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JeepMatt
C'mon the U
Premium
join:2001-12-28
Wilmington, DE
kudos:2
Reviews:
·Verizon FiOS
·Comcast

High Error Count on Arris 722G

Previously our Arrist 722G rarely showed any errors on the Stats page.

However, for the past 2 weeks - I'm seeing a huge increase in errors across all 4 DS channels - in a 1 week period over 200,000 uncorrectables.

SNR and Signal levels remain in great condition, however these errors are really concerning me. I've tried hard rebooting, reconnecting all of the coax connections, but no matter what channel it locks on, the errors pop up almost instantly.

Thoughts?
--
"ONE team - ONE city - ONE dream!!"



koitsu
Premium,MVM
join:2002-07-16
Mountain View, CA
kudos:23

Screenshot please.



JeepMatt
C'mon the U
Premium
join:2001-12-28
Wilmington, DE
kudos:2
Reviews:
·Verizon FiOS
·Comcast

Click for full size
As you can see - this is in just 40 minutes of rebooting. Have tried 2 different Arris modems (had a backup left here) - both showing same symptoms.

Cables are tight at all locations.
--
"ONE team - ONE city - ONE dream!!"


gar187er
I do this for a living

join:2006-06-24
Dover, DE
kudos:4
reply to JeepMatt

when im out working on the main lines, the SECOND my screwdriver, or nut driver touches a seizure screw, it creates thousands of codeword errors....same if im tweaking on an amp's response board or change a pad....i wouldnt sweat it, cause its not really "high"...
--
I'm better than you!



EG
The wings of love
Premium
join:2006-11-18
Union, NJ
kudos:9

1 recommendation

reply to JeepMatt

The bottom line would be *are you actually having any connectivity issues* or just focusing on the modem stuff ?



telcodad

join:2011-09-16
Lincroft, NJ
kudos:5

said by JeepMatt:

Previously our Arrist 722G rarely showed any errors on the Stats page.

However, for the past 2 weeks - I'm seeing a huge increase in errors across all 4 DS channels - in a 1 week period over 200,000 uncorrectables.

SNR and Signal levels remain in great condition, however these errors are really concerning me. I've tried hard rebooting, reconnecting all of the coax connections, but no matter what channel it locks on, the errors pop up almost instantly.

Thoughts?

said by EG:

The bottom line would be *are you actually having any connectivity issues* or just focusing on the modem stuff ?

I think if I had seen the same thing, I'd be concerned too, even if I wasn't noticing any connectivity problems "yet."

I'd want to fix whatever may be degrading before it began causing problems.


EG
The wings of love
Premium
join:2006-11-18
Union, NJ
kudos:9

1 recommendation

Understood but his bit errors are very low (depending on the actual up time of the modem or if they were recently reset) in relation to the actual amount of *octets* so it may be *much ado about nothing*. Many times *stats* trigger false alarms and unnecessary worry to the observer especially if they are a non-techy / average home user type..



JeepMatt
C'mon the U
Premium
join:2001-12-28
Wilmington, DE
kudos:2
Reviews:
·Verizon FiOS
·Comcast

Click for full size
Well here's what they are after 5 hours -

On DS1 - they've gone from 66,379 to 834,000

Again, not really seeing any degrading of service - but when we used to see 0 if any uncorrected - it just caught my eye... and raised my concern.

There's almost a million on DS2, and ironically none on DS3.


telcodad

join:2011-09-16
Lincroft, NJ
kudos:5
reply to EG

said by EG:

Understood but his bit errors are very low (depending on the actual up time of the modem or if they were recently reset) in relation to the actual amount of *octets* so it may be *much ado about nothing*. Many times *stats* trigger false alarms and unnecessary worry to the observer especially if they are a non-techy / average home user type..

Even though the errors are relatively low, there was a sudden significant increase that may indicate that trouble is brewing.

It's similar to a PSA test for men. If the reading suddenly jumps up, after a long string of similar, lower readings, even if it is still below the concern threshold, that's usually not a good sign.


EG
The wings of love
Premium
join:2006-11-18
Union, NJ
kudos:9

This seems like it can turn in to a forever argument of *splitting hairs* telcodad See Profile.

I'm out !



koitsu
Premium,MVM
join:2002-07-16
Mountain View, CA
kudos:23

2 edits
reply to JeepMatt

Click for full size
Thanks for the screenshot. Despite what others say, I am of the opinion that the extremely high rate of uncorrectable codewords is a sign of a problem.

