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gjett1's avatar
New Contributor III
6 years ago

Uncorrectables on ALL downstream channels. What could be the problem?

I live in Springfield, VA. I have a Netgear CM600 modem and have been receiving uncorrectables of hundreds of thousands and millions in a very limited uptime (< 24 hours). I am having this problem on every channel operating between 649-813MHz. The amount of uncorrectables varies, but is still very high for all of them.

Alongside this problem, I have been experiencing network instability and modem crashing about every hour or so.

Side note: I have tested a different modem (Arris SB6190) and have gotten the same, if not worse, results.

The event log for each modem has showed me a different combination of errors like:

-RCS Partial Service

-SYNC Configuration Time out

-Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out

-No Ranging Response received - T3 time-out

Cox Technical Support, including the technician who came into my house, said that everything on their side looked good (GREEN).

This problem arose after changing my Motorola SURFboard modem to something from this decade (ie. SB6190 and CM600) due to a small UPLOAD SIDE packet loss issue (1-3%) I was having while gaming online. Never any crashing until now.

Between the times when these errors occur in the event log, my internet is lightning fast (besides the upload packet loss issue still being present).

>These are the values for DOWNSTREAM with the Netgear CM600 at an uptime of around 90 minutes.

<tabindex=-1>Downstream Bonded Channels
Channel Lock Status Modulation Channel ID Frequency Power SNR Correctables Uncorrectables
1 Locked QAM256 3 687000000 Hz 9.1 dBmV 39.2 dB 214828 132675
2 Locked QAM256 1 675000000 Hz 9.3 dBmV 38.5 dB 65347 12412
3 Locked QAM256 2 681000000 Hz 9.6 dBmV 39.3 dB 92489 14832
4 Locked QAM256 4 693000000 Hz 9.3 dBmV 39.3 dB 219991 161237
5 Locked QAM256 5 699000000 Hz 8.8 dBmV 39.1 dB 232634 167674
6 Locked QAM256 6 705000000 Hz 8.5 dBmV 38.9 dB 231551 125552
7 Locked QAM256 7 711000000 Hz 8.4 dBmV 38.8 dB 206782 73208
8 Locked QAM256 8 717000000 Hz 8.1 dBmV 38.6 dB 159890 36191
9 Locked QAM256 17 771000000 Hz 8.7 dBmV 39.1 dB 37129 42243
10 Locked QAM256 18 777000000 Hz 8.8 dBmV 39.1 dB 30994 4741
11 Locked QAM256 19 783000000 Hz 8.9 dBmV 39.2 dB 24894 2178
12 Locked QAM256 20 789000000 Hz 8.4 dBmV 38.9 dB 22073 3062
13 Locked QAM256 21 795000000 Hz 7.9 dBmV 38.7 dB 15069 2258
14 Locked QAM256 22 801000000 Hz 7.5 dBmV 38.4 dB 12652 1561
15 Locked QAM256 23 807000000 Hz 7.2 dBmV 38.3 dB 20874 5991
16 Locked QAM256 24 813000000 Hz 7.8 dBmV 38.6 dB 58248 76267


<tabindex=-1>Upstream Bonded Channels
Channel Lock Status US Channel Type Channel ID Symbol Rate Frequency Power
1 Locked ATDMA 1 2560 Ksym/sec 17154000 Hz 44.5 dBmV
2 Locked ATDMA 2 5120 Ksym/sec 21984000 Hz 46.0 dBmV
3 Locked ATDMA 3 5120 Ksym/sec 28414000 Hz 47.0 dBmV
4 Locked ATDMA 4 5120 Ksym/sec 34844000 Hz 47.5 dBmV
5 Not Locked Unknown 0 0 Ksym/sec 0 Hz 0.0 dBmV
6 Not Locked Unknown 0 0 Ksym/sec 0 Hz 0.0 dBmV
7 Not Locked Unknown 0 0 Ksym/sec 0 Hz 0.0 dBmV
8 Not Locked Unknown 0 0 Ksym/sec 0 Hz 0.0 dBmV

(I assume that I do not have the option for 8 Upstream channels because the Arris SB6190 did not even list the last 4 channels)

Could this problem possibly be inside my home?

The technician took out a splitter from my setup and placed my internet cable on a splitter with an amplifier. The problem does not seem to have changed though.

I have another, higher-level, technician coming in 2 days. Is there anything that I can show them to help pinpoint the problem?

