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Interpreting "cm error codewords"

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Interpreting "cm error codewords"

How are you supposed to interpret the "CM Error Codewords" table on the DPC3941T Cisco gateway? There are 24 columns. Do they represent the past 24 hours of activity, one column per hour? Or do they correlate to 24 columns in the "downstream" table thats above the codewords table? 

 

Also how bad are correctable codeword errors? Will they affect the application thats streaming data? For example last night while watching youtube on my TV it paused and displayed "loading" several times. I also notice a lot of correctable (but no uncorrectable) codewords in that table in columns 1 and 18-24.

Expert

Re: Interpreting "cm error codewords"


@chuckh1958 wrote:

How are you supposed to interpret the "CM Error Codewords" table on the DPC3941T Cisco gateway? There are 24 columns. Do they represent the past 24 hours of activity, one column per hour? Or do they correlate to 24 columns in the "downstream" table thats above the codewords table? 

 

The amount you see per column is individual for that corresponding channel, not for any period of time. They are cumulative from the time that a modem is first powered up until a re-boot (manual or spontaneous) of the modem occurs.

 

Also how bad are correctable codeword errors? Will they affect the application thats streaming data? For example last night while watching youtube on my TV it paused and displayed "loading" several times. I also notice a lot of correctable (but no uncorrectable) codewords in that table in columns 1 and 18-24.

 

The correctable errors aren't really a problem as they have been corrected but they can be used as a reference to a connection / communication problem that is going on if they are numerous. The uncorrectable errors are the fatal ones. The more numerous that they are, the worse the impairment is.


Please post a screenshot of the *Downstream Power Level*, the *Upstream Power Level*, and the *SNR* (Signal to Noise Ratio) numbers including all of the columns of those bit errors.




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Re: Interpreting "cm error codewords"

Thanks for answering my question, Will the correctable errors correct fast enough that I wont see a streaming video hang and display "loading"?

 

I have another question too that you may be able to answer. The manual for the DPC3941T says it supports management both by telnet and ssh but I've not been able to connect to it either way. Is it using non-standard ports for those protocols?  I'd like to use acommand line interface to schedule regular reboots as my problems go away for a few days after a reboot.

 

Anyway here's the up/downstream number.

 

Downstream

Index

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

Lock Status

Locked

Locked

Locked

Locked

Locked

Locked

Locked

Locked

Locked

Locked

Locked

Locked

Locked

Locked

Locked

Locked

Locked

Locked

Locked

Locked

Locked

Locked

Locked

Locked

Frequency

519 MHz

495 MHz

501 MHz

513 MHz

525 MHz

531 MHz

537 MHz

567 MHz

573 MHz

579 MHz

585 MHz

591 MHz

597 MHz

603 MHz

609 MHz

615 MHz

621 MHz

633 MHz

639 MHz

645 MHz

651 MHz

657 MHz

675 MHz

681 MHz

SNR

40.946 dB

40.946 dB

40.366 dB

40.366 dB

40.366 dB

40.946 dB

40.366 dB

40.366 dB

40.946 dB

40.366 dB

40.366 dB

40.366 dB

40.946 dB

40.366 dB

40.366 dB

40.366 dB

40.366 dB

40.366 dB

40.366 dB

40.946 dB

40.366 dB

40.366 dB

40.366 dB

40.946 dB

Power Level

4.800 dBmV

4.900 dBmV

4.700 dBmV

4.600 dBmV

4.600 dBmV

4.900 dBmV

5.000 dBmV

6.100 dBmV

5.600 dBmV

6.200 dBmV

6.100 dBmV

6.300 dBmV

6.000 dBmV

6.200 dBmV

6.500 dBmV

6.700 dBmV

6.400 dBmV

6.600 dBmV

6.700 dBmV

6.800 dBmV

6.200 dBmV

5.900 dBmV

6.100 dBmV

6.100 dBmV

Modulation

256 QAM

256 QAM

256 QAM

256 QAM

256 QAM

256 QAM

256 QAM

256 QAM

256 QAM

256 QAM

256 QAM

256 QAM

256 QAM

256 QAM

256 QAM

256 QAM

256 QAM

256 QAM

256 QAM

256 QAM

256 QAM

256 QAM

256 QAM

256 QAM

 

