Switching Apparatus Congestion Alleviation via Packet Dropping
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Solution Overview
Problem
Network congestion occurs when a recipient device in a Fibre Channel network system processes data packets slowly, leading to buffer overflow and blocking of data flows to other devices due to the buffer-to-buffer credit mechanism, causing congestion and potential data packet loss.
Innovation Solution
Implementing a method in the switching apparatus to detect data packets destined for slow-processing devices, track the time periods between packet receipt and corresponding flow control signals, calculate an average, and compare it to a threshold; if exceeding, drop data packets to alleviate congestion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the buffer-to-buffer credit mechanism is used to control data packet flows, then data packet loss is prevented and retransmission frequency is reduced, but congestion occurs when a recipient device processes packets slowly, causing buffer overflow and blocking flows to other devices
Solution Approach 1:
The patent changes the parameter of buffer management by implementing selective packet dropping based on congestion detection. When the egress queue is full and congestion is detected, the system dynamically adjusts the buffer utilization parameter by dropping packets at the input queue, preventing buffer overflow while maintaining flow control credits available for other destinations.
Solution Approach 2:
The patent extracts the problematic packets destined for slow-processing devices from the overall data flow. By detecting congestion conditions and selectively dropping only those packets that would contribute to buffer overflow, the system removes the harmful elements while preserving the buffer-to-buffer credit mechanism for healthy flows.
2Reliability
If the egress queue buffers all incoming data packets to prevent loss, then data packet loss is avoided, but the ingress queue becomes full when the egress queue is full, blocking flows to other recipient apparatuses
Solution Approach 1:
The patent segments the buffer management into two distinct queues: an ingress queue for incoming packets and an egress queue for outgoing packets. By implementing separate queue management with selective dropping at the ingress queue, the system simplifies overall management while maintaining reliability, as each queue can be independently controlled based on its specific congestion conditions.
3Reliability
If data packets are buffered at the switch to ensure delivery, then data loss is prevented, but congestion spreads to other flows when a single recipient device is slow
Solution Approach 1:
The patent applies preliminary anti-action by detecting congestion conditions before they can propagate to other flows. When the egress queue is full and congestion is detected, the system proactively drops packets at the ingress queue destined for the slow device, preventing the congestion from spreading to other recipient apparatuses and maintaining overall network health.
Solution Approach 2:
The patent applies local quality by implementing congestion-specific packet dropping only for packets destined to the congested recipient device. The buffer-to-buffer credit mechanism continues to function normally for other healthy flows, allowing each flow to be managed with appropriate quality characteristics based on its specific conditions.
Data Source
AI summary
In one embodiment, a method is provided for alleviating congestion in a network system. In this method, the receipt of data packets destined for a destination apparatus is detected. Flow control signals are also received with each flow control signal corresponding to a data packet. Various time periods are tracked with each time period being between the detection of the receipt of a data packet and the receipt of tracked corresponding flow control signal. An average of the time periods is calculated and this average is compared to a threshold. One or more data packets are dropped in reference to the comparison.