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OFrabjousDay
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4 Messages

Friday, April 15th, 2022 5:41 PM

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Frequent Downstream Errors & Very High Uncorrectable Codewords

My service has been fluctuating between excellent and awful lately. I have the Netgear CM1000v2 modem with DOCSIS 3.1 and I'm on the 600 Mbps plan.

The downstream OFDM channel seems to have power levels that go up and down significantly. The Uncorrectable Codewords are very high at times when I notice a problem, and low when things are fine. Logs show many instances of CM-Status code 1, 4, 5 - along with 21 and 23. It's very obvious when errors are happening because the mouse pointer on my remote work session skips around and is sluggish (VMware horizon).  Also, I get a lot of buffering and disconnects when streaming  video.

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3 years ago

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CCGina

Official Employee

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800 Messages

3 years ago

Hi @OFrabjousDay!

 

Sorry to hear about the lagginess you're seeing! You sound like you're pretty comfortable with tech, but just to cover all the bases, is the coaxial cable unkinked and unbent? Are the connections at either end snug, but not super tight? Is there a splitter on the line inside? Do you see any damage, fraying or corrosion on connections?

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OFrabjousDay

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4 Messages

@XfinityGina​ Hi, there is a home run from the entry point in my attic to the cable modem.  Everything is tightly connected and there are no splitters.

3 years ago

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CCGina

Official Employee

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800 Messages

I appreciate you checking! It's one of the easier things to rule out as a first step :) 

 

Are you using a separate router with the CM1000v2? Or are the downstream errors and uncorrectables happening while hardwired? You also mentioned remote work, do you use a VPN? If you're using one or both of those, can you let us know if the same issues occur if the router and/or VPN are removed from the equation? 

I no longer work for Comcast.

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Official Employees are from multiple teams within Xfinity: CARE, Product, Leadership.
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3 years ago

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OFrabjousDay

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4 Messages

The CM1000V2 is modem only and I have Google Wifi setup in the house.  I have tested from wired and wifi and that does not appear to be the issue.  When I have a problem, the power level on downstream OFDM drops significantly and SNR/MER drops drastically as well.  Not sure if this is a capacity issue, or a problem between the house and comcast, but nothing changes on my side that would explain the problem.  I thought I had posted statistics before, but here they are again.

Stats example when things are working:
Downstream Bonded Channels
Channel	Lock Status	Modulation	Channel ID	Frequency	Power	SNR / MER	Unerrored Codewords	Correctable Codewords	Uncorrectable Codewords
1	Locked	QAM256	5	549000000 Hz	3.8 dBmV	40.3 dB	249574076	0	0
2	Locked	QAM256	1	525000000 Hz	3.5 dBmV	38.4 dB	248454742	0	0
3	Locked	QAM256	2	531000000 Hz	3.7 dBmV	39.1 dB	248458441	0	0
4	Locked	QAM256	3	537000000 Hz	3.6 dBmV	39.9 dB	248462273	0	0
5	Locked	QAM256	4	543000000 Hz	3.5 dBmV	40.1 dB	248466191	0	0
6	Locked	QAM256	6	555000000 Hz	4.0 dBmV	40.5 dB	248469484	0	0
7	Locked	QAM256	7	561000000 Hz	3.8 dBmV	40.3 dB	248473893	0	0
8	Locked	QAM256	8	567000000 Hz	3.9 dBmV	40.4 dB	248477469	0	0
9	Locked	QAM256	9	573000000 Hz	3.5 dBmV	40.4 dB	248481547	0	0
10	Locked	QAM256	10	579000000 Hz	3.9 dBmV	40.3 dB	248485037	0	0
11	Locked	QAM256	11	585000000 Hz	3.6 dBmV	40.1 dB	248489192	0	0
12	Locked	QAM256	12	591000000 Hz	3.8 dBmV	39.8 dB	248492680	0	0
13	Locked	QAM256	13	597000000 Hz	3.9 dBmV	39.0 dB	248496501	0	0
14	Locked	QAM256	14	603000000 Hz	3.5 dBmV	39.8 dB	248500238	0	0
15	Locked	QAM256	15	609000000 Hz	3.4 dBmV	40.2 dB	248504049	0	0
16	Locked	QAM256	16	615000000 Hz	3.7 dBmV	40.4 dB	248507579	0	0
17	Locked	QAM256	17	621000000 Hz	3.6 dBmV	38.3 dB	248511295	0	0
18	Locked	QAM256	18	627000000 Hz	3.8 dBmV	33.3 dB	248515574	7	0
19	Locked	QAM256	19	633000000 Hz	3.6 dBmV	34.9 dB	248518568	181	0
20	Locked	QAM256	33	495000000 Hz	3.2 dBmV	40.1 dB	248523080	0	0
21	Locked	QAM256	34	507000000 Hz	3.3 dBmV	39.7 dB	248526721	0	0
22	Locked	QAM256	35	513000000 Hz	3.6 dBmV	40.3 dB	248517404	0	0
23	Locked	QAM256	36	519000000 Hz	3.6 dBmV	39.3 dB	248518046	0	0
24	Locked	QAM256	38	471000000 Hz	3.6 dBmV	40.6 dB	248501867	0	0
25	Locked	QAM256	39	477000000 Hz	3.6 dBmV	40.5 dB	248505840	0	0
26	Locked	QAM256	40	483000000 Hz	3.7 dBmV	40.5 dB	248509412	0	0
27	Locked	QAM256	41	489000000 Hz	3.5 dBmV	40.5 dB	248513117	0	0
28	Locked	QAM256	42	447000000 Hz	3.4 dBmV	40.5 dB	248515992	0	0
29	Locked	QAM256	43	453000000 Hz	3.7 dBmV	40.5 dB	248519746	0	0
30	Locked	QAM256	44	459000000 Hz	3.5 dBmV	40.4 dB	248523012	0	0
31	Locked	QAM256	45	465000000 Hz	3.7 dBmV	40.3 dB	248524895	0	0
32	Not Locked	Unknown	0	0 Hz	0.0 dBmV	0.0 dB	0	0	0

