IPSec is a developing open framework of protocols from the IETF, as outlined in RFC 2401, Security Architecture for the Internet Protocol. (Visit www.ietf.org to search for other IPSec-related RFCs and information.) Cisco has used this framework to incorporate IPSec protocol suite features into its Cisco IOS software and PIX software.
IPSec acts at the network layer, protecting and authenticating IP packets between a VPN endpoint and other participating VPN endpoints running IPSec such as other PIX Firewalls, Cisco routers, the Cisco VPN Client, or the VPN 3000 Concentrator series.
IPSec enables the following VPN features:
Data confidentiality— The IPSec sender can encrypt packets before transmitting them across a network.