that point. I replaced it with the SB8200 to rule out the modem going bad as the culprit, but it is still happening on the SB8200 so that isn't the case. I also use a Netgear Nighthawk R6700v3 router for my home LAN, but both of the scenarios above happened before this on the old router, so it's not a factor. I've had it happen while the modem is connected directly to my desktop computer so I ruled out the router as a culprit weeks ago.

 

The erratic nature of the issue has been a problem as well as far as resolution. As it happens without warning and under no specific circumstance, the first technician visit on 5/2 resulted in the usual "Your signal levels are fine and we aren't seeing any timeouts" when they tested the cable itself. The technician was nice enough to schedule a visit the following Wed 5/8 to run a new cable to the apartment as the current one was 20+ years old. As has been the case so far, everything was fine the entire rest of the day and it suddenly had the disconnect scenario later that night. I scheduled a third tech for last Fri 5/10 and the same technician came out. It essentially consisted of him standing outside my front door telling me they have been actively monitoring the line since they installed it and haven't seen any signal issues or timeouts. He said they would monitor it this past weekend and let me know this past Tuesday if they saw anything out of the ordinary. As I never heard back, I assume they once again didn't catch this happening or they forgot to do so. Either way, not thrilled about the complete disregard to check factors beyond my local node or escalate this.

 

At this point, I'm starting to wonder if they aren't looking in the right place or far enough upstream. When I've checked the modem status page on both the CM1000 I was previously using and my current SB8200 as one of the two scenarios is occurring, something stands out pretty clearly. The downstream OFDM channel (159 on the 678 MHz frequency in my case) SNR suddenly plummets near or well below 30 db. The other downstream channels remain completely fine and stay within acceptable SNR as you will see below in the screenshots I will post. How low that downstream OFDM SNR gets seems to effectively determine if I get the speed loss scenario or the full on disconnects due to excessive damaged frames scenario I mentioned above. When the OFDM channel isn't experiencing the SNR drop, it has the same great signal level and SNR as the other downstream channels and my connection/speed is fantastic. Also, in either scenario, when I check to see if there are any outages in the area, there are none but it does think there is a problem with my equipment as a result of that SNR drop above it is seeing on that channel.

 

I'm well aware high noise/low power levels can impact SNR and basically cause what I'm seeing above, but where exactly is the ingress if the technician ruled out my local cable run up to the local node? Also, why did it start so suddenly when I had been using DOCSIS 3.1/OFDM for many months prior to this happening? It sounds to me like there is an ingress issue somewhere, but not somewhere a dispatched technician normally checks or gets alerts on since it doesn't cause an area-wide outage.

 

At this point, I'm at whits end with this and any input/assistance from a Comcast technician/forum expert would be appreciated. I've also been making logs of times/dates these issues occur when I can actually catch it and have told the tech I mentioned above about the low SNR on the OFDM channel but it's clear he just dismisses it because he isn't seeing anything to match what I was telling him. Can someone please check my CMTS/Headend upstream power level/SNR if I provide them dates/times this occurred to cross-reference against along with their MAC addresses?

 

With that said, here is the modem status page when I caught it earlier this morning 5/17 around 7:10AM EST. I woke up to it so unfortunately I don't know when the SNR drop happened, but this status page is accurate for how it normally looks when I have either the speed or disconnects. The OFDM channel is highlighted.

 

