This read-write value sets the Peak Cell Rate for this channel in cells per second, the upper bound enforced by the first leaky-bucket policer against both CLP-0 and CLP-1 cells, applicable to UBR, CBR, VBR, and ABR connections, with a default of 50. It's the primary traffic-contract ceiling for the connection, and cells arriving faster than this rate are subject to the GCRA1 policing action, tagging or discard. An admin provisioning a higher-bandwidth PVC would calculate the corresponding cells-per-second figure and set bbChanUpcPCR accordingly, rather than leaving it at the low default of 50.