performance – Slow file transfer speeds over gigabit ethernet

Within my setup are:

  • 1 FTTP router with Cat5e internet cable out
  • 1 Netgear GS308E gigabit switch, connected to the router via Cat6.
  • 2 devices (1 Raspberry Pi4, 1 thinkpad with gigabit ethernet connection), both connected to the switch via Cat5e and Cat6 cables respectively.

The RPi4 as 2 external USB 3.0 WD Passports connected to USB 3.0 ports.
The thinkpad has an internal SSD.
The RPi4 also has a gigabit ethernet connection.

When copying files from the RPi4 to the thinkpad using either scp or wget, I receive an average speed of 4.3MB/sec.
The sample file used in an ISO image with a size of 4GB.
For wget, The RPi4 hosts a temporary web server using python -m SimpleHTTPServer.
I’ve tested internal copying on the RPi4 from one WD passport to another, and from one WD passport to the RPi4 local SD card, and according toiotop, I’m gaining write speeds well over 20MB/Sec and read speeds between 50MB/Sec and 80MB/Sec.

I don’t know of any software configuration either on the router, switch or the source and destination devices that could be throttling the transfer speed.

What other options can I take to further diagnose the issue?