What is IPSEC and how it works

IPSEC (Internet Protocol Security) are 3 cryptographic protocols useful to encrypt communications through a network, usually used for VPN, but applicable to protect the IP (Internet Protocol) in different cases. IPSEC is part of IPV6 while optional for IPV4. The 3 protocols composing IPSEC are AH (Authentication Header), ESP (Encapsulating Security Payload) and IKE (Internet Key Exchange). While AH and ESP work in different ways, both of them can be combined to provide different functions.