Strange results after "upgrading" comcast service ("XB3"@240mbps --> "XB6"@600mbps)

[Dragaan]

Hello all.  This is a first post for me, and I figured this may be a good place to put it...  Anyway, here's the story:

I've always used testmy.net to test my internet speeds ever since discovering it many years ago.  I've always had Comcast, and each time they've given me more speed it would show up just fine on testmy.net, no matter how many times, either in a row or over time, that I tested (except for very rare anomalies).  Things were always stable.  Just recently we went to the comcast office to pay a bill and discuss our data cap (1TB...).  Actually, my father went there, so I'm not sure exactly how everything went, but he came back saying "i upgraded the plan for basically the same price, but now we get 600mbps and no data cap -- we just MUST use this new modem".  The new modem turned out to be the XB6 (monolithic, odd-looking device they now are calling an xFI gateway or something).  Our old device was what they called the XB3, and we were getting 240mbps, which was ALWAYS stable via ethernet.  Both devices also provide WiFi, but I'm the only one who doesn't use the WiFi - I ONLY use ethernet (I'm the only PC in the house).  Anyway, I plug their mysterious, mandatory modem in and voila!  721.6 mbps!  What an improvement!  I tested again and again, each time getting roughly 500-700, which I thought was odd since my speed had always been a rock solid # in the past, but I figured it was just due to us now having such a high speed that even a tiny drop during the test would now show up.  Either way, I was satisfied.  

Fast forward 1-2 weeks.  I had been periodically testing the connection since we got this new modem/plan, and even though things seemed stable at the start, I am now getting TOTALLY different results most tests.  Anywyere from 5mbps to 760, and all numbers in between.  At really off hours it'll show up near 700 on 1 or 2 of the US destinations and also the Toronto one (I'm in Chicago, btw), but Dallas has been getting worse and worse, to the point where now it's almost never showing 600-700 and almost always showing about 100-200 (and it's not uncommon to see <20).  Upload speeds are usually fine, as I only get 22-24 with my comcast.  During the day, esp prime time, it's much worse and more random across all of the fastest destinations for me.  I realize there are TONS of people staying home and using the internet with the whole covid-19 thing , but is this normal for everyone?  I mean, super prime time hours never seemed to affect my speed in the past (superbowl, etc).  Why would Dallas (by far the best destination for me theoretically and in the past) be giving me such horrible results?  Why is my connection showing up so poorly and so randomly when using this site ever since I swapped to this "XB6" modem?  Until/unless I can figure this out, I'd much rather just go back to the 240mbps plan if that way my connection is rock solid.  Anything more than that is just icing anyway, usually only benefiting me when downloading huge steam games....  

Oh, I'd also like to mention that literally every single other test on the internet gives me ~700mbps without fail.  Testmy.net is the only one producing these results, but it's the only site I have trusted in the past so (obviously) I don't know what to make of it.

I'm sorry for the wall o text, and I thank any of you who do read it all and try and help me.  This has been driving me nuts lately.

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PS - Here is a link showing the different comcast modems.- https://www.xfinity.com/support/articles/broadband-gateways-userguides

The ones I brought up, the XB6 and the XB3 are 2nd and 3rd from the top.  Also, I forgot to mention that after realizing my XB6 came with a "mobile hotspot" that set up a separate wifi network for "anyone with their own comcast plan" to use, I quickly disabled it (even though they said it shouldn't affect our personal network speeds...).  No change.  If anything, the results (esp Dallas) are even slower.

[Dragaan]

While skimming over the net, I did notice 1-2 other folks describe VERY similar stories (many talk about the wifi coverage/speed, but I have seen a few that describe very closely to what I'm saying with ethernet).  Unfortunately, I haven't seen any of these mention a reason or solution. ?

[Pgoodwin1]

Do some test my ping testing to the various test my test servers and post back with those results.

 

I do not know how stable you can expect your results to be using Ethernet in your house at this high ISP plan speeds.  If you’re not connected directly to the modem gateway then wiring length and quality may be coming into play. Outside your house, I don’t know how stable their system is either at those high speeds. My plan is a Charter (Time Warner) 200 Mbps plan and it varies about +/- 10 % typically Round 210 Mbps. That’s via wireless. The one computer I have that’s connected via Ethernet typically maxes out around 150 Mbps though. Not sure if that’s because my house cabling is CAT5E instead of CAT6.

[Dragaan]

I did a latency test the other day.  I'll post it here.  I also did a 6 hour, once-every-15-min test but I ended up restarting my pc without remembering to save the results.  I did glance at them when it was on like test 22 or something, and I noticed that very few of the tests (it was download only - from dallas) were in the 600-700 range (which is what i should be getting).  I recall seeing many tests that were under 100mbps, including one I glanced at that was 3.9mbps....

Every single time I test, including right now, Dallas gives absolutely the worst results, by far.  Again, this never happened in the last decade or so.  Only since this very recent plan/modem swap.  Until now it was rock solid and I'd get whatever result my plan was, be it 50mbps, 75mbps, 90, 120, or 240.

I also have noticed that, even with other sites (NY, Miami, etc), I get the worst results when I do a combined test.  Afterwards, if I click "express test - 200 MB", I can usually get a high speed result.  Right now I am getting 500-700mbps with the express test on NY and Miami after trying to do a combined test on them and only getting like 100 or 200 mbps.  This is just all very weird to me.  I've been so used to rock solid results for so long.... I wish I knew more about modern networking, etc...

Anyway, here's the latency result from yesterday:

[Dragaan]

I also seem to always get  60-90 MB/s (that's bytes) downloads on Steam if I download a large game.  All other "normal" speed tests give me ~700mbps at all times.  It's only testmy.net that's being weird, but I have trusted the site for so long so it is driving me crazy.  I mean, it SHOULD be the most accurate test just based on how it operates... ?

 

I'm sure most people, upon hearing that, would tell me not to worry as long as things seem to be "working".  Personally, it just doesn't jive with me at ALL if I suspect my ISP (comcast.....) is manipulating things by prioritizing packets/traffic  (Steam, netflix, etc,. esp during this time) or using throttling techniques, etc. Not without explicitly letting me know.  This service isn't cheap... (100+ per mo).  Ever since the open internet fiasco in the courts, we've just been holding these huge ISPs on their "scout's honor" to not do this type of thing...  

[Dragaan]

Btw, my modem/"gateway" is right next to my PC.  It's always connected via 3' cable.  I've always used 5e, but since this has been happening I've tested cat6 250mhz and cat6 550mhz as well (both also 3 feet), but results are always the same.  Always connected via ethernet, never wifi.

[mudmanc4]

@Dragaan ,with those speeds I might try turning on multi threading

[Dragaan]

I have tried multi-threaded.  Results are always garbled...  Mixed.  Right now every test I try, from every host (even multi-threaded), is basically random.  600+ (which is what I pay for and what, for a week or so, was always showing up) is now very rare - best results are usually 300-500ish.  100-200 very common.  Sub-100 not uncommon.  

 

Upload speed never really changes.  Comcast gives terrible upload speeds, though.  Was at 11mbps for what seemed like a decade.  Just now got bumped up to 22.

Oh well, I guess if you guys here are stumped then it's pretty hopeless.  Probably going to try my best to revert back to old plan (or at least device -- although they made it pretty clear I MUST use this new device with my new plan).  I just knew something was up when they actually forced their hardware on people. (for the first time ever)