Network speed between two gigabit ethernet connected PCs

I'm following up on this post regarding network speed testing using iPerf3 to test the connection speed between a desktop PC and a dock-connected MS Surface Pro 4 (so it's connected to gigabit ethernet), both running Windows 10 and both showing truly abysmal speeds in things like copying files/folders between machines.

After disabling AV and anti-malware on both machines, I tested again and found that the speed in either direction using iPerf3 was never more than about 600Mbps, though file copying from the desktop PC to the SP4 reported speeds of less than 1Mbps, which was a serious concern. Oddly enough, file operations between each of the PCs and my QNAP NAS are at least 70MB/s so the woeful PC-to-PC performance is a surprise.

As suggested by someone in my previous post on this subject, I installed Ubuntu and iPerf3 on a couple of bootable USB thumb drives and booted both PCs with them. iPerf3 speed testing shows around 950 Mbps in either direction between the desktop and SP4, so that discounts any hardware issues.

The above must mean that Windows 10 must have really poor inter-PC networking, but if so then I'm at a loss to know what to do about it. The performance is so bad that it's much quicker for me to copy my files from the desktop PC to a folder on the NAS, then copy those files from the NAS to my SP4 - copying directly between those two PCs is excruciatingly slow otherwise.

Has anyone else encountered similar issues with Windows 10 PC-to-PC networking?

In reply to a post by joconnell:

Has anyone else encountered similar issues with Windows 10 PC-to-PC networking?

Yes, with Symantec, McAfee or any other third party antimalware installed. Do you have that sort of software?

If you don't and are just using Win10 with its built in Defender, then it could be a network card driver issue.

Given the PC to NAS is quick, but PC to laptop is slow, the problem could be the laptop writing to its disk?

Have you already tried to reset the Windows networking stacks to defaults - I believe it is done via netsh commands?

In the past it was more common for people to tweak various settings for dial-up and then for DSL, in part to compensate for the asymmetry of Internet connections, rather than for general purpose networking / LAN.

But yes it does not surprise me, the BSDs tend to have more mature network stacks and, in common with Linux drivers, there is much less tendency to install things which affect packet processing as much as with Windows, where anti-malware and virtualisation tends to install various software-based filters.

Given that Windows can now be run from a USB stick, that might be another way to test a vanilla setup without having to factory reset the machine. As the iPerf tests are run using RAM and the network, disk speeds won't be a factor.

For file transfer performance, have you tried creating a small RAMdisk on both Windows machines. Old school I know, modern computers tend to have sufficient RAM to easily afford 1GB for temporary downloads and tests.

You could compare Windows file sharing with protocols like FTP and HTTP, to help show whether it's OS or protocol-specific.

Seems quite normal to me. Disable windows defender and firewall and you might see a performance increase.

If its important to you, you could change to 10gbe.

In reply to a post by dan_miles86:

Seems quite normal to me.

I've seen 900 Mbps between two PCs running Win10 with Defender enabled. Not sure 600 is good, and 1 Mbps is obviously broken!

In reply to a post by jchamier:

In reply to a post by dan_miles86:

Seems quite normal to me.

I've seen 900 Mbps between two PCs running Win10 with Defender enabled. Not sure 600 is good, and 1 Mbps is obviously broken!

Indeed, I've never needed to adjust any settings in a default Win 10 install in order to get full gigabit speed to my Synology DS918+

To me it looks like it could be an IP conflict

In reply to a post by robertcrowther:

Indeed, I've never needed to adjust any settings in a default Win 10 install in order to get full gigabit speed to my Synology DS918+

Same with a DS214+.

To me it looks like it could be an IP conflict

I wondered about a broken NIC, but more likely faulty cable!

I doubt it's a cable fault as they managed to get full speed on a Linux install.

In reply to a post by robertcrowther:

I doubt it's a cable fault as they managed to get full speed on a Linux install.

Then its got to be driver. Or some third party security software that may not have fully uninstalled (e.g. demo supplied with the PC).

Edited by jchamier (Sat 20-Jun-20 13:08:35)

As they have said "The performance is so bad that it's much quicker for me to copy my files from the desktop PC to a folder on the NAS, then copy those files from the NAS to my SP4 - copying directly between those two PCs is excruciatingly slow otherwise."

It doesn't look to me like a driver or third party software, it does however show classic symptoms of either an IP address conflict, or I have seen in the past where laptops will still try and use wireless connection even though the ethernet is plugged in