[Solved-ish] Low (actual) speeds on 802.11ax (Linux)

[ApeironTsuka]

The issue:

`iw wlp3s0 link` shows RX topping out usually around 1.2-1.4gbps and TX topping out 1.7-1.9gbps.

iperf3 reports ~400mbps desktop->router and ~600mbps router->desktop.

It doesn't seem normal for the slower RX link to have 50% higher speed.

 

This same ~400mbps speed limit occurs when on wired 1gbps, as well. This limit gets hit even when TX drops as low as 1.2gbps.

 

For comparison, a laptop on the same network running the same distro/packages etc, but with a Realtek 8812au chipset (802.11ac) has a TX of 867mbps and gets the same ~400mbps (averaging closer to 390mbps) laptop->router iperf3 results.

 

What needs to be tweaked? I'm fairly positive that I should be seeing at least 800mbps desktop->router with this TX link speed.

 

Hardware/software:

NIC is an Intel AX200 chipset, iwlwifi driver using firmware 63.c04f3485.0 cc-a0-63

Debian Bookworm with kernel 5.14.9 (5.14.0-2 from the repo).

 

Router is an ASUS RT-AX3000 (same as RT-AX56U, but that model name is specific to Best Buy if I recall. No idea why) with asuswrt-merlin 386.3_2.

 

Raw numbers/results:

 

# iw wlp3s0 link | grep bitrate
        rx bitrate: 1441.3 MBit/s 160MHz HE-MCS 7 HE-NSS 2 HE-GI 0 HE-DCM 0
        tx bitrate: 1921.5 MBit/s 160MHz HE-MCS 9 HE-NSS 2 HE-GI 0 HE-DCM 0

 

$ iperf3 -c 192.168.2.1
Connecting to host 192.168.2.1, port 5201
[  5] local 192.168.2.3 port 45520 connected to 192.168.2.1 port 5201
[ ID] Interval           Transfer     Bitrate         Retr  Cwnd
[  5]   0.00-1.00   sec  36.7 MBytes   308 Mbits/sec   31    676 KBytes
[  5]   1.00-2.00   sec  47.5 MBytes   398 Mbits/sec    0    759 KBytes
[  5]   2.00-3.00   sec  48.8 MBytes   409 Mbits/sec    0    822 KBytes
[  5]   3.00-4.00   sec  46.2 MBytes   388 Mbits/sec   62    626 KBytes
[  5]   4.00-5.00   sec  48.8 MBytes   409 Mbits/sec    0    683 KBytes
[  5]   5.00-6.00   sec  48.8 MBytes   409 Mbits/sec    0    738 KBytes
[  5]   6.00-7.00   sec  50.0 MBytes   419 Mbits/sec    0    788 KBytes
[  5]   7.00-8.00   sec  47.5 MBytes   398 Mbits/sec    0    833 KBytes
[  5]   8.00-9.00   sec  47.5 MBytes   398 Mbits/sec   29    641 KBytes
[  5]   9.00-10.00  sec  47.5 MBytes   398 Mbits/sec    0    718 KBytes
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bitrate         Retr
[  5]   0.00-10.00  sec   469 MBytes   394 Mbits/sec  122             sender
[  5]   0.00-10.00  sec   467 MBytes   392 Mbits/sec                  receiver

iperf Done.

 

$ iperf3 -c 192.168.2.1 -R
Connecting to host 192.168.2.1, port 5201
Reverse mode, remote host 192.168.2.1 is sending
[  5] local 192.168.2.3 port 45524 connected to 192.168.2.1 port 5201
[ ID] Interval           Transfer     Bitrate
[  5]   0.00-1.00   sec  65.6 MBytes   550 Mbits/sec              
[  5]   1.00-2.00   sec  75.0 MBytes   629 Mbits/sec              
[  5]   2.00-3.00   sec  71.5 MBytes   600 Mbits/sec              
[  5]   3.00-4.00   sec  64.4 MBytes   540 Mbits/sec              
[  5]   4.00-5.00   sec  73.6 MBytes   617 Mbits/sec              
[  5]   5.00-6.00   sec  75.7 MBytes   635 Mbits/sec              
[  5]   6.00-7.00   sec  74.8 MBytes   627 Mbits/sec              
[  5]   7.00-8.00   sec  75.9 MBytes   637 Mbits/sec              
[  5]   8.00-9.00   sec  74.8 MBytes   628 Mbits/sec              
[  5]   9.00-10.00  sec  74.1 MBytes   622 Mbits/sec              
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bitrate         Retr
[  5]   0.00-10.00  sec   727 MBytes   610 Mbits/sec    0             sender
[  5]   0.00-10.00  sec   725 MBytes   608 Mbits/sec                  receiver

iperf Done.

