[c-nsp] BGP flowspec S/RTBH for large DDoS

[Satish Patel]

I was reading http://gurudatt28227.blogspot.com/2015/03/ddos-mitigation-using-bgp-flowspec-ddos.html

And they said BGP flowspec S/RTBH isn't useful for large number of
sources attackers.

We are getting 20G DDoS sometime on link and it has many many sources
does S/RTBH with flowspec mitigate them? is there any limit of
flowspec?