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BruceSHoward
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Monday, March 23rd, 2020 9:00 AM

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Download speed suddenly dropped from 81 to 32 Mbps

Download speed suddenly dropped from approx. 80 MBPS to 30 MBPS on March 15, 2020.  Had Comcast tech on phone 3/22/2020 and he had me connect directly to my Netgear CM1000 cable modem.  I rebooted the modem (power down/power back up) and ran a speed test. Download speed was back up to 80....but about five minutes later it was back down to 30.  I don't know if the tech did anything on his end that helped in the short term but then was automatically reset.

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5 years ago

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darkangelic

Gold Problem Solver

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2K Messages

5 years ago

Do you live in a community affected by a shelter in place order to combat COVID-19? Could just be a lot of people at home or using public Xfinity WiFi eating up bandwidth. 

Did you try testing at different times of day (including late at night, when bandwidth use is lowest) to account for this? 

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BruceSHoward

Regular Visitor

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2 Messages

5 years ago

I ran an Xfinity Speed Test, with direct connection to the cable modem, at 0235 (2:35AM) and had a dowload speed of 32 mbps.  Prior to March 15th, 2020 I was always running at approx. 81 mbps.  I reviewed the trouble shooting advice and also performed a factory reset on my Netgear CM-1000 modem.  Here are the modem parameters:

Frequency start Value
This field below allows you to modify the frequency the cable modem start with its scan during initialization and registration. Enter the new start frequency and restart the cable modem for it to take effect.
Starting Frequency
Startup Procedure
Procedure Status Comment
Acquire Downstream Channel 663000000 Hz Locked
Connectivity State OK Operational
Boot State OK Operational
Security Enable BPI+
IP Provisioning Mode Honor MDD IPv6 only
Downstream Bonded Channels (Partial Service)
Channel Lock Status Modulation Channel ID Frequency Power SNR / MER Unerrored Codewords Correctable Codewords Uncorrectable Codewords
1 Locked QAM256 33 663000000 Hz -1.4 dBmV 38.4 dB 55758053 0 0
2 Locked QAM256 5 483000000 Hz 1.1 dBmV 29.5 dB 54077850 45 0
3 Locked QAM256 6 489000000 Hz 1.5 dBmV 33.0 dB 54081448 0 0
4 Locked QAM256 7 495000000 Hz 1.6 dBmV 41.0 dB 54085567 0 0
5 Locked QAM256 8 507000000 Hz 1.5 dBmV 41.4 dB 54089025 0 0
6 Locked QAM256 9 513000000 Hz 1.0 dBmV 41.5 dB 54092736 0 0
7 Locked QAM256 10 519000000 Hz 0.7 dBmV 41.4 dB 54096256 0 0
8 Locked QAM256 11 525000000 Hz 1.3 dBmV 38.3 dB 54100617 0 0
9 Locked QAM256 12 531000000 Hz 1.1 dBmV 38.4 dB 54104463 0 0
10 Locked QAM256 13 543000000 Hz 0.7 dBmV 38.4 dB 54108257 0 0
11 Locked QAM256 14 549000000 Hz 0.9 dBmV 42.2 dB 54106326 0 0
12 Locked QAM256 15 555000000 Hz 1.1 dBmV 42.7 dB 54110072 0 0
13 Locked QAM256 16 561000000 Hz 0.8 dBmV 42.4 dB 54113523 0 0
14 Locked QAM256 17 567000000 Hz 1.3 dBmV 29.1 dB 54114354 3273 0
15 Locked QAM256 18 573000000 Hz 2.2 dBmV 31.2 dB 54120865 23 0
16 Locked QAM256 19 579000000 Hz 1.9 dBmV 38.8 dB 54124636 0 0
17 Locked QAM256 20 585000000 Hz 2.0 dBmV 42.5 dB 54128405 0 0
18 Locked QAM256 21 591000000 Hz 2.0 dBmV 42.2 dB 54131933 0 0
19 Locked QAM256 22 597000000 Hz 2.6 dBmV 42.1 dB 54135874 0 0
20 Not Locked Unknown 0 0 Hz 0.0 dBmV 0.0 dB 0 0 0
21 Locked QAM256 24 609000000 Hz 2.1 dBmV 32.5 dB 54139492 0 0
22 Locked QAM256 25 615000000 Hz 0.9 dBmV 40.9 dB 54143821 0 0
23 Locked QAM256 26 621000000 Hz 1.5 dBmV 40.7 dB 54146941 0 0
24 Locked QAM256 27 627000000 Hz 1.6 dBmV 40.3 dB 54150963 0 0
25 Locked QAM256 28 633000000 Hz 0.7 dBmV 39.9 dB 54154814 0 0
26 Locked QAM256 29 639000000 Hz 0.6 dBmV 39.7 dB 54156960 0 0
27 Locked QAM256 30 645000000 Hz 0.5 dBmV 39.4 dB 54160893 0 0
28 Locked QAM256 31 651000000 Hz 0.0 dBmV 39.0 dB 54164392 0 0
29 Locked QAM256 32 657000000 Hz -1.3 dBmV 38.5 dB 54168363 0 0
30 Locked QAM256 34 669000000 Hz -1.5 dBmV 38.2 dB 54171919 0 0
31 Locked QAM256 35 675000000 Hz -1.2 dBmV 37.8 dB 54174162 0 0
32 Locked QAM256 36 681000000 Hz -2.1 dBmV 37.7 dB 54174204 1 0
Upstream Bonded Channels
Channel Lock Status Modulation Channel ID Frequency Power
1 Locked ATDMA 1 30100000 Hz 46.0 dBmV
2 Locked ATDMA 2 36500000 Hz 45.5 dBmV
3 Locked ATDMA 3 17300000 Hz 45.5 dBmV
4 Locked ATDMA 4 23700000 Hz 46.0 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, 1 159 722000000 Hz 0.0 dBmV 36.3 dB 1126 ~ 2969 47168592 2468142 0
2 Not Locked 0 0 0 Hz -3.4 dBmV 0.0 dB 0 ~ 4095 0 0 0
Upstream OFDMA Channels
Channel Lock Status Modulation / Profile ID Channel ID Frequency Power
1 Not Locked Unknown 0 0 Hz 0 dBmV
2 Not Locked Unknown 0 0 Hz 0 dBmV

