This document discusses network as a service (NaaS) and software-defined networking (SDN). It notes that traditional networks use expensive and inflexible hardware, but SDN allows networks to be virtualized and controlled through software. The document outlines an SDN implementation that uses a network API to manage access control lists and network configuration for thousands of networks in a cost-effective and scalable way. It provides performance metrics showing the SDN implementation can process hundreds of thousands of flows with low latency and without delaying the first packet.