Mysterious throughput drop with faster Modems

[Smokin_Joe]

I am having problems trying to increase my Internet Speed from my ISP.
I was paying for a 60mbs connection with a DCM475 cable modem. The throughput on my system was always in the 75-80mbs. (modem+TL-ER6020+DGS-3200+TPlink AP's+RT-AC88U+DGS-3200+TL WR1043ND)
If I was using openvpn on a subnetted AC88u my vpn throughput was approx 75mbs.
So through the vpn, or outside the vpn, my network my speeds were faster, than the service I was paying for.
I was paying $62/mo for 60mbs. They offered me a faster service package for less money. 75mbs for $45/mo problem is the modem that they wanted me to use caused my vpn throughput to drop to 40mbs. I cancelled the service, returned the new modem and put my old one back in.
Recently fibre optic was installed in my neighborhood.
Fibre Optic wanted $80/mo for 150mbs. My isp was offering 150 for $69/mo and since I was already paying $62/mo I decided to try it.
Not Good.
The new tc4350 will give me 175mbs connected directly to my laptop.
If I connect it to my TL-ER6020 router and to my laptop I get a speed drop of 50mbs....from 175mbs to 125mbs. If I connect through my AC88u on the openvpn it drops to 40mbs....
These speed results are only using the new TC 4350 + ER6020+AC88u nothing else on my network was connected...
system mode is NAT, 13 DHCP clients and Reservations
They are all in a user group called Guests and they each have a session limit of 150 but that didn't affect the throughput on the 60mbs service and shouldn't cause an issue now. I may test it with it turned off to confirm.
DMZ disabled
No Flow or Bandwidth control
Firewall
ARP Spoofing Defense turned on, Attack Defense has all boxes checked except Block IP options
No Mac filtering, No url filtering, No Web Filtering, no Access rules
UPnP is enabled but shows no entries....ever...
What am I missing?
What could cause such a throughput drop when the modem and speed are changed?

 

[ColinTaylor]

I don't know why your Asus is getting such low speeds, but on a 175Mbps line you're pushing the limits of the TL-ER6020.

The SNB review of the the TL-ER6020 shows a raw WAN-LAN throughput of ~160Mbps and an iperf throughput of 110-127Mbps

 

[System Error Message]

when in doubt, ditch the vpn router. Vpn routers are old outdated stuff superceeded by the current line of consumer hardware. your asus is already faster and provides more features.

 

[Smokin_Joe]

I don't know why your Asus is getting such low speeds, but on a 175Mbps line you're pushing the limits of the TL-ER6020.

The SNB review of the the TL-ER6020 shows a raw WAN-LAN throughput of ~160Mbps and an iperf throughput of 110-127Mbps

Bummer...
Thank you ColinTaylor

 

[Smokin_Joe]

when in doubt, ditch the vpn router. Vpn routers are old outdated stuff superceeded by the current line of consumer hardware. your asus is already faster and provides more features.

Good advice...thank you..system error message...
You two have given me great insight...

 

[sfx2000]

If one has been playing around with Traffic Shaping - clear the rules and start over...

 

[Smokin_Joe]

sfx2000
I think ColinTaylor and system error message have given me the answer. I will be confrming later today...

 

[Smokin_Joe]

I disconnected the tp link er6020 and connected the Asus AC88U directly to the modem and connected my laptop to the AC88U.
178mbs download 15mbs up no vpn turned on...
VPN turned on went down to 40 to 45 mbs
With the vpn turned on and at the closest server the speed struggles at 20 and builds from there to hit 40....
Now remember with the slower 60 mbs service and a different modem I had steady speeds of 70+mbs with or without the vpn service turned on...
This is the second attempt with different modem.
I have modem+ac88u+er6020+the rest of my network as before....i have switched the posiions of the first two routers and I now have 145mbs in my office, up from 120mbs, before the change but the vpn brings the speed down to 40ish
Next step?

