In the realm of Software-Defined Wide Area Networking (SD-WAN), much of the early excitement centred on traffic steering—the ability to dynamically direct application flows across multiple WAN paths based on real-time link performance, application type, or business policy. While powerful in concept, traffic steering is no longer a pressing concern in modern SD-WAN architectures that leverage packet-based bonding. In such implementations, the very premise of steering traffic across individual paths becomes irrelevant.
This article explores why traffic steering is a moot point in bonded packet-based SD-WAN, how packet-based and session-based load balancing differ, and why modern implementations, such as Fusion’s SD-WAN, achieve superior results without relying on the legacy concept of traffic steering.
Session-Based vs. Packet-Based Load Balancing in SD-WAN
Session-Based Load Balancing
In traditional SD-WAN implementations—especially those using session-based architectures—each network session (typically defined as a five-tuple of source IP, destination IP, source port, destination port, and protocol) is mapped to a specific WAN link at the session’s start. Once assigned, all packets belonging to that session flow across the chosen link until the session terminates.
This approach allows the SD-WAN to maintain session integrity without the need for sophisticated reordering mechanisms. However, it comes with limitations:
Underutilisation of links: If one link is congested and another is idle, active sessions cannot shift mid-flow.
Delayed response to performance degradation: Re-steering a session requires detection, closure, and re-establishment, which is reactive.
Dependent on traffic steering logic: Optimal performance is reliant on accurate and responsive traffic steering algorithms.
Packet-Based Load Balancing
Packet-based bonding takes a more advanced approach. Instead of sending entire sessions down one path, individual packets from the same session are distributed across multiple WAN links simultaneously. This allows full bandwidth utilisation and real-time failover, as traffic flows can dynamically adapt at the packet level.
Key advantages include:
Maximum bandwidth utilisation: All available links are used in parallel, regardless of session.
Real-time failover: If a link fails mid-session, only a few packets are lost. The session continues seamlessly over the remaining paths.
Dynamic compensation for link quality: Algorithms can favour higher-quality links on a per-packet basis, adjusting instantly to jitter, packet loss, or latency.
Why Traffic Steering Becomes Irrelevant
In a bonded, packet-based architecture, traffic steering no longer applies in the traditional sense. Here’s why:
1. All Links Are Active for All Traffic
Traffic isn’t “steered” to a specific path based on performance—it’s dynamically split per packet across all links. This means there's no need to “decide” which path is best for a particular session or application. The bonded tunnel continuously evaluates each link’s performance in real time and assigns each packet to the optimal path at that moment.
2. Session-Aware Traffic Steering Isn’t Needed
Because packets can be reassembled in-order by the receiving SD-WAN node, the concept of assigning sessions to a single WAN path for consistency becomes obsolete. Packet ordering and flow integrity are preserved by the overlay layer, freeing the system from session stickiness requirements.
3. Failure Handling Is Instantaneous
With packet-based bonding, failure detection and failover do not require session termination or reassignment. Since every packet is evaluated independently, traffic can bypass faulty links without human intervention or complex re-routing logic.
Traffic steering assumes a network operator must configure or automate policy-based routing to improve performance. In bonded packet-based systems, there’s nothing to configure. The optimisation is automatic, granular, and reactive at microsecond-level resolution.
Nepean Network’s SD-WAN: A Case Study in Bonded Resilience
Nepean Network’s SD-WAN platform exemplifies the power of bonded packet-based routing. Its platform creates a virtualised tunnel that spans up to three separate WAN circuits. Whether combining fibre, fixed wireless, or LTE, Nepean Network’s SD-WAN:
Sends split packets across all active links.
Monitors link health at sub-second intervals.
Reacts in real time to latency, jitter, or packet loss.
Delivers single IP continuity, masking link disruptions.
Eliminates the need for manual steering policies.
The result is no downtime, no decisions, and no steering. Whether you're running VoIP, cloud applications, or real-time industrial telemetry, all flows are bonded across every path with optimal use of available bandwidth.
Wrap
Traffic steering, once a core feature of SD-WAN, is rendered obsolete by packet-based bonding. When every packet can be optimally routed in real time, the notion of “steering” entire sessions to specific links becomes not just unnecessary but counterproductive.
Bonded packet-based SD-WAN solutions like Nepean Network’s offer superior performance, resilience, and simplicity. In these environments, steering is not only moot—it’s a relic of an older network philosophy. The future lies in intelligent, real-time, per-packet optimisation, not reactive per-session redirection.
