Hierarchical ATM Scheduler for Priority Propagation
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Solution Overview
Problem
Conventional ATM interface mechanisms are limited in prioritizing traffic, leading to inefficient bandwidth usage and unfairness during congestion, as they do not effectively separate traffic by ATM class and prioritize high-priority traffic over low-priority traffic.
Innovation Solution
A hierarchical ATM cell shaper system with layer three priority information and cell-based priority DRR scheduling, utilizing two cell scheduler scoreboards and weighting values to prioritize high-priority traffic and proportionally share bandwidth among virtual channels, ensuring high-priority traffic is sent ahead of low-priority traffic even under severe congestion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional ATM interface mechanisms are used for traffic propagation, then the system structure remains simple, but traffic prioritization is insufficient and bandwidth usage is inefficient
Solution Approach 1:
The scheduling mechanism segments traffic into multiple priority classes (high priority and low priority queues) and further divides low priority traffic into active and pending queues based on weighting values. This segmentation enables differentiated service levels while managing complexity through structured organization of traffic flows.
Solution Approach 2:
The patent introduces a hierarchical scheduling dimension with multiple levels: virtual channel level, virtual path level, and output interface level. It also adds temporal dimension through time slots and weighting values, creating a multi-dimensional scheduling framework that resolves prioritization needs without overwhelming complexity.
2Reliability
If traffic is not separated by ATM class, then the system operation is simpler, but high-priority traffic cannot be prioritized over low-priority traffic
Solution Approach 1:
The system applies local quality differentiation by assigning different service characteristics to different traffic classes at each scheduling level. High priority traffic receives preferential treatment with guaranteed bandwidth, while low priority traffic shares remaining bandwidth proportionally based on weighting values, creating localized quality differences without requiring complex global management.
Solution Approach 2:
The patent implements preliminary action through advance scheduling decisions at virtual channel and virtual path levels before traffic reaches the output interface. Weighting values are pre-configured to determine bandwidth allocation ratios, and time slots are predetermined, allowing the system to make prioritization decisions in advance rather than reacting to congestion conditions.
3Productivity
If bandwidth is not proportionally shared among virtual channels, then the scheduling mechanism is simpler, but fairness during congestion is compromised
Solution Approach 1:
The system uses parameter changes through weighting values that can be dynamically adjusted to control bandwidth allocation ratios among virtual channels. These weighting parameters allow proportional sharing of remaining bandwidth after high priority traffic is served, enabling fair resource distribution without complex real-time calculations at the output interface.
Data Source
AI summary
According to various embodiments, high priority traffic is obtained from one of a plurality of virtual channels servicing high priority traffic. High priority traffic is placed in a high priority queue. Low priority traffic is obtained from one of a plurality of virtual channels. A weighting value associated with an element in the active queue is determined. The element corresponds to a virtual channel associated with the low priority traffic. The low priority traffic is placed either in a low priority traffic active queue or a low priority traffic pending queue based on the weighting value.