Optimal vCDN Placement in Fixed Broadband Networks: A Multi-Objective ILP Formulation with Partial Caching
This paper proposes a multi-objective Integer Linear Programming (ILP) formulation for optimal virtual Content Delivery Network (vCDN) placement in fixed broadband networks. The proposed framework jointly minimizes backhaul traffic and end-to-end latency across a six-tier topology spanning OLT, Tier 2/Tier 1 aggregation, Provider Edge, Transport Backbone, and International Gateway nodes. Key contributions include a partial caching model with ratio α***(0,1] that increases cache diversity by 1/α (Theorem 1), a view-time threshold mechanism with effective utilization factor ηⱼ, and a placement efficiency metric Φ that quantifies performance gain per unit deployment cost. Proof-of-concept simulation confirms 81.2% average RTT reduction (5.704 ms → 1.075 ms), directly validating the latency component of the ILP objective.