Ethernet MAC Sublayer Cut-Through Forwarding with CTF-Tag Protection

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Solution Overview

Problem

Existing Ethernet MAC sublayer protocols incur significant latency due to 'store and forward' frame handling, which is detrimental to time-critical applications like industrial, audio/video, and internal data center communications, and lack methods for cut-through forwarding that may introduce errors.

Innovation Solution

Implement a cut-through forwarding mode in the Ethernet MAC sublayer by segmenting frames into chunks, allowing transmission to start before the entire frame is received, and using a CTF-Tag for error detection and correction.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If store and forward frame handling is used, then error detection can be performed on complete frames, but transmission latency increases significantly

Engineering Contradiction:

Improveerror detection capabilityVSAvoidtransmission latency

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent segments the frame transmission process into multiple chunks, allowing the MAC sublayer to forward received chunks immediately without waiting for the complete frame. This segmentation enables cut-through forwarding where partial frames are transmitted while maintaining the ability to perform error detection on complete frames through the CTF-Tag mechanism.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent implements preliminary error detection capabilities by including a CTF-Tag with each chunk that contains error detection information. This allows error checking to begin in advance while the rest of the frame is still being received and transmitted, reducing overall latency while maintaining reliability.

Inventive Principle:

Principle #10Preliminary action

2Speed

If cut-through forwarding is implemented to reduce latency, then transmission speed improves, but error detection capability deteriorates

Engineering Contradiction:

Improvetransmission speedVSAvoiderror detection capability

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The patent introduces a CTF-Tag as an intermediary element that accompanies each chunk during cut-through forwarding. This tag contains error detection information that enables reliable error checking even as frames are transmitted in progress rather than waiting for complete frame reception.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Loss of time

If frames are transmitted before complete reception, then latency is reduced, but frame integrity may be compromised

Engineering Contradiction:

Improvetransmission latencyVSAvoidframe integrity

Core Design Contradiction:

Loss of timeVSManufacturing precision

Solution Approach 1:

The patent implements a feedback mechanism where the CTF-Tag contains error detection information that is verified during transmission. This feedback loop ensures that even though frames are transmitted before complete reception, the integrity of the transmitted data can be verified and errors can be detected and corrected.

Inventive Principle:

Principle #23Feedback

Data Source

PatentEP4391497B1Ethernet mac sublayer supporting cut-through forwarding

Publication Date: 2025.08.06 MITSUBISHI ELECTRIC R&D CENTRE EUROPE BV

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AI summary

The present disclosure relates to a method for transmitting an Ethernet MAC frame, implemented by a communication device having an egress port to form the frame to be transmitted based on received data of said frame. The method comprises: - Checking whether, among said data of the frame, at least one parameter (chunk, transmitChunkOffset, chunkPresent) related to a segmentation of said frame is present, and in this case, - Start forming the frame at the egress port without waiting for a reception of all the frame data, according to a cut-through forwarding mode.