if (!is_array($this->rate) {
    throw new IsntAFuckingArrayException();
}

if (!isset($this->rate['in'])) {
    throw new TheInRateIsMissingCuntsException();
}

switch ($this->nastype) {
    case 'cisco':
        // NYI
        break;
    case 'plns':
        !is_array($reply['mpd-filter']) ? $reply['mpd-filter'] = sprintf('') : array_push($reply['mpd-filter'], sprintf(''));
        break;
    case 'mikrotik':
        $reply['MT-Rate-Limit'] = sprintf('%s/%s', $this->rate['in'], $this->rate['out']);
        break;
}