IPSec Concepts

This section provides an overview of IPSec concepts.

IPSec provides security to IP flows through the use of authentication and encryption.

Authentication verifies that data is not altered during transmission and ensures that users are communicating with the individual or organization that they believe they are communicating with.
Encryption makes data confidential by making it unreadable to everyone except the sender and intended recipient.

IPSec comprises two encapsulation protocols:

Encapsulating Security Payload (ESP) provides confidentiality and authentication functions to every data packet.
Authentication header (AH) provides authentication to every data packet.

Both protocols are defined with two modes of operation:

Tunnel mode completely encapsulates the original packet within another IP header.
Transport mode keeps the original header and does not add the extra IP header.