Random Throttling

[Lincoln30TT]

Greetings,

Comcast Extreme 105 (130/25)
Arris 6121
Asus RT-AC66U

I have a RT-AC66U I’ve been using for about a year and a half. Over the past 6 months my WiFi speed on both bands has been throttled to 30/25 on 2.4m and 40/25 on 5g. In the past I was getting the same WiFi speeds as the wired speeds. I’ve tried a master reset, changing the channels using WiFi analyzer, only having one device on the network at a time, change the SSID and password, upgrading the firmware and nothing seems to change.

My thought was the router was on its way out so I picked up a RT-AC68U. Guess what, same issue. Can’t seem to get faster than 40/25 even with only one WiFi device connected. Wired speed is on point at 130/25 all day long.

I contacted Comcast to get some help and after they remoted into my network, they stated my modem was bad which is causing my poor WiFi speeds. This seems odd to me since my wired speeds from the modem are correct. I’m willing to buy a new modem, but after just dropping $150 on the 68U, I’m bit hesitant to spend another $120 on a modem.

Any ideas?

Thanks in advance!

 

[Klueless]

Well that's a bit perplexing ... especially after trying to isolate the problem and all. Six months ago? Did anything happen six months ago? Add a baby monitor, cordless phone or something like that? Of course that wouldn't really account for both 2.4 and 5 GHz but ... Did you relocate your equipment? Like closer to a microwave, next to your TV or under a metal shelf?

I see you used WiFi Analyzer and already changed channels as indicated. I assume WiFi analyzer is saying you've a great signal now?

I can see your reluctance to spend another $120 without at least trying to verify what Comcast told you. Instead of running an Internet speed test try running a speed test internal to your own network. I use NetStress but most would suggest iPerf. You load one copy on a PC anchored to Ethernet and load another copy on a laptop. You move your laptop from Ethernet to 5 GHz and then to 2.4 GHz recording your speeds as you go. Now if those speeds are crazy good as compared to your Internet speed tests and service levels then you might assume Comcast is correct and your modem is dropping more packets than not. If they're also crappy you might have some more local troubleshooting to do.

You might also try something called Ping Plotter. It does a tracert and then pings everything between you and the endpoint. It's purpose is to show where you're losing packets. It could be with a router that resides in the Comcast infrastructure or ... it just might point to your modem.

Good Luck!

 

[Lincoln30TT]

Well that's a bit perplexing ... especially after trying to isolate the problem and all. Six months ago? Did anything happen six months ago? Add a baby monitor, cordless phone or something like that? Of course that wouldn't really account for both 2.4 and 5 GHz but ... Did you relocate your equipment? Like closer to a microwave, next to your TV or under a metal shelf?

I see you used WiFi Analyzer and already changed channels as indicated. I assume WiFi analyzer is saying you've a great signal now?

I can see your reluctance to spend another $120 without at least trying to verify what Comcast told you. Instead of running an Internet speed test try running a speed test internal to your own network. I use NetStress but most would suggest iPerf. You load one copy on a PC anchored to Ethernet and load another copy on a laptop. You move your laptop from Ethernet to 5 GHz and then to 2.4 GHz recording your speeds as you go. Now if those speeds are crazy good as compared to your Internet speed tests and service levels then you might assume Comcast is correct and your modem is dropping more packets than not. If they're also crappy you might have some more local troubleshooting to do.

You might also try something called Ping Plotter. It does a tracert and then pings everything between you and the endpoint. It's purpose is to show where you're losing packets. It could be with a router that resides in the Comcast infrastructure or ... it just might point to your modem.

Good Luck!

First off, thank you for the reply and mostly your time.

To answer some of your questions; nothing has changed in the past 6 months. All hardware is the same and nothing has moved.

You are correct. WiFi analyzer says my signal/channel is spot on. I even tried changing the channels to 1,6 and 11 with no luck.

I did a makeshift LAN test using ES File Explorer and my NAS. I moved a 500mb video file across the network in 28 seconds. Which by my calculations puts my LAN at roughly 120mbps. Same test uploading to Google Drive and it took 133 seconds. I was moving that file at roughly 3.75mbps. Per your recommendation, I'm still going to use the tools you listed above this evening. I'll post the results tomorrow.

I'm still thrown off since my wired connection is fast and appears to be stable. Only have issues with external WiFi data... Very odd!

 

[Klueless]

I did a makeshift LAN test using ES File Explorer and my NAS. I moved a 500mb video file across the network in 28 seconds. Which by my calculations puts my LAN at roughly 120mbps. Same test uploading to Google Drive and it took 133 seconds. I was moving that file at roughly 3.75mbps.

