Throttling, Spectrum and a VPN
Throttling, Spectrum and a VPN
A few weeks ago we cut cable with Spectrum but kept the internet connection. Since then our internet download and upload speeds have become very erratic. Enough so that there are often long pauses in connectivity, not completely "kicked off" but slowed down. This has become very frustrating. Unfortunately Spectrum is the only internet provider in our area. I understand that this is refereed to as throttling, the question is how to deal with it. Will adding a VPN help?
Re: Throttling, Spectrum and a VPN
No. A VPN hides your connection. Makes it seem like you are connecting from somewhere else. You still need a good internet connection.
Did you change any equipment when you got rid of cable? Something seems fishy. What is your download speed you purchased? 100? 200?
Did you change cable modem or router? Have you tried speed tests hooked directly to the router?
I would call spectrum and ask if they are throttling. It seems shady unless you are paying for a lower tier internet speed.
I would move the router to a different cable outlet. Make sure all connections coming in to the cable modem are tight.
If connected through a router, change bands. There could be interference.
Did you change any equipment when you got rid of cable? Something seems fishy. What is your download speed you purchased? 100? 200?
Did you change cable modem or router? Have you tried speed tests hooked directly to the router?
I would call spectrum and ask if they are throttling. It seems shady unless you are paying for a lower tier internet speed.
I would move the router to a different cable outlet. Make sure all connections coming in to the cable modem are tight.
If connected through a router, change bands. There could be interference.
Re: Throttling, Spectrum and a VPN
I am doubtful Spectrum is throttling you. We have been with them for decades almost entirely without their TV service and speeds are always as advertised. More likely something else changed when you removed the TV equipment (different equipment, loose coax connection, etc.) If you can’t trace it yourself, call them and they will troubleshoot and send a tech if necessary.
Re: Throttling, Spectrum and a VPN
Are you sure they're throttling? Have you called their tech support for assistance?
Re: Throttling, Spectrum and a VPN
It may be something with how they configured your Internet-only plan. For example, when there were still analog cable stations transmitted without encryption, they'd install a filter at your house line to filter out the frequencies for the analog stations. These frequencies were close to the cable modem upload frequencies, so the filter could interfere with the cable modem.
You might want to start by looking at your cable modem logs. Try using your web browser to go to 192.168.100.1. If that doesn't work, try 192.168.0.1 or 192.168.1.1. Those are usually the IP addresses for their cable modems. My modem is not password-protected except for "advanced" features, but your mileage will vary depending on what modem you have.
You might want to start by looking at your cable modem logs. Try using your web browser to go to 192.168.100.1. If that doesn't work, try 192.168.0.1 or 192.168.1.1. Those are usually the IP addresses for their cable modems. My modem is not password-protected except for "advanced" features, but your mileage will vary depending on what modem you have.
Re: Throttling, Spectrum and a VPN
There was no change in equipment we simply unhooked the cable box and returned it to Spectrum.bloom2708 wrote: ↑Wed Jan 06, 2021 6:59 pm No. A VPN hides your connection. Makes it seem like you are connecting from somewhere else. You still need a good internet connection.
Did you change any equipment when you got rid of cable? Something seems fishy. What is your download speed you purchased? 100? 200?
Did you change cable modem or router? Have you tried speed tests hooked directly to the router?
I would call spectrum and ask if they are throttling. It seems shady unless you are paying for a lower tier internet speed.
I would move the router to a different cable outlet. Make sure all connections coming in to the cable modem are tight.
If connected through a router, change bands. There could be interference.
Download speed is up around 100 but varies and some times "freezes" when doing a speed test.
We did not change the router/modem. It is a combined router/modem from Spectrum.
I have not tried a peed test directly from the router not sure how to do that.
Re: Throttling, Spectrum and a VPN
I will give this a try, thank you.Mudpuppy wrote: ↑Wed Jan 06, 2021 8:49 pm You might want to start by looking at your cable modem logs. Try using your web browser to go to 192.168.100.1. If that doesn't work, try 192.168.0.1 or 192.168.1.1. Those are usually the IP addresses for their cable modems. My modem is not password-protected except for "advanced" features, but your mileage will vary depending on what modem you have.
