private function getRootDse()
    {
        if (!$this->rootDse) {
            $rootDse = $this->ldap->getRootDse();
            if (!$rootDse instanceof ActiveDirectory) {
                throw new UnsupportedRootDseException($rootDse);
            }
            $this->rootDse = $rootDse;
        }

        return $this->rootDse;
    }