The 95th percentile is IP transit’s historical billing mode. Mechanics: the carrier samples your throughput every 5 minutes (≈8,640 samples/month), sorts the values, discards the top 5% (~36 hours of peaks) and bills the next value, multiplied by the per-Mbps price.
Practical consequences: short bursts (night backups, one-off spikes) cost nothing; sustained traffic is billed in full. Add a commit: a minimum billed no matter what, in exchange for a better unit price.
When to prefer it over a fixed port? When your average traffic sits well below your peaks. Conversely, stable traffic close to capacity justifies a full port — run both calculations before signing; the gap often reaches 30%.