Re: Throttling, Spectrum and a VPN
I'll also add that I've been having a lot of little hiccups at the network level with Spectrum. What that means is the cable modem can communicate with the head end perfectly fine (so the modem status page says everything is great), but I can't get packets through even when I try by IP address. It fails at the first external hop.
This tells me that a local Spectrum router is at fault. Whether it's overloaded or failing, I couldn't say since I can't look at it. Before I took my current vacation from work, it happened pretty regularly in the 8-10am time range, which lends a little more weight to the "overloaded" theory. Any Zoom meetings I had during that time would freeze up and I ended up using my phone quite a few times.
So if you don't see anything in the cable modem logs, that doesn't mean everything is great. It just means the problems are at a higher level than the cable modem can see. Start keeping your own notes about when the hiccups occur to see if the hiccups have a time-based pattern, like my 8-10am pattern, which would indicate your neighborhood is oversubscribed, rather than any specific throttling for your account.
This tells me that a local Spectrum router is at fault. Whether it's overloaded or failing, I couldn't say since I can't look at it. Before I took my current vacation from work, it happened pretty regularly in the 8-10am time range, which lends a little more weight to the "overloaded" theory. Any Zoom meetings I had during that time would freeze up and I ended up using my phone quite a few times.
So if you don't see anything in the cable modem logs, that doesn't mean everything is great. It just means the problems are at a higher level than the cable modem can see. Start keeping your own notes about when the hiccups occur to see if the hiccups have a time-based pattern, like my 8-10am pattern, which would indicate your neighborhood is oversubscribed, rather than any specific throttling for your account.
Re: Throttling, Spectrum and a VPN
I’d also suggest that you do your speed test from a pc or laptop connected directly to your router with a network cable. That way you eliminate any potential wifi issues that could be occurring in your home.
Re: Throttling, Spectrum and a VPN
"You might want to start by looking at your cable modem logs. Try using your web browser to go to 192.168.100.1. If that doesn't work, try 192.168.0.1 or 192.168.1.1. Those are usually the IP addresses for their cable modems. My modem is not password-protected except for "advanced" features, but your mileage will vary depending on what modem you have.
[/quote]
I was able to access the modem logs through Routernetwork.com Here are some things I found:
Under system logs under today, yesterday, month and 90 days there were a lot that read critical, error, or warning. The event logs for the same time periods were clean. The firewall logs had a lot of DENY: Inbound or outbound access request for the same framework time.
Also testing under testing connectivity, connectivity to the internet read inactive packets sent 4 packets received 0 but at other times it would read packets sent 4 packets received 4 active.
Check IVP4 Address results read connectivity: none but at another times it reads connectivity: ok
Any help to make me understand this is appreciated.
[/quote]
I was able to access the modem logs through Routernetwork.com Here are some things I found:
Under system logs under today, yesterday, month and 90 days there were a lot that read critical, error, or warning. The event logs for the same time periods were clean. The firewall logs had a lot of DENY: Inbound or outbound access request for the same framework time.
Also testing under testing connectivity, connectivity to the internet read inactive packets sent 4 packets received 0 but at other times it would read packets sent 4 packets received 4 active.
Check IVP4 Address results read connectivity: none but at another times it reads connectivity: ok
Any help to make me understand this is appreciated.
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Re: Throttling, Spectrum and a VPN
VPN won't help, it still depends on your underlying internet connection.
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Re: Throttling, Spectrum and a VPN
Put a 75 ohm terminator cap on the now-unused plug where the cable box connected. Or, even better, remove the splitter that was dividing the signal between the cable box and the internet modem and connect the loose ends through a female-female connector. Both of these are inexpensive parts from a hardware or electronics store.
Re: Throttling, Spectrum and a VPN
You should not have needed to use a domain name to access the cable modem status page. This sounds more like how you would access the WiFi router. Do you have a combination cable modem / WiFi router? Are there brands and/or model numbers on the device(s)? If so, what are they?
