This document provides an overview of IPsec (Internet Protocol Security). It describes IPsec as a set of protocols that provide security at the IP layer by enabling encryption of packets and authentication of packet headers and payloads. The document outlines IPsec's main methods (Authentication Header and Encapsulating Security Payload), how it operates in tunnel and transport modes, its four main services (confidentiality, integrity, authentication, anti-replay), and key components of the IPsec architecture like the Internet Key Exchange and Security Association Database.