Adapter link 25% of what it was
I have had a TP mains-wired network running successfully for many years now and monitor the speed to the internet on a quarterly basis. In the last quarter or two, the speed seems to have dropped from 45Mbps to around 11Mbps. Connecting via wi-fi gives me the proper speed of 45Mbps so I know it's the network that's the problem. The TP-link utility is showing 143Mbps between my PC adapter and the router adapter. Technical support are saying that the speed I'm getting is reasonable and I should expect some degradation in speed due to the network, but this doesn't make sense to me. I would have thought that the limiting factor to my internet access would be my broadband speed, not the speed of my tp-link network. It seems daft that my wi-fi speed is faster than a wired network. I have swapped all the adapters and cables around, and reset the devices to factory settings. Something has happened in the last few months and I can't think what. Can anyone help?