Multipath Packet Switching Cell Dropping Mechanism
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Solution Overview
Problem
Packet switching devices face challenges in efficiently managing congestion by dropping cells across multiple paths, leading to performance degradation, especially in multicast packets where all cells of a packet are dropped if one is dropped, causing severe blocking and unfair prioritization among packets.
Innovation Solution
A multipath packet switching mechanism that partitions packets into cells and determines whether to drop or forward each cell based on packet-variant and cell-invariant fields, using hashing and a drop threshold reflective of congestion, to ensure fair and priority-based cell dropping, independent of layer-3 packet flow, and adjusting drop values to manage congestion dynamically.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If cells of packets are forwarded through multiple paths in a packet switching device, then bandwidth capacity and forwarding speed are improved, but congestion management becomes complex and cell dropping fairness deteriorates
Solution Approach 1:
The patent segments the packet switching device into multiple independent buffered stages, each capable of autonomous congestion management decisions. This segmentation allows each stage to independently manage cells on different paths without complex centralized coordination, thereby maintaining high bandwidth capacity while reducing overall system complexity.
Solution Approach 2:
The patent implements feedback mechanisms where each buffered stage monitors its own congestion state and adjusts cell dropping decisions accordingly. This localized feedback approach enables effective congestion management without requiring complex global coordination across multiple paths, resolving the contradiction between productivity and device complexity.
2Adaptability or versatility
If conventional congestion management drops cells independently across multiple paths, then individual path flexibility is improved, but packet integrity deteriorates due to non-uniform cell dropping
Solution Approach 1:
The patent merges the dropping decisions for all cells belonging to the same packet across multiple paths by implementing uniform dropping at buffered stages. This ensures that either all cells of a packet are forwarded or all are dropped, maintaining packet integrity while still allowing flexible path selection and congestion management.
Solution Approach 2:
The buffered stages are designed with universal functionality to handle cells from multiple paths uniformly. Each stage can independently make dropping decisions that apply consistently across all paths for a given packet, thereby maintaining both path flexibility and packet integrity through a multi-functional design.
3Reliability
If cells are dropped at early buffered stages to manage congestion, then congestion control is improved, but blocking severity increases and prioritization fairness deteriorates
Solution Approach 1:
The patent implements preliminary congestion management at buffered stages by making dropping decisions before cells are fully committed to transmission paths. This preliminary action allows the system to control congestion proactively while maintaining fairness through consistent application of dropping policies across all paths, reducing severe blocking effects.
Data Source
AI summary
In one embodiment, cells of a same packet are sent among multiple paths within a packet switching device. Each of these cells is associated with a same drop value for use in determining whether to drop or forward the cell at multiple positions within a packet switching fabric of a packet switching device in light of a current congestion measurement. In one embodiment, the drop value is calculated at each of these multiple positions based on fields of the cell that are packet variant, but not cell variant, so a same drop value is calculated by each cell of a packet. In one embodiment, at least one of these fields provides entropy (e.g., a timestamp of the packet) such that a produced drop value has, or approximately has, an equal probability of being any value within a predetermined range for fairness purposes.