Switch Controller NACK Storm Reduction via Header Extraction

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Solution Overview

Problem

In reliable multicast communications, the sender experiences a storm of negative acknowledgment (NACK) messages due to network congestion, leading to increased network load, bandwidth consumption, and processing power usage.

Innovation Solution

A switch controller and a sending controller are implemented to prevent NACK storms by sending only the header of the multicast packet back to the sender upon failure, thereby reducing unnecessary retransmissions and network congestion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a reliable multicast protocol is used to ensure each IP packet reaches its destination, then delivery reliability is improved, but a storm of NACK messages occurs causing network congestion and increased processing load at the sender

Engineering Contradiction:

Improvedelivery reliabilityVSAvoidNACK message storm

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent extracts only the essential acknowledgment information (header with sequence number and NACK bit) from the full NACK message and sends it back to the sender. This extraction principle reduces the volume of feedback messages while preserving the core function of reliable delivery confirmation, thereby preventing NACK storms while maintaining reliability.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent segments the acknowledgment process into two parts: (1) receivers send selective NACK bits for only the packets they missed, and (2) the sender uses these segmented NACK bits to determine which specific packets need retransmission. This segmentation prevents the explosion of full NACK messages while maintaining reliable delivery.

Inventive Principle:

Principle #1Segmentation

2Reliability

If full NACK messages are sent from each receiver to the sender upon packet loss, then delivery reliability is maintained, but network bandwidth consumption and processing power usage at the sender increase significantly

Engineering Contradiction:

Improvedelivery reliabilityVSAvoidbandwidth consumption

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The patent extracts only the critical acknowledgment data (sequence number and NACK bit) from complete NACK messages and transmits this minimal information back to the sender. This extraction significantly reduces bandwidth consumption while preserving the essential function of confirming packet delivery failures for reliable multicast.

Inventive Principle:

Principle #2Taking out (Extraction)

3Reliability

If full NACK messages are sent from each receiver to the sender upon packet loss, then delivery reliability is maintained, but processing power usage at the sender increases due to handling multiple NACK messages

Engineering Contradiction:

Improvedelivery reliabilityVSAvoidprocessing power usage

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent extracts only the essential NACK information (sequence number and NACK bit) from full NACK messages, reducing the processing burden on the sender. The sender only needs to handle these compact header segments rather than complete NACK messages, significantly reducing CPU usage while maintaining reliable delivery through selective retransmission.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent segments the acknowledgment handling into: (1) receivers generating compact NACK bits for missed packets, and (2) the sender processing these segmented NACK bits to identify which specific packets require retransmission. This segmentation dramatically reduces processing power requirements while preserving delivery reliability.

Inventive Principle:

Principle #1Segmentation

4Reliability

If conventional reliable multicast protocol is used, then packet delivery is ensured, but end-to-end latency increases due to NACK message storms and retransmissions

Engineering Contradiction:

Improvepacket deliveryVSAvoidend-to-end latency

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent extracts only the minimal necessary acknowledgment information (header with NACK bit) from full NACK messages, enabling faster feedback to the sender. This extraction reduces the time required for acknowledgment transmission and processing, thereby reducing end-to-end latency while maintaining reliable packet delivery through efficient selective retransmission.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent segments the reliable delivery mechanism into compact NACK bit feedback and targeted retransmission, eliminating the need for full NACK message exchanges. This segmentation accelerates the acknowledgment process and reduces retransmission delays, thereby reducing end-to-end latency while ensuring packet delivery reliability.

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS20250150384A1Switch controller, sending controller and methods for use in switch controller and sending controller

Publication Date: 2025.05.08 HUAWEI TECH CO LTD

AI summary

A switch controller, where the switch controller includes a processor that is configured to: receive a multicast packet from a sender, where the multicast packet includes a header and a payload, determine that an attempt to forward the multicast packet through one or more ports fails for at least one of the one or more ports, determine that a header-forwarding bit in the header is set, and send the header of the multicast packet to the sender.