An overlay network is a network where all the nodes correspond to nodes in an underlying network and are connected through logical or virtual links.
In other words, an overlay network is layered on top of another network.
We restricted some Droplet network traffic to help prevent malicious actions, like reflected DDoS attacks. A reflection amplification attack, or reflexted DDoS attack, is a type of Distributed Denial-of-Service cyberattack where attackers magnify the amount of traffic generated in order to overwhelm the target and disrupt or shut down systems and services. Overlay networks are a workaround solution.