Epoch Data Retransmission for Packet Switch Error Recovery

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Solution Overview

Problem

Epoch-based scheduling in high-throughput packet switches is prone to packet drops due to internal bit transmission errors, especially as port pipe speed increases, making it costly to require perfect transmission links.

Innovation Solution

Implementing a retransmission mechanism where ingress units guarantee data integrity beyond the transmission epoch and egress units check for errors, generating a signal for corrupted data, prompting the ingress unit to retransmit the epoch data, while allowing discarding of temporarily held data without errors.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If epoch-based scheduling is used in high-throughput packet switches, then throughput and transmission speed are improved, but packet drop frequency increases due to internal bit transmission errors

Engineering Contradiction:

ImprovethroughputVSAvoidpacket drop frequency

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The ingress unit performs preliminary action by guaranteeing data integrity beyond the transmission epoch, maintaining data in a temporarily held state after transmission. This allows the egress unit to detect errors and request retransmission without causing packet drops, thus preserving throughput while improving reliability

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The egress unit checks for errors in received epoch data and generates a feedback signal when corruption is detected. This feedback mechanism enables the ingress unit to retransmit corrupted data, reducing packet drop frequency while maintaining high throughput through efficient error recovery

Inventive Principle:

Principle #23Feedback

2Speed

If port pipe speed is increased to enhance throughput, then transmission rate is improved, but tolerance to backplane errors decreases

Engineering Contradiction:

Improvetransmission rateVSAvoiderror tolerance

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The system provides beforehand cushioning by implementing error detection and retransmission mechanisms that prepare for potential transmission errors. The ingress unit maintains data beyond the epoch boundary and the egress unit performs error checking, creating a safety buffer that allows high transmission rates without sacrificing error tolerance

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Data Source

PatentUS7843830B1Resilient retransmission of epoch data

Publication Date: 2010.11.30 DELL MARKETING CORP

AI summary

Apparatus and methods for epoch retransmission in a packet network device are described. In at least one embodiment, epoch receivers check received epoch data for errors. When an error is detected, a receiver is allowed to request that the entire epoch be retransmitted. All epoch senders retain transmitted epoch data until the time for requesting a retransmission of that data is past. If retransmission is requested by any receiver, the epoch is “replayed.” This approach mitigates the problem of dropping multiple packets (bundled in a large epoch) due to an intraswitch error with the epoch. Other embodiments are also described and claimed.