You say you aren't experiencing any issues, but chances are you probably are -- whenever this happens the individual frames have to be retransmitted back to the CMTS and even though that can happen very fast, sometimes it may take repeated attempts (which I can assure you is happening especially given such a high rate of UNCs!). So yes, you are impacted by this. Some degree of UNC is permitted -- but your rate is extreme (i.e. way outside the norm), which absolutely means there is something anomalous going on.

This may require a lot of work on your part I'm sorry to say -- I know for the issue I spent months dealing with (which did eventually get fixed, I really need to follow up on that and explain what all got done/etc.) -- but you should try rebooting your modem several times (literally 20-30 reboots are sometimes required) to see if you can get other negotiated frequencies.

See if you can figure out what specific frequencies show high amounts of UNC and others which do not. There may be a certain frequency range (or multiple ranges) that are affected, while others may not be. Write down which ones show high rates and which ones don't. This will probably take you a week or two, I'm sorry to say.

For my issue, I ended up writing a perl script that polled the modem via its web interface every 120 seconds + made use of dygraphs to accomplish [interactive] graphing of my SNRs on a per-frequency basis. I've attached a screenshot to show you what my issue looked like before, during, and after repair -- it's quite obvious when things got fixed (hint: mid-January). My issue was with 747MHz and higher (shown in that graph as magenta and teal colours), and the root cause was an internally degraded pair of cable runs between utility poles (the cable inside had somehow become degraded, as there was no visible damage externally). The "interference" itself in that frequency range is caused by a nearby LTE cellular tower (possibly repeater), either AT&T or Verizon (still not sure). Also FYI (WRT my issue): on May 21st Comcast for my area moved from the frequency range shown in my picture to 561MHz-603MHz. Cute timing...

The reason I mention this is that WRT the issue I experienced, I would see extreme bursts of UNC on channels/frequencies experiencing interference, while frequencies outside of that range saw the normal number of correctable codewords and acceptable UNCs. When the UNCs were incrementing, I would notice Youtube videos and other constant network I/O services (Youtube, Hulu, Netflix, torrents, or ANYTHING that kept a steady flow of network I/O going) stalling hard for 4-5 seconds, then recovering. It's tricky to diagnose because this kind of behaviour can manifest itself at a different layer unrelated to cable technology (i.e. packet loss at the IP/TCP level, high latency, Internet routing problems, etc.). So it takes some skill/familiarity to figure out root causes of such things.

If you know people in your neighbourhood (specifically people who live within a couple doors/houses next to you) who also have Comcast for their Internet connection, I would suggest talking to them and asking if you can use their computer to check out their cable modem. Takes about 30 seconds (if that) and you'll get an idea if the issue is isolated to you or not.

You need to get a maintenance tech (this is not the same thing as a "service technician" -- maintenance techs are sometimes called "network techs") out there looking at things with and actual metre. You may have someone on your node who is blasting crap/interference across specific frequency ranges. If there is such a customer, Comcast *will* address it (often by clipping/shutting off the nasty customers' connection).

P.S. -- The "Downstream Channel X" number means jack squat. It's just an incrementing index number; it's akin to saying "I have four apples, they are apple #1, apple #2...". The DCID and UCID (Downstream Channel ID and Upstream Channel ID) are just "channel numbers" (different than the index number), which also do not have any real relevance (I base this off of many conversations I've had with Comcast maintenance techs) -- it's just a "channel" number with regards to DOCSIS. What's is of relevance is the frequency, power, and SNR.
--
Making life hard for others since 1977.
I speak for myself and not my employer/affiliates of my employer.

harald

join:2010-10-22
Columbus, OH
kudos:1

1 recommendation

reply to JeepMatt

SNR, as reported by a modem, is just a mathematical calculation based upon the ratio of current correctable errors to the total packet count.

If the "SNR" is acceptable, then the packet errors are acceptable.



JeepMatt
C'mon the U
Premium
join:2001-12-28
Wilmington, DE
kudos:2
Reviews:
·Verizon FiOS
·Comcast

1 recommendation

Just to follow up on the thread -

Wrote my friends in the Executive Department - next day they called and they did say that they discovered issues in my area with errors on the modems.

Come back home a week later from the beach house - and now modem errors are 0 across the board.

So, there definitely was a problem (for those saying there wasn't)
--
"ONE team - ONE city - ONE dream!!"