Packet Path Selection Using DRR for Clos Load Balancing
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Solution Overview
Problem
Existing network technologies face challenges in load balancing packets due to collisions caused by hashing, leading to packet drops, especially in Clos networks, where flow-based load balancing between network interface cards results in uneven distribution and potential bandwidth inefficiencies.
Innovation Solution
Implementing Deficit Round Robin (DRR) scheduling with overage monitoring and binary tree path selection in network interface devices to distribute packets evenly across multiple paths, using programmable packet processing pipelines and match-action units to manage byte allocations and congestion metrics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If hashing of packets is used for flow recognition, then flow-based load balancing is achieved, but collisions occur leading to packet drops
Solution Approach 1:
The patent segments the flow recognition process by using multiple hash functions instead of a single hash function. Each hash function processes packets differently, and the results are combined to select egress paths. This segmentation reduces collision probability while maintaining load balancing efficiency across multiple egress paths.
Solution Approach 2:
The patent introduces an intermediary mechanism (multiple hash functions and path selection logic) between packet arrival and egress path selection. This intermediary layer processes packet headers through multiple hash functions, combines results, and selects paths based on least recently used criteria, thereby reducing direct hash collisions while maintaining balanced distribution.
2Reliability
If bandwidth speed up is used to tolerate packet drops, then elephant flows are protected, but network complexity increases
Solution Approach 1:
The patent implements self-service mechanisms where the network device automatically monitors packet distribution across egress paths and dynamically adjusts path selection based on observed patterns. The system serves itself by tracking least recently used paths and automatically rebalancing traffic without external intervention, protecting elephant flows while maintaining manageable complexity through automated adaptation.
Solution Approach 2:
The patent introduces dynamic path selection that adapts to changing traffic patterns in real-time. The egress path selection is not static but changes based on the least recently used criterion, allowing the system to dynamically respond to traffic variations and protect elephant flows without requiring complex predetermined configurations.
3Productivity
If flow-based load balancing is used between network interface cards, then traffic distribution is achieved, but uneven distribution occurs leading to bandwidth inefficiency
Solution Approach 1:
The patent implements feedback mechanisms by monitoring which egress paths have been recently used and using this information to influence subsequent path selections. The least recently used criterion provides feedback about past path usage, enabling the system to automatically balance traffic more evenly across available paths and improve overall bandwidth utilization efficiency.
Data Source
AI summary
Examples described herein relate to a network interface device comprising a multi-stage programmable packet processing pipeline circuitry to determine a path to transmit a packet based on relative network traffic transmitted via multiple paths. In some examples, determine a path to transmit a packet is based on Deficit Round Robin (DRR). In some examples, the programmable packet processing pipeline circuitry includes: a first stage to manage two or more paths, wherein a path of the two or more paths of the first stage is associated with two or more child nodes, a second stage to manage two or more paths, wherein a path of the two or more paths of the second stage is associated with two or more child nodes, and at least one child node is associated with the determined path.