Deploying COXcast in Software-Defined PONs: Architectures, Mechanisms, and Demonstrations

To address the growing demand for efficient multicast service delivery in Passive Optical Networks (PONs), this study integrates the software-defined networking paradigm with the Code-Oriented eXplicit multicast (COXcast) mechanism. The proposed framework introduces the architecture, mechanisms, and demonstrations of COXcast-enhanced Software-Defined PONs (SD-PONs). However, the scalability of the original COXcast design is limited, as an increase in the number of OLTs/ONUs significantly enlarges the packet header size. This expansion, constrained by the Maximum Transmission Unit (MTU), reduces the effective payload capacity. To address this limitation, the Check-bits Doping (CBD) method is introduced, which augments the original COXcast by embedding verification check bits in the output port bitmap (OPB). This enhancement prevents non-participating OLTs/ONUs from forwarding multicast traffic, while enabling controllable traffic leakage. Compared to the original COXcast, CBD effectively reduces protocol overhead and processing complexity, improves scalability, and is particularly advantageous for point-to-multipoint (P2MP) network scenarios, such as combo PONs.