ISO/IEC ISP 10612 is applicable to interworking units concerned with operating in the Open Systems Interconnection (OSI) environment. It specifies a combination of OSI Base standards that collectively provide a MAC relay function between LAN subnetworks. This part of ISO/IEC ISP 10612 is applicable to interworking units operating betwen CSMA/CD and FDDI LAN subnetworks. ISO/IEC ISP 10612-1 specifies the relay function and LAN subnetwork-independent requirements, ISO/IEC ISP 10612-2 specifies the CSMA/CD LAN subnetwork-dependent requirements, ISO/IEC ISP 10608-14 specifies the FDDI LAN subnetwork-dependent requirements, and this part of ISO/IEC ISP 10612 defines the profile RD51.54.