I believe the only real way to mitigate against DDOS attacks is to make sure you've got a lot of bandwidth, that your router can handle as much data as the DDOSer can throw at it and that it can detect and throw away DDOS packets. This isn't easy, and I doubt any home systems are able to do a good job at this. Even the best professional hosting finds it hard - it has to be taught which packets are part of the DDOS (e.g. filtering by country, or some other fingerprint).