  • gjett1 Actually, I think the best people to contact would be the AWS customer, which is the gaming company.  The trick will be to get the attention of upper management with specific details to support your case.  Otherwise, your complaint will likely be immediately filed in the "circular file" system. 

    Send a detailed letter via certified mail to a member or members (i.e. CEO, Senior VP).  It may help to select "restricted delivery" which means that either the addressee or an authorized agent for the addressee must sign.  That's an extra attention getter.  Otherwise, whoever normally gets the mail at the company will sign for it.  You don't need to pay extra for a return receipt unless you want to.

    If that fails, then file an online complaint with the Better Business Bureau (BBB) against the gaming company and reference your certified letter(s).

    How does that sound to you?

  • gjett1 Oh, I see now.  The Motorola SB6121 was only a 4x4 modem, while the Netgear CM600 is a 24x8 modem and the Arris SB6190 is a 32x8 modem.  In your case, you appear to have gone from 4 downstream channels to 16 downstream channels.  Your connection doesn't appear to be handling the new total of 16 downstream channels very well. 

    I think you are correct when you stated that the issue now points at Cox side (facilities, cabling) after having tried 2 newer modems, both running 16 downstream channels, with the same result.  As an aside, I wonder if your SNRs are rather misleading because of the high downstream power levels.

    All the best in getting Cox to resolve it quickly during the next visit.

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  • Rob_H_'s avatar
    Contributor II

    For an uptime of only approx. 90 minutes, that's a fair amount of correctables and correctables on the downstream channels.  Not sure if you were "gaming" during that 90-minute window that would exacerbate the rate of codeword error accumulations.  The downstream power levels are a bit higher than what I'm accustomed to seeing.  It sounds like your older modem could handle the hotter downstream signal levels above 7 dBmV.

    BTW, with regard to your upstream packet loss that started it all, is the gaming server you're connected to located at Amazon Web Services (AWS)?

    • gjett1's avatar
      New Contributor III

      The game specifically is Fortnite. EpicGames definitely uses AWS for their servers.

      Edit: With regard to the gaming during this period. I do believe I tried a few matches to see if the packet loss issue was remedied (of course, it wasn't).

      Double Edit: I cannot believe I am just finding out about this upload packet loss problem between Cox and AWS

      How have they not acknowledged that yet?

      • Rob_H_'s avatar
        Contributor II

        gjett1In regards to gaming on the AWS servers, in a nutshell, we were able to isolate the problem to the AWS 54.239 (and possibly 52.239) network.  We found that by pinging with a packet size somewhere between 128 bytes and 256 bytes and higher, the packet loss began at the AWS 54.239 (and possibly 52.239) network when the source IP address originated from the Cox network.  When the same test was run using a T-Mobile hotspot, there was no packet loss observed.  The same lack of packet loss was reported by someone else using a VPN over their Cox connection.  This suggests to me that there is a Quality of Service (QoS) issue with the handling of the larger packets by the 54.239 (and possibly 52.239) networks at AWS when the source IP originated on Cox.  When the user connects using a T-Mobile hotspot or even a VPN over their Cox connection, the AWS 54.239 (and possibly 52.239) network sees a source IP address other than Cox and there is no packet loss observed.   The gaming companies are paying AWS to host their gaming applications and therefore AWS should promptly respond to and address demonstrated concerns presented by those companies.  This type of issue would be addressed by a Tier 3 type group or higher at AWS.

  • Rob_H_'s avatar
    Contributor II

    BTW, regarding your modem issues, it just occurred to me that the RF receive side of the new Netgear CM600 modem may not be as good as the older Surfboard modem or is defective and is, therefore, requesting that the Cox CMTS send higher signal levels downstream which it may have trouble handling since they are all over 7 dBmV.  Not sure, off the top of my head, what range of downstream power levels that new CM600 modem can properly handle.

    • gjett1's avatar
      New Contributor III

      Would a defective modem not be ruled out by similar values being shown with the SB6190 on the same system? Is two bad modems more likely than a problem on Cox's end?

      • Rob_H_'s avatar
        Contributor II

        gjett1 I see your point.  I may have overlooked that detail you originally included.    I'm now going back to my original thought of that older surfboard having a better RF receiver (i.e. better sensitivity, selectivity, noise floor) or that older surfboard modem didn't run 256 QAM on the downstream channels (i.e. 64 QAM).  Regardless, it sounds like there is some work to be done by Cox.  What model of surfboard did the CM600 replace?