TLS stands for “Transport Layer Security” and is the successor of SSL, the Secure Sockets Layer protocol [SSL3] (see Bibliography) designed by Netscape. TLS is an Internet protocol, defined by IETF1, described in RFC 4346 and also in [RESCORLA] (see Bibliography). The protocol provides confidentiality, and authentication layers over any reliable transport layer. The description, below, refers to TLS 1.0 but also applies to TLS 1.1 [RFC4346] (see Bibliography) and SSL 3.0, since the differences of these protocols are minor. Older protocols such as SSL 2.0 are not discussed nor implemented in GnuTLS since they are not considered secure today. GnuTLS also supports X.509 and OpenPGP [RFC4880] (see Bibliography).
[1] IETF, or Internet Engineering Task Force, is a large open international community of network designers, operators, vendors, and researchers concerned with the evolution of the Internet architecture and the smooth operation of the Internet. It is open to any interested individual.