Answer:
A protocol that secures IP communications by authenticating and encrypting each IP packet.
Step-by-step explanation:
IPSec means Internet Protocol Security, is a set of protocols that modify the existing Internet Protocol (IP), providing mutual authentication, negotiation of cryptographic keys, data encryption, data integrity, and several other functions.
It was developed in the 90's, and basically IPSec creates a VPN (Virtual Private Network) tunnel to set up a private two-way connection between systems.