Insufficient access (50)

[root@daniel openldap]# ldapadd -Y EXTERNAL -H ldapi:/// -f base.ldif
SASL/EXTERNAL authentication started
SASL username: gidNumber=0+uidNumber=0,cn=peercred,cn=external,cn=auth
SASL SSF: 0
adding new entry "dc=dadlab,dc=bn"
ldap_add: Insufficient access (50)
        additional info: no write access to parent