Ethernet Ring Topology Discovery in Building Management Systems
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Solution Overview
Problem
Current building management systems (BMS) with Ethernet ring networks lack a mechanism to accurately determine the order and connection scheme of devices, making it difficult to verify correct connections and troubleshoot faults in Media Redundancy Protocol (MRP) rings.
Innovation Solution
A method and system that utilize a ring topology generator to broadcast device discovery commands, query the ring supervisor, and increment counts based on ring port responses to determine the topology of devices in an Ethernet ring, ordering them based on their proximity to the forwarding port.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If MRP ring protocol is used for robust network connectivity, then fault tolerance is improved, but the ability to determine device order and connection topology deteriorates
Solution Approach 1:
The system performs preliminary topology discovery by broadcasting device discovery commands before normal operation. The ring topology generator proactively gathers connection information from all devices in the ring, establishing a complete topology map in advance. This preliminary action ensures topology information is captured before any faults occur, resolving the contradiction by obtaining topology data without affecting the fault tolerance of MRP protocol operation.
Solution Approach 2:
The ring topology generator acts as an intermediary between the MRP ring protocol and the topology determination function. It broadcasts discovery commands, collects responses from devices, and processes the information to determine device order and connections. This intermediary approach allows topology information to be gathered without interfering with the normal fault-tolerant operation of the MRP protocol, thus resolving the information loss problem while maintaining reliability.
2Measurement precision
If device discovery commands are broadcast to determine topology, then topology determination accuracy is improved, but network traffic and processing overhead increase
Solution Approach 1:
The system uses periodic broadcasting of device discovery commands at specific intervals rather than continuous transmission. The ring topology generator broadcasts discovery commands periodically, allowing the network to return to normal traffic patterns between discovery cycles. This periodic approach maintains accurate topology information while significantly reducing network traffic overhead and energy consumption compared to continuous discovery.
3Measurement precision
If Ethernet ports are temporarily disabled to verify ring openness, then topology verification accuracy is improved, but network availability decreases
Solution Approach 1:
The system performs preliminary verification by temporarily disabling an Ethernet port only when topology determination is needed, before normal operation resumes. The ring topology generator disables a port, verifies the ring opens, then immediately re-enables it. This preliminary verification action occurs briefly and does not impact long-term network availability, resolving the contradiction by minimizing the time port is disabled while ensuring accurate topology verification.
Solution Approach 2:
The Ethernet port state is dynamically changed from enabled to disabled and back to enabled during the verification process. The system adapts the port state temporarily for verification purposes, then returns it to its normal operational state. This dynamic approach allows accurate topology verification through state changes while minimizing the duration of unavailability, thus resolving the contradiction between verification accuracy and network availability.
Data Source
AI summary
A system and method of determining a topology of devices in an Ethernet network of a building management system (BMS). The method includes discovering a number and identification of devices within the Ethernet ring. The method further includes, for each device discovered in the Ethernet ring, disabling an Ethernet port of one of the device in the Ethernet ring; broadcasting a ring port request onto the Ethernet ring; receiving a ring port response from each of the devices having received the ring port request; and incrementing a count associated with each device based on receiving a ring port response from the device. The method then repeats the above steps until each device in the Ethernet ring has had an Ethernet port disabled. The method further includes determining the topology of the devices in the Ethernet ring by ordering the devices in the Ethernet ring based on the value of the count associated with each device.