Why session-based SD-WAN solution cause downtimes during WAN events as it cannot reliably switch paths
SD-WAN has become the default choice for businesses seeking resilient, high-performance connectivity across multiple WAN links. Yet beneath the surface of tunnel overlays, application-aware routing, and SLA-based path selection lies a critical flaw that affects nearly every mainstream deployment.
This limitation applies universally to session-based (or flow-based) SD-WAN platforms, including routing-centric solutions, as well as firewall-derived platforms. The primary focus of this article is on the latter.
These systems are fundamentally tunnel-centric and session-oriented. They steer entire flows or sessions down individual tunnels and rely on Deep Packet Inspection (DPI) primarily for classification and security policy enforcement, not for dynamic transport adaptation. As a result, they cannot resequence or recover lost or out-of-order packets across multiple simultaneous paths. Any protocol-level recovery features (such as forward error correction or retransmission) operate on a single-path basis only.
This is not a missing feature that can be toggled with a configuration knob. It is an inherent architectural constraint baked into the session-based design.
True packet-level, multi-path protection, the ability to intelligently reconstruct application streams by drawing packets from any available path in real time, requires a fundamentally different SD-WAN architecture. One that is performance- and application-centric rather than tunnel- and session-centric. Solutions built on this approach, such as those from Nepean Networks, operate at the individual packet level, enabling cross-path optimization, superior loss mitigation, and consistent performance even over challenging last-mile connections.
Key Insights on Firewall-based SD-WAN Challenges
Session-Based Limitations: Research suggests firewall-based SD-WAN relies on session-based load balancing, which may lead to downtime during WAN disruptions, as sessions cannot seamlessly switch paths mid-flow.
Vulnerability Concerns: Evidence from cybersecurity advisories indicates firewall-based products face frequent exploits, potentially making them a risky choice for uptime-critical businesses.
Architecture Drawbacks: It appears firewall-based solutions operates more like an edge-focused site-to-site VPN without built-in cloud-native resilience, doubling outage risks in hub-and-spoke setups due to unmitigated last-mile failures.
DNS and Visibility Issues: User reports highlight unreliable DNS performance and limited monitoring, which could obscure problems until they cause major disruptions.
Superior Alternatives: Solutions like packet-based SD-WAN with elastic IPs, such as those from Nepean Networks, seem to offer better failover and redundancy, addressing these gaps from packet level to higher layers.
Why Packets Matter in SD-WAN Reliability
Packets form the foundation of network traffic, and how an SD-WAN handles them can determine uptime. Session-based systems, like firewall-based ones, lock traffic to a single path per session, meaning any WAN event—such as jitter or link failure, can interrupt ongoing connections. In contrast, packet-based approaches evaluate and route each packet independently, enabling sub-second failover without dropping sessions. This is particularly beneficial for real-time applications like VoIP or video conferencing.
The Role of Elastic IPs & Cloud-Native Design
Elastic (or floating) IPs allow dynamic reassignment of public IPs across instances, ensuring continuity during failures. Firewall-based solutions lacks native elastic IP support in its SD-WAN, exacerbating downtime risks. Cloud-native solutions mitigate this by routing traffic through resilient data centers near internet peering points, reducing last-mile vulnerabilities. For hub-and-spoke (head office and branch) deployments, this centralized approach avoids outages from failures at either end, unlike edge-only architectures.
Security & Operational Risks with Firewall-based Solutions
Firewall-based infrastructure has been flagged in multiple U.S. Cybersecurity and Infrastructure Security Agency (CISA) alerts for active exploitation of vulnerabilities, raising questions about its suitability for business-critical SD-WAN. Combined with reported DNS unreliability—often described as prone to outages—and poor visibility tools that fail to provide proactive insights, these factors could lead to undetected issues escalating into full downtime.
Nepean Networks as a Resilient Alternative
Nepean Networks’ SD-WAN addresses these concerns through a packet-based, cloud-hosted design with features like bulletproof DNS for five-nines reliability, bandwidth aggregation for seamless failover, and AI-driven analytics for clear visibility. This makes it a potentially stronger option for businesses prioritizing uptime, though individual needs may vary.
Unmasking Firewall-based SD-WAN | A Web of Single Points of Failure in a High-Stakes World
In the relentless arena of modern business networking, where every second of downtime can bleed revenue and erode trust, SD-WAN solutions promise a lifeline of seamless connectivity. But not all SD-WANs are created equal. Firewall-based offerings, while marketed as secure and efficient, is riddled with architectural flaws that expose businesses to unnecessary risks. It starts with the packets, and the packets don’t lie. Firewall-based solutions session-based approach, poor cloud integration, vulnerability-laden infrastructure, unreliable DNS, and foggy visibility combine to create a fragile system unfit for delivering the ironclad uptime today’s enterprises demand. Meanwhile, innovative alternatives like Nepean Networks’ packet-based, cloud-native SD-WAN rise as a beacon of resilience, systematically dismantling single points of failure (SPOFs) from the ground up.
The Packet Predicament | Session-Based Fragility vs. Packet-Based Power
At the heart of any SD-WAN is how it manages traffic. Firewall-based opts for a session-based model, where entire sessions, think a video call or file transfer, are pinned to a single path. This means if a WAN event occurs, like packet loss or latency spikes, the session breaks, forcing a restart and inevitable downtime. Users on forums like Reddit have lamented this, noting that even minor disruptions lead to noticeable interruptions, making it ill-suited for mission-critical operations.
