Control Plane Signaling for High Availability Network Devices
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Solution Overview
Problem
Current control plane management schemes in high availability network devices, such as routers, fail to quickly detect and respond to changes in off-card assemblies, leading to loss of bandwidth and reliability issues, particularly during activity switches, and existing reset mechanisms are inefficient and costly due to their inability to target specific logic and handle independent reset instructions effectively.
Innovation Solution
A method and system that utilize serial interfaces with status and clock lines to monitor activity indications and reset instructions from redundant control plane cards, allowing for selective and prioritized reset of off-card assembly components, thereby optimizing control plane signaling and reducing system costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If redundant control planes are implemented for high availability, then system reliability is improved, but control plane signaling complexity and response time to off-card assembly changes deteriorate
Solution Approach 1:
The control plane is segmented into active and inactive roles, with each control plane card independently capable of detecting off-card assembly changes. The off-card assembly is segmented to have independent detection capability for activity switches. This segmentation allows distributed decision-making without requiring complex inter-card signaling protocols.
Solution Approach 2:
The off-card assembly performs self-detection of control plane activity switches by monitoring its own interface connections. Each control plane card independently monitors its own status without requiring complex handshaking with the other card. This self-service approach simplifies the overall control plane signaling while maintaining high availability.
2Ease of manufacture
If traditional reset mechanisms are used for off-card assemblies, then system cost increases due to additional signals, but reset functionality is provided
Solution Approach 1:
The serial interface protocol is designed to serve multiple functions: data communication, status monitoring, and reset control. By embedding the reset function within the existing serial interface rather than adding dedicated reset signals, the system reduces pin count and manufacturing cost while maintaining reliable reset capability. The same interface wires carry both operational data and control signals.
3Speed
If control plane cards use independent reset instructions, then reset responsiveness is improved, but conflict between redundant control planes occurs
Solution Approach 1:
The reset control mechanism is made dynamic by allowing either control plane card to issue reset instructions based on real-time detection of off-card assembly changes. The system dynamically determines which card is active and allows that card to control the reset, rather than using a static predetermined assignment. This dynamic approach maintains responsiveness while preventing conflicts through real-time status monitoring.
Data Source
AI summary
A method for resetting a component of an off-card assembly in a redundant system, the redundant system having first and second control plane cards coupled to the off-card assembly by respective serial interfaces, each serial interface including a respective status line and a respective clock line, each status line for providing a respective activity indication and a respective reset instruction, each clock line for providing a respective clock signal, the method comprising: monitoring respective activity indications and clock signals from the first and second control plane cards by the off-card assembly to determine which of the first and second control plane cards is an active card; and, selecting the reset instruction from the active card to reset the component, thereby resolving any conflict between respective reset instructions.