I assume that was over the 5 GHz band? Your calculation confuses me. Transferring to google drive took about 5 times longer (133 / 28) so speed should be about 1/5th (20%) of the 120 Mbps number? Making this adjustment (120 / 5) suggests you were uploading at about 25 Mbps which is the speed you pay for (130/25) ...

BTW ... since you're using Asus are you learning anything from the Real Traffic Monitor? Like when you run an Internet Speed Test from an Ethernet node the chart should show you what it looks like "fully pegged" at 130/25. What's it look like when you run from 5 and 2.4 GHz?

And, I was remiss in asking, are all wireless clients giving you sub-optimal performance?

 

[Deleted member 22229]

I can see your reluctance to spend another $120 without at least trying to verify what Comcast told you.

Most likely Comcast recommended a new modem because his current model is End of Life and can not support future speeds and docsis specs coming soon. I doubt they meant the current device was defective. The 6121 is only a 4x4 channel modem and indeed is listed as EOL on the comcast network.

 

[dlandiss]

I moved a 500mb video file across the network in 28 seconds. Which by my calculations puts my LAN at roughly 120mbps. Same test uploading to Google Drive and it took 133 seconds. I was moving that file at roughly 3.75mbps.

That's pretty confusing. M = Mega, m = milli. B = Bytes, b = bits.

 

[sfx2000]

I contacted Comcast to get some help and after they remoted into my network, they stated my modem was bad which is causing my poor WiFi speeds. This seems odd to me since my wired speeds from the modem are correct. I’m willing to buy a new modem, but after just dropping $150 on the 68U, I’m bit hesitant to spend another $120 on a modem.

Rule out the CM - here's some info...

The SB6121 is DOCSIS 3.0 - so you're fine there - it's good up to 172Mbps up/down - so as long as you have a good connection...

Look at the modem logs - if you're seeing a lot of timeouts (T3/T4) and/or poor signal quality... it's probably not you...

You should be able to access the internal webserver for diags at the following URL - http://192.168.100.1

• Downstream power level (Receive): -15dbmV to +15dbmV
• Upstream (Transmit): 40-52 dBmV
• Carrier/Noise Ratio: 35 db and higher

If they're not within those ranges, it's likely a truck-roll for Comcast - I'm assuming you have a direct run for the CM - or at minimum, a single splitter between the demarc between their side and your side where the CM is connected.

A new modem is not $120 - the Moto/Arris SB6183 can be found on the Amazon (retail package at that) for between 60 to 80 bucks, and it is a solid modem.

If they are all in good ranges, it's likely not the CM - then you need to look for environmental issues that affect your WiFi...

Even there - two things...

1) direct PC connection to the cable modem - if speeds are good there - it could be the router
2) PC to Router over ethernet - if speeds are good, then it's wifi, if not - check the router - reset to defaults and reconfigure as needed.

Be methodical in your approach, and you'll find the problem, if one exists...

 

[sfx2000]

One more thought - check the AC adapters for the modem and the router - I've seen older adapters fail soft - e.g. they're good enough to power the device, but under load, they'll fail to deliver proper current, and this can cause all sorts of problems...

These AC adapters are pretty cheap, and designed to a price point - they're kinda like BMW's - engineered to run fine through the warranty period - after that...

 

[Klueless]

So ... did you wind up with a new modem? Or did you find something else that fixed your problems?

 

[Lincoln30TT]

Thanks for all the replies and I apologize for my delayed response.

After going back and forth with Comcast, I ended up purchasing a Netgear CM600. They supposedly did a couple upgrades to my lines remotely as well. I'm happy to say everything is running the way it should. I even upgraded my service to the Extreme 300. Not sure how a cable modem could cause issues with the WiFi only, but I guess it's possible. Below are my current stats. I returned the new router and still using my 1.5 year old Asus.

Comcast Extreme 300 (300/25)
Netgear CM600
Asus RT-66U

Wired Speed = 350/30
WiFi 2.4 = 95/30
WiFi 5 = 140/30

Thank you to everyone who took the time to read my post and reply!

 

[Klueless]

Glad to hear the new modem did the trick!

Perhaps the old modem / old "lines" were causing lost packets. Since "wired" is faster you probably could afford to lose more packets before you noticed a degradation in performance. With wireless being slower losing packets would be a noticeable performance hit? I'm just guessing ...

 

[sfx2000]

After going back and forth with Comcast, I ended up purchasing a Netgear CM600. They supposedly did a couple upgrades to my lines remotely as wel

you probably didn't need to pick up a new modem - they should have pushed a new config to your SB6121 and go from there...