SD-WAN HA Switchover Using Exit Status Comparison
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Solution Overview
Problem
Existing SDWAN environments face challenges in accurately predicting failure severity due to the use of individual failure types for switchover decisions, leading to inconsistent and nondeterministic outcomes that can result in black holing or application degradation.
Innovation Solution
Implement a method where HA routers communicate their exit statuses to each other and apply an algorithm based on local and far-end exit statuses, using a state table to determine switchover decisions, rather than relying on individual failure decrements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If individual failure types are used for switchover decisions, then the system can respond to specific failures, but the switchover decisions become inconsistent and nondeterministic
Solution Approach 1:
The patent changes the parameters used for switchover decisions from individual failure types to aggregate exit status categories (e.g., available/unavailable). By categorizing multiple failure types into standardized exit status parameters, the system achieves deterministic and consistent switchover decisions while reducing the complexity of failure prediction.
2Reliability
If stateful features run only on active node, then failover can be simplified, but service availability may be compromised during switchover
Solution Approach 1:
The patent implements preliminary actions by pre-categorizing exit statuses and pre-defining switchover thresholds before failures occur. The system evaluates exit statuses (available/unavailable) and compares them against predefined thresholds to determine switchover decisions, ensuring service availability is maintained while managing HA complexity through advance preparation.
3Reliability
If exit statuses are evaluated without considering far-end router states, then local failover can be quick, but black holing or application degradation may occur
Solution Approach 1:
The patent implements feedback mechanisms where each router evaluates not only its local exit statuses but also the exit statuses of far-end routers. This bidirectional feedback ensures that switchover decisions are coordinated across the network, preventing black holing and application degradation while maintaining reasonable switchover times through efficient status comparison.
Data Source
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AI summary
In one aspect, a method includes determining, at a first node in an active state, a local wide area network (WAN) tunnel state of a WAN tunnel of the first node based on a forwarding table of the first node; determining, at the first node, a local direct internet access (DIA) path state of a DIA path of the first node based on a DIA tracker; receiving, at the first node, state information associated with a second node, wherein the state information includes a far-end WAN tunnel state and a far-end DIA path state associated with the second node; comparing, at the first node, the local WAN tunnel state and the local DIA path state with the far-end WAN tunnel state and the far-end DIA path state of the second node, respectively to yield a comparison; and based on the comparison, switching, by the first node, to a standby state.