Question Slow data transfer over LAN but only between two specific computers and only when managed but one of them

May 25, 2019
briefly, I have 4 Windows PC's connected through a ethernet switch, let's name them A, B, C, D.
The network is working fine, except when I try to transfer files between A and B, and only when I use A to execute the file transfer, the file transfer drops below 10Mbps.
So, to recap:
  • if I'm operating from A and try to copy files to or from B, the transfer rate is slow
  • if I do the same file transfer using B or even C or D (always copying to or from A and B), the transfer rate is OK
  • if I'm operating from A and I copy files to or from C or D, the file transfer is OK.
I hope this makes sense.
A is a Win10 Pro, the others Win 7.
I'm not going too much into detail at the moment, but maybe this description can already ring a bell to someone, just to get a hint of what might be the source or nature of the problem.
Thanks in advance


Curious about the problem...

First: switch? Verify: switch or router? I would expect router....

Either way, update your post to include applicable make(s) and model(s).

Before doing any file transfers open Task Manager on each computer involved. Observe what takes place with respect to all successful file transfers first. Then execute the A to B transfer. Look for what changes.

You can use Resource Monitor in the same manner.

If, A to C succeeds and A to B fails (slow) then compare C's configuration settings to B's configuration settings.

A successful file transfer, slow or fast, indicates to me that the hardware is okay.

Therefore, the problem is likely some misconfiguration or other inability between A and B.

And your overall description makes me believe that "B" is the culprit and perhaps misconfigured with respect to B's relationship with "A".
May 25, 2019
Ralston18, thanks, I did what you suggested. While doing those tests, I happened to disable the software firewall (Comodo) on both computers A and B, and the data transfer got back to normal Gigabit rates, even when I re-enabled the firewalls
Unfortunately, I have no Idea what's wrong with Comodo. I can only add that the other computers, C and D, have a different firewall, which must be less hostile to my file transfer attempts.
I'll try to narrow down the causes, though I'll probably give up and change software, eventually. I'll post in case of success.
Thanks for answering