In article <20041001155410.GZ24823@NetBSD.org>,
Emmanuel Dreyfus <manu@netbsd.org> wrote:
>Hello
>
>IPsec NAT traversal (NAT-T for short) is needed when any end of an IPsec
>communication are behind a network address translator. This is extremlely
>useful when using IPsec for remote user access VPN. NetBSD does not 
>implement it.
>
>I wrote the code, and it works, but it cannot be included in the tree because
>of a legal problem: it seems MS holds a US patent on it. 
>
>I don't live in a country where software patents are legal, so I don't care, 
>I will use my code without contributing it to the tree. If you would like
>to see NAT-T committed in NetBSD, then it is time to offer your help.
>
>We need someone that will read carefully the patent description and check
>if that covers what we do. If it does, then the position of other free OS
>whould be checked: Linux integrated it, what was their legal conclusions? (for
>instance, maybe they found prior art). What did OpenBSD did? 
>
>The last option can be to request a license from Microsoft, the problem there
>will be to find the right person to speak with.

Look at:

http://www.sandelman.ottawa.on.ca/ipsec/2003/06/msg00110.html

christos