Two suspect NICs at this point:
– Intel® 82579LM found in some HP laptops. Disabling the IPV6 TCP checksum offloading resolves the problem.
– Realtek RTL8111E – The problem is inconsistent
Since rolling out dual-stack IPV6 to our consumer Internet customers, we’ve had a couple of customer incidents with very slow IPV6 TCP performance to dual-stacked websites (facebook, Wikipedia.org, …). The problems only occurs with Windows 7/8/10 PCs connected via Ethernet NICs. Disabling IPV6 TCP checksum offloading will resolve the performance issues in some cases, but not in all cases. We have tried updating the Windows NIC driver to the latest version, but that didn’t help. I’m wondering if anybody else has seen this issue with Windows PCs.