Shared Headroom Space with Randomized Flow Control
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Solution Overview
Problem
In packet-switching networks, high incoming packet rates can lead to packet drops due to buffer overflow, with current solutions relying on large, unnecessarily reserved headroom based on worst-case scenarios, resulting in low buffer utilization and throughput degradation.
Innovation Solution
Implementing a shared headroom space with randomized flow-control thresholds, where the XOFF message is transmitted based on a pseudo-random threshold between a deterministic and a randomized offset, reducing the required headroom size and synchronizing flow-control events, thereby minimizing packet drops.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If large headroom is reserved based on worst-case scenarios, then packet drops are minimized, but buffer utilization decreases and throughput degrades
Solution Approach 1:
The patent applies dynamics by making the flow-control threshold randomized rather than fixed. The threshold dynamically adjusts based on a pseudo-random value selected from a range, allowing the system to adapt to varying traffic patterns while maintaining simplicity. This resolves the contradiction by enabling the buffer to be more aggressively utilized without sacrificing reliability, as the randomized threshold prevents synchronized flow-control events that would otherwise require large headroom reserves.
2Reliability
If fixed flow-control thresholds are used, then flow-control events are predictable, but synchronized flow-control events occur leading to excessive headroom requirements
Solution Approach 1:
The patent applies asymmetry by introducing a pseudo-random offset to the flow-control threshold. Instead of using a symmetric fixed threshold for all ports, each port gets an asymmetric threshold adjusted by a random value. This asymmetry desynchronizes flow-control events across different ports, preventing the synchronization problem that leads to excessive headroom requirements while maintaining flow-control effectiveness.
3Reliability
If worst-case waiting times are used for headroom provisioning, then lossless operation is guaranteed, but buffer resources are wasted
Solution Approach 1:
The patent applies parameter changes by modifying the flow-control threshold parameter from a fixed worst-case value to a randomized value within a range. This parameter change allows the system to operate with smaller headroom reserves while maintaining lossless operation, as the randomized threshold prevents the synchronized worst-case scenarios that would otherwise require excessive buffer resources.
Data Source
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AI summary
The various embodiments of the invention provide mechanisms to reduce headroom size while minimizing dropped packets. In general, this is done by using a shared headroom space between all ports, and providing a randomized delay in transmitting a flow-control message.