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EPoC - THE UPCOMING IEEE P802.3bn STANDARD FOR EPON PROTOCOL OVER COAX OVERVIEW AND IMPACT Mark Laubach Broadcom® Corporation Abstract node on the MDU campus. CableLabs® DOCSIS® [4] while becoming increasingly Following the interest from both the more popular, is not as widely deployed as in Chinese and North American cable industries, other parts of the world. Cable operators use the IEEE Standards Association approved a government funded optical fiber in the streets project under the IEEE 802.3 Standard For and are looking at the opportunity of Ethernet Working Group with the scope of transparently extending existing EPON extending the EPON protocol over coaxial services over legacy coaxial cabling present in (EPoC) networks. The P802.3bn EPoC Task a large majority of older and new multi- Force is in progress, developing a physical tenant/dwelling units (MxU). In North layer standard for symmetric and asymmetric America, High Speed Data (HSD) residential operation of up to 10 Gb/s on point-to- services are provided using DOCSIS multipoint coaxial distribution plants technology. Some cable operators are comprising either active or passive media. increasingly deploying EPON to primarily EPoC objectives, key technical and capture business market services and cellular performance considerations, and resulting backhaul. Metro Ethernet Forum (MEF) architecture are presented. Select [5]. service performance and contracted comparisons of EPoC with the DOCSIS 3.1 Service Level Agreements (SLAs) are pro PHY including common component forma. architectures are noted. The resulting PHY standard will enable several deployment Both Chinese nd North American models, increasing the number of options operators appear to have a similar desire for available to cable operators as part of their the simplicity of Ethernet at gigabit speeds future service growth. and for extending the life of existing coax cable networks. Key requirements for EPoC INTRODUCTION will be maintaining unified management and Quality of Service (QoS). DOCSIS Ethernet Protocol over Passive Provisioning of EPON (DPoE™ [6]) is Networks (EPON) was first standardized in straightforward to extend managed EPoC 2004 as part of the IEEE 802.3 Working systems. IEEE P1904.1 Service Group’s [1] Ethernet in the First Mile (EFM) Interoperability in EPON (SIEPON) is also initiative. Both 1 Gbit/s and 10 Gbit/s EPON available for seamless management [7]. standards are incorporated in the 802.3-2012 - IEEE Standard for Ethernet [2]. The P802.3bn Additionally, EPON and EPoC Task Force [3] extends the 10Gbps EPON directly support the step-wise migration from point-to-multipoint solution over cable back-end legacy MPEG-2 transport to MPEG- operator coax networks via a new physical 4 video distribution via IP over Ethernet. In layer. Initial interest for EPoC developed in the future, a large Ethernet-based gigabit pipe China and followed shortly by North to the home and business will be fundamental America. The motivation in both markets is for cost-effective growth and evolution. different. In China, Hybrid Fiber-Coaxial When available in the future, a cable operator (HFC) solutions are deployed extensively, will then have a choice to deploy IP over with a typical architecture of placing the fiber DOCSIS 3.1 or over EPON/EPoC based on For EPON, the IEEE Ethernet 802.3- their business needs. 2012 standard [2] defines the MAC and PHY Service and Application Architecture sublayers for a service provider OLT and a subscriber ONU. Two wavelengths are used Figure 1 shows an example of the on the fiber for full-duplex operation, one for target applications for a mix of EPON and continuous downstream channel operation and EPoC technologies that leverages fiber-deep another for upstream burst mode operation. access architectures of current networks and The OLT MAC controls time-division sharing the extension to existing coaxial distribution of the upstream channel for all ONUs via the infrastructure. Multipoint MAC Control Protocol (MPCP). Figure 1 illustrates an existing EPON Similarly, the EPoC architecture Optical Line Terminal (OLT) connection consists of a service provider Coax Line through a Passive Optical Network (PON) Terminal (CLT) and a subscriber Coax made up of optical fiber and passive splitters. Network Unit (CNU). The EPoC CLT and EPoC services are expected to extend the CNU MAC sublayers will be substantially same range of services as that of EPON: for similar to respective layers found in the OLT example, Residential, Business, Multiple and ONU. Minimal augmentation to MPCP Dwelling, and Cellular Backhaul. DPoE will be necessary to account for new packet Management will be extended to EPoC. burst overheads. Similar to the DOCSIS system, the EPoC PHY employs a full-duplex EPoC Architecture point-to-multipoint architecture, and the downstream and upstream communication