Upstream

Index

1

2

3

Lock Status

Locked

Locked

Locked

Frequency

30 MHz

23 MHz

36 MHz

Symbol Rate

5120 KSym/sec

5120 KSym/sec

5120 KSym/sec

Power Level

36.250 dBmV

35.750 dBmV

36.250 dBmV

Modulation

64 QAM

64 QAM

64 QAM

Channel Type

ATDMA

ATDMA

ATDMA

 

 

CM Error Codewords

Unerrored Codewords

2562612535

0

0

0

0

0

0

0

2558830182

2558835910

0

2558840366

2558842887

2558850947

2558853850

2558856061

2558860028

2558864776

2558874154

2558880360

2558883808

2558888206

2558893034

2558894267

Correctable Codewords

15

0

0

0

0

0

0

0

5

1

0

3

13

3

4

2

5

4

23

34

24

23

37

40

Uncorrectable Codewords

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

 

Expert

Re: Interpreting "cm error codewords"

The RF signal stats are fine. The correctable errors are very low (all depending on the last time the modem was re-booted). And no uncorrected errors.

 

AFAIK, the forward error correction works so fast that it should not affect streaming video. Although latency critical online gaming may be affected slightly.

 

AFAIK, you can't Telnet or SSH in to a straight cable modem. There are scripts that can be used for scheduling reboots. Google for info.

 

[edit]

 

O/k I see that you are using a combo gateway device. You should be able to telnet / SSH in to the router portion provided that the proper ports are open. Are you familiar with the PuTTy application for SSH via the LAN ? The gateway device has to have an SSH server.

 

Perhaps your buffering issue is being caused by a WAN network and / or remote server capacity / congestion issue ?

 

Is this with a WiFi connection ? If so, for a test, does a computer hardwired directly to the router / gateway device with an ethernet cable have the same problem ?



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Re: Interpreting "cm error codewords"

I'm using all WiFi for my network. The buffering issue generally occurs on a 50 inch TV and I really dont want to run an ethernet cable to it because its on the opposite end of the house and would be too much work. Needless to say I dont want to carry the TV to the gateway either Smiley Wink. I get good signal strength at the TV and bandwidth measured on my phone sitting next to it is around 60mb/s. I'm streaming HD which only requires about 5mb/s. There's nothing else in the house consuming bandwidth at the time either.

 

I am familiar with PuTTY but usually use the ssh command line in Cygwin (a Linux emulator on Windows).  I've tried to connect to the gateway with both and it times out. I've also tried telnet and that times out too. I've not been able to find anything in the built-in web-based gateway dashboard (http://10.0.0.1) to enable or disable ssh or telnet. The closest thing I've found is the ability to enable remote management via http or https but I have not turned that on. I shouldnt need to since I'm accessing the gateway from the LAN. 

 

I've not found any scripts online to reboot this gateway either. The only ways I've been able to do it is to pull the plug, press the reset button, or navigate the built-in web site to the reset button. 

 

Expert

Re: Interpreting "cm error codewords"


@chuckh1958 wrote:

I'm using all WiFi for my network. The buffering issue generally occurs on a 50 inch TV and I really dont want to run an ethernet cable to it because its on the opposite end of the house and would be too much work. Needless to say I dont want to carry the TV to the gateway either Smiley Wink.

 

O/k well then the definitive test can't be performed as to determine / narrow down whether this is a general connection to the Comcast system / internet at large, or whether it is a WiFi only problem..

 

I get good signal strength at the TV and bandwidth measured on my phone sitting next to it is around 60mb/s. I'm streaming HD which only requires about 5mb/s. There's nothing else in the house consuming bandwidth at the time either.

 

That may be so but it still could be a local WiFi  channel congestion / noise issue.

 

I've tried to connect to the gateway with both and it times out. I've also tried telnet and that times out too. I've not been able to find anything in the built-in web-based gateway dashboard (http://10.0.0.1) to enable or disable ssh or telnet.

 

It likely doesn't support it. Not many routers do let alone the Comcast gateways which are typically devoid of features / not at all robust.

 

 


 



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Re: Interpreting "cm error codewords"

Verizon routers support at least telnet. Not sure about ssh. 

 

I really doubt there's any channel congestion where I live. We live in the woods at least 100 yards from the nearest neighbor. I cant see any of my neighbors SSIDs when I look for available wireless networks either.