Network infrastructure has evolved from a technological convenience to fundamental infrastructure essential for contemporary society. This article establishes network infrastructure as critical infrastructure through a novel socio-technical framework integrating three dimensions: technical architecture, economic dependencies, and social equity considerations. Unlike existing critical infrastructure models that examine technical performance and economic impact in isolation, this framework demonstrates that infrastructural criticality emerges specifically from the intersection of these dimensions with equity considerations—a relationship previously untheorized in infrastructure scholarship. The analysis reveals a reliability-inclusion nexus where infrastructure design decisions either enable or constrain digital participation, directly affecting economic opportunity and social mobility. For instance, rural communities experiencing frequent broadband outages cannot sustain remote employment or telemedicine consultations, while urban students with consistent connectivity access sophisticated educational platforms that their rural peers cannot reliably reach—disparities that compound systematically over academic years and career trajectories. Infrastructure engineers face substantial ethical responsibilities, as their technical choices regarding capacity placement, redundancy design, and sustainability practices impact millions of lives across generations. The primary contribution of this work is a theoretically-grounded framework that redefines critical infrastructure assessment by positioning equity as constitutive rather than supplementary, enabling policymakers to establish regulatory frameworks that mandate equitable access and providing engineers with actionable principles for balancing technical performance against equity imperatives. Recognition as critical infrastructure enables appropriate policy frameworks, investment prioritization, and workforce development while demanding intentional focus on equitable access rather than profit-maximizing deployment strategies.