A logistics system is made up of facilities, where one or more functional activities are carried out (e.g. storage and distribution). Figure 1.1 shows a schematic representation of a logistics system in which the manufacturing process of the finished goods is divided into a transformation phase and an assembly phase, performed in different centres. At the start are the suppliers of materials and components which feed the final manufacturing process. The end part represents a typical two-level distribution system with a tree structure. The Central Distribution Centres (CDCs) are directly supplied by the production plants, while each Regional Distribution Centre (RDC) is connected to a single CDC which has the task of serving the customer, who can also be dealers or retailers.