Network Switch Class-Specific Flow Control
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Solution Overview
Problem
The IEEE 802.3 flow control standard lacks provisions for quality of service, causing high-priority traffic to be delayed alongside low-priority traffic when flow control is exercised, thereby preventing effective quality of service in network switches.
Innovation Solution
A network switching device with an ingress module for receiving data frames of varying classes of service and an egress module that exercises flow control by sending pause and pause release frames specific to each class of service, using counters to manage buffer occupancy and dynamically adjust flow control thresholds based on buffer reservations and availability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If IEEE 802.3 flow control is applied to regulate inbound data flow, then buffer overflow is prevented, but all classes of service are delayed equally including high-priority traffic
Solution Approach 1:
The patent segments the single flow control mechanism into multiple class-specific flow control mechanisms. Each class of service has its own pause threshold and flow control regulation, allowing differential treatment of traffic classes. This segmentation enables high-priority traffic to be exempted from pausing when lower-priority traffic triggers flow control, thus preventing unnecessary delays for time-sensitive traffic while still protecting against buffer overflow.
Solution Approach 2:
The patent applies local quality by making flow control parameters (pause thresholds, pause frame sending decisions) specific to each class of service rather than uniform across all traffic. The egress module evaluates buffer occupancy separately for each class and sends pause frames selectively based on class-specific thresholds. This allows different parts of the traffic flow (different classes) to experience different flow control behaviors, ensuring that critical traffic maintains quality of service while non-critical traffic is regulated.
2Loss of substance
If flow control pauses all traffic when buffers are full, then data loss is prevented, but quality of service differentiation cannot be achieved
Solution Approach 1:
The patent introduces dynamics by making flow control behavior adaptive and configurable per class of service. Pause thresholds can be dynamically adjusted based on buffer occupancy levels specific to each class. The system can adaptively decide which classes to pause and which to continue transmitting based on current buffer states and priority levels. This dynamic, class-specific approach enables both data loss prevention and quality of service differentiation to coexist.
Solution Approach 2:
The patent changes parameters by introducing class-specific pause thresholds and flow control parameters rather than using a single uniform threshold. Each class of service can have different threshold values, pause durations, and flow control characteristics. These parameter changes enable the system to differentiate quality of service while maintaining data loss prevention through appropriate parameter selection for each traffic class.
3Device complexity
If a single pause threshold is used for all traffic classes, then flow control implementation is simple, but high-priority traffic cannot be protected from delays
Solution Approach 1:
The patent segments the single pause threshold into multiple class-specific pause thresholds. The egress module maintains separate threshold values for different classes of service and evaluates buffer occupancy against the appropriate threshold when making flow control decisions. This segmentation increases implementation complexity slightly but enables protection of high-priority traffic by allowing the system to recognize when high-priority buffers are occupied and exempt such traffic from pausing.
Solution Approach 2:
The patent introduces an intermediary mechanism (the egress module's class-specific flow control logic) that sits between the buffer occupancy detection and the pause frame sending decision. This intermediary evaluates the class of service for affected traffic, checks class-specific thresholds, and makes intelligent decisions about which classes to pause. This intermediary layer adds complexity but enables sophisticated quality of service protection while maintaining relatively straightforward implementation based on existing pause frame mechanisms.
Data Source
AI summary
A network switching device, and corresponding method and computer program, comprising an ingress module adapted to receive frames of data from a channel, wherein each frame of data has one of a plurality of classes of service, and to store the data in one or more buffers; and an egress module adapted to exercise flow control on the channel for each of the classes of service when the number of the buffers storing frames of data received from the channel and having the class of service but not yet transmitted from the network switching device exceeds a predetermined threshold for the class of service.