Some of this is likely normal. Some of this might indicate an error. We'd need to see details from the actual logs and know the brand/model involved to be able to tell you one way or the other.Bigfish wrote: ↑Sun Jan 17, 2021 7:51 pm Under system logs under today, yesterday, month and 90 days there were a lot that read critical, error, or warning. The event logs for the same time periods were clean. The firewall logs had a lot of DENY: Inbound or outbound access request for the same framework time.
This just means that sometimes it can access the network, and sometimes it can't. But you already knew that since that's what prompted you to look further into the issue.Bigfish wrote: ↑Sun Jan 17, 2021 7:51 pm Also testing under testing connectivity, connectivity to the internet read inactive packets sent 4 packets received 0 but at other times it would read packets sent 4 packets received 4 active.
Check IVP4 Address results read connectivity: none but at another times it reads connectivity: ok
For example, "sent 4 packets received 0" and "sent 4 packets received 4" sounds like a ping operation. With a ping operation, you send essentially an "are you there?" message (packet) to a well-known Internet site and wait to see if it responds with "yes, here I am". If you have no network connectivity, you'll receive no response to the 4 messages sent. If you have good network connectivity, you'll have a response for all 4 messages sent. If your connection is spotty, you'll only have 1-3 respond.
Re: Throttling, Spectrum and a VPN
The modem is a Technicolor modem/router supplied by Spectrum.
Technicolor Model TC87171
Rating 120V AC 60Hz 1.2A
Technicolor Model TC87171
Rating 120V AC 60Hz 1.2A
Re: Throttling, Spectrum and a VPN
Okay, that is a combination cable modem/WiFi router. I personally refuse to accept anything above a cable modem because I don't trust a cable company to properly secure a WiFi router, but that's another issue for another post.
On the Troubleshooting -> Logs page, what are some of the "Critical" errors that do not involve logging in to the unit? For example, on my cable modem (different model) event log page, there are "Lost MDD" timeout, T4 timeout, T3 timeout, and TLV-11 Illegal errors when Spectrum was down for maintenance last week.
I also see random T3 timeout errors interspersed throughout the log that correspond to small Internet outages (<5 minutes). But there are also other times when I lose connection and there's nothing in the logs, which would indicate an issue further upstream within Spectrum, rather than an issue between my cable modem and Spectrum.
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Re: Throttling, Spectrum and a VPN
It always seems like whenever there are erratic, intermittent issues with the the internet, I replace my modem that's usually right around 4 years old, and everything works perfectly again.
I'm not saying that's definitely the issue, but it just seems like clockwork they got out every few years and they are difficult to troubleshoot because it's intermittent and not consistent. I'm usually able to trace the issue to likely being a modem problem by directly connecting an ethernet line from a laptop to the modem and seeing of the problem is still there and not an issue with my router.
I'm not saying that's definitely the issue, but it just seems like clockwork they got out every few years and they are difficult to troubleshoot because it's intermittent and not consistent. I'm usually able to trace the issue to likely being a modem problem by directly connecting an ethernet line from a laptop to the modem and seeing of the problem is still there and not an issue with my router.
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Re: Throttling, Spectrum and a VPN
The OP should contact the ISP. It's their service, they own the circuit and they can run tests to look for packet loss / latency. The original questions of throttling (it's not) and VPN (does not help) are already answered.
