Hierarchical SD-WAN Regional Fallback Paths for Tunnel Failover
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Solution Overview
Problem
In hierarchical SD-WAN deployments, there is no per-region ultimate fallback path, leading to data-plane disruption when all tunnel interfaces lose connectivity, breaking the underlying principle of requiring both core and primary access regions to be up on a border router.
Innovation Solution
Configuring tunnel interfaces as last-resort-circuits that operate on a per-region basis, activating a fallback tunnel interface only when all other interfaces in that region lose connectivity, ensuring end-to-end data plane connectivity across multiple regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single last-resort-circuit is configured at the WAN edge device level, then the device can maintain basic connectivity when all WAN circuits are lost, but the hierarchical multi-region deployment loses the intended fallback functionality because devices operating across multiple regions cannot maintain per-region connectivity
Solution Approach 1:
The patent segments the network into multiple hierarchical regions (core region, transit region, access region) and configures separate last-resort-circuit tunnel interfaces for each region. This allows independent fallback path management per region, ensuring that connectivity loss in one region does not affect other regions, thereby resolving the contradiction between maintaining reliability and managing complexity.
Solution Approach 2:
The patent introduces a regional dimension to the traditional device-level fallback mechanism. Instead of a single device-level last-resort-circuit, the system implements region-specific tunnel interfaces that operate independently across the hierarchical network structure, adding spatial granularity to the fallback mechanism.
2Reliability
If per-region fallback paths are implemented in hierarchical SD-WAN, then data plane connectivity is maintained across multiple regions, but the system requires complex regional segmentation and independent tunnel interface management
Solution Approach 1:
The network is segmented into distinct hierarchical regions with dedicated tunnel interfaces for each region. Border routers configure region-specific last-resort-circuit tunnel interfaces that independently monitor and maintain connectivity within their respective regions, enabling granular control over data plane connectivity.
Solution Approach 2:
The system pre-configures multiple region-specific tunnel interfaces as last-resort-circuits before connectivity failures occur. Each tunnel interface is prepared in advance with appropriate routing policies and monitoring mechanisms, enabling rapid activation when regional connectivity is lost without requiring complex real-time decision-making.
3Ease of operation
If traditional last-resort-circuit functionality is used without regional differentiation, then configuration is simple, but connectivity disruption occurs when all tunnel interfaces in a hierarchical multi-region deployment lose connectivity
Solution Approach 1:
The patent divides the network into hierarchical regions and configures independent last-resort-circuit tunnel interfaces for each region. This segmentation allows the system to maintain continuous operation across regions by ensuring that each region has its own fallback path, preventing complete connectivity loss.
Solution Approach 2:
The border router is designed to perform multiple functions: it operates as a regular routing device for normal traffic and simultaneously maintains region-specific last-resort-circuit tunnel interfaces for fallback connectivity. This multi-functionality enables the device to provide both simplified configuration and continuous operation across regions.
Data Source
AI summary
In one embodiment, a method includes determining, by a network node, that a first plurality of tunnel interfaces resides in a core region of a network and determining, by the network node, that a second plurality of tunnel interfaces resides in an access region of the network. The method also includes configuring, by the network node, a first tunnel interface as a core regional fallback path for the core region of the network and configuring, by the network node, a second tunnel interface as an access regional fallback path for the access region of the network.