This read-only value reports the highest bandwidth utilization, in bytes per second, recorded for the FDDI interface since the peak was last reset. Admins use it to identify the worst-case throughput the ring has experienced, which is useful for capacity planning even if current utilization looks normal. If ctFDDIPeakBytes shows a much higher figure than the current ctFDDIBytes reading, it confirms the ring experienced a traffic burst at some point that isn't reflected in the current snapshot.