Internal Program Version: Cyrus SASL  2.1.28

SASL is the Simple Authentication and Security Layer, a method for
adding authentication support to connection-based protocols. To use
SASL, a protocol includes a command for identifying and authenticating
a user to a server and for optionally negotiating protection of
subsequent protocol interactions. If its use is negotiated, a
security layer is inserted between the protocol and the connection.

http://asg.web.cmu.edu/sasl