Subscriber-to-subscriber service quality measurements are taken end-to-end as defined in Figure 1/E.434. These measurements are taken: to relate network quality to customers' expectations which are based upon previous experience with the network; to ensure that objective measures are made of the network; to ensure that acceptable thresholds of quality are Wing met; to ensure that regulatory requirements are met; to ