As the name suggests, the IP Security ( or IPSEC ) protocol suite is used to
provide security for IP communications. A host that directly participates in IPSEC
communications is referred to as an IPSEC Peer. Peers work together to
establish Security Associations ( or SAs ) that can be used to protect network
traffic. As with any method of secure communication, the two parties involved
must agree on a common set of parameters that define how the data will be
secured and have access to common key material that can be used to perform
the actual cryptographic services. Since the IPSEC protocol suite is used as a
means to secure network traffic, security policies need to be defined so that a
Peer can determine which traffic will require security processing.