Jason wrote:

Recently, and I don't know if this is the fault of Windows or
of changes that Spectrum may have made, web surfing has slowed down. I
can watch the process in the corner of the screen when I click a link
and the steps that used to happen instantly take several seconds or
stall completely partway through. My system has also grown cranky
connecting to the net in the first place when the system boots.
Sometimes I have to disable and re-enable WiFi several times to get past
the "connected but no internet" problem. For fun(?), I tried disabling
IPv6 in network properties for the WiFi adapter. This has gone a good
way towards restoring performance. So, my questions a is IPV6
generally necessary and could disabling it have caused the performance
improvement I'm seeing or is that just a coincidence?

Have you yet tried tried temporarily disabling your anti-virus (and
other security) software and then test networking performance?

Have you enabled monitoring in some software and left it logging? I did
that once or twice with SysInternals' Process Monitor. Filtering only
changes what you see but everything still gets logged (and why you can
change the filters to see other events). As the log file got huge, it
was slowing the data bus with all the events getting appended to the
log.

Have you tried rebooting Windows into its safe mode w/networking and
test without loading all the startup programs?

Did you change the router/modem to use something /other/ than the
default login credentials and also use a strong password? If you have
not tweaked your router/modem, see what happens when you reset it. If
you have a separate router, AP, or other networking components between
the computer and the cable modem, run a CAT5/6 Ethernet cable directly
from the computer to the cable modem and retest performance.

From your description, it appears you are using wi-fi from computer to
the cable modem. See what happens when you use a wired connection
between computer and modem. Also, since you are using Windows 10, and
because Microsoft wants to push updates when they become available to
use their customers as involuntary unpaid beta testers, they might've
pushed a driver update but one that doesn't match your particular wi-fi
hardware but instead a family of products or for the wrong version of
the hardware. Make sure Windows 10 is configured to NOT push hardware
updates. If the wired connections works okay, check if using a driver
from the OEM or hardware maker specifically for the hardware that YOU
have gets wi-fi speed back to normal.

I don't know if Spectrum offers their own network speed test tool. If
not, you could use Speedtest.net. Then call Spectrum to get your cable
modem re-provisioned. I've once experienced myself and heard of several
others where the ISP re-provisioned their cable modem but pushed the
wrong attributes giving me and other a lower speed tier. They've also
screwed the TV decoder set-top box that gave me a lower service tier, so
I had to call them to check what plan to which I was subscribe and make
sure they re-provisioned the set-top box to honor for what I was paying.

Have you gone into the cable modem's diagnostics or tools to check what
all is connected to the modem? Maybe you've got a host that is choking
on download a huge amount of traffic, or there's a host connected to
your modem via wi-fi that you don't know about and haven't authorized.