ISO/IEC ISP 10612 is applicable to interworking units concemed with operating in the Open Systems Interconnection (OSI) Local Area Network environment. It specifies a combination of OSI standards that collectively provide a MAC relay function. This part of ISO/IEC ISP 10612 specifies requirements dependent an the type of subnetwork and applicable to an interworking unit which is attached to an ISO/IEC 8802-3 CSMA/CD LAN subnetwork and relaying to another subnetwork not necessarily of the same type.