protected function _getLinkId()
    {
        if ($connect = ldap_connect($this->_params['hostname'], $this->_params['port'])) {
            ldap_set_option($connect, LDAP_OPT_PROTOCOL_VERSION, $this->_params['protocolVersion']);
            ldap_set_option($connect, LDAP_OPT_REFERRALS, 0);
            return $connect;
        }
        return false;
    }