Downstream Bonded Channels  
Channel ID Lock Status Modulation Frequency Power SNR/MER Corrected Uncorrectables  
21 Locked QAM256 603000000 Hz 8.2 dBmV 40.6 dB 0 0  
1 Locked QAM256 477000000 Hz 8.6 dBmV 41.1 dB 0 0  
2 Locked QAM256 483000000 Hz 8.5 dBmV 41.5 dB 0 0  
3 Locked QAM256 489000000 Hz 8.4 dBmV 41.3 dB 0 0  
4 Locked QAM256 495000000 Hz 8.3 dBmV 41.4 dB 0 0  
5 Locked QAM256 507000000 Hz 8.5 dBmV 41.2 dB 0 0  
6 Locked QAM256 513000000 Hz 8.6 dBmV 41.2 dB 0 0  
7 Locked QAM256 519000000 Hz 8.6 dBmV 41.4 dB 0 0  
8 Locked QAM256 525000000 Hz 8.6 dBmV 41.3 dB 0 0  
9 Locked QAM256 531000000 Hz 8.7 dBmV 41.2 dB 0 0  
10 Locked QAM256 537000000 Hz 8.8 dBmV 40.7 dB 0 0  
11 Locked QAM256 543000000 Hz 8.7 dBmV 41.0 dB 0 0  
12 Locked QAM256 549000000 Hz 8.7 dBmV 41.1 dB 0 0  
13 Locked QAM256 555000000 Hz 8.6 dBmV 41.1 dB 0 0  
14 Locked QAM256 561000000 Hz 8.6 dBmV 40.6 dB 0 0  
15 Locked QAM256 567000000 Hz 8.4 dBmV 41.0 dB 0 0  
16 Locked QAM256 573000000 Hz 8.2 dBmV 40.9 dB 0 0  
17 Locked QAM256 579000000 Hz 8.1 dBmV 40.8 dB 0 0  
18 Locked QAM256 585000000 Hz 8.2 dBmV 40.7 dB 0 0  
19 Locked QAM256 591000000 Hz 8.1 dBmV 40.6 dB 0 0  
20 Locked QAM256 597000000 Hz 8.1 dBmV 40.7 dB 0 0  
22 Locked QAM256 609000000 Hz 8.1 dBmV 40.9 dB 0 0  
23 Locked QAM256 615000000 Hz 8.0 dBmV 40.8 dB 0 0  
24 Locked QAM256 621000000 Hz 8.1 dBmV 40.5 dB 0 0  
25 Locked QAM256 627000000 Hz 7.9 dBmV 40.5 dB 0 0  
26 Locked QAM256 633000000 Hz 7.7 dBmV 40.4 dB 0 0  
27 Locked QAM256 639000000 Hz 7.9 dBmV 39.3 dB 0 0  
28 Locked QAM256 645000000 Hz 8.0 dBmV 39.7 dB 0 0  
29 Locked QAM256 651000000 Hz 7.9 dBmV 40.2 dB 1 0  
30 Locked QAM256 657000000 Hz 7.9 dBmV 40.2 dB 0 0  
31 Locked QAM256 663000000 Hz 7.8 dBmV 40.2 dB 1 0  
32 Locked QAM256 669000000 Hz 7.7 dBmV 40.2 dB 24 8  
159 Locked Other 678000000 Hz 4.1 dBmV 0.0 dB 141555430 1176  
                 
Upstream Bonded Channels    
Channel Channel ID Lock Status US Channel Type Frequency Width Power    
1 1 Locked SC-QAM Upstream 36500000 Hz 6400000 Hz 40.0 dBmV    
2 2 Locked SC-QAM Upstream 30100000 Hz 6400000 Hz 41.0 dBmV    
3 3 Locked SC-QAM Upstream 23700000 Hz 6400000 Hz 41.0 dBmV    

 

This is what the status page looks like when it's working normally. 

 

Downstream Bonded Channels
Channel ID Lock Status Modulation Frequency Power SNR/MER Corrected Uncorrectables
29 Locked QAM256 651000000 Hz 6.6 dBmV 40.2 dB 0 0
1 Locked QAM256 477000000 Hz 7.6 dBmV 41.1 dB 0 0
2 Locked QAM256 483000000 Hz 7.5 dBmV 41.4 dB 0 0
3 Locked QAM256 489000000 Hz 7.4 dBmV 41.3 dB 0 0
4 Locked QAM256 495000000 Hz 7.4 dBmV 41.4 dB 0 0
5 Locked QAM256 507000000 Hz 7.5 dBmV 41.4 dB 0 0
6 Locked QAM256 513000000 Hz 7.5 dBmV 41.3 dB 0 0
7 Locked QAM256 519000000 Hz 7.5 dBmV 41.2 dB 0 0
8 Locked QAM256 525000000 Hz 7.5 dBmV 41.3 dB 0 0
9 Locked QAM256 531000000 Hz 7.6 dBmV 41.0 dB 0 0
10 Locked QAM256 537000000 Hz 7.7 dBmV 40.5 dB 0 0
11 Locked QAM256 543000000 Hz 7.6 dBmV 39.3 dB 0 0
12 Locked QAM256 549000000 Hz 7.5 dBmV 37.7 dB 0 0
13 Locked QAM256 555000000 Hz 7.4 dBmV 39.9 dB 0 0
14 Locked QAM256 561000000 Hz 7.4 dBmV 41.0 dB 0 0
15 Locked QAM256 567000000 Hz 7.2 dBmV 40.9 dB 0 0
16 Locked QAM256 573000000 Hz 7.0 dBmV 40.4 dB 0 0
17 Locked QAM256 579000000 Hz 6.9 dBmV 39.8 dB 0 0
18 Locked QAM256 585000000 Hz 7.0 dBmV 36.5 dB 0 0
19 Locked QAM256 591000000 Hz 6.8 dBmV 39.1 dB 0 0
20 Locked QAM256 597000000 Hz 6.9 dBmV 39.3 dB 0 0
21 Locked QAM256 603000000 Hz 7.0 dBmV 39.6 dB 0 0
22 Locked QAM256 609000000 Hz 6.8 dBmV 39.9 dB 0 0
23 Locked QAM256 615000000 Hz 6.8 dBmV 40.2 dB 0 0
24 Locked QAM256 621000000 Hz 6.8 dBmV 40.0 dB 0 0
25 Locked QAM256 627000000 Hz 6.7 dBmV 40.2 dB 0 0
26 Locked QAM256 633000000 Hz 6.4 dBmV 40.2 dB 0 0
27 Locked QAM256 639000000 Hz 6.6 dBmV 39.3 dB 0 0
28 Locked QAM256 645000000 Hz 6.7 dBmV 39.9 dB 0 0
30 Locked QAM256 657000000 Hz 6.6 dBmV 40.3 dB 0 0
31 Locked QAM256 663000000 Hz 6.4 dBmV 40.1 dB 0 0
32 Locked QAM256 669000000 Hz 6.4 dBmV 40.0 dB 0 0
159 Locked Other 678000000 Hz 7.2 dBmV 38.2 dB 39863821 0
               
