6.8. Task 6.8: Implementing an IPSec VPN Using AES
New in Microsoft Windows Vista and in Microsoft Windows Server 2008 is the Windows Firewall with Advanced Security. This new implementation of the Windows personal firewall introduces a significant improvement in the IPSec VPN. Earlier versions of Windows that implemented IPSec (Windows 2000 through Windows XP) used Triple Data Encryption Standard (3DES) as its strongest encryption. Windows Vista and Server 2008 use the newer, stronger Advanced Encryption Standard (AES), with three different key lengths to choose from. AES is currently considered "uncrackable."
If you're interested in the nitty-gritty of how AES works, see "Keep Your Data Secure with the New Advanced Encryption Standard," ...