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[zpl]

Hello, I encountered a problem while using it. I only installed the installation package for Windows Packet Filter and tested its speed using iperf3. It dropped directly from 10Gb to 2.5Gb. That’s right, I only installed the installation package and did not run any sample programs

[Vadim Smirnov]

This is probably related to Jumbo Frames. Some hardware can reach 10 Gbps only when Jumbo Frames are enabled, while the standard Windows Packet Filter driver build limits the maximum Ethernet frame size to 1514 bytes:

#ifdef JUMBO_FRAME_SUPPORTED
#define MAX_ETHER_FRAME 9014
#else
#define MAX_ETHER_FRAME 1514
#endif

So, even if no sample application is running, installing the standard driver may affect throughput on such hardware.

To enable Jumbo Frame support, the driver has to be rebuilt with JUMBO_FRAME_SUPPORTED defined.

[george456]

That’s definitely not expected. Just installing the Windows Packet Filter driver shouldn’t normally reduce your throughput from 10 Gb/s to around 2.5 Gb/s without any filtering application running.

A few things I’d check:

• Make sure the NIC driver didn’t change or get reconfigured after the installation.
• Verify that features like RSS, RSC, and Large Send Offload are still enabled, as those can have a big impact on 10 Gb performance.
• Try uninstalling the Windows Packet Filter package and rerun the same iperf3 test to confirm the performance drop is directly related.
• If possible, test with the latest version of the driver and the WFP package, as there may have been fixes since the version you’re using.

Out of curiosity, what network adapter are you using (Intel, Mellanox, Broadcom, etc.) and which version of Windows? That information might help narrow down whether it’s a driver compatibility issue or something specific to the filter driver.

[zpl]

we have identified the issue. We were previously using a virtual machine with a virtual network card, but after switching to a physical machine, this phenomenon no longer occurred. The model of the virtual network card is Red Hat VirtIO Ethernet Adapter

[gilshehbaz9]

That’s a pretty significant drop, especially going from 10Gb to around 2.5Gb just from installing the driver. It’s interesting that the issue disappeared after moving from the VM to a physical machine. The VirtIO network adapter seems like an important detail here, since virtual NICs can behave quite differently with packet-filtering drivers and offloading features. Glad you were able to narrow it down.

[iricah21]

If the speed drops immediately after installing the driver, even with no sample running, I’d first compare the NIC settings before and after installation. Windows Packet Filter works at the NDIS level, so the driver can affect things like NIC offloading even when nothing is actively filtering packets.

I’d especially check RSS, Large Send Offload and the adapter’s MTU/Jumbo Frame settings, then run the same iperf3 test after uninstalling the filter to confirm the difference.

The 10 Gb → 2.5 Gb drop is pretty large, so I’d also be interested in which NIC/driver you’re using and whether this is on physical hardware or a VM.
If it’s a VM, I’d test the same package on a physical machine as well, virtual NIC implementations can behave quite differently with NDIS filters.

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