[SOLVED] Unreliable connection / high packet loss / high uncorrectables / Cox

[wptlrn]

A couple of months ago we began having significant problems with our previously reliable internet. Cox tech support told me that the signal looked "weak" on their end and so sent a tech. The tech confirmed the signal was bad but thought it was because of a problem with the box (I think he called it a tap) on the pole outside. But because he didn't have time to fix it, he put in an amplifier, called a supervisor, told me the supervisor would call me back, and left.

Supervisor never called.

Fast forward a week, the problem remains, and I call tech support again. They tell me someone already went to fix the box/tap. But the problem remains, so a second tech comes. The second tech confirms problems with the signal, replaces some connectors outside, including an old one from an old telephony service.

The problem gets better for a week or so, but is now back. Packet loss ranges from 0 to as high as nearly 50%. I even got a few "PING: transmit failed. General failure." at one point.

In the course of troubleshooting, I check the modem signal levels myself, and see the below. From what I can gather, the power and SNR levels are OK, but the corrected/uncorrectables are extremely high. Googling suggests installing a MoCA filter might help, so I've ordered some. I've also ordered a new cable modem.

Channel	Lock Status	Modulation	Channel ID	Frequency	Power	SNR	Corrected	Uncorrectables
1	Locked	256QAM	21	903.00 MHz	-2.60 dBmV	32.96 dB	3469181	15134936
2	Locked	256QAM	1	783.00 MHz	6.40 dBmV	37.64 dB	148312	832542
3	Locked	256QAM	2	789.00 MHz	6.80 dBmV	38.61 dB	340	3212
4	Locked	256QAM	3	795.00 MHz	6.60 dBmV	37.64 dB	275	2145
5	Locked	256QAM	4	801.00 MHz	7.50 dBmV	38.61 dB	237	2153
6	Locked	256QAM	5	807.00 MHz	7.10 dBmV	38.61 dB	204	2055
7	Locked	256QAM	6	813.00 MHz	6.40 dBmV	37.64 dB	401	3138
8	Locked	256QAM	7	819.00 MHz	6.10 dBmV	37.64 dB	391	2193
9	Locked	256QAM	8	825.00 MHz	5.20 dBmV	37.64 dB	15640	40825
10	Locked	256QAM	9	831.00 MHz	4.30 dBmV	36.61 dB	195030	640385
11	Locked	256QAM	10	837.00 MHz	3.10 dBmV	36.39 dB	81407	461393
12	Locked	256QAM	11	843.00 MHz	2.40 dBmV	35.78 dB	954226	5462733
13	Locked	256QAM	12	849.00 MHz	1.70 dBmV	35.78 dB	9501	2122
14	Locked	256QAM	13	855.00 MHz	0.40 dBmV	34.93 dB	38851	2945
15	Locked	256QAM	14	861.00 MHz	0.10 dBmV	34.48 dB	83281	2831
16	Locked	256QAM	15	867.00 MHz	-0.40 dBmV	34.35 dB	121472	3055
17	Locked	256QAM	16	873.00 MHz	-0.20 dBmV	34.35 dB	106864	2151
18	Locked	256QAM	17	879.00 MHz	-0.40 dBmV	34.35 dB	101284	2164
19	Locked	256QAM	18	885.00 MHz	-0.10 dBmV	35.08 dB	63932	2240
20	Locked	256QAM	19	891.00 MHz	-0.80 dBmV	34.35 dB	95436	3125
21	Locked	256QAM	20	897.00 MHz	-1.60 dBmV	33.49 dB	125114	3167
22	Locked	256QAM	22	909.00 MHz	-3.50 dBmV	32.24 dB	13440855	79337484
23	Locked	256QAM	23	915.00 MHz	-3.90 dBmV	31.99 dB	15245735	95548338
24	Locked	256QAM	24	921.00 MHz	-4.70 dBmV	31.34 dB	15191205	95274441
25	Locked	256QAM	25	927.00 MHz	-4.80 dBmV	31.60 dB	5004	65560
26	Locked	256QAM	26	933.00 MHz	-5.20 dBmV	31.20 dB	731324	2717
27	Locked	256QAM	27	939.00 MHz	-6.50 dBmV	29.70 dB	1770157	2384
28	Locked	256QAM	28	945.00 MHz	-7.40 dBmV	29.30 dB	5257792	2836
29	Locked	256QAM	29	951.00 MHz	-7.40 dBmV	29.10 dB	7923058	1914
30	Locked	256QAM	30	957.00 MHz	-6.90 dBmV	29.50 dB	3769993	3038
31	Locked	256QAM	31	963.00 MHz	-7.50 dBmV	29.10 dB	7501271	2645
32	Locked	256QAM	32	969.00 MHz	-7.70 dBmV	28.90 dB	22142363	1727