 

[Columbo]

Is your modem to your bandwidth a 1 gigabit port? You may need a modem with 2.5gbps ethernet ports. You cannot send data beyond what your modem ethernet port is capable of. Your speeds look similar to wifi ac. I am guessing your wireless ax speeds exceed the speed of your ethernet port which is causing your slower than expected wifi speeds. If you have a computer with 2.5gbps or 10gigabit port. You could then sling it via your wifi ax wifi. Your real world speeds are half of your bandwidth so you would see wireless ax speeds in the neighborhood of 800-900mbps.

[Alex Atkin UK]

15 hours ago, ApeironTsuka said:

The issue:

`iw wlp3s0 link` shows RX topping out usually around 1.2-1.4gbps and TX topping out 1.7-1.9gbps.

iperf3 reports ~400mbps desktop->router and ~600mbps router->desktop.

It doesn't seem normal for the slower RX link to have 50% higher speed.

 

This same ~400mbps speed limit occurs when on wired 1gbps, as well. This limit gets hit even when TX drops as low as 1.2gbps.

 

For comparison, a laptop on the same network running the same distro/packages etc, but with a Realtek 8812au chipset (802.11ac) has a TX of 867mbps and gets the same ~400mbps (averaging closer to 390mbps) laptop->router iperf3 results.

 

What needs to be tweaked? I'm fairly positive that I should be seeing at least 800mbps desktop->router with this TX link speed.

 

Sadly that is not a given, this is not at all an unusual thing to happen with WiFi, I see it myself.

 

On a good day I get 850Mbit, on a bad day it can be just about anything, and the link rate will be the same.

 

Although if you're only getting 400Mbit with everything wired (you do not make it clear if one device is wired or both) then this suggest a different issue entirely.

5 hours ago, Columbo said:

Is your modem to your bandwidth a 1 gigabit port? You may need a modem with 2.5gbps ethernet ports. You cannot send data beyond what your modem ethernet port is capable of. Your speeds look similar to wifi ac. I am guessing your wireless ax speeds exceed the speed of your ethernet port which is causing your slower than expected wifi speeds. If you have a computer with 2.5gbps or 10gigabit port. You could then sling it via your wifi ax wifi. Your real world speeds are half of your bandwidth so you would see wireless ax speeds in the neighborhood of 800-900mbps.

Not sure what you mean here, real world speed should not be half when using wired ethernet.  Gigabit ethernet should handle around 940Mbit in both directions at the same time.

When two wired devices talk to each other, they bypass the router entirely staying in the integrated switch.

When two wireless devices talk to each other, yes that would be halved but it wont even touch the wired ethernet.

When one device is wired and another is wireless, you have the full Gigabit to play with.  Its only WiFi itself where you may end up getting half the throughput, depending on conditions.

[ApeironTsuka]

11 hours ago, Columbo said:

Is your modem to your bandwidth a 1 gigabit port? You may need a modem with 2.5gbps ethernet ports. You cannot send data beyond what your modem ethernet port is capable of. Your speeds look similar to wifi ac. I am guessing your wireless ax speeds exceed the speed of your ethernet port which is causing your slower than expected wifi speeds. If you have a computer with 2.5gbps or 10gigabit port. You could then sling it via your wifi ax wifi. Your real world speeds are half of your bandwidth so you would see wireless ax speeds in the neighborhood of 800-900mbps.

 

5 hours ago, Alex Atkin UK said:

Sadly that is not a given, this is not at all an unusual thing to happen with WiFi, I see it myself.

 

On a good day I get 850Mbit, on a bad day it can be just about anything, and the link rate will be the same.

