protected function _vcl_backend($name, $host, $port, $options = array()) {
        $tpl = <<<EOS
backend {{name}} {
    .host = "{{host}}";
    .port = "{{port}}";

EOS;
        $vars = array(
            'host'  => $host,
            'port'  => $port,
            'name'  => $name,
        );
        $str = $this->_formatTemplate($tpl, $vars);
        foreach ($options as $key => $value) {
            $str .= sprintf('   .%s = %s;', $key, $value).PHP_EOL;
        }
        $str .= '}'.PHP_EOL;
        return $str;
    }