2.1 Transport
LDAP transport is specified in section 3.1.1.3, and in [RFC2251] section 5 (for LDAPv3), in [RFC1777] section 3 (for LDAPv2), and in [RFC1798] section 3.1 (for both LDAPv2 and LDAPv3).
When sending any control to the DC which does not require a controlValue field, the client sets the controlValue field of the Control structure to an OctetString of length zero and explicitly encodes this rather than omitting the controlValue field as indicated in [RFC2251] section 4.12.1. The server MUST ignore any controlValue provided in such requests.