Upstream Bonded Channels  
Channel Channel ID Lock Status US Channel Type Frequency Width Power  
1 1 Locked SC-QAM Upstream 36500000 Hz 6400000 Hz 41.0 dBmV  
2 2 Locked SC-QAM Upstream 30100000 Hz 6400000 Hz 41.0 dBmV  
3 3 Locked SC-QAM Upstream 23700000 Hz 6400000 Hz 42.0 dBmV  

 

UPDATE: I've been watching it consistently throughout the day and just checked it at 6:40PM EST on 5/17. Everything is normal at the moment, but I'm starting to notice ingress on the higher frequencies, including the OFDM one. I did indeed get knocked offline for about 2 minutes from the bad signal coming in around 8:40PM. However, I got lucky last night and the ingress wasn't bad enough after that to knock me completely offline, but I did have slowdown/partial disconnects most of the night intermittently.

 

Downstream Bonded Channels
Channel ID Lock Status Modulation Frequency Power SNR/MER Corrected Uncorrectables
29 Locked QAM256 651000000 Hz 5.6 dBmV 40.0 dB 25 47
1 Locked QAM256 477000000 Hz 6.7 dBmV 40.8 dB 0 0
2 Locked QAM256 483000000 Hz 6.5 dBmV 41.2 dB 0 0
3 Locked QAM256 489000000 Hz 6.4 dBmV 41.1 dB 0 0
4 Locked QAM256 495000000 Hz 6.3 dBmV 41.1 dB 0 0
5 Locked QAM256 507000000 Hz 6.4 dBmV 40.6 dB 0 0
6 Locked QAM256 513000000 Hz 6.4 dBmV 40.7 dB 0 0
7 Locked QAM256 519000000 Hz 6.4 dBmV 40.6 dB 0 0
8 Locked QAM256 525000000 Hz 6.4 dBmV 41.0 dB 9 0
9 Locked QAM256 531000000 Hz 6.4 dBmV 40.9 dB 0 0
10 Locked QAM256 537000000 Hz 6.5 dBmV 40.3 dB 1 0
11 Locked QAM256 543000000 Hz 6.4 dBmV 40.6 dB 0 0
12 Locked QAM256 549000000 Hz 6.3 dBmV 40.8 dB 0 0
13 Locked QAM256 555000000 Hz 6.3 dBmV 40.6 dB 0 0
14 Locked QAM256 561000000 Hz 6.3 dBmV 40.7 dB 17 0
15 Locked QAM256 567000000 Hz 6.1 dBmV 40.6 dB 0 0
16 Locked QAM256 573000000 Hz 5.9 dBmV 40.3 dB 0 0
17 Locked QAM256 579000000 Hz 5.8 dBmV 39.8 dB 0 0
18 Locked QAM256 585000000 Hz 5.9 dBmV 39.2 dB 2 0
19 Locked QAM256 591000000 Hz 5.8 dBmV 38.4 dB 1 0
20 Locked QAM256 597000000 Hz 5.9 dBmV 37.9 dB 0 0
21 Locked QAM256 603000000 Hz 5.9 dBmV 38.1 dB 0 0
22 Locked QAM256 609000000 Hz 5.8 dBmV 38.8 dB 1 0
23 Locked QAM256 615000000 Hz 5.7 dBmV 39.3 dB 2 0
24 Locked QAM256 621000000 Hz 5.7 dBmV 39.5 dB 0 0
25 Locked QAM256 627000000 Hz 5.5 dBmV 39.7 dB 1 0
26 Locked QAM256 633000000 Hz 5.3 dBmV 39.8 dB 1 0
27 Locked QAM256 639000000 Hz 5.4 dBmV 38.4 dB 5 37
28 Locked QAM256 645000000 Hz 5.6 dBmV 39.1 dB 10 48
30 Locked QAM256 657000000 Hz 5.7 dBmV 40.0 dB 18 64
31 Locked QAM256 663000000 Hz 5.8 dBmV 39.8 dB 18 66
32 Locked QAM256 669000000 Hz 6.2 dBmV 40.0 dB 17 70
159 Locked Other 678000000 Hz 9.1 dBmV 37.5 dB 1170706318 3441

 

UPDATE 2: Now I'm really curious to know where this signal noise is happening upstream. I don't know the exact time the SNR issue started and ended today 5/18 between 2PM and 8PM EST, but by the time I noticed it, I had an insane amount of uncorrectables and my download speed was stuck at 35 Mbps (normal being around 930 Mbps) until I rebooted the modem to clear up the garbage/damaged frames. Apparently my original thought of it being strictly on the higher frequencies (>639 MHz) was an understatement.

