Introduction

A typical global supply chain in modern industry is a cyber-physical network of multiple part suppliers at different geographical locations and multiple production plants and distribution centers, where supplied parts are assembled into finished products and next distributed to customers. Figure 1.1 shows a schematic diagram of a multi-tier supply chain network, where each vertical level (suppliers, producers, distribution centers, customers) is called a tier or echelon, and the arcs represent material flows. For example, a large and complex multi-tier supply chain network of Ford Motor Company (e.g., Simchi-Levi et al. 2015) consists of over 50 manufacturing plants, ten tiers of suppliers, including 1400 tier 1 supplier companies with 4400 manufacturing sites in over 60 countries. Six million vehicles produced annually, require 55,000 different part types with a complex bill of materials.