Dynamic range window violation

Hi thanks for the reply.

Just one splitter at the demarc on the attenuator is on the line, which all were installed recently by different technicians over the last two weeks. The rest of my coax is a home run from my demarc to my modem.

After yesterday's technician visit and the addition of new attenuators, I am still receiving the dynamic range window violations, but in addition now I'm getting t3 timeouts... 😵

Dynamic Range Window violations won't directly cause uncorrectable errors on your channels, but an overall problem might cause both DRW violations and uncorrectable errors. Uncorrectable errors are a downstream data transmission issue.

A dynamic range window violation is an upstream problem that happens when your modem sends a ranging request and then gets back a power level request for a channel is more than 12 dBmV above the lowest power level in the upstream channel set.

Basically, at least 2 times per minute, your modem asks the Cox system "how loudly should I transmit on each channel?" If Cox comes back with numbers like 45, 44, 43, 41 then that's all good. But if it comes back and asks for numbers like 38, 36, 52, 39 that would be a dynamic range window violation because the highest value (52) is more than 12 above the lowest value (36).

I've tried to get someone to give me more information but so far I've had to learn all of this on my own while trying to troubleshoot my own problems. I don't know how bad a DRW violation is overall but it does seem like upstream data like video calls will glitch momentarily when a DRW violation happens. I think the DRW violation itself is probably caused by a momentary spike of noise on one of the upstream channels. Like I said I don't know this for sure but this makes sense based on what I've been learning.

When my connection was working well I would get two or three DRW violations per week at most. Then when my connection started to go bad, I was getting up to 40 DRW violations per hour. Now I'm getting T3 timeouts which is a more serious type of upstream issue that causes a complete interruption of data for a short time.

No one has been able to provide any real information about how serious DRW violations are, but I think of them as an early warning of problems that are going to get worse later.

I'll also say that two of your channels are at the highest recommended power level for 4 bonded channels (51 dBmv). Even though that's technically within spec, it leaves no room for error. Any little thing is going to send the power level above the recommended range. It's hard to get techs to understand that because they only look at the raw number, but that high of an upstream power seems like a developing problem. Some techs will also quote the highest power for a single channel which is 61 dBmV but if you're only using one channel you aren't getting your full upload speed so for the real modern world 51 dBmV is the maximum.

How often are you seeing this message? If you're seeing it a few times a week it's harmless. Every cable network is going to get a momentary glitch every now and then. If you're seeing it several times per hour you probably need Cox to check for intermittent noise on the line.

I also wish that we could get some details from Cox, but it seems like they prefer not to go into technical details on the forum. That leaves us to figure things out on our own. I wonder if these DRW violations are even important in DOCSIS 3.1. Take a look at this information:

8.3.3 Dynamic Range Window
The Dynamic Range Window defines a 12dB range of Transmit Power Levels for the CM to use for each of the channels in its Transmit Channel Set. The DRW is controlled by the CMTS and communicated to the CM in the RNG-RSP or in the TCC encodings of the REG-RSP-MP or the DBC-REQ message.

8.3.3.1 Dynamic Range Window When Operating with a DOCSIS 3.1 CMTS
The top of the DRW is defined as P1.6hi – P1.6load_min_set [DOCSIS PHYv3.1]. The CMTS manages the Dynamic Range Window for the modem, ensuring that the CM is not ranged at a value that would result in a violation of the Dynamic Range Window. If the CMTS commands the modem to use a transmit power level P1.6r_n, that would result in a violation of the Dynamic Range Window, the CM performs the commanded adjustment and indicates an error in the Bit 15 or 14 of the SID field of the RNG-REQ Messages.

8.3.3.2 Dynamic Range Window When Operating With a DOCSIS 3.0 CMTS
The top of the DRW is defined as Phi - Pload_min_set [DOCSIS PHYv3.0]. The CMTS manages the Dynamic Range Window for the modem. If the CMTS commands the modem to do something which would result in a violation of the Dynamic Range Window, the CM will reject or ignore the command.

In other words, under DOCSIS 3.0, a DRW violation would actually cause the cable modem to reject the ranging response and who knows what kind of problem that might cause. But with DOCSIS 3.1 the modem makes the adjustment anyway and then sends an information message back to the CMTS. But since it made the adjustment maybe there's no harm done.

In terms of what causes this message in the first place, my guess is a spike of upstream noise. But maybe it's not even that. Maybe it's completely harmless. In any case the DRW violation doesn't prevent the modem from doing what it's been requested to do. So maybe it doesn't matter at all.