After several days Wan throuput drops from 1Gbps down to 300Mbps
* Note the firmware version was just upgraded so this issue was with the previous version from 2022.
I have my AC5400 sitting behind an ISP-provided Fibre Modem that is running in routed mode (ISP Modem is running 192.168.0.x/24 and AC5400 is on 192.168.1.x/24). Except for my TV set-top box which pairs directly to the ISP modem over its WiFi, all wired and wireless devices in my house are connected to the AC5400 and on the 192.168.1.x subnet.
My traffic pattern means that several times throughout the day it is not unusual for my Linux server to download at network saturation for the 1Gbps hardware I am using in my house (the ISP Modem can run over 3Gbps uplink and downlink when using internal speed test tools meaning the WAN can handle this speed without issue). Running Ookla's speed test utility from Linux shows that I am getting the full 1Gbps that the wired network in my house allows in each direction...
bergang@hda:~/data_nbk_gh/Archive/temp/rename$ speedtest
Speedtest by Ookla
Server: Bell Canada - Ottawa, ON (id: 54836)
ISP: Bell Canada
Idle Latency: 1.60 ms (jitter: 0.23ms, low: 1.14ms, high: 1.69ms)
Download: 938.39 Mbps (data used: 491.0 MB)
11.92 ms (jitter: 0.87ms, low: 1.98ms, high: 23.21ms)
Upload: 938.34 Mbps (data used: 871.4 MB)
5.48 ms (jitter: 1.09ms, low: 1.71ms, high: 21.03ms)
Packet Loss: 0.0%
Result URL: https://www.speedtest.net/result/c/85f78478-b58f-4a0c-8f99-ce606e0b4a11
What I am experiencing is that over the course of several days (can be as many as 10) this speed will drop to about one-third of the 1Gbps which is normal (about 300-330 Mbps). Rebooting the AC5400 restores the network performance to normal. I have looked at the CPU and memory resources on the router and there does not seem to be a significant change from before and after the reboot. I am thinking that it could be related to socket management between the two routers but am wondering if there is some way that this can be diagnosed better.
I have written a cron utility to catch this condition and send me an email when it occurs so I know to reboot the router. The test looks to see if uplink or downlink has fallen below 800 Mbps every 15 minutes and will trigger if 12 consecutive tests fail (this prevents normal network activity from appearing like a network slowdown if the test runs during a high-traffic event). Here is the pattern of its occurrence over the last several months (the utility generates a set/clear log event into a text file on the server)...
Aug 02 2023 09:00:27.038 : Internet speed test has fallen below threshold
Aug 02 2023 20:30:18.569 : Internet speed test is now above threshold
Aug 10 2023 06:30:23.412 : Internet speed test has fallen below threshold
Aug 10 2023 09:45:17.161 : Internet speed test is now above threshold
Aug 30 2023 21:30:28.428 : Internet speed test has fallen below threshold
Aug 31 2023 01:45:15.285 : Internet speed test is now above threshold
Sep 04 2023 01:45:22.502 : Internet speed test has fallen below threshold
Sep 04 2023 13:15:18.376 : Internet speed test is now above threshold
Sep 07 2023 22:00:31.355 : Internet speed test has fallen below threshold
Sep 08 2023 01:00:17.739 : Internet speed test is now above threshold
Sep 12 2023 12:00:17.949 : Internet speed test has fallen below threshold
Sep 13 2023 01:30:17.501 : Internet speed test is now above threshold
Sep 23 2023 12:30:28.748 : Internet speed test has fallen below threshold
Sep 23 2023 19:45:20.678 : Internet speed test is now above threshold
Sep 29 2023 03:00:32.344 : Internet speed test has fallen below threshold
Sep 30 2023 04:15:14.836 : Internet speed test is now above threshold
Oct 05 2023 00:15:33.428 : Internet speed test has fallen below threshold
Oct 06 2023 05:00:15.724 : Internet speed test is now above threshold