Backplane QoS via Ingress-Egress Feedback Messaging
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Solution Overview
Problem
High-performance Internet routers with switched backplanes face challenges in maintaining quality of service (QoS) due to congestion issues, as the crossbar switch lacks QoS capabilities, leading to unfair packet dropping and inefficiencies in traffic management, particularly when ingress queues exceed egress queue capacities.
Innovation Solution
A messaging system is implemented across the switched backplane, utilizing ingress and egress queue managers to generate congestion and resume messages based on queue thresholds and timers, which propagate feedback to reduce packet rates and ensure fair traffic distribution, thereby enforcing QoS policies across the network.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a switched backplane is used to improve routing performance, then packet transfer speed increases, but QoS capability is lost leading to unfair packet dropping
Solution Approach 1:
The patent implements a feedback mechanism where egress queue managers send congestion notifications back to ingress queue managers. This feedback loop enables the system to detect congestion conditions and adjust packet transmission rates accordingly, restoring QoS control to the switched backplane environment.
Solution Approach 2:
The patent introduces queue managers as intermediary entities between ingress and egress queues. These queue managers mediate the congestion control process by receiving packets from ingress queues, managing them according to QoS policies, and forwarding to egress queues, thereby enabling QoS capability in the switched backplane.
2Productivity
If multiple ingress queues are mapped to a single egress queue, then traffic aggregation is achieved, but congestion causes unfair packet dropping
Solution Approach 1:
The patent applies local quality control by treating different ingress queues differently based on their individual congestion conditions. Each ingress queue is monitored independently, and congestion notifications are sent selectively to affected ingress queue managers, enabling differentiated packet dropping policies that ensure fairness while maintaining traffic aggregation benefits.
3Device complexity
If congestion control is implemented at egress queues only, then simple management is achieved, but ingress queues cannot respond to congestion conditions
Solution Approach 1:
The patent extends the feedback mechanism to include ingress queue managers. Egress queue managers send congestion notifications back through the switched backplane to ingress queue managers, enabling ingress queues to reduce their transmission rates in response to congestion conditions, thereby improving overall congestion response effectiveness.
4Ease of operation
If the crossbar switch handles all traffic, then centralized control is achieved, but QoS policies cannot be enforced
Solution Approach 1:
The patent segments the congestion control function by distributing queue managers to individual blades and ports throughout the router. Each queue manager independently manages its local queues and enforces QoS policies locally, while still operating within the centralized switched backplane architecture, thus maintaining both ease of operation and QoS enforcement capability.
Data Source
AI summary
A method and system is provided to enable quality of service across a backplane switch. An egress queue manager on one blade communicates with an ingress queue manager on the same or on another blade where each blade is connected via a backplane switch. The egress queue managers communicate the congestion to ingress queue managers using a messaging scheme. The ingress queue managers determine when to reduce or resume the packet sending rates of ingress queues mapped to congested egress queues or to destinations on congested blades. Each ingress queue manager maintains information about the status of egress queue congestion on its own blades. Normal rates of dequeuing packets from ingress queues are resumed only when the related congestion on all of the egress queues or related destinations has subsided.