[cotillion]

At this scale you pretty much need to apply some sort of DDoS scrubbing service. Your ISP might already have one they can route traffic through or if you have your own AS you can let a DDoS service announce the target prefixes.

A game i run was recently hit with a 102 Ggbps CLDAP reflection attack. We were down for a while until our ISPs DDoS protection detected it after that we were mostly unaffected. If the attack is difficult to separate from legitimate traffic you'll still suffer though.