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For about one year now, I've had an Arris SB8200 cablemodem and Cox 300Mbps Internet tier, and this has worked esssentially flawlessly in that time. I've had Cox Internet even longer with very few issues - until about two days ago.
I noticed decreased download speeds, and when I logged into my account, I was notified that an "issue" in my area was detected, and I assumed my speed issue would be resolved when the issue was solved. About two hours later, the issue was clear, but my Internet speeds were still decidedly abnormal. I then noticed that the middle-two lights on the front panel of the cablemodem indicated the *downstream* connection was DOCSIS 3.1 (bonded downstream), colored blue, but the *upstream* light was now *green*, indicating only DOCSIS 3.0. This is a change from the previous behavior in which both up and down lights were bonded (blue).
That was two days ago. The problem has persisted, across multiple reboots of my cablemodem, and reboots of the firewall appliance that receives the Ethernet out from the cablemodem. I contacted Cox and they said the signal looked clear, but they agreed that my struggle to reach 200Mbps (usually topping out around 170-190) is not consistent with the 300Mbps service tier. They went so far as to re-provision the modem, all to no avail.
I took a look at my cablemodem serivce page, and it shows that the upstream channels hover between 39.0 and 42 dBmV. I found that Arris states the required upstream signal must be between 45-55 dBmV.
A bit of Googling has revealed a bit of warfare normally has to be undertaken to get Cox to increase power to the upstream channels, which is precisely what the Arris tech support rep told me when I reached out to them for assistance (cablemodem is only one year old and under warranty). He flatly stated the ISP must increase channel strength. Excerpt of my upstream channel status listed below:
I traced the line all the way back to the Cox input, eliminating an intermediate cable in the attic, and directly attached the Cox coax to the cablemodem and powered it up - no difference - bonded down, unbonded up. This means the signal to the modem from Cox is too low. But if I know from research Arris says Cox has to increase power, but Cox will refuse, what on earth do I do? Go out and drop another $200 on a new/different cablemodem?
Any suggestions appreciated.
SoonerDave said: This is a change from the previous behavior in which both up and down lights were bonded (blue).
Cox doesn't use DOCSIS 3.1 for upstream. There is no OFDM channel on the upstream, only the downstream. Must have been a glitch with the modem.
SoonerDave said: I found that Arris states the required upstream signal must be between 45-55 dBmV.
Says a Arris Tier 1 rep. not official. IMO the sweet spot for upstream is 42, which you are near. If anything, it should be a tad lower.
Can you show your downstream power levels too?
...probably just meant "bonded" upstream.
No, wasn't just what the rep said, their docs said the same thing. And this modem had both lights blue for the year I've had it up and running until the last few days, when the slow issues started. Maybe I'm crazy and wrong, but I find it hard to believe that's purely coincidental.