I want to develop test application (something like IpSec, but much simple) that implement enacapsulating all IP packets of "PC" in some "another packets" with encription. This "another packets" are sent to another computer (smth like "proxy") that unpack original IP packets and send them to their original destination. Then this "proxy" receive packets for "PC" and decript them, incapsulate and send to "PC" and etc. Application must support working with NAT. I know that IPSec with NAT works only using NAT traversal therefore "another packets" will be udp, i.e. I'll encapsulate Ip in UDP with some encription.
I realize that winpcap not really that I need for develop such application. Can I develop such application without special hardware, using only soft? What kind of tools should I use (maybe I need to write own driver)?
Ok, If you want to encapsulate your data into ip packets, then that is one thing. here you say you wan t to encapsulate IP packets
considering OSI layers : wiki
As IP packets are layer 2 you wan't to reimplement layer 2. I think it is something you can only find in drivers, and therefore hard dependent.