Internet Key Exchange version 2 (IKEv2) is a tunneling protocol, based on IPsec, that establishes a secure VPN communication between VPN devices and defines negotiation and authentication processes for IPsec security associations (SAs).
In IKEv2 terminology, the first phase consists of the (usually four) messages that create the IKEv2 SA and the first associated IPsec Security Association (known as a child SA).
The four messages
IKE_SA_INIT: IPSec-Connection Initialisation
IKE_AUTH: Authenticaton of Communication counterparts
CREATE_CHILD_SA: Key change and invoking additional CHILD_SA
INFORMATIONAL: Further Exchange of Information
The IKEv2 SA is a protected tunnel that allows for subsequent messages to be sent cryptographically protected; this allows the sending of encrypted and authenticated notification messages, reliable dead-peer detection, and creation of additional child SAs.
