Frame Ordering in Redundant Communication Networks
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Solution Overview
Problem
In communications networks utilizing redundancy protocols like HSR and PRP, frames may arrive at nodes in the wrong order due to differing path lengths, leading to increased latency and potential confusion for higher layer protocols.
Innovation Solution
An apparatus and method that detect out-of-order frames by comparing sequence numbers, and insert the frames with smaller sequence numbers into the transmission queue ahead of frames with larger sequence numbers, ensuring correct order without additional buffering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If frames are transmitted via multiple redundant paths, then reliability of message delivery is improved, but frames may arrive in wrong order causing increased latency
Solution Approach 1:
The patent applies preliminary action by checking the sequence number of incoming frames against the expected sequence number before forwarding. When a frame with a smaller sequence number arrives later (out of order), the system proactively identifies this condition and holds the frame in a buffer until the correct frame arrives, preventing out-of-order delivery to higher layers and reducing effective latency.
2Stability of the object's composition
If frames are buffered to correct order, then frame order is improved, but additional buffering increases device complexity
Solution Approach 1:
The patent applies local quality by implementing ordering correction only for specific frames that are detected to be out of order, rather than buffering all frames. The system maintains simple FIFO buffering for normal operation and only activates selective holding when sequence number anomalies are detected, thus maintaining frame order stability without significantly increasing device complexity.
Data Source
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AI summary
Processing frames in a communications network is presented. An apparatus is configured to receive frames and relay the frames further. Frames are received (500) of a stream from more than one route, each frame comprising a sequence number. A sequence number of received one or more frames is detected (502) to be smaller than the sequence number of a frame receiver earlier. The frame that was received earlier with a greater sequence number is (504) in a transmission queue maintained by the apparatus and not yet been relayed further. The one or more frames are inserted (506) in a transmission queue causing the relaying of the one or more frames before the relaying of the earlier frame that was received previously with a greater sequence number.