Acronym for Simple Authentication and Security Layer. Originating with RFC 2222, written by John Myers while at Netscape Communications, SASL is a method for adding authentication support to connection-based protocols. SASL takes effect when a protocol initiates a command for identifying and authenticating a user to a server. SASL also includes an option for negotiating protection of subsequent protocol interactions. With this option in effect, SASL places a security layer between the protocol and the connection.