http://www.rfc-editor.org/rfc/rfc6066.txt
RFC 6066: Transport Layer Security (TLS) Extensions: Extension Definitions, D. Eastlake 3rd2011-01-01T23:00:00-00:00This document provides specifications for existing TLS extensions. It is a companion document for RFC 5246, "The Transport Layer Security (TLS) Protocol Version 1.2". The extensions specified are server_name, max_fragment_length, client_certificate_url, trusted_ca_keys, truncated_hmac, and status_request. [STANDARDS-TRACK]