Virtual Switch Split Handling Using an STP Spanning Tree Link
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Solution Overview
Problem
In a virtual switch, a split can occur when both links between the conductor and standby devices are disconnected, leading to two conductor devices associating with the same stack MAC address, causing repeated MAC address movement and disrupting layer-2 forwarding.
Innovation Solution
Implementing an additional STP link between the conductor and standby devices, with an STP instance managing port states to prevent loop formation and ensure only one segment continues to use the stack MAC address, thereby selecting an active segment during a split.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an additional STP link is implemented between conductor and standby devices, then loop prevention and active segment selection capability are improved, but device complexity increases
Solution Approach 1:
The patent introduces an STP (Spanning Tree Protocol) instance as an intermediary mechanism on the additional link between conductor and standby devices. This STP instance acts as a mediator that automatically prevents loops by blocking ports when loops are detected, while also enabling active segment selection during splits without requiring complex custom control logic in the network devices.
2Adaptability or versatility
If STP instance is operated on the additional link to manage port states, then active segment selection capability is improved, but processing overhead increases
Solution Approach 1:
The STP instance operates autonomously on the additional link, self-managing port state transitions (blocking/forwarding) based on loop detection and segment split conditions. This self-service mechanism eliminates the need for external control plane intervention or complex custom algorithms, reducing processing overhead while maintaining adaptability for active segment selection.
3Productivity
If conductor devices maintain communication via stack links, then data traffic exchange is improved, but vulnerability to splits increases
Solution Approach 1:
The patent segments the communication paths by introducing a separate additional link between conductor and standby devices, distinct from the stack links used for data traffic. This segmentation allows the stack links to optimize for data throughput while the additional link with STP optimizes for control plane reliability and loop prevention, isolating the impact of splits to specific segments.
Data Source
AI summary
A network device of a virtual switch, which includes a second network device and operates on a unified control plane, is provided. During operation, the network device maintains a link between its first port and a second port of the second network device. Here, the first link can be distinct from a second link used for exchanging data traffic of the virtual switch. The network device operates a spanning tree protocol to place the first and second ports in respective port states, which include a forwarding state and a blocked state. If the second link becomes unavailable, the network device determines that the virtual switch has split into a first segment comprising the network device and a second segment comprising the second network device. If the first port state is in the blocked state, the network device suspends communication via a respective port of the first segment.