Realtek
Realtek PCIe GbE Family Controller
This is the single most common wired-LAN controller in consumer computing, integrated on a huge range of desktop boards and laptops as the standard gigabit port. It handles link negotiation up to 1 Gbps along with the usual offload and power-saving features. Because the same chip sits behind so many brand names, read the exact controller string in Device Manager, then on a branded machine fetch the version your PC maker validated rather than a bare Realtek build.
