The Multi-Border Router (multi-root) topology extends any Wi-SUN architecture model by introducing more than one active Border Router. This approach increases resilience, capacity, and coverage by providing multiple entry points between the mesh and external IP networks.

While this topology offers strong redundancy and scalability benefits, it requires careful coordination to ensure that all Border Routers operate consistently.

Key characteristics

  • Multiple Border Routers operate in parallel, each managing its own Wi-SUN PAN within the same overall deployment.

  • Devices associate with one Border Router at a time but can rejoin another if their current Border Router becomes unavailable.

  • RPL builds and maintains routing paths within each PAN independently.

  • Having multiple Border Routers increases resilience by allowing nodes to recover connectivity through alternative PANs when their Border Router becomes unreachable.

When to use

Choose the Multi-Border Router topology if:

  • Network resilience and fault recovery are important — service can continue through another Border Router if one becomes unavailable.

  • The deployment spans a large area or supports many devices, requiring distributed load handling.

  • Redundancy and fault tolerance are important for critical infrastructure.

  • Large-scale networks benefit from multiple upstream connections to external IP infrastructure.

Suitable for large-scale or mission-critical deployments where continued operation is required even if one Border Router fails.

Pros and cons

  • Pros

    • Improves reliability by eliminating single points of failure.

    • Provides additional coverage and throughput capacity.

    • Enhances resilience for mission-critical applications.

  • Cons

    • Requires tight synchronization of policies, addressing, and credentials.

    • Increases routing complexity, as the network design must handle devices that may join from multiple Wi-SUN subnets.

    • Troubleshooting becomes more challenging due to variable traffic paths.

Considerations

Multi-Border Router deployments introduce specific design requirements:

  • Addressing: Each Border Router must present a distinct routed prefix (either a unique static prefix or a unique delegated sub-prefix). Shared prefixes across Border Routers will cause conflicts.

  • Policy consistency: Admission policies, security credentials, and timing parameters must remain identical across all Border Routers.

  • Network dynamics: With multiple roots, routes may shift based on link quality or availability. It is necessary to monitor this variability to ensure predictable performance.

  • Monitoring: Software tools and dashboards must be able to account for multiple entry points and visualize traffic distribution.