________________________________________
Upstream Bonded Channels
Channel	Lock Status	Modulation	Channel ID	Frequency	Power
1	Locked	ATDMA	1	35600000 Hz	41.5 dBmV
2	Locked	ATDMA	2	29200000 Hz	41.5 dBmV
3	Locked	ATDMA	3	22800000 Hz	41.3 dBmV
4	Locked	ATDMA	4	16400000 Hz	42.5 dBmV
5	Locked	ATDMA	5	39600000 Hz	39.0 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, 2, 3	37	762000000 Hz	1.4 dBmV	29.5 dB	1108 ~ 2987	16188675	15026223	764228
2	Not Locked	0	0	0 Hz	3.0 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

-------------------------------------------------------------------------------

Stats when things are not so great:

Procedure	Status	Comment
Acquire Downstream Channel	549000000 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	5	549000000 Hz	2.7 dBmV	39.7 dB	972416677	44	0
2	Locked	QAM256	1	525000000 Hz	2.8 dBmV	31.0 dB	971305240	19	0
3	Locked	QAM256	2	531000000 Hz	2.8 dBmV	33.3 dB	971314445	20	0
4	Locked	QAM256	3	537000000 Hz	2.7 dBmV	36.9 dB	971317851	56	0
5	Locked	QAM256	4	543000000 Hz	2.5 dBmV	38.6 dB	971320379	48	0
6	Locked	QAM256	6	555000000 Hz	2.8 dBmV	40.1 dB	971325169	18	0
7	Locked	QAM256	7	561000000 Hz	2.7 dBmV	38.0 dB	971328293	57	0
8	Locked	QAM256	8	567000000 Hz	2.7 dBmV	38.8 dB	971330899	204	0
9	Locked	QAM256	9	573000000 Hz	2.0 dBmV	40.2 dB	971337061	256	0
10	Locked	QAM256	10	579000000 Hz	2.5 dBmV	38.3 dB	971339739	303	0
11	Locked	QAM256	11	585000000 Hz	2.3 dBmV	36.5 dB	971346598	414	0
12	Locked	QAM256	12	591000000 Hz	2.2 dBmV	33.2 dB	971348501	441	0
13	Locked	QAM256	13	597000000 Hz	2.2 dBmV	29.8 dB	971352099	1821	0
14	Locked	QAM256	14	603000000 Hz	1.9 dBmV	34.6 dB	971363266	310	0
15	Locked	QAM256	15	609000000 Hz	1.8 dBmV	40.1 dB	971370169	165	0
16	Locked	QAM256	16	615000000 Hz	1.8 dBmV	40.2 dB	971374204	166	0
17	Locked	QAM256	17	621000000 Hz	1.8 dBmV	30.3 dB	781784353	1274101	2031328
18	Not Locked	Unknown	0	0 Hz	0.0 dBmV	0.0 dB	0	0	0
19	Locked	QAM256	19	633000000 Hz	1.5 dBmV	0.0 dB	691007144	12429416	34754836
20	Locked	QAM256	33	495000000 Hz	2.7 dBmV	39.9 dB	971392622	47	0
21	Locked	QAM256	34	507000000 Hz	2.7 dBmV	36.5 dB	971394867	25	0
22	Locked	QAM256	35	513000000 Hz	2.9 dBmV	38.7 dB	971385782	12	0
23	Locked	QAM256	36	519000000 Hz	2.8 dBmV	33.5 dB	971386459	11	0
24	Locked	QAM256	38	471000000 Hz	3.1 dBmV	40.6 dB	971371385	10	0
25	Locked	QAM256	39	477000000 Hz	3.2 dBmV	40.6 dB	971376040	15	0
26	Locked	QAM256	40	483000000 Hz	3.2 dBmV	40.7 dB	971379432	22	0
27	Locked	QAM256	41	489000000 Hz	2.9 dBmV	40.5 dB	971384313	27	0