 

[CaptainSTX]

I disconnected the tp link er6020 and connected the Asus AC88U directly to the modem and connected my laptop to the AC88U.
178mbs download 15mbs up no vpn turned on...
VPN turned on went down to 40 to 45 mbs
With the vpn turned on and at the closest server the speed struggles at 20 and builds from there to hit 40....
Now remember with the slower 60 mbs service and a different modem I had steady speeds of 70+mbs with or without the vpn service turned on...
This is the second attempt with different modem.
I have modem+ac88u+er6020+the rest of my network as before....i have switched the posiions of the first two routers and I now have 145mbs in my office, up from 120mbs, before the change but the vpn brings the speed down to 40ish
Next step?

If your VPN provider offers a desk top app try runing it on your PC connected to the router and also on the PC when directly connected to the modem. This will give you an idea of what speed the VPN provider can handle.

 

[sfx2000]

I think ColinTaylor and system error message have given me the answer. I will be confrming later today...

Sounds good - guess you don't need my help - but still check the QoS settings first...

 

[Smokin_Joe]

CaptainSTX...interesting...might try that...
Currently we know that PIA can provide matching service on their system up to 75mbs.
I would be happy if I could have the 75mbs throughput from PIA on the faster internet service.
Both options for me, less money for faster service or more money for even faster service ends up forcing me to change the modem and that causes my vpn throughput to decline in speed.

 

[Smokin_Joe]

Sounds good - guess you don't need my help - but still check the QoS settings first...

The QoS is turned off...

 

[Smokin_Joe]

Does anyone have any idea why a modem that is used for a faster service cause a vpn that is tunneling through it to slow down?
In order to provide faster service on the cable internet have they changed the workings or design of the modem and how it functions?

 

[System Error Message]

Does anyone have any idea why a modem that is used for a faster service cause a vpn that is tunneling through it to slow down?
In order to provide faster service on the cable internet have they changed the workings or design of the modem and how it functions?

there could be some reasons. It highly depends on the config used to connect to it. VLANs, PPP and so on add overhead and processing so the VPN router would need to use more CPU. It also depends on things like routing and ISP traffic shaping as VPN traffic is easy to identify but openVPN not so easy unless one uses layer 7 which requires a lot of processing power to do.

 

[Smokin_Joe]

there could be some reasons. It highly depends on the config used to connect to it. VLANs, PPP and so on add overhead and processing so the VPN router would need to use more CPU. It also depends on things like routing and ISP traffic shaping as VPN traffic is easy to identify but openVPN not so easy unless one uses layer 7 which requires a lot of processing power to do.

I have done actually a cut and paste using these instructions...
https://www.snbforums.com/threads/h...with-asus-routers-380-68-updated-08-24.33638/
https://www.snbforums.com/threads/h...and-other-vpn-providers-380-69_2-03-29.30851/
https://www.privateinternetaccess.com/helpdesk/guides/routers/merlin/merlin-firmware-openvpn-setup
Using all three sources and defaulting to yorgi's instructions I created a usable basic subnet of my main guest network that I had my home network behind.
The vpn router is a RT-AC88U.
Speeds were a very stable 60+mbps behind the PIA vpn (ipvanish could only give 256 encryption and was limited to 40mbps, PIA offered 128 encryption so I changed VPN providers to PIA)
I have no QOS, traffic shaping or anything else but the basic "all traffic" turned on.
DCM475 modem provides 60mbps throughput on vpn and TC4350 modem provides 30mbps throughput on vpn. (DCM475 can only be used on 60mbps or lower service, according to my isp, and the TC4350 has to be used for anything faster)
These figures are from direct connection to modem and router(AC88U) to pc or after repositioning routers and through my complete network, no (significant) change in vpn throughput speed.

 

[sfx2000]

DCM475 modem provides 60mbps throughput on vpn and TC4350 modem provides 30mbps throughput on vpn. (DCM475 can only be used on 60mbps or lower service, according to my isp, and the TC4350 has to be used for anything faster)

that's interesting... they should be the same - both modems (the Thomson DC475 and the Technicolor TC4350) are DOCSIS 3.0, and the older modem should be good for around 300 Mbps downlink...

Some concern with the TC4350, as this is an Intel PUMA6 based modem, and that chipset has issues across multiple vendors.

What's interesting is you reported seeing half the bandwidth between the DCM and the TC... can you confirm that you're full duplex on the Modem to Router interface?

Do you see the same with no VPN in play? Wireless and Wired...

60mbps throughput

How are you testing this?