Upstream Bonded Channels
Channel	Lock Status	US Channel Type	Channel ID	Symbol Rate	Frequency	Power
1	Locked	ATDMA	1	5120 kSym/s	19.10 MHz	38.00 dBmV
2	Locked	ATDMA	6	2560 kSym/s	14.30 MHz	38.50 dBmV
3	Locked	ATDMA	4	5120 kSym/s	38.40 MHz	39.50 dBmV
4	Locked	ATDMA	3	5120 kSym/s	32.00 MHz	39.00 dBmV
5	Locked	ATDMA	2	5120 kSym/s	25.60 MHz	39.00 dBmV

Any insight into how to further troubleshoot would be greatly appreciated.

Thanks!

 

[bill001g]

You should not need a moca filter unless you actually run moca in your house. Now a neighbor could be injecting moca into the network but that would mess up everyone around you, still moca is designed to coexist with most cables systems.

What looks bad is power levels. The indivual numbers are not way out of range but generally you see all of them about the same value. In your case you have a bunch with positive db and a bunch with a similar negative db.

There is not much you can do this is many times outside your house. All you could try is to replace any cables in your house. I would connect the modem as close as possible to where the cable comes in with no splitters and see if the numbers are any different.

You might see errors in the log also but again there is not much you can do about it the ISP needs to fix it.

 

[SamirD]

^^^^ All of that
and then also ask your isp for service credits. I had the same problem start at one of my sites and got a 15% credit just for asking.

 

[wptlrn]

Thank you!

I just plugged in a new modem, have been using it for about 15-30 minutes, and the connection seems to be better--see screenshot here. Could it just be that the modem, which was purchased in 2018, needs to be replaced?

If the issue comes back, I will definitely try plugging in the modem closer to the source. It's an old house (relatively new to us) and I wouldn't be surprised if the cabling is janky.

 

[kanewolf]

Thank you!

I just plugged in a new modem, have been using it for about 15-30 minutes, and the connection seems to be better--see screenshot here. Could it just be that the modem, which was purchased in 2018, needs to be replaced?

If the issue comes back, I will definitely try plugging in the modem closer to the source. It's an old house (relatively new to us) and I wouldn't be surprised if the cabling is janky.

Running a coax across the floor directly to the outside of the house is the best way to eliminate in-house coax.
Some of your channels have a -7db signal. That is kind of low. Your signal variability is also pretty wide (+7db to -7db). You could definitely have some in-house cabling problems.

 

[gggplaya]

You lose I think 3.5db of signal for every split in your house. So if you have a 2 way splitter, you lose 3.5db. If you have a 3 way splitter you lose 7db etc...

If you do not have cable TV, you should plug your cable modem directly into the line coming into the house. Leave out any splitters.

If you do have cable TV, get a 2 way splitter. Split the line coming into your house with 1 of those into your modem. For cable tv, you can split the other line with another multisplitter to all your outlets.

 

[kanewolf]

You lose I think 3.5db of signal for every split in your house. So if you have a 2 way splitter, you lose 3.5db. If you have a 3 way splitter you lose 7db etc...

You are correct. -3.5db per 2 way split. A 3 way split has ONE -3.5db port and TWO -7db ports. A 3 way or 4 way split can be thought of as stacked two way splits.

 

[wptlrn]

Thanks everyone. I investigated the lines in my basement and am reasonably confident there's no splitter. I've ordered a long new RG6 cable and will try directly connecting to the line coming into the house and will update this with the results.

 

[SamirD]

Keep in mind that you won't be able to fix marginal signal issues and really need the isp to fix that at the source. Your solution might work for a while and then when signal goes out of spec further, it will break again.

 

[gggplaya]

Thanks everyone. I investigated the lines in my basement and am reasonably confident there's no splitter. I've ordered a long new RG6 cable and will try directly connecting to the line coming into the house and will update this with the results.

This is all you can do. Like SamirD says, if what you've down here doesn't fix the problem. The rest is all up to the ISP to fix.