 

and the event log, following a factory reset:

Time Priority Description
2020-03-25, 07:55:30 Notice (6) CM-STATUS message sent. Event Type Code: 24; Chan ID: 159; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: 1.;CM-MAC=14:59:c0:75:e1:e8;CMTS-MAC=00:59:dc:79:f7:24;CM-QOS=1.1;CM-VER=3.1;
2020-03-25, 07:55:02 Notice (6) CM-STATUS message sent. Event Type Code: 16; Chan ID: 159; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: 1.;CM-MAC=14:59:c0:75:e1:e8;CMTS-MAC=00:59:dc:79:f7:24;CM-QOS=1.1;CM-VER=3.1;
2020-03-25, 07:48:00 Notice (6) CM-STATUS message sent. Event Type Code: 2; Chan ID: 23; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: N/A.;CM-MAC=14:59:c0:75:e1:e8;CMTS-MAC=00:59:dc:79:f7:24;CM-QOS=1.1;CM-VER=3.1;
2020-03-25, 07:48:00 Notice (6) CM-STATUS message sent. Event Type Code: 1; Chan ID: 23; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: N/A.;CM-MAC=14:59:c0:75:e1:e8;CMTS-MAC=00:59:dc:79:f7:24;CM-QOS=1.1;CM-VER=3.1;
2020-03-25, 07:47:59 Warning (5) MDD message timeout;CM-MAC=14:59:c0:75:e1:e8;CMTS-MAC=00:59:dc:79:f7:24;CM-QOS=1.1;CM-VER=3.1;
2020-03-25, 07:47:56 Notice (6) CM-STATUS message sent. Event Type Code: 4; Chan ID: 23; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: N/A.;CM-MAC=14:59:c0:75:e1:e8;CMTS-MAC=00:59:dc:79:f7:24;CM-QOS=1.1;CM-VER=3.1;
2020-03-25, 07:47:49 Notice (6) CM-STATUS message sent. Event Type Code: 5; Chan ID: 23; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: N/A.;CM-MAC=14:59:c0:75:e1:e8;CMTS-MAC=00:59:dc:79:f7:24;CM-QOS=1.1;CM-VER=3.1;
2020-03-25, 07:39:43 Notice (6) CM-STATUS message sent. Event Type Code: 2; Chan ID: 23; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: N/A.;CM-MAC=14:59:c0:75:e1:e8;CMTS-MAC=00:59:dc:79:f7:24;CM-QOS=1.1;CM-VER=3.1;
2020-03-25, 07:26:11 Warning (5) Dynamic Range Window violation
2020-03-25, 07:26:11 Warning (5) RNG-RSP CCAP Commanded Power Exceeds Value Corresponding to the Top of the DRW;CM-MAC=14:59:c0:75:e1:e8;CMTS-MAC=00:59:dc:79:f7:24;CM-QOS=1.1;CM-VER=3.1;
2020-03-25, 07:26:11 Warning (5) Dynamic Range Window violation
2020-03-25, 07:26:11 Warning (5) RNG-RSP CCAP Commanded Power Exceeds Value Corresponding to the Top of the DRW;CM-MAC=14:59:c0:75:e1:e8;CMTS-MAC=00:59:dc:79:f7:24;CM-QOS=1.1;CM-VER=3.1;
2020-03-25, 07:26:11 Warning (5) Dynamic Range Window violation
2020-03-25, 07:26:11 Warning (5) RNG-RSP CCAP Commanded Power Exceeds Value Corresponding to the Top of the DRW;CM-MAC=14:59:c0:75:e1:e8;CMTS-MAC=00:59:dc:79:f7:24;CM-QOS=1.1;CM-VER=3.1;
2020-03-25, 07:26:05 Notice (6) DS profile assignment change. DS Chan ID: 32; Previous Profile: ; New Profile: 1.;CM-MAC=14:59:c0:75:e1:e8;CMTS-MAC=00:59:dc:79:f7:24;CM-QOS=1.1;CM-VER=3.1;
Time Not Established Notice (6) Honoring MDD; IP provisioning mode = IPv6
Time Not Established Critical (3) No Ranging Response received - T3 time-out;CM-MAC=14:59:c0:75:e1:e8;CMTS-MAC=00:59:dc:79:f7:24;CM-QOS=1.1;CM-VER=3.1;
Time Not Established Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=14:59:c0:75:e1:e8;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;
Time Not Established Warning (5) Lost MDD Timeout;CM-MAC=14:59:c0:75:e1:e8;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;
Time Not Established Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=14:59:c0:75:e1:e8;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;
Time Not Established Warning (5) Lost MDD Timeout;CM-MAC=14:59:c0:75:e1:e8;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;
Time Not Established Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=14:59:c0:75:e1:e8;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;

 

Any help is greatly appreciated.

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EG

Expert

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111.6K Messages

5 years ago

The SNR is too low / out of spec on some of the downstream channels. Looks like there is some noise ingressing into the line(s) somewhere. It may be best to get a tech out to investigate its source and correct it. Good luck !

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