In a short time, IEEE EPON has progressed from initial trials to a market-leading optical access technology that supports business and residential services, including IPTV, VoIP, commercial- grade data services, and cellular backhaul. Due to EPON's simplicity and flexibility, various standards development organizations have embarked on standardization projects aimed at integrating EPON with existing network architectures. Also, several network operators have developed EPON solutions that address their specific deployment environments or relevant regulations. The IEEE P1904.1 SIEPON project is creating an open international system-level specification that provides for multivendor interoperability of EPON equipment while accommodating the rich and varied nature of the existing deployments and standards. The development of a unified EPON data path architecture is one of the key achievements of the SIEPON project. This flexible architecture supports multiple service models, multiple provisioning and management concepts, and diversity of deployment environments and regulatory requirements.