Re: Throttling, Spectrum and a VPN
Here are some logs from yesterday:
Time Priority Description
Mon Jan 18 19:34:03 2021 Critical (3) Http login:admin from IP address 192.168.0.7
Sun Jan 17 21:28:23 2021 Error (4) Missing BP Configuration Setting TLV Type: 17.9;CM-MAC=b4:2a:0e:5d:7d:88;CMTS-MAC=00:17:10:93:66:86;CM-QOS=1.1;CM-VER=3.0;
Sun Jan 17 21:28:21 2021 Error (4) Missing BP Configuration Setting TLV Type: 17.8;CM-MAC=b4:2a:0e:5d:7d:88;CMTS-MAC=00:17:10:93:66:86;CM-QOS=1.1;CM-VER=3.0;
Sun Jan 17 21:28:05 2021 Notice (6) Overriding MDD IP initialization parameters; IP provisioning mode = IPv6
Sun Jan 17 21:27:57 2021 Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=b4:2a:0e:5d:7d:88;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
Sun Jan 17 21:27:38 2021 Critical (3) SYNC Timing Synchronization failure - Failed to acquire FEC framing;CM-MAC=b4:2a:0e:5d:7d:88;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
Sun Jan 17 21:27:29 2021 Critical (3) Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=b4:2a:0e:5d:7d:88;CMTS-MAC=00:17:10:93:66:86;CM-QOS=1.1;CM-VER=3.0;
Sun Jan 17 21:27:29 2021 Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=b4:2a:0e:5d:7d:88;CMTS-MAC=00:17:10:93:66:86;CM-QOS=1.1;CM-VER=3.0;
Sun Jan 17 21:27:28 2021 Critical (3) Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=b4:2a:0e:5d:7d:88;CMTS-MAC=00:17:10:93:66:86;CM-QOS=1.1;CM-VER=3.0;
Sun Jan 17 21:27:28 2021 Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=b4:2a:0e:5d:7d:88;CMTS-MAC=00:17:10:93:66:86;CM-QOS=1.1;CM-VER=3.0;
Sun Jan 17 21:27:25 2021 Critical (3) Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=b4:2a:0e:5d:7d:88;CMTS-MAC=00:17:10:93:66:86;CM-QOS=1.1;CM-VER=3.0;
Sun Jan 17 21:27:25 2021 Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=b4:2a:0e:5d:7d:88;CMTS-MAC=00:17:10:93:66:86;CM-QOS=1.1;CM-VER=3.0;
Sun Jan 17 21:27:23 2021 Critical (3) Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=b4:2a:0e:5d:7d:88;CMTS-MAC=00:17:10:93:66:86;CM-QOS=1.1;CM-VER=3.0;
Sun Jan 17 21:27:22 2021 Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=b4:2a:0e:5d:7d:88;CMTS-MAC=00:17:10:93:66:86;CM-QOS=1.1;CM-VER=3.0;
Sun Jan 17 21:27:04 2021 Warning (5) MDD message timeout;CM-MAC=b4:2a:0e:5d:7d:88;CMTS-MAC=00:17:10:93:66:86;CM-QOS=1.1;CM-VER=3.0;
Sun Jan 17 21:27:02 2021 Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=b4:2a:0e:5d:7d:88;CMTS-MAC=00:17:10:93:66:86;CM-QOS=1.1;CM-VER=3.0;
Sun Jan 17 20:18:56 2021 Critical (3) Http login:admin from IP address 192.168.0.7
Sun Jan 17 18:19:17 2021 Critical (3) Http login:admin from IP address 192.168.0.21
Sun Jan 17 10:37:01 2021 Error (4) Missing BP Configuration Setting TLV Type: 17.9;CM-MAC=b4:2a:0e:5d:7d:88;CMTS-MAC=00:17:10:93:66:86;CM-QOS=1.1;CM-VER=3.0;
Sun Jan 17 10:37:01 2021 Error (4) Missing BP Configuration Setting TLV Type: 17.8;CM-MAC=b4:2a:0e:5d:7d:88;CMTS-MAC=00:17:10:93:66:86;CM-QOS=1.1;CM-VER=3.0;
Sun Jan 17 10:21:47 2021 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=b4:2a:0e:5d:7d:88;CMTS-MAC=00:17:10:93:66:86;CM-QOS=1.1;CM-VER=3.0;
Time Priority Description
Mon Jan 18 19:34:03 2021 Critical (3) Http login:admin from IP address 192.168.0.7
