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Internet speeds have fallen off a cliff in the last 48 hours
Modem: Motorola MB8600 (firmware 8600-18.2.12)
Location: Lexington, KY
Starting about 48 hours ago, my normally stable speeds (as tested automatically by speedtest every few hours) have fallen off a cliff. I'm on the ultimate 500 package so my speeds normally are in the 480Mbps range. According to my logs, starting on the morning of 12 Nov, speeds began dropping until they bottomed-out at around 30Mbps around 6am on 13 Nov. Since then, they've oscillated between 30Mbps and 150Mbps (using wired ethernet). It's interesting to note that only downstream speeds have been affected. Upstream speeds have been rock-solid.
Of note is the weather: we had light rain starting early Friday morning through Saturday afternoon. The rain might not be related since the issue didn't appear until after the rain had mostly tapered off.
Here's a plot of the speedtest results (taken every 3 hours) where you can clearly see something happened starting Saturday morning.
Here's the corresponding ping loss statistics for that time period. This measures packet loss to the first hop upstream from me in Spectrum's network.
(Ignore the Sunday evening spike...that's an artifact of me rebooting the modem).
Of note from the ping loss plot is that we see very sporadic loss (1 packet per 60 sec) up until Saturday afternoon where we see a fairly frequent, though still minor, packet loss (1-2 packets per 60 sec). This maps pretty well to when the drop in speeds began...
Here is the corresponding downstream SNR plot:
And the corresponding downstream power plot:
Note: The SNR plot does not show the SNR values for the OFDM PLC channel since it's much lower than I anticipated when I created the logging database. I'll attach an image of the actual signal stats below. For the power plot, you can see all the QAM channels are grouped together and the OFDM channel is much weaker.
(Also, ignore the Sunday evening spike on the power plot. That's just an artifact of me rebooting the cable modem; the job that queries the modem's stats retrieved garbage for that interval). Neither the SNR nor Power plots appear to show any sudden events on Saturday that correspond to the gradual decrease in speeds.
Finally, here's a snapshot of the modem's signal level page:
The only thing of note is the OFDM PLC channel. In my experience, it has always had a much lower power level and SNR ratio than the QAM channels though in the past the OFDM power level has hovered in the range of 1-2dB. Now it's at 0.3dB. It's not clear to me whether this OFDM behavior is expected or not. The uncorrected error count could be the smoking gun, though.
On a whim, this morning I decided to connect my modem via an RG6 cable directly to the grounding block on the side of the house. So the modem is connected directly to Spectrum's cable outside and one of my computers is connected directly to the modem so I'm bypassing all the wiring and network gear inside the house. I then re-ran a wired speedtest. Results: 44.84Mbps down / 23.27 Mbps up. This seems to suggest that either the problem is the cable modem or something upstream from me.
Things I've tried:
- Rebooted the modem. No change.
- Rebooted the firewall. No change.
- Bypassed the house wiring and connected directly to the Spectrum cable outside. No change.