 

Downstream Bonded Channels
Channel ID Lock Status Modulation Frequency Power SNR/MER Corrected Uncorrectables
9 Locked QAM256 531000000 Hz 7.5 dBmV 40.7 dB 7547889 1131714
1 Locked QAM256 477000000 Hz 7.7 dBmV 41.0 dB 3216895 141423
2 Locked QAM256 483000000 Hz 7.5 dBmV 41.5 dB 3511012 164037
3 Locked QAM256 489000000 Hz 7.4 dBmV 41.3 dB 3711086 186395
4 Locked QAM256 495000000 Hz 7.3 dBmV 41.2 dB 3630923 178325
5 Locked QAM256 507000000 Hz 7.4 dBmV 41.0 dB 4041362 229886
6 Locked QAM256 513000000 Hz 7.4 dBmV 40.5 dB 4436845 305790
7 Locked QAM256 519000000 Hz 7.4 dBmV 40.2 dB 4692748 381725
8 Locked QAM256 525000000 Hz 7.4 dBmV 39.9 dB 4853681 469209
10 Locked QAM256 537000000 Hz 7.6 dBmV 40.8 dB 7258405 857700
11 Locked QAM256 543000000 Hz 7.6 dBmV 40.8 dB 5244846 836861
12 Locked QAM256 549000000 Hz 7.5 dBmV 40.9 dB 7542913 1163227
13 Locked QAM256 555000000 Hz 7.5 dBmV 40.9 dB 7628479 1338309
14 Locked QAM256 561000000 Hz 7.6 dBmV 40.8 dB 7591914 1380064
15 Locked QAM256 567000000 Hz 7.4 dBmV 40.8 dB 5327099 1287348
16 Locked QAM256 573000000 Hz 7.3 dBmV 40.8 dB 7726103 1856813
17 Locked QAM256 579000000 Hz 7.1 dBmV 40.7 dB 7712488 2006734
18 Locked QAM256 585000000 Hz 7.3 dBmV 40.7 dB 7516702 2071598
19 Locked QAM256 591000000 Hz 7.2 dBmV 40.6 dB 7601934 2307281
20 Locked QAM256 597000000 Hz 7.2 dBmV 40.5 dB 7514130 2535627
21 Locked QAM256 603000000 Hz 7.3 dBmV 40.4 dB 4961705 2237018
22 Locked QAM256 609000000 Hz 7.2 dBmV 40.3 dB 7099518 2771434
23 Locked QAM256 615000000 Hz 7.2 dBmV 40.3 dB 7271637 3270677
24 Locked QAM256 621000000 Hz 7.2 dBmV 40.4 dB 7217737 3503993
25 Locked QAM256 627000000 Hz 7.0 dBmV 40.1 dB 6744786 3344897
26 Locked QAM256 633000000 Hz 6.7 dBmV 40.0 dB 6561038 3744826
27 Locked QAM256 639000000 Hz 6.9 dBmV 39.1 dB 6193764 4514100
28 Locked QAM256 645000000 Hz 7.0 dBmV 39.5 dB 6249292 4648648
29 Locked QAM256 651000000 Hz 6.9 dBmV 40.1 dB 5539933 5454379
30 Locked QAM256 657000000 Hz 6.8 dBmV 40.0 dB 3307059 3378511
31 Locked QAM256 663000000 Hz 6.8 dBmV 39.9 dB 2803457 3335515
32 Locked QAM256 669000000 Hz 6.7 dBmV 39.9 dB 2519908 3323432
159 Locked Other 678000000 Hz 7.7 dBmV 38.8 dB 738808269 11436

 

Official Employee

Re: Daily speed and connectivity issues on Gigabit internet

Hello DeityZero, thank you for taking the time out of your busy day to reach out to us here regarding this concern. I understand how frustrating it can be to have issues with your speeds when you need them to work the most, but there's no need to worry I can definitely help you with diagnosing the issue and get it repaired. We don't want you to constantly have to worry about if your internet will be up to par everyday so let's get the ball rolling, to continue please send me a private message with your full name by clicking on my name (ComcastAmir) and then click "Send a message".


I am an Official Comcast Employee.
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