Sun Jan 17 21:28:23 2021 Error (4) Missing BP Configuration Setting TLV Type: 17.9;CM-MAC=b4:2a:0e:5d:7d:88;CMTS-MAC=00:17:10:93:66:86;CM-QOS=1.1;CM-VER=3.0;
Sun Jan 17 21:28:21 2021 Error (4) Missing BP Configuration Setting TLV Type: 17.8;CM-MAC=b4:2a:0e:5d:7d:88;CMTS-MAC=00:17:10:93:66:86;CM-QOS=1.1;CM-VER=3.0;
Sun Jan 17 21:28:05 2021 Notice (6) Overriding MDD IP initialization parameters; IP provisioning mode = IPv6
Sun Jan 17 21:27:57 2021 Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=b4:2a:0e:5d:7d:88;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
Sun Jan 17 21:27:38 2021 Critical (3) SYNC Timing Synchronization failure - Failed to acquire FEC framing;CM-MAC=b4:2a:0e:5d:7d:88;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
Sun Jan 17 21:27:29 2021 Critical (3) Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=b4:2a:0e:5d:7d:88;CMTS-MAC=00:17:10:93:66:86;CM-QOS=1.1;CM-VER=3.0;
Sun Jan 17 21:27:29 2021 Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=b4:2a:0e:5d:7d:88;CMTS-MAC=00:17:10:93:66:86;CM-QOS=1.1;CM-VER=3.0;
Sun Jan 17 21:27:28 2021 Critical (3) Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=b4:2a:0e:5d:7d:88;CMTS-MAC=00:17:10:93:66:86;CM-QOS=1.1;CM-VER=3.0;
Sun Jan 17 21:27:28 2021 Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=b4:2a:0e:5d:7d:88;CMTS-MAC=00:17:10:93:66:86;CM-QOS=1.1;CM-VER=3.0;
Sun Jan 17 21:27:25 2021 Critical (3) Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=b4:2a:0e:5d:7d:88;CMTS-MAC=00:17:10:93:66:86;CM-QOS=1.1;CM-VER=3.0;
Sun Jan 17 21:27:25 2021 Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=b4:2a:0e:5d:7d:88;CMTS-MAC=00:17:10:93:66:86;CM-QOS=1.1;CM-VER=3.0;
Sun Jan 17 21:27:23 2021 Critical (3) Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=b4:2a:0e:5d:7d:88;CMTS-MAC=00:17:10:93:66:86;CM-QOS=1.1;CM-VER=3.0;
Sun Jan 17 21:27:22 2021 Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=b4:2a:0e:5d:7d:88;CMTS-MAC=00:17:10:93:66:86;CM-QOS=1.1;CM-VER=3.0;
Sun Jan 17 21:27:04 2021 Warning (5) MDD message timeout;CM-MAC=b4:2a:0e:5d:7d:88;CMTS-MAC=00:17:10:93:66:86;CM-QOS=1.1;CM-VER=3.0;
Sun Jan 17 21:27:02 2021 Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=b4:2a:0e:5d:7d:88;CMTS-MAC=00:17:10:93:66:86;CM-QOS=1.1;CM-VER=3.0;
Sun Jan 17 20:18:56 2021 Critical (3) Http login:admin from IP address 192.168.0.7
Sun Jan 17 18:19:17 2021 Critical (3) Http login:admin from IP address 192.168.0.21
Sun Jan 17 10:37:01 2021 Error (4) Missing BP Configuration Setting TLV Type: 17.9;CM-MAC=b4:2a:0e:5d:7d:88;CMTS-MAC=00:17:10:93:66:86;CM-QOS=1.1;CM-VER=3.0;
Sun Jan 17 10:37:01 2021 Error (4) Missing BP Configuration Setting TLV Type: 17.8;CM-MAC=b4:2a:0e:5d:7d:88;CMTS-MAC=00:17:10:93:66:86;CM-QOS=1.1;CM-VER=3.0;
Sun Jan 17 10:21:47 2021 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=b4:2a:0e:5d:7d:88;CMTS-MAC=00:17:10:93:66:86;CM-QOS=1.1;CM-VER=3.0;
Re: Throttling, Spectrum and a VPN
The events on Sunday January 17th at 21:27 would correspond with the cable modem having to reboot due to line issues or an outage in your area. You might also see these errors for a maintenance window, but 9:27pm is not a normal time for maintenance.
