Bits per second (BPS) is a metric, one of the core rate units a thorough DDoS test is built to measure. It counts the volume of data crossing a network link each second, usually expressed in gigabits per second (Gbps) or terabits per second (Tbps) at DDoS scale. BPS is the dimension that defines volumetric attacks: amplification and reflection vectors aim to push enough bits to saturate the upstream pipe, so legitimate packets are dropped at the congested link before they ever reach the origin.
Why it matters in DDoS testing
A link has a hard bandwidth ceiling, and once it is full, no downstream defense matters, because the loss already happened upstream. BPS is the metric that tells you whether scrubbing capacity and transit provisioning exceed the floods you expect. A test measures BPS at the saturation point to confirm where the volumetric ceiling sits and whether mitigation engages before the pipe fills.
The amplification vectors that drive this metric are covered in understanding DDoS attack vectors.