@Kevin_Z Thank you for your reply. But my router is AX6000, not AX11000. And I have already disabled QoS, no device are in priority. Besides, I was exchanged a new AX6000. So I think is similar to...

Hi TP-Link I have an ISP providing 1,000 mb/s in house fiber cable connection, the fiber cable will connect to their modem, and then a Cat.6 cable connects my Archer AX6000 router. I've purchased my...