I would agree with this up-thread advice to either terminate the cable TV split or remove the splitter going to the cable TVs:
If you don't know how to do this, Spectrum can send a technician out to do it for you (depending on how you feel about having outside workers in your house during the pandemic). Do note that this will not solve the problem if the issue is in the wiring outside of your house. Depending on how bad the signal is at the curb, Spectrum may or may not do anything about it. My signal the the curb is borderline, but just far enough within nominal range that they won't replace the cable.
I would agree with this up-thread advice to either terminate the cable TV split or remove the splitter going to the cable TVs:
When I went to Internet-only, I knew which "leg" of my coax system went to the cable modem and I removed all splitters to hook that "leg" directly up to the incoming coax line. I also had new coax run a few years ago, so its a dedicated, fresh line.cartophile wrote: ↑Sun Jan 17, 2021 8:07 pm Put a 75 ohm terminator cap on the now-unused plug where the cable box connected. Or, even better, remove the splitter that was dividing the signal between the cable box and the internet modem and connect the loose ends through a female-female connector. Both of these are inexpensive parts from a hardware or electronics store.
If you don't know how to do this, Spectrum can send a technician out to do it for you (depending on how you feel about having outside workers in your house during the pandemic). Do note that this will not solve the problem if the issue is in the wiring outside of your house. Depending on how bad the signal is at the curb, Spectrum may or may not do anything about it. My signal the the curb is borderline, but just far enough within nominal range that they won't replace the cable.
Re: Throttling, Spectrum and a VPN
A few more facts.
My computer is a Lenovo and is about 12 feet from the modem/router. My wife has a new iMac, her computer is in the next room about 24 feet from the modem/router. She has many more connectivity problems than I do.
I removed the splitter on Saturday, the cable goes directly from the wall outlet to the modem.
We had a Spectrum tech come to the house a few weeks ago. He checked the connections but did nothing else. I will call them again but decided to do some trouble shooting on my own. first.
My computer is a Lenovo and is about 12 feet from the modem/router. My wife has a new iMac, her computer is in the next room about 24 feet from the modem/router. She has many more connectivity problems than I do.
I removed the splitter on Saturday, the cable goes directly from the wall outlet to the modem.
We had a Spectrum tech come to the house a few weeks ago. He checked the connections but did nothing else. I will call them again but decided to do some trouble shooting on my own. first.
Re: Throttling, Spectrum and a VPN
There are many reasons why your wife's iMac could be having more issues. Just off the top of my head, I can think of factors such as distance, materials in the wall/room causing interference, her iMac being close enough to a neighbor's WiFi router which is causing interference, or the iMac might have a more sensitive WiFi adapter that doesn't like to hold on to weak signals or deal with interference.
Ultimately, if it's a line issue, it doesn't matter how good or bad the WiFi router part of it is. If the cable modem part has to reboot due to a line issue, then no WiFi will be working during that time. You need to check the modem log after every disconnect to see if you have entries like what you had last night.
There are also splitters between the wall outlet and the line from Spectrum, otherwise you'd have only one wall outlet. Those are the ones to be concerned about right now. The easiest non-technical way to think about it is Spectrum is trying to "power" (deliver signal) to all the coax outlets in your house, but you only need it to go to the one outlet with the modem. Every time it splits, the signal gets "weaker". If you're already dealing with poor cable quality in the neighborhood, the splitters can cause just enough of a decrease in signal quality to cause issues.
Another possibility, like Illumination already pointed out, is that the cable modem/WiFi router device might be going bad. Spectrum doesn't charge a rental fee for cable modems, so you could ask for a replacement device. However, since you have an integrated modem/WiFi device, asking Spectrum to swap out the device means you'll have to reconfigure all of your WiFi devices for the new device once it's delivered.