Talk to Jeff Wheeler. He can help you out with ddos attacks. He is the best in the market with helping these issues. If you need him contact info, let me know.
You can either purchase a riverhead device for 90K (And have the bandwidth to filter the attack plus have enough to keep the network up without lag) or colo with your tier1 provider and get them to give your router some heavy bandwidth.
Then you setup your ASN's to your on-site router or a router in another IDC (Multi-Home). So all your traffic will pass to router 1 (At the Tier1 IDC) that would be the device auto-nulling or filtering out unwanted traffic.
Typically if your on a low budget its extremely hard to filter or "eliminate" DDoS.
