[1] RFC 5246 - The Transport Layer Security (TLS) Protocol Version 1.2 ( 版) <http://tools.ietf.org/html/rfc5246#page-79>
connection
A connection is a transport (in the OSI layering model definition)
that provides a suitable type of service. For TLS, such
connections are peer-to-peer relationships. The connections are
transient. Every connection is associated with one session.