28	Locked	QAM256	42	447000000 Hz	3.1 dBmV	40.5 dB	971388276	41	0
29	Locked	QAM256	43	453000000 Hz	3.3 dBmV	40.6 dB	971386818	760	3508
30	Locked	QAM256	44	459000000 Hz	3.1 dBmV	40.4 dB	883960120	536	2105
31	Locked	QAM256	45	465000000 Hz	3.3 dBmV	40.4 dB	971397857	37	0
32	Not Locked	Unknown	0	0 Hz	0.0 dBmV	0.0 dB	0	0	0

________________________________________
Upstream Bonded Channels
Channel	Lock Status	Modulation	Channel ID	Frequency	Power
1	Locked	ATDMA	1	35600000 Hz	41.5 dBmV
2	Locked	ATDMA	2	29200000 Hz	41.3 dBmV
3	Locked	ATDMA	3	22800000 Hz	40.8 dBmV
4	Locked	ATDMA	4	16400000 Hz	40.5 dBmV
5	Locked	ATDMA	5	39600000 Hz	39.3 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, 2, 3	37	762000000 Hz	2.5 dBmV	7.8 dB	0 ~ 4095	46593564	25158191	20875190
2	Not Locked	0	0	0 Hz	2.5 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

3 years ago

0

OFrabjousDay

Visitor

 • 

4 Messages

My work is not using a VPN connection.  It connects through a secure site using VMware Horizon.

3 years ago

0

CCGina

Official Employee

 • 

800 Messages

I appreciate the data, and the clarification on VMware Horizon, that's not a tool I've run across before. 

 

It sounds like the next step here is for us to look into our systems, so please send us a direct message, using the following instructions:

 

(Full credit to @BruceW for this excellent explanation and @Again for the picture!) 

"Search for Xfinity Support" won't work. To send a "Direct Messaging" message to Xfinity Support:

 • Click "Sign In" if necessary

 • Click the "Direct Messaging" icon:

 

 

or https://comca.st/3vnOvqQ

 • Click the "New message" (pencil and paper) icon

 • The "To:" line prompts you to "Type the name of a person". Instead, type "Xfinity Support" there

 •  - As you are typing a drop-down list appears. Select "Xfinity Support" from that list

 •  - An "Xfinity Support" graphic replaces the "To:" line

 • Type your message in the text area near the bottom of the window

 • Press Enter to send it

See https://comca.st/3Ocew5b for an example.

I no longer work for Comcast.

I am an Official Xfinity Employee.
Official Employees are from multiple teams within Xfinity: CARE, Product, Leadership.
We ask that you post publicly so people with similar questions may benefit from the conversation.
Was your question answered? Please, mark a reply as the Accepted Answer.tick

3 years ago

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