Goodput is a metric, one of the truth numbers a thorough DDoS test is built to measure. It is the throughput of useful, legitimate application data actually delivered to real users, as distinct from raw throughput, which counts every byte on the wire including the attack traffic and the retransmissions it provokes. A link can show high aggregate bandwidth while goodput collapses toward zero, because the pipe is full of flood packets and dropped legitimate requests.
Why it matters in DDoS testing
Raw bandwidth graphs lie under attack: a saturated link looks busy whether it is serving customers or absorbing a flood. Goodput is the metric that separates "the service is up" from "the service is reachable but useless." A test measures goodput alongside total throughput so operators can see the real availability a mitigation preserves, not just the volume it is moving.
Why this distinction matters for resilience is examined in DDoS resilience testing.