Dummy Packet Injection for FIFO Queue HOL Blocking Prevention

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Solution Overview

Problem

Existing data forwarding systems experience Head-Of-Line (HOL) blocking issues due to empty queues, which can stall the process and lead to delays in data packet ordering and transmission, especially when dealing with multiple data sources and varying packet arrival times.

Innovation Solution

A system comprising multiple FIFO input queues with a mechanism to de-queue data packets based on their time stamps, and the use of dummy packets to prevent queue stalls by transmitting them to empty queues after a predetermined period, ensuring that data packets are ordered and transmitted correctly without stalling the system.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If data packets are forwarded only when all queues have packets, then time ordering is maintained, but system productivity decreases due to frequent stalling

Engineering Contradiction:

Improvetime ordering accuracyVSAvoiddata forwarding throughput

Core Design Contradiction:

Manufacturing precisionVSProductivity

Solution Approach 1:

The patent introduces dummy packets as intermediary elements to mediate between the time ordering requirement and system productivity. When queues become empty, dummy packets are injected to maintain the 'all queues have packets' condition, allowing the de-queuing process to continue without stalling while preserving time order through proper timestamp assignment

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The system performs preliminary actions by detecting empty queues in advance and injecting dummy packets before the system would otherwise stall. This proactive approach prevents productivity loss by ensuring the de-queuing condition is always met, while the dummy packets are designed to not interfere with actual data packet time ordering

Inventive Principle:

Principle #10Preliminary action

2Reliability

If dummy packets are transmitted to empty queues, then HOL blocking is prevented, but device complexity increases

Engineering Contradiction:

Improvequeue operation continuityVSAvoidpacket management complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent extracts the dummy packet generation and management functionality as a separate, dedicated component within the forwarding system. This modular approach handles the complexity of dummy packet injection, timestamp assignment, and differentiation from real data packets in an isolated manner, reducing the overall system complexity while maintaining reliability

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

Dummy packets are designed as disposable, short-living objects that serve a specific temporary purpose (preventing HOL blocking) and are then discarded. They use simplified structures with minimal processing requirements, reducing the complexity burden while effectively maintaining queue operation continuity

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Data Source

PatentUS9246850B2Apparatus and method for receiving and forwarding data

Publication Date: 2016.01.26 NAPATECH

AI summary

A method and apparatus adapted to prevent Head-Of-Line blocking by forwarding dummy packets to queues which have not received data for a predetermined period of time. This prevention of HOL may be on an input where data is forwarded to each of a number of FIFOs or an output where data is de-queued from FIFOs. The dummy packets may be provided with a time stamp derived from a recently queued or de-queued packet.