I've got an interesting puzzle for you:
- I've got two computers connected to the same LAN wirelessly.
- Computer A is using 802.11ac wireless protocol. Computer B is using 802.11n.
- I begin uploading files from computer A to computer B.
- Initially the upload speed is 70 Mbps but a few minutes later it drops to 3Mbps.
- When the upload speed decreases:
- It only affects computer A. Computer B works just fine.
- Internet speeds are limited in the same way (as reported by http://www.speedtest.net/).
- Download speeds don't seem to be impacted at all.
- Disconnecting and reconnecting computer A to the wireless network fixes the problem for a few minutes. Then it returns.
- As far as I can tell, my router does not have any QoS enabled. I am using OpenWrt 18.06 on a Linksys 1900ACS v2.
- The NIC on computer A is called "D-Link DWA-192 AC1900 Wi-Fi USB 3.0 Adapter".
- Both Computer A and B are running Windows 10.0.17134.228.
Any ideas what could be causing this and how to fix it?