Asymmetrical Peer Forwarding in SD-WAN Clusters
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Solution Overview
Problem
Asymmetric routing in SD-WAN environments can break stateful features like firewall, NAT, NBAR, DPI, and Snort, leading to increased latency and reduced end-to-end performance.
Innovation Solution
The system dynamically assigns and relinquishes flow ownership between nodes in an SD-WAN cluster, minimizing peer forwarding and ensuring symmetrical routing without disrupting stateful features.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple edge routers advertise prefixes for both LAN-side traffic and WAN-side traffic in an all-active cluster, then load balancing and high availability are improved, but asymmetric routing occurs which breaks stateful features
Solution Approach 1:
The patent implements asymmetrical peer forwarding where the forward path and return path can traverse different nodes in the cluster. Specifically, outbound traffic from LAN to WAN may be handled by one edge router while the return traffic from WAN to LAN is handled by a different edge router. This asymmetrical design allows multiple nodes to remain active simultaneously while maintaining proper stateful feature operation through coordinated forwarding between nodes.
Solution Approach 2:
The patent introduces a control mechanism that acts as an intermediary between different edge routers in the cluster. This control system coordinates the forwarding behavior, allowing one node to forward traffic to another node when needed. The intermediary control ensures that stateful features are maintained by managing which node handles which direction of traffic flow, enabling asymmetrical routing patterns without breaking firewall, NAT, or other stateful services.
2Productivity
If asymmetrical routing is implemented to improve load balancing, then productivity is improved, but latency increases due to broken stateful features
Solution Approach 1:
The patent implements dynamic flow ownership assignment where edge routers can assume ownership of specific traffic flows and maintain that ownership for the duration of the flow. This dynamic approach allows the system to adapt to changing traffic patterns while maintaining consistent routing for each flow, preventing the latency issues that would arise from repeated state synchronization. The ownership assignment is updated based on traffic patterns to optimize load balancing while avoiding unnecessary peer forwarding operations.
3Adaptability or versatility
If peer forwarding is used to handle asymmetrical traffic, then adaptability is improved, but device complexity increases
Solution Approach 1:
The patent implements a self-service mechanism where each edge router independently determines whether it should handle a particular traffic flow or forward it to another node in the cluster. Each node maintains local state information and makes autonomous decisions about flow ownership based on this state, eliminating the need for complex centralized control or extensive inter-node communication. The routers serve themselves by independently managing their own forwarding decisions while maintaining cluster-wide consistency through shared state information.
Data Source
AI summary
In one embodiment, a method includes receiving, by a first node of a node cluster in a software-defined wide area network (SD-WAN), traffic from a wide area network (WAN), assigning, by the first node of the node cluster, flow ownership of the traffic to the first node, and communicating, by the first node of the node cluster, the traffic to a local area network (LAN). The method also includes receiving, by the first node of the node cluster, return traffic from a second node of the node cluster and detecting, by the first node of the node cluster, a diversion of the return traffic. The method further includes relinquishing, by the first node of the node cluster, the flow ownership and assigning, by the first node of the node cluster, the flow ownership to the second node of the node cluster.