This read-write integer serves as the key used to correlate cell/frame count records with their start and end call-detail records; it is not supported on FRSM12. An administrator or billing/accounting system relies on frCDRNumber to tie a connection's traffic counters back to the specific record documenting when that traffic period started and ended. For example, a usage-billing process matching cell counts to call records for a PVC would use frCDRNumber as the join key linking the counters to the corresponding start/end record entry.