is TLS an EXTERNAL SASL mechanism

["Michalski, Rafał" <RMichalski@eragsm.pl>]

Hi,

Being new to protocol, I started with reading 
the IBM book Understanding LDAP.
The book states that TLS communication is an EXTERNAL 
SASL mechanism.
This is also RFC 2222 (SASL) requirement.
But my browser doesn't report such a mechanism
in Openldap installation.
Command  'ldapsearch -Z -x' works,
'ldapsearch -Z' reports 'Unknown authentication method'.
It looks as if only PLAIN mechanism was available through TLS?

Rafal