MNLF Scheduling Algorithm for Minimizing Router Queue Sizes
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Solution Overview
Problem
The GPS/WFQ scheduling algorithms do not minimize queue sizes in packet-switched routers, as they do not minimize the maximum normalized service lag, leading to larger queues than necessary.
Innovation Solution
The Maximum-Normalized-Lag-First (MNLF) scheduling algorithm is proposed, which assigns initial and incremental normalized service lag values to traffic flows, selecting packets for service based on maximum normalized lag to minimize queue sizes and achieve near-minimal queue sizes by updating lag values in each time slot.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If GPS/WFQ scheduling algorithms are used to provide fairness guarantees, then fairness is improved, but queue sizes increase
Solution Approach 1:
The patent changes the scheduling parameter from virtual finishing time (GPS/WFQ) to normalized service lag (MNLF). By defining and tracking normalized service lag for each traffic flow and selecting the flow with maximum normalized service lag for service, the system achieves near-minimal queue sizes while maintaining fairness guarantees. This parameter transformation resolves the contradiction between fairness and queue size minimization.
2Reliability
If GPS/WFQ algorithms schedule multiple traffic flows, then fairness is achieved, but memory requirements increase
Solution Approach 1:
The patent transforms the scheduling decision parameter from complex virtual finishing time calculations to simpler normalized service lag values. Each traffic flow is assigned an initial normalized service lag and an increment value, with the server selecting flows based on maximum normalized service lag. This parameter simplification reduces memory requirements while preserving fairness guarantees.
3Reliability
If GPS/WFQ algorithms are used to schedule traffic flows, then fairness is maintained, but transmission link utilization decreases
Solution Approach 1:
The patent implements continuous service to the transmission link by selecting the traffic flow with maximum normalized service lag at each time slot. This ensures that the server is always productive when the link is available, eliminating idle periods that occur in GPS/WFQ when no flow has the minimum virtual finishing time. The continuous selection process maintains fairness while maximizing link utilization.
Data Source
AI summary
A method to schedule multiple traffic flows through a multiplexer server to provide fairness while minimizing the sizes of the associated queues, is proposed. The multiplexer server minimizes a quantity called the maximum Normalized Service Lag for each traffic flow. In each time-slot, the normalized service lag of every traffic flow may be updated by adding the normalized lag increment value, whether or not there is a packet in the queue associated with the flow. In each time-slot, a multiplexer server selects a traffic flow to service with an available packet and with the maximum normalized service lag. When the traffic rate requested by each traffic flow is stable, the multiplexer server schedule may repeat periodically. Efficient methods to compute periodic schedules are proposed. The methods can be applied to packet-switched Internet routers to achieve reduced queue sizes and delay.