<![CDATA[Large retail, logistics, and financial enterprises operate geographically dispersed branch networks in which wide area network scalability, availability, and recovery performance directly affect business continuity. This study investigates the scalability limitations of software-defined wide area network architectures for enterprise networks with more than 20,000 branches. It develops a distributed, pod-based Aruba SD-WAN architecture designed for this operating scale. The proposed architecture partitions branches into routing pods of approximately 3,000 sites, with each pod anchored by redundant head-ends distributed across two geographically separated data centers configured in an active-passive arrangement. Each branch employs a dual-gateway edge with four prioritized IPSec tunnels to provide path redundancy and deterministic failover. Analytical models are formulated to relate branch population to pod count, head-end requirements, aggregate tunnel volume, and control-plane peering load. The architecture is evaluated for branch populations ranging from 3,000 to 30,000 sites using control-plane capacity, tunnel scalability, availability, and operational recovery as the principal evaluation measures. The results indicate that hierarchical pod partitioning maintains routing and peering loads within platform capacity limits while supporting progressive branch expansion. Operational measurements show that head-end failover is completed within one minute, while inter-data-center failover is completed within three minutes. The architecture also provides predictable control-plane behavior by limiting the routing domain and distributing tunnel and peering workloads across independent pods. This approach further reduces the concentration of routing dependencies and enables incremental capacity expansion without redesigning the entire enterprise network. These findings demonstrate that distributed pod-based partitioning can provide a scalable and resilient SD-WAN architecture for hyperscale enterprise branch networks, enabling controlled growth while maintaining operational continuity and predictable failover performance]]>
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