What is a denial-of-service (DoS) attack and what impact does it have on a target network?

What will be an ideal response?

A DoS attack is when a large volume of illegitimate traffic is forced onto a network such that it is not part of normal operation but must be dealt with by the devices connected to the network.Even firewalls are insufficient to stop a significant flood of traffic.The packets used for DoS are generally simple traffic that affects operation of the network by volume rather than complexity.This can cause legitimate traffic to be blocked out of the network and slow or stop normal network operation.