Overflow Control Mechanism (OCM) for Ethernet Passive Optical Networks (EPONs)

1— The non-fragmentable nature of Ethernet data frames, as well as operation of the priority oriented packet schedulers in the Optical Network Units (ONUs) along with heavy network load conditions and the lack of detailed knowledge about the queues composition at the Optical Line Terminal (OLT) level, result in the creation of upstream channel slot remainders. Non-preemptive packet schedulers and multithreshold reporting processes defined vaguely by the IEEE 802.3 – 2005 standard result in either increased packet delay or EPON system incompatibility, respectively, since threshold processing was never officially defined in the scope of the referred EPON standard. In this paper, we propose an alternative approach, based on basic modifications of the standard and extended GATE MultiPoint Control Protocol (MPCP) Data Unit (DU) formats and meaning, allowing for the OLT packet scheduling agent to grant always exactly the requested slot size, thus preventing the creation of any upstream channel slot remainders. It is estimated that roughly 3% of the upstream bandwidth can be salvaged when slot remainders are absent in the upstream channel transmission.