This sets the peak cell rate for rate queue 5 on this port, the second of the four low-priority queues (4-7). A second low-priority queue on this port lets the admin separate two different best-effort traffic classes, for example two different data customers sharing this trunk, each with its own burst ceiling. If queue 4 carries a bulk-transfer application and queue 5 carries interactive but non-critical traffic, pportPeakCellRate5 could be tuned lower to keep the bulk transfer from swamping it.