Security Associations

IPSec uses Security Associations (SA) to specify the protocols to be used for encryption and authentications. Security associations is a database record which specify security parameters controlling security operations. They are referenced by the sending host and established by the receiving host. An index parameter called the Security Parameters Index (SPI) is used. Security Associationss are in one direction only and a second securioty association must be established for the transmission to be bi-directional.