channels will utilize RF spectrum as assigned Similar to DOCSIS 3.1 PHY OFDM, by a cable operator for their coax network. EPoC will require the allocation of dedicated EPoC Topology RF spectrum in both downstream and upstream directions. Provisioning of in-band Figure 2 illustrates the three topology service requires co-existing with other cable models for EPoC. Each model follows a Node operator services in either direction (e.g., + N approach, where N represents the greatest video, data, voice) without mutual number of amplifiers on a single path between interference As an operational note on the Coax Line Terminal (CLT) and a Coax differences in upstream use, EPoC is the sole Network Unit (CNU). N varies from 0 (e.g., user of its assigned spectrum, where DOCSIS Node + 0), and represents a passive network 3.1 OFDMA may share the same upstream RF or segment, to a preferred depth of 3. Higher channel with legacy DOCSIS via TDMA N values are also considered. A traditional scheduling of different burst types. HFC architecture is included in the topology. In a practical implementation, the System Models conversion from EPON digital fiber to EPoC coax will be implemented as a single unit Two system models have been under device that is placed in the field adjacent to discussion in the EPoC Task Force, as shown the fiber node. For example, the conversion in Figure 3. The first is a CLT with one more device in Figure 2 is shown by an ONU CNUs directly interconnected by a coaxial coupled with a CLT. distribution network. This system model follows the scope of the standard. Product realization would be a CLT that is colocated and EPoC PHY frames as the PCS encoding, in a headend as illustrated in the Complete i.e., the FEC and line encoding, are different. HFC Network topology shown in Figure 2. The EPON preamble and LLID are retained, The second and more preferable and therefore the same over both media. system model is enabled by the EPoC standard, but is outside the scope of the IEEE The second architecture is a bridge 802.3 Working Group. This model is a FCU. In this case, the PON port on the FCU traditional EPON with an OLT and multiple and each ONU is a member of the OLT’s ONU devices together with one or more Fiber MPCP domain on the PON with an LLID Coax Unit (FCU) converters that interconnect assigned by the OLT. On the coaxial network between PON with a coax distribution port, each CNU is a member of the FCU’s network using EPoC. This second model MPCP domain with an LLID assigned by the permits CNUs to appear as ONUs to DPoE, FCU. There would likely be no requirement and is, therefore, the manageable equivalent for LLID values to be retained across the to EPON ONUs. bridge. Rather, the LLID would become part The FCU has two implementation of the internal frame forwarding mechanism. architectures that can be considered. The first QoS flows may be individually retained; is a repeater FCU, where the OLT MPCP is however, it may make sense to aggregate transparently extended over the coax network. flows in the upstream to support OLT Here, each CNU’s MPCP is part of the single scheduling of traffic from the FCU to the MAC domain that includes both CNUs and OLT. ONUs. The OLT provides scheduling and MAC control over both the optical media and The architecture and specifications of the coax distribution network. The repeater both the repeater FCU and bridge FCU are FCU converts between EPON PHY frames beyond the scope of this paper. It is expected that details would be forthcoming from the guiding project documents. The first is the cable industry as the IEEE P802.3bn standard IEEE-SA Project Authorization Request work progresses towards finalization. (PAR) which sets the scope, the project area (e.g., amendment to the 802.3 Ethernet DETAILS OF IEEE P802.3bn EPoC standard), and other details. The PAR is the agreement between the IEEE SA, the 802 The work of the IEEE P802.3bn EPoC LMSC, and the 802.3 Working Group. Upon PHY Task force is in progress at this time, issuance of a PAR, the 802.3 Working Group and the progress of the Task Force can be charters a Task Force. The second document viewed on the project website located at [3]. is Criteria for Standards Development (CSD) also known as the 5 Criteria or 5Cs. The The IEEE Standards Association CSD/5Cs is a requirement the 802 LMSC and provides an open public process that consists the 802.3 Working Group. The third of consensus building and a technical document is the set of Objectives that selection process. In IEEE 802 and 802.3, constitute an agreement between the 802.3 participation is by an individual, and technical Working Group and the Task Force. Access to consensus is indicated by a 75% or greater past and current project documents for 802.3 vote of Yes versus No on decisions at face-to- is available at [1] and specifically for face meetings and on ballots.

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