Metrics are a measure which is used in calculating the next host to route a packet to. A metric can be used directly or it can be used as an element in an algorithm. Metrics are quantifiable and are constantly analyzed to increase or optimize business performance. A number of metrics that are watched by businesses include sales revenue, customer loyalty and retention, the cost of a customer acquisition, operating productivity, the size of the business' gross margin, monthly profit or loss, overhead costs, variable cost percentages, inventory size and hours worked per process. There is no limit to the subject matter that a business could attach a metric to.