Anonymous Used when only read-only access to non-protected entries and attributes is needed when binding to the LDAP server.
Simple Simple authentication is not recommended for production deployments not using the ldaps secure protocol since it sends a cleartext password over the network.
CRAM-MD5 The Challenge-Response Authentication Method (CRAM) based on the HMAC-MD5 MAC algorithm (RFC 2195).
DIGEST-MD5 This is an improvement on the CRAM-MD5 authentication method (RFC 2831).
GSSAPI GSS-API is Generic Security Service API (RFC 2744). One of the most popular security services available for GSS-API is the Kerberos v5, used in Microsoft's Windows 2000 platform.