Cloud and AI/ML workloads are posing unprecedented new requirements on the wide-area network: it must combine strict availability, massive growth, and feature agility. It became increasingly clear that traditional WAN designs were ill-equipped to adapt to these requirements.

We highlight a problem that the networking community has largely overlooked: ensuring that the inputs to network controllers in Software-Defined Network (SDN) WANs correctly reflect the state of the network. We show that "incorrect" inputs are a common cause of major outages in production and propose new directions to address these.

Motivated by our experiences operating a global WAN, we argue that SDN's reliance on infrastructure external to the data plane has substantially complicated the challenge of maintaining high availability. We propose a new decentralized SDN (dSDN) architecture in which SDN control logic instead runs within routers, eliminating the control plane's reliance on external infrastructure and restoring fate-sharing between control and data planes. We present dSDN as a simpler approach to realizing the benefits of SDN in the WAN. Despite its much simpler design, we show that dSDN is practical from an implementation viewpoint, and outperforms centralized SDN in terms of routing convergence and SLO impact.