Uncorrectable codewords but service is good

[toolcubed]

Hello community. I have an XB6 (bridged). From time to time, I log into the gateway to check stats and notice that the amount of uncorrectable codewords across many channels (not all) increases over time. After rebooting the gateway, they get cleared out and drop to 0…but after a while, they climb back up, with some channels showing thousands and some even tens of thousands of uncorrectable codewords. Again, it’s only on some channels. Most channels stay at 0.

With that said, I never have problems with my service. My connection never goes down (unless Rogers has a problem in the area impacting everyone) and my speeds are consistently high all the time. Power levels across all 32 channels and even the two OFDM channels are mostly around 0db (some are around +1db). SNR levels are all around 40db. Upstream levels look good too (40-41.8db on the four QAM channels and 37.7db on the OFDMA channel). Everything is rock solid. No connection or service issues whatsoever.

Any idea what could be causing the uncorrectable codewords, and why they’re not causing any issues? Should I be concerned even though I don’t have any problems with my service?

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@toolcubed wrote:

Hello community. I have an XB6 (bridged). From time to time, I log into the gateway to check stats and notice that the amount of uncorrectable codewords across many channels (not all) increases over time. After rebooting the gateway, they get cleared out and drop to 0…but after a while, they climb back up, with some channels showing thousands and some even tens of thousands of uncorrectable codewords. Again, it’s only on some channels. Most channels stay at 0.

Any idea what could be causing the uncorrectable codewords, and why they’re not causing any issues? Should I be concerned even though I don’t have any problems with my service?

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Uncorrectable codewords are indicative of RF impairments on the cable plant, and could be caused by any of a number of things (often noise ingress) anywhere on the signal path to your modem.  Uncorrectable codewords also equate to packet loss, so ideally you want your uncorrectables to be zero, or close to zero.

If I see a few uncorrectables, I don't worry about it too much.  Most network protocols will retransmit lost packets.  If uncorrectables occur too often, your network performance may suffer... noticeably.

I would also look to see at what rate the uncorrectable errors accumulate during the day, between morning and evening.  If you see a huge spike overnight, it could simply be due to maintenance activity in your area.  If you see a huge number of uncorrectables accumulating over the course of the day, you should ask Rogers to investigate, and also ask them to check to see whether it is just your connection or whether your neighbours are affected as well.

[toolcubed]

Thanks. Now that you mention packet loss, there’s almost always packet loss on my neighbourhood’s CMTS. It’s been that way for years, and when I told Rogers about it when I first noticed it (years ago), they refused to do anything about it. I tried escalating it several times without any luck. Interestingly, it hasn’t caused any noticeable problems for me, but now I’m wondering if that’s the source of my uncorrectables.