Abnormal (slow) routed downstream speed over WiFi (Intel 6235)

Stellarator · 2019-12-14 12:45:11

Colleagues, I'm out of ideas and so seeking for your help.

I have a rather old laptop (ASUS U500VZ) with Intel Centrino Advanced-N 6235 and Qualcomm Atheros AR8151 chipsets. Technically, all works fine. But I have a strange issue with downstream (routed traffic?) speed over WiFi. Unfortunately, I did not pay attention to this and I can not now unequivocally say whether this behavior was original from the moment when I installed Arch half-year ago or something changed after update of the system or external hardware (I changed my WiFi router to the new one (Asus RT-AX88U) a couple of weeks ago).

What I'm exactly talking about is that single stream communication from Internet is limited to 12-15 Mbit/sec.

What tests have I tried so far:

Legend (all speed figures in megabits per second):

Internet - ~40 Mbit/sec limited by ISP wire connection (pure Ethernet)
Router - RT-AX88U (a/b/g/n/ac/ax router), very default settings, all clients connected over 5GHz network
Laptop - Asus U500VZ, Linux 5.4.2-arch1-1, very default sysctl settings, default drivers, etc
Desktop - Broadcom WiFi chipset, Windows 10 (connected over WiFi)
VPS (some Internet server with 100+ MBit/sec bandwidth, dedicated CPU, no load)
Speedtest server (randomly chosen initially but constant over all tests)

Info from wavemon at the time of tests:

freq: 5260 MHz, ctr1: 5270 MHz, channel 52 (width: 40 MHz)
rx rate: 243.0 Mbit/s MCS 14 40MHz, tx rate: 270 Mbit/s MCS 6 40MHz short GII

- Laptop Speedtest shows 14 Mbit/sec download / 46 Mbit/sec upload
- Desktop Speedtest shows 45 Mbit/sec download / 46 Mbit/sec upload

- File download (ssh) from VPS to Laptop over WiFi - 14 Mbit/sec
- File upload (ssh) from Laptop to VPS over WiFi - 50 Mbit/sec

- File download (ssh) from VPS to Laptop over wired connection - 46 Mbit/sec
- File upload (ssh) from Laptop to VPS over wired connection - 52 Mbit/sec

- File download (ssh) from Router to Laptop over WiFi - >200 Mbit/sec (!)
- File upload (ssh) from Laptop to Router over WiFi - >200 Mbit/sec

- Laptop random torrent download (many connections) - 45 Mbit/sec (!)

I tried to change/remove iwlwifi module options - the same results.
Ping to the router is very stable (1 ms or less)
All connected devices works fine (phones, another Asus laptop (UX390UA) with Arch (for me) / Windows (for wife) - U/D connections are steady in Arch and/or Windows).
Local connections between devices works OK (including my Laptop)
No suspicious entries are found in iptables/etc on the router (as I said it has very default settings).

I tried to reboot with current LTS. Interestingly enough that dowstream speed from the Router dropped too (~40 Mbit / sec). No other changes.

All this would be clear if it were not so high download speed on the local network (from Router / neighbors). I'm stuck, really... (What am I missing?)

Zod · 2019-12-14 21:19:16

If it were me, I would probably install Wireshark (or the like) .

User Guide

seth · 2019-12-14 21:34:40

What options? Incl. "options iwlwifi 11n_disable=8", https://wiki.archlinux.org/index.php/Ne … ss#iwlwifi ?

Stellarator · 2019-12-15 08:43:57

Thanks, seth. This was the first option that I tried. No difference and as I understand it relates to the upstream speed (which is already good). All above measurements were made without any options at all. So to exclude various power saving nuances (which, as practice has shown, also do not affect anything).

The main difference between all my current devices is that my laptop has 802.11n card and all other devices connect over 802.11ac. But I don't understand at all what this can influence. To aggravate the situation, it should be noted that I headed the division of a large telecom operator , so things like Wireshark (thanks, Zod) are not new for me. But, unfortunately, WiFi technologies are not my competence, I was engaged in a broadband over landlines. And a misunderstanding of the reason(s) of mentioned behavior - infuriates me additionally.

So, I want to try using USB WiFi (802.11ac) whistle when I find a suitable somewhere around. And probably will dive into wireshark's dumps (but I need some spare time for this step). My intuition tells me that the whole situation is somehow related with 802.11n. But I didn't find any similar options (like transmission antenna aggregation) for Broadcom chipsets (which is used on Asus router) and in any case, everything is complicated in terms of tuning from the router side (hardware part and its setup is more or less proprietary thing as I understand). And again, local speeds are normal both ways...

A kind of congestion on the way from the Internet(?!) But at which step? And why only for one client?

Arch Linux

#1 2019-12-14 12:45:11

Abnormal (slow) routed downstream speed over WiFi (Intel 6235)

#2 2019-12-14 21:19:16

Re: Abnormal (slow) routed downstream speed over WiFi (Intel 6235)

#3 2019-12-14 21:34:40

Re: Abnormal (slow) routed downstream speed over WiFi (Intel 6235)

#4 2019-12-15 08:43:57

Re: Abnormal (slow) routed downstream speed over WiFi (Intel 6235)

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