 

[System Error Message]

I have done actually a cut and paste using these instructions...
https://www.snbforums.com/threads/h...with-asus-routers-380-68-updated-08-24.33638/
https://www.snbforums.com/threads/h...and-other-vpn-providers-380-69_2-03-29.30851/
https://www.privateinternetaccess.com/helpdesk/guides/routers/merlin/merlin-firmware-openvpn-setup
Using all three sources and defaulting to yorgi's instructions I created a usable basic subnet of my main guest network that I had my home network behind.
The vpn router is a RT-AC88U.
Speeds were a very stable 60+mbps behind the PIA vpn (ipvanish could only give 256 encryption and was limited to 40mbps, PIA offered 128 encryption so I changed VPN providers to PIA)
I have no QOS, traffic shaping or anything else but the basic "all traffic" turned on.
DCM475 modem provides 60mbps throughput on vpn and TC4350 modem provides 30mbps throughput on vpn. (DCM475 can only be used on 60mbps or lower service, according to my isp, and the TC4350 has to be used for anything faster)
These figures are from direct connection to modem and router(AC88U) to pc or after repositioning routers and through my complete network, no (significant) change in vpn throughput speed.

that's interesting... they should be the same - both modems (the Thomson DC475 and the Technicolor TC4350) are DOCSIS 3.0, and the older modem should be good for around 300 Mbps downlink...
Some concern with the TC4350, as this is an Intel PUMA6 based modem, and that chipset has issues across multiple vendors.
What's interesting is you reported seeing half the bandwidth between the DCM and the TC... can you confirm that you're full duplex on the Modem to Router interface?
Do you see the same with no VPN in play? Wireless and Wired...
How are you testing this?

the asus AC88U does not have much hardware acceleration for VPN so while VPN speeds may be lower than a hardware accelerated VPN router (most VPN router will not accelerate openVPN) and processing power is limited, however in total the asus ac88u's faster WAN speed despite slower VPN is a much better choice, because you dont want to not be able to max out your WAN and VPN provider speeds do vary at times as their server loads vary.

Make sure that hardware acceleration is enabled on the asus for full NAT speeds, and i believe you may be able to use adaptive or auto QoS with hardware acceleration but im not sure about it as i remember it as a feature that came out with that router. That should free up the CPU to handle your VPN . If you truely want VPN at much faster speeds assuming your provider supports it you're looking at a totally different router altogether.

Modems do sync for both DSL and cable so the chipset does actually matter, in a case of compatibility with the cabinet. If both chips used by ISP and your modem are the same brand, you will get better sync speeds. I tested 3 very different modems on VDSL, the one given by the ISP which uses a qualcomm chip and very efficient router as well (integrated) gave the fastest speeds and the router itself had a very good latency. Using another modem that was recommended or widely used on the ISP which i think uses broadcom gave 3Mb/s less (76Mb/s down to 73mb/s) while the netgear one which apparently was falsely marketed initially in some places (its too bad i didnt screenshot that early on) achieved a sync speed of only 71Mb/s. The modem given by ISP was the fastest while the modem widely used was also reliable, but the netgear was actually unreliable (freezes in modem only mode). Try to find out what chip brand your ISP uses in their exchange/cabinet and ask for a modem that matches it. Most of the time the modem given by ISP is the best choice but sometimes ISPs that use multiple different chips in their exchange may have multiple models that all look similar and give out a different modem instead. And also what SFX mentioned about the intel chip having issues. The reason for compatibility is that different brands may sync up differently (some low level hardware algorithm stuff) so matching the chip brand used tends to achieve the best performance, which is why modem testing doesnt really work as well like with routers.

 

[Smokin_Joe]

that's interesting... they should be the same - both modems (the Thomson DC475 and the Technicolor TC4350) are DOCSIS 3.0, and the older modem should be good for around 300 Mbps downlink...

My ISP is a reseller...Teksavvy over Shaw equipment..and Shaw dictates to Teksavvy as to the equipment it can use on different serve levels...I am forced to change to TC4350 on anything over 60mbps speed.

Some concern with the TC4350, as this is an Intel PUMA6 based modem, and that chipset has issues across multiple vendors.

