Layer 4 Load Balancing with Passive Server Load Inference

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Solution Overview

Problem

Layer 4 load balancers in data centers struggle with suboptimal workload distribution due to lack of awareness of instantaneous server load states, leading to resource overload or starvation, especially in heterogeneous virtualized environments, and require manual weight configuration, increasing management overhead.

Innovation Solution

Implementing a load balancing strategy that passively learns server processing capacities using network features and Kalman filters to infer instant load states, dynamically distributing workloads based on Shortest Expected Delay (SED) scores without manual configuration, using network observations like flow durations and queue lengths.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If layer 4 load balancers use traditional load balancing methods, then the system is simple to operate, but the workload distribution is suboptimal and does not reflect instantaneous server load states

Engineering Contradiction:
Improveease of operationVSAvoidworkload distribution optimization
Core Design Contradiction:
Ease of operationVSProductivity

Solution Approach 1:

The load balancer passively learns server processing capacities and infers instant load states by observing network features (flow durations, queue lengths) without requiring manual configuration or additional control planes. The system serves itself by automatically adapting to heterogeneous virtualized environments through passive learning and inference mechanisms

Inventive Principle:
Principle #25Self-service

Solution Approach 2:

The load balancer continuously observes network features from data plane traffic and uses this feedback to infer server load states and update its understanding of server processing capacities. This closed-loop feedback mechanism enables dynamic adaptation to changing workload conditions without manual intervention

Inventive Principle:
Principle #23Feedback

2Productivity

If manual weight configuration is used for load balancing, then workload distribution can be controlled, but management overhead increases

Engineering Contradiction:
Improveworkload distribution controlVSAvoidmanagement overhead
Core Design Contradiction:
ProductivityVSDevice complexity

Solution Approach 1:

The system eliminates manual weight configuration by automatically learning server processing capacities through passive observation of network features. The load balancer infers appropriate weighting based on observed flow durations and queue lengths, completely removing the need for manual intervention in workload distribution control

Inventive Principle:
Principle #25Self-service

Solution Approach 2:

The patent replaces manual mechanical configuration (setting weights) with an automated inference system that uses Kalman filters and network feature observation. This substitution transforms a manual control mechanism into an automated intelligent system that adapts dynamically

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

3Device complexity

If layer 4 load balancers lack awareness of instantaneous server load states, then the system is simpler, but resource overload or starvation occurs

Engineering Contradiction:
Improvesystem complexityVSAvoidresource allocation fairness
Core Design Contradiction:
Device complexityVSReliability

Solution Approach 1:

The load balancer observes network features (flow durations, queue lengths) from data plane traffic and uses this feedback to infer instantaneous server load states. This enables the system to make reliability-aware load balancing decisions while maintaining layer 4 simplicity

Inventive Principle:
Principle #23Feedback

Solution Approach 2:

The patent introduces an intermediary inference layer that translates observable network features into estimates of server load states. The Kalman filter acts as an intermediary that processes noisy observations to produce reliable estimates of instantaneous server capacity and queue length

Inventive Principle:
Principle #24Intermediary (Mediator)

4Productivity

If heterogeneous virtualized environments are deployed, then resource utilization can be optimized, but load balancing becomes more difficult without manual configuration

Engineering Contradiction:
Improveresource utilizationVSAvoidconfiguration complexity
Core Design Contradiction:
ProductivityVSDevice complexity

Solution Approach 1:

The system dynamically adjusts load balancing parameters (weights) based on observed network features and inferred server capacities. Instead of static manual configuration, the parameters change automatically in response to changing conditions in heterogeneous virtualized environments

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The load balancer continuously updates its understanding of server processing capacities and queue lengths based on observed flow durations and network features. These dynamic parameter changes enable optimal workload distribution across heterogeneous resources without manual reconfiguration

Inventive Principle:
Principle #35Parameter changes

Data Source

PatentUS12425342B2Layer 4 load aware load balancing
Publication Date: 2025.09.23 CISCO TECHNOLOGY INC
  • US12425342B2 patent drawing
  • US12425342B2 patent drawing
  • US12425342B2 patent drawing

AI summary

Load aware load balancing may be provided. Flow duration data associated with a plurality of flows associated with a plurality of servers may be obtained. Then a plurality of queue lengths respectively associated with the plurality of servers may be obtained. Next, a Shortest Expected Delay (SED) score may be determined for each of the plurality of servers based on the flow duration data and the plurality of queue lengths. A flow may then be assigned to a one of the plurality of servers having the lowest SED score.