Although setting up and maintaining an IPsec setup is far beyond the scope of this book, let's look at a simple IPsec example to show how labeled IPsec is enabled on such a system. Remember that the labeled network controls on the interface, node, and peer levels, as mentioned earlier, are automatically enabled the moment labeled IPsec is used.
In an IPsec setup, there are two important concepts to be aware of:
The security policy database (SPD) contains the rules and information for the kernel to know when communication has to be handled by a particular IP policy (and as a result, handled through a security association).
The security association database (SAD) contains the individual security associations. A security association (SA) is a one-way channel between two hosts and contains all the security information about the channel. In the case of labeled IPsec, it also contains the context information of the client that caused the security association to materialize.
Security...