1. Security extensions to IP. Traditionally, encryption takes place at the application layer or above. IPsec provides generic encryption for IP packets in such a way that applications are not necessarily aware of the process. IPsec source code is freely available. Key point: IPsec's main use today is when tunneling traffic for VPNs. It can also work for generic encryption of data between two hosts. Algorithms: Diffie-Hellman From Hacking-Lexicon