When running network performance tests using iperf3 within powershell against the loopback interface, I max out around 12-13 Gbits/sec, as measured by the network activity within the Windows10 Resource Monitor.

I'm trying to figure out where this Windows10 loopback interface gets this speed from or where it might be configured. There's no apparent powershell commands/options or registry entries to modify this setting.

So the basis of my question is: can the loopback interface (and it is an interface, not to be confused with an adapter) by modified, and if it can, where is that modification performed?

If it cannot be modified, where/how does it pick up this ~10Gbps setting from.

Other things I have tried:

  • Adding the Microsoft KM-Test loopback adapter; no difference.
  • Changing the Receive Window Auto-Tuning level to experimental; slightly improves performance.
  • Uninstalled all other actual network adapters, such as LAN & Wifi; no difference.
  • Modifying the window size / socket buffer size in the iperf command.

My definitions:

  • Loopback interface is the Loopback Pseudo-Interface as shown in the output of powershell: netsh int ipv4 show int
  • Using iperf3 as per https://iperf.fr/iperf-download.php
  • iperf server command: iperf3.exe -s -D
  • iperf client command: iperf3.exe -c -t 100 (run for 100 seconds).

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