SSL provides endpoint authentication and communications privacy, as well as possibility for one-way or mutual authentication using certificates. The protocol allows client/server applications to communicate without being subject to eavesdropping, tampering, or message forgery. SSL runs on layers beneath application protocols (for example, HTTP, SMTP, and so on) and above the TCP transport protocol. SSL is able to use a number of symmetric and asymmetric encryption algorithms. The certificates used in the communication must conform to the X.509 standard.

IPSec is a set of protocols for securing packet flows and key exchange by encrypting and/or authenticating all IP packets. As IPSec is an obligatory part of IPv6 (and optional in IPv4), it can be expected that it will become increasingly widespread. IPSec provides end-to-end security for packet traffic — even for UDP packets, because it operates over the IP layer. In PNS, IPSec is used to construct Virtual Private Networks (VPNs). Please refer to Chapter 16, Virtual Private Networks for more details.