This read-write enumeration controls Frame Relay Consolidated Link Layer Management (CLLM) behavior on the port: when off, received CLLM messages are discarded and none are generated; when on, the unit generates CLLM messages on the FR-NET side when a PVC becomes congested or blocked, and processes received ones. An administrator enables this to allow congestion notification via CLLM messages rather than only in-band congestion bits. For example, turning this on for a heavily loaded FR-NET connection would let the unit proactively notify the network when a specific PVC becomes congested or blocked.