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 bare standards that collectively provide a MAC relay function between LAN subnetworks. This part of ISO/IEC ISP 10612 is applicable to interworking units operating between Token Ring LAN subnetworks. ISO/IEC ISP 10612-1 specifies the relay function and LAN subnetwork-independent requirements, ISO/IEC ISP 10612-3 specifies the Token Ring LAN subnetwork-dependent requirements, and this part of ISO/IEC ISP 10612 defines the profile RD53.53.