 

[wptlrn]

So I've now attached a new RG6 cable directly to the line coming into the house. (It's actually slightly attenuated, as the line coming into the house is first routed to another section of the basement to ground the line, before making a u-turn back to the initial point of entry, at which point it's connected to the internal wiring that goes through the wall into my office, which is on the second floor. It's that latter connection that I disconnected. Now, as a temporary measure, the line goes through the window to connect my modem with the grounded line.)

It's been nearly 24 hours and my signals now look like this. The 800 MHz signals are still significantly lower than the 400 MHz ones, but in both absolute and relative terms things seem to have improved. Certainly, the internet connection has been stable. Safe to say this is evidence that the main culprit was the interior cabling? Or, do these figures suggest that there are still issues that might still eventually cause problems?

Thanks everyone for all your help so far!

 

[bill001g]

Now you have me very confused. This almost looks like a different internet connection.

The first is using 32 channels and the second is using 24 channels. The first group of channels are the same but then one modem uses 900mhz and the other 300/400 mhz.

This in some ways would be what I would suspect if a ISP supported different types of docsis connections. What is also strange is the signal levels on the first group of channels is much less it should be better if there is less cable. The number overall are a little better because they are closer but the ones that go to -10 are marginal.

So maybe explain again what you changed.

 

[wptlrn]

Now you have me very confused. This almost looks like a different internet connection.

The first is using 32 channels and the second is using 24 channels. The first group of channels are the same but then one modem uses 900mhz and the other 300/400 mhz.

This in some ways would be what I would suspect if a ISP supported different types of docsis connections. What is also strange is the signal levels on the first group of channels is much less it should be better if there is less cable. The number overall are a little better because they are closer but the ones that go to -10 are marginal.

So maybe explain again what you changed.

Yes, I've changed a few things since the OP.

1. Installed a new modem. Previous one was Arris SB6190. Now I am trying a Motorola MB7621.

2. Removed an amplifier that a Cox tech had previously installed to try to ameliorate the problem.

3. Installed a new RG6 cable to replace in-wall cabling. Now the setup looks like this: Cox's outside line to a basement wall hole <connector 1> line running through basement wall hole to ground block in other part of basement <ground block 2> line back to outside through basement wall hole <connector 3> new RG6 line to modem through second floor window. (Connectors 1 and 3 are female-to-female connectors like this one. Ground block 2 is a ground block like this one. The only aspect of this setup I've changed is the last step. Previously, the line went from connector 3 BACK through the basement wall hole and then through the wall up to the second floor office's wall jack. Now, instead of making that u-turn, it goes up to the office through the window.)

 

[bill001g]

Maybe connect it back to the cable that is not running though the window just to see if you get a usable connection since re running the cable correctly is going to be some effort.

With this many things change it is hard to say which fixed it. The change in the radio frequencies alone is a big difference since cable tends to pass the lower frequencies better.

If you are getting the speed you pay for on the "new" modem using that modem is likley ok. Many times you need to use the ones with 32 channels if you are getting gigabit service from the ISP.

 

[gggplaya]

Those inline grounding blocks are fine, as long as it's not a multi-way splitter. The signal loss is negligible. The extra length looping down to the basement and back up should also be negligible as longs as it's really copper. If it's CCA cable, I don't know, I personally don't use the stuff, but even that should be ok.

 

[SamirD]

So I've now attached a new RG6 cable directly to the line coming into the house. (It's actually slightly attenuated, as the line coming into the house is first routed to another section of the basement to ground the line, before making a u-turn back to the initial point of entry, at which point it's connected to the internal wiring that goes through the wall into my office, which is on the second floor. It's that latter connection that I disconnected. Now, as a temporary measure, the line goes through the window to connect my modem with the grounded line.)

It's been nearly 24 hours and my signals now look like this. The 800 MHz signals are still significantly lower than the 400 MHz ones, but in both absolute and relative terms things seem to have improved. Certainly, the internet connection has been stable. Safe to say this is evidence that the main culprit was the interior cabling? Or, do these figures suggest that there are still issues that might still eventually cause problems?

Thanks everyone for all your help so far!

Well, you have zero correctables and uncorrectables so that's super. Now I'd run packetlosstest.com and see if you have any more loss. If not, run fast.com and dslreports.com/speedtest and if those are okay then I think you've found the culprit.