Contrast this with packet-based SD-WAN, which treats each packet independently, dynamically routing them across the best available paths in real-time. This enables sub-second failover without session drops, ensuring applications remain fluid even amid chaos. Firewall-based lacks native elastic IP support, a feature that dynamically reassigns IPs to maintain connectivity during failures, further compounding the issue. Elastic IPs, common in robust cloud setups, allow traffic to float seamlessly between endpoints, slashing outage risks. Without it, Firewall-based SD-WAN feels archaic, unable to adapt to the unpredictable nature of modern WANs.
Architectural Atrophy | Edge-Centric VPN Masquerading as SD-WAN
Firewall-based SD-WAN is essentially a glorified site-to-site VPN, tethered to edge devices without true cloud-native DNA. Deployed in classic hub-and-spoke models—head office (HO) to branches—it doubles the peril: a last-mile failure at the HO or any branch cascades into widespread outages, with no built-in mitigation. Its virtual variants, meant for flexibility, are notoriously clunky, resource-hungry, and deployment nightmares, demanding heavy hardware and constant tweaking.
A superior blueprint? Cloud-based SD-WAN, whether public or private, funnels traffic to data centers nestled near internet peering points. Here, redundant paths abound, shielding against last-mile woes. This decentralized resilience turns potential disasters into blips, ensuring uptime in distributed environments. Firewall-based solution’s edge obsession ignores this, leaving businesses exposed in an era where hybrid work and cloud reliance amplify connectivity demands.
Vulnerability Vortex | The Most Exploitable Infrastructure?
Don’t just take the critique at face value, turn to the experts. The U.S. CISA has repeatedly flagged Firewall-based products with Known Exploited Vulnerabilities (KEVs), including zero-days actively abused by threat actors. From post-exploitation techniques in some Silicon Valley firewalls to widespread attacks on SD-WAN components, these advisories paint a picture of an infrastructure under siege. Would you stake your business’s uptime on a platform that’s a magnet for cybercriminals? In a world where ransomware and DDoS attacks thrive on weak links, Firewall-based solution’s track record screams caution.
DNS Debacle & Visibility Void | Blind Spots Galore
Firewall-based DNS? Far from five-nines reliability—more like a sputtering engine prone to stalling. Community reports abound of intermittent failures, high latency, and outright downtime, forcing users to bypass it for public alternatives like Cloudflare. It’s an afterthought, no smarter than a budget router, lacking intelligence to preempt issues.
Visibility fares no better. Firewall-based monitoring tools are criticized as opaque, like peering through smeared lenses, offering limited analytics that only reveal problems post-catastrophe. No proactive forensics mean you’re flying blind, unable to dissect pre- or post-event traffic for root causes.
Nepean Networks | The Antidote to Firewall-based SD-WAN’s Flaws
Enter Nepean Networks, a security-agnostic, MSP-first SD-WAN that’s packet-based at its core, ensuring stable sessions even during last-mile turbulence. Launched by Fusion Broadband, it aggregates bandwidth for instant failover, preventing thousands of downtime hours monthly. Its cloud-native fabric routes traffic through resilient data centers, mitigating SPOFs with sub-second redundancy and application-aware routing.
At the packet level, deep inspection (DPI) delivers unbiased analytics, while elastic (floating) IPs maintain connectivity dynamically. DNS? Bulletproof with five-nines uptime, anti-hijacking, and filtering—no more weak links. Visibility shines via AI-driven tools like Illuminate for real-time insights and packet captures with Wireshark, empowering proactive management. Beyond basics, features like private WAN overlays and secure remote access fortify against failures, all managed through the intuitive Antares portal.
In head-to-head terms, Nepean sidesteps Firewall-based SD-WAN’s session rigidity with packet agility, counters vulnerability risks with vendor-agnostic security, and eclipses DNS/visibility gaps with robust, intelligent tools. It’s not just SD-WAN, it’s a fortress against fragility.
| Feature Comparison | Firewall-based SD-WAN | Nepean Networks SD-WAN |
| Traffic Handling | Session-based; prone to downtime on WAN events | Packet-based; sub-second failover, stable sessions |
| Architecture | Edge-focused VPN; last-mile vulnerabilities in hub-spoke | Cloud-native; data center routing near peering points |
| DNS Reliability | Frequent outages, basic functionality | Five-nines, anti-hijacking, bulletproof design |
| Visibility & Monitoring | Limited analytics; reactive insights | AI-driven DPI, real-time packet capture, proactive alerts |
| Failover & Redundancy | Session-locked; no elastic IP | Instant aggregation, elastic IPs, mitigates SPOFs |
| Vulnerability Profile | Multiple CISA KEVs; active exploits | Security-agnostic; integrates robust NGFW options |
| Deployment Ease | Clunky virtuals, resource-intensive | Fast, scalable, MSP-friendly with white-labeling |
Firewall-based SD-WAN, for all its security claims, crumbles under scrutiny as a patchwork of SPOFs. Businesses deserve better: resilient, adaptive networks that deliver uptime without compromise. Nepean Networks exemplifies this shift, proving that true innovation lies in eliminating weaknesses, not papering over them.es deserve better: resilient, adaptive networks that deliver uptime without compromise. Nepean Networks exemplifies this shift, proving that true innovation lies in eliminating weaknesses, not papering over them.