Relay Device Loop Path Detection Multi-Master Networks
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Solution Overview
Problem
In CC-Link IE networks with multiple masters, conventional loop-path detection methods can incorrectly identify a loop path, leading to improper port blocking, especially when additional masters connect to the network.
Innovation Solution
A relay device with multiple communication ports and a frame identification unit that monitors and counts network-existence-confirmation frames from each master, determining a loop path by comparing the count with a set threshold and controlling frame transmission and reception to prevent loop formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the conventional loop-path detection method counts network-existence-confirmation frames from all masters collectively, then loop paths can be detected in single-master networks, but in multi-master networks the total count may exceed the threshold even when no loop exists, causing false port blocking
Solution Approach 1:
The patent segments the frame counting process by creating separate counters for each master device. Instead of a single collective counter that aggregates frames from all masters, the system now maintains individual counters (first counter for first master, second counter for second master, etc.). This segmentation allows each master's frame transmission pattern to be evaluated independently, preventing false loop detection when multiple masters are present in the network.
2Object-affected harmful factors
If the relay device blocks ports based on total frame count threshold, then loop paths can be eliminated in single-master networks, but additional masters may be improperly blocked even when transmitting normally
Solution Approach 1:
The patent applies segmentation by dividing the monitoring function into separate monitoring instances for each master. Each master's network-existence-confirmation frames are counted independently against the threshold, rather than aggregating all frames from all masters. This ensures that normal burst transmissions from additional masters do not trigger false loop detection and port blocking, while still effectively preventing storms caused by actual loop paths.
3Device complexity
If a single threshold is used for all masters, then detection is simple in single-master networks, but multi-master networks require differentiated monitoring to avoid false detections
Solution Approach 1:
The patent segments the detection mechanism into master-specific monitoring units. Each master device is associated with its own counter and monitoring logic, allowing precision measurement of each master's frame transmission pattern. While this increases structural complexity compared to a single counter, it maintains conceptual simplicity through consistent application of the same threshold-based logic to each segmented counter, enabling accurate loop detection in multi-master networks.
Data Source
AI summary
A layer-2 switch, forming a communication network along with a communication terminal, includes a plurality of communication ports, frame identification units to identify a specific frame that is regularly transmitted from the communication terminal in the communication network, a setting unit to set a monitoring cycle and a reception threshold for detecting a loop path in the communication network, a monitoring unit to identify, for each of the communication ports, a plurality of communication terminals that are a source of the specific frame, and to count the number of the specific frames received from each of the communication terminals within the monitoring cycle, and a determination unit to determine whether a loop path is detected for each of the communication ports by comparing a counter value, which indicates the number of the specific frames, with the reception threshold, and to execute control to stop transmission and reception of the frame at the communication port at which a loop path is detected.