 

Although if you're only getting 400Mbit with everything wired (you do not make it clear if one device is wired or both) then this suggest a different issue entirely.

 

Quote

Not sure what you mean here, real world speed should not be half when using wired ethernet.  Gigabit ethernet should handle around 940Mbit in both directions at the same time.

When two wired devices talk to each other, they bypass the router entirely staying in the integrated switch.

When two wireless devices talk to each other, yes that would be halved but it wont even touch the wired ethernet.

When one device is wired and another is wireless, you have the full Gigabit to play with.  Its only WiFi itself where you may end up getting half the throughput, depending on conditions.

 

The speed over ethernet was only an example. There's nothing on the network that's wired anymore (not counting the modem upstream from the router). The ethernet speed might also have been a red herring - I should retest it later today if I can find a cable long enough to reach.

 

The tests were done with the network otherwise idle and one direction at a time. Since the iperf3 server was running on the router itself, there's no extra hops involved. Unless I'm mistaken, the full wireless bandwidth should have been available.

 

 

Edit:

Sigh. I should have done this particular test sooner.

 

Hooked laptop up over ethernet and tested laptop->desktop/desktop->laptop (desktop still wireless). Full ethernet speed (940mbps) in the test between them. Rules out the desktop.

 

Seems like however the router itself is routing traffic internally is the issue? Would still like to fix that, if possible, but I assume it's not.

Edited October 20, 2021 by ApeironTsuka
More testing

[Columbo]

I didn't say that wired has any loss in speed or bandwidth. I said that wireless is generally half of what the bandwidth is. Wireless AC typically has a max speed of 850mbps regardless of the theoretical bandwidth because the band has a max throughput of 850mbps. There are some wireless bands that have 1700mbps bands but they are limited by the ethernet port speed. I have not tested it but in theory you could sling wireless AX between two wireless AX computers. Your speed would be limited halved by the maximum band transfer rate. 

 

I have a mesh network with wilress AC. I have wired backhauls with Cat6 and a gigabit internet connection. My band is somewhere in that 800-850mbps band. It pushes up to 625mbps wireless but typically in the 450mbps-500mbps range. Without wireless backhaul, it would push 380mbps + or minus 20mbps. 

 

If your band has a bandwidth of 1750mbps you should be able to get 50% (875mbps) of that in your iperf test. A gigabit connection is good for 940mbps. 

[Alex Atkin UK]

On 10/20/2021 at 3:39 PM, ApeironTsuka said:

Hooked laptop up over ethernet and tested laptop->desktop/desktop->laptop (desktop still wireless). Full ethernet speed (940mbps) in the test between them. Rules out the desktop.

 

Seems like however the router itself is routing traffic internally is the issue? Would still like to fix that, if possible, but I assume it's not.

I'm super confused now as in your original post you said "this still happens when wired", what have you done differently this time?

Were you always running the test to an iperf3 server running ON the router and if so why as this isn't going to tell you how fast your devices can talk to each other?

[ApeironTsuka]

1 hour ago, Alex Atkin UK said:

I'm super confused now as in your original post you said "this still happens when wired", what have you done differently this time?

Were you always running the test to an iperf3 server running ON the router and if so why as this isn't going to tell you how fast your devices can talk to each other?

Yeah, I was running the iperf3 server on the router itself. I didn't have anything connected to the network that could even approach AX (everything else is AC) and I had (apparently incorrectly) assumed the router itself wouldn't have any issues saturating the link in either direction.

 

The test was specifically testing the speed between the desktop and router because I have a drive connected over USB 3 as a NAS. Given my previous assumption, I never thought to check if the router wasn't keeping up.

[Alex Atkin UK]

5 hours ago, ApeironTsuka said:

Yeah, I was running the iperf3 server on the router itself. I didn't have anything connected to the network that could even approach AX (everything else is AC) and I had (apparently incorrectly) assumed the router itself wouldn't have any issues saturating the link in either direction.

 

The test was specifically testing the speed between the desktop and router because I have a drive connected over USB 3 as a NAS. Given my previous assumption, I never thought to check if the router wasn't keeping up.

Understandable, they do not exactly promote that routers are far too weak to do all the stuff they advertise, at least at good speeds.