Connectivity- and Security-Aware Edge Node Placement for Smart Cities: A Composite Scoring Framework for IXP-anchored Deployment in CDN-Desert Regions

Increasingly, Sub-Saharan African urban areas are being transformed into smart cities even though they remain Content Delivery Network (CDN) deserts, where internet content and services are served from distant points of presence, increasing latency and the cost for traffic. Internet Exchange Point (IXP)-anchored edge nodes are well positioned to reduce reliance on expensive, high-latency international transit. Existing edge-placement methods, however, prioritize latency and path resilience, ignoring the routing security posture of these edge nodes. This becomes critical once the edge nodes carry latency-sensitive, personal identification information (PII) and secure smart city workloads such as traffic and surveillance data, e-government portals, health-related and financial data. This paper proposes a composite function that makes routing and placement decisions to be determined by both connectivity-scale term and a macro-level network hygiene term. Using data across seven Anglophone Sub-Saharan African IXPs, the framework was evaluated with 60 and 500 workloads, while connectivity and security-coverage terms were sourced from PeeringDB and Internet Society's Pulse IXP Tracker respectively. Weights between connectivity and security were estimated using entropy weighting, CRITIC and the Analytic Hierarchy Process. The placement function was evaluated against 3 baselines – connectivity only, equal and random weights. Within the seven-node exploratory sample, connectivity and security-hygiene were found to be weakly correlated with the GIXA being an outlier. Ultimately, the framework offers a practical placement template for security-conscious smart city edge deployment in underserved markets.