Daily Periodic and Random Internet loss with a Motorola MT8733

Sorry for the novel here, but it gets old having to provide the history of what has been occurring every time I reach out to Xfinity support so I figured I would give the forum a try given the large number of customers experiencing the same/similar type of problems with Internet service.

I have been having random and now a periodic loss (every 12 hours) of Internet connectivity with a Motorola MT8733 modem.  After contacting support about this issue, a commercial service tech was sent to my house to verify the wiring along with the signal levels which were said to all be correct and that he didn’t know why I would be having this issue.  The only potential concern identified by the tech at the time was some uncorrected errors.  He said he would open a ticket to monitor my service for 10-days with a follow up call which I found never occurred during a subsequent call to tech support.  I mentioned that there are numerous reports of these types of problems online and in the forum and he indicated that the modem is approved for use and should not be a problem but that maybe I received a bad modem.  To rule this out I returned the modem and installed the replacement with no improvement.

After the visit by the tech, I stopped resetting the modem and let it self-recover to determine how long it was offline each time I lose Internet connectivity.  Since the onsite visit I have been running a program pinging the modem and a Google Public DNS IP every 10 seconds to generate a log of when my Internet service drops.  I also have been recording the power levels daily looking for any changes or values out of range.

Currently my modem drops the connection at 1AM and 1PM give or take a few minutes each day along with some random drops usually after I have made some change to my setup to determine if it has any effect.  I have contacted Xfinity support multiple times with no resolution.  Each time they refresh the signal and resync everything and ask me to see if the problem goes away which it never does.  Using the Chat in the App always leads to resetting the modem as the only option which I know does not correct the problem. During a recent support call I was told to contact Motorola to see if there were any settings that needed to be made for Xfinity. 

Yesterday I contacted Motorola tech support and after providing them my power levels and event log, and my home setup, they thought there might be an issue with the splitter on the incoming cable which has only about 3-5 feet of cable between it and the block at the service entrance to my house. I had a brand new one previously provided by Xfinity so I replaced it with no apparent improvement. After the change Motorola said, “The uptime on the modem is only 6 minutes and there are already corrected errors on the OFDM channel” Asking them what should be expected their reply was “On the OFDM channel you should have zero errors, but in 6-7 minutes you've got almost 1 million”.  They then asked if I had a wall plate which I do, and it has less than 8 feet of cable from it to the location in the basement where the splitter is.

I told the Motorola tech that I would move the modem to the basement to eliminate the wall plate from the picture.  They said that some levels might not be set correctly, not sure what they were referring to but needed an Event Log with a bigger uptime, something around 24 h.  After reviewing my event log Motorola said the following:

According to the errors from the logs, you have 16 & 24 event type codes, T3 timeout, and Dynamic Range Window Violation

Event Type Code 16 which is an intermittent spike in noise in the lines, and the subsequent Code 24 which is that noise resolving. 

Dynamic Range Window Violation essentially means the CMTS/Tap on the pole is trying to assign the modem bad information. The modem refuses. The CMTS/Tap on the pole forces the Modem to reboot.

T3 time-out occurs when your cable modem cannot effectively communicate with the ISP'S CMTS. The modem will send up-ranging requests to your ISP and display a “no ranging response received” error if the CMTS fails to respond. The cable modem is therefore resetting its cable interface and restarting the registration process. This typically is caused by noise on the upstream that causes the loss of MAC-layer messages.

I asked the tech that if after I move the modem to the basement, eliminating all customer wiring other than the 3-5 feet of cable from the service entrance to the input of the splitter and the 3 foot cable from the splitter to the modem and the problem still occurs if this confirms the issue is external to my house and their response was “I believe is something with their CMTS not communicating accordingly with your modem. But unfortunately, I can't figure out what is exactly so you will have to check again with a technician”

I’ve been running with this configuration since yesterday and like clockwork at 1:02PM yesterday and at 1:03AM this morning my Internet went down (usually lasts 5-7 minutes, occasionally longer).  After resetting the modem this morning to clear out some uncorrected errors that most likely were caused when moving the modem and reattaching cables, I took a screen capture of the power levels and within a few minutes the corrected errors were showing up on the OFDM channel that Motorola was concerned about.  I was monitoring these yesterday and they were occurring at an average rate of 234K/minute.

The issue appears to be with the infrastructure in my area not being able to handle the higher data rates and increased traffic from people working from home and streaming more data on the network.  I was upgraded to a 1.2Gbps plan last March which coincidentally seems to be when these types of problems may have started, only to get worse as time progressed.

I would think that a periodic loss of Internet connectivity would be something that could be monitored by Xfinity to try and get to the root cause, but all interactions with support to this point only result in a refresh and resync of the modem which obviously is not fixing the problem.

I’d really appreciate it if someone from Xfinity can contact me about this problem so that I can get it resolved. I can’t adjust my work schedule around the times when I know I’m going to lose connectivity or drop offline during meetings when the random events occur.