The problem seems on your computer, when I check on value on my PC, it has 1.0Gbps Full Deplex this option. Suggest to check the built-in network adapter on your PC

http://forum.tp-link.com/showthread.php?101094-Security-Flaws-Severe-flaws-called-quot-KRACK-quot-are-discovered-in-the-WPA2-protocol

See a tp-link notice posted here: http://forum.tp-link.com/showthread.php?101094-Security-Flaws-Severe-flaws-called-quot-KRACK-quot-are-discovered-in-the-WPA2-protocol Waiting for the update from...

http://forum.tp-link.com/showthread.php?101094-Security-Flaws-Severe-flaws-called-quot-KRACK-quot-are-discovered-in-the-WPA2-protocol

How about test the speed with pc connected to the modem directly without the switch, and also from Deco directly? Are you testing on the same computer with the same quality cable? What's the Ethernet...

Are those tests run at the same location? Can you check the wireless link speed on your computer when it connects to deco in router and ap mode?