Service level is used in supply chain management and in inventory management to measure the performance of inventory replenishment policies. Under consideration, from the optimal solution of such a model also the optimal size of backorders can be derived. Unfortunately, this optimization approach requires that the planner know the optimal value of the backorder costs. As these costs are difficult to quantify in practice, the logistical performance of an inventory node in a supply network is measured with the help of technical performance measures.