This read-write enumeration (mapEFCI(1), setEFCIzero(2)) controls, for service-interworking channels only, whether the Frame Relay FECN bit is mapped onto the ATM cell's EFCI bit. An administrator sets mapEFCI so that frame-relay-side congestion signaling is preserved across the interworking boundary into the ATM cells carrying that traffic. For example, on an SIW channel experiencing frame-relay congestion, setting chanFECNconfig to mapEFCI ensures the corresponding ATM cells' EFCI bit reflects that same congestion state rather than always reading zero.