The Simple Authentication and Security Layer (SASL) is a framework for providing authentication and authorization to comunications protocols. It is defined in RFC 2222 . The design attempts to separate the implementation of authentication mechanisms from the implementation of communications protocols. The result is a set of available mechanisms that a server and client can select among. SASL is currently found in SMTP, IMAP, LDAP, BEEP, XMPP and in HTTP authentication. Some common mechanisms are ANONYMOUS , PLAIN, LOGIN, [CRAM-MD5] , [DIGEST-MD5] , NTLM and Kerberos.tcllib 1.8 contains an implementation of SASL that supports the most common mechanisms. TclSASL is a Tcl interface to the cyrus-sasl library which supports all those implemented by that library. See Marshall T. Rose's excellent "Using SASL: Pluggable Security" .Also see SASL and TWAPI.