EPON OLT Shared LAN Emulation with LLID Management
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Solution Overview
Problem
In Ethernet Passive Optical Networks (EPON), it is challenging to form and match multiple independent physical ports for connecting Optical Network Units (ONUs) to an Optical Line Terminal (OLT), leading to difficulties in bridging data between networks with different structures, such as point-to-multipoint and point-to-point configurations.
Innovation Solution
A shared LAN emulation method is introduced, utilizing Logical Link Identifiers (LLIDs) to manage and identify ONUs, learn MAC addresses, and bridge data frames, providing a single matched interface between the MAC and LLC layers, and preventing collisions by using Virtual LAN identifiers and destination MAC addresses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple independent physical ports are formed to connect multiple ONUs to OLT, then each ONU can have dedicated MAC layer connections, but it becomes very difficult to form and match the plurality of independent physical ports
Solution Approach 1:
The patent merges multiple physical ports into a single shared physical port on the OLT. Multiple ONUs share this single physical port through time-division multiplexing, where each ONU is assigned a unique LLID. The MAC layer is enhanced to handle multiple logical connections over this single physical interface, eliminating the need to form and match multiple independent physical ports while maintaining dedicated connection reliability for each ONU.
Solution Approach 2:
The single physical port on the OLT is designed to serve multiple functions by supporting multiple ONUs simultaneously. The port can dynamically allocate resources to different ONUs based on their communication needs, performing both point-to-point and point-to-multipoint functions through the shared LAN emulation mechanism.
2Productivity
If a point-to-multipoint structure is used to share optical resources, then maintenance costs are low and resource sharing is intensive, but bridging data between networks with different structures becomes difficult
Solution Approach 1:
The patent introduces a Shared LAN Emulation (SLE) layer as an intermediary between the physical point-to-multipoint PON infrastructure and the logical point-to-point network requirements. This SLE layer performs bridging functions that translate between the point-to-multipoint physical structure and point-to-point logical connections, enabling compatibility between different network structures while maintaining resource sharing efficiency.
Solution Approach 2:
The network architecture is segmented into distinct functional layers: the physical layer handles point-to-multipoint resource sharing, while the SLE layer handles point-to-point bridging operations. This segmentation allows each layer to optimize for its specific function without compromising the other, maintaining both resource sharing efficiency and network structure compatibility.
3Ease of operation
If multiple MAC layers are created to match the number of ONUs, then each ONU has dedicated MAC handling, but it requires a plurality of physical connection ports which are difficult to form and match
Solution Approach 1:
Instead of creating multiple physical ports, the patent creates multiple virtual copies of MAC layer functionality within the shared physical port. Each ONU receives a virtual MAC interface through the SLE layer that behaves like a dedicated physical port, but all these virtual interfaces share the single physical connection. This eliminates the need to physically form and match multiple ports while maintaining ease of MAC layer management.
Data Source
AI summary
Disclosed herein is a shared Local Area Network (LAN) emulation method and apparatus. The method includes the following four steps. At the first step, a Logical Link Identifier (LLID) management table is set up to assign unique LLIDs to a plurality of Optical Network Units (ONUs) and manage the assigned LLIDs so as to identify the plurality of ONUs connected to a single Optical Line Terminal (OLT). Thereafter, a MAC address table is set up for the LLIDs to learn MAC addresses of the ONUs. Thereafter, the unique LLIDs are assigned to ONUs when the ONUs request registration from the OLT. Finally, data frames, which are received by a Shared LAN Emulation (SLE) layer of the OLT, are bridged using the LLIDs, VIDs of Virtual LANs to which the ONUs belong and destination MAC addresses of the data frames so as to provide a single matched port between a Logical Link Control (LLC) layer and a MAC layer of the OLT.