What's interesting is you reported seeing half the bandwidth between the DCM and the TC... can you confirm that you're full duplex on the Modem to Router interface?

Do you see the same with no VPN in play? Wireless and Wired...

How are you testing this?

By disconnecting the network from the modem and reinstalling just the RT-AC88U to the modem and hardwired my laptop...Asusi7 running window 10

I don't know if the modem to router interface is on full duplex or not....sorry not a pro...good question thou and I will check..I have an appointment arriving in a moment so will be offline for a bit
***Update...full duplex...***
Do you see the same with no VPN in play? Wireless and Wired...No...
No Vpn wired directly to the TC4350 and I get 175Mbps speed on a 150mbps service.
No wireless test because modem not wireless.
Modem+Er6020+PC 125Mbps no vpn...
Modem+Er6020+RT-AC88U+125mbps no vpn 125mbps vpn 45mbps
after ColinTaylor and system error message pointed out a few things I reversed the routers.
Modem+RT-AC88U+ER6020+PC 145mbps no vpn 40-45 vpn turned on.
Ok...now my network has a weak link in throughput...ER6020 maxes out at 125mbps no vpn if used as gateway..but it will allow 145mbps no vpn if used as subnet to Gateway RT-AC88U
My throughput with a vpn turned on with the any of the above configurations yields 40-50mbps at best....using the TC4350 hooked directly to the RT-AC88U.
The DCM475 would yield between 60-75mbps from my office downstream of modem+3 routers+2 Managed switches(my whole network active) with the vpn turned on and 75-85mbps with it turned off using a 60mbps service..

 

[Smokin_Joe]

the asus AC88U does not have much hardware acceleration for VPN so while VPN speeds may be lower than a hardware accelerated VPN router (most VPN router will not accelerate openVPN) and processing power is limited, however in total the asus ac88u's faster WAN speed despite slower VPN is a much better choice, because you dont want to not be able to max out your WAN and VPN provider speeds do vary at times as their server loads vary.

Make sure that hardware acceleration is enabled on the asus for full NAT speeds, and i believe you may be able to use adaptive or auto QoS with hardware acceleration but im not sure about it as i remember it as a feature that came out with that router. That should free up the CPU to handle your VPN . If you truely want VPN at much faster speeds assuming your provider supports it you're looking at a totally different router altogether.

Modems do sync for both DSL and cable so the chipset does actually matter, in a case of compatibility with the cabinet. If both chips used by ISP and your modem are the same brand, you will get better sync speeds. I tested 3 very different modems on VDSL, the one given by the ISP which uses a qualcomm chip and very efficient router as well (integrated) gave the fastest speeds and the router itself had a very good latency. Using another modem that was recommended or widely used on the ISP which i think uses broadcom gave 3Mb/s less (76Mb/s down to 73mb/s) while the netgear one which apparently was falsely marketed initially in some places (its too bad i didnt screenshot that early on) achieved a sync speed of only 71Mb/s. The modem given by ISP was the fastest while the modem widely used was also reliable, but the netgear was actually unreliable (freezes in modem only mode). Try to find out what chip brand your ISP uses in their exchange/cabinet and ask for a modem that matches it. Most of the time the modem given by ISP is the best choice but sometimes ISPs that use multiple different chips in their exchange may have multiple models that all look similar and give out a different modem instead. And also what SFX mentioned about the intel chip having issues. The reason for compatibility is that different brands may sync up differently (some low level hardware algorithm stuff) so matching the chip brand used tends to achieve the best performance, which is why modem testing doesnt really work as well like with routers.

Place holding....ok now that I read it I really am lost...lol
system error message do you think I can get that kind of info out of them?
I do know that shaw tells Teksavvy what they can use for different speeds and I am beginning to think Shaw is trying to cause them/me issues.
I might be going to a buddies place tomorrow to hook my RT-AC88U onto his Shaw modem and test the vpn and no vpn speed...he is on Shaw 150mbps service and it is rock solid.

 

[umarmung]

https://help.teksavvy.com/hc/en-us/articles/200315110-Approved-Cable-Modems-Ontario-Rogers-Network-

Every 250Mbps device on that list seems to be Puma 6, including your Technicolor TC4350, except for the TP-Link TC7650.

Ditch it and get the TP-Link. Simple.