We have wrote a bit on what is TDI. Basically most personal firewall are using TDI for various reasons:
- It’s a driver so it has the false sense it’s hard to remove.
- It’s been with us since 1995 on Win95.
- It has the ability to view traffic as stream or packets.
TDI is being phased out by Microsoft, and according to their documentation the next Windows version might not support it anymore so investing in TDI can be quite risky.