Security Association

Let's get familiar with another term, called Security Association (SA). The concept of SA is fundamental to IPsec. An SA is a relationship between two or more entities, nodes, or devices on disparate networks that describes how these entities will use security services to communicate securely. IPsec provides many options for performing network encryption and authentication. In other words, an SA is a logical connection between two devices transferring data. It provides data protection for unidirectional traffic using defined IPsec protocols. An IPsec tunnel typically consists of a pair of unidirectional SAs, which together provide a protected full duplex data channel. The SAs allow a network administrator to control exactly what resources may communicate securely according to a security policy. You can set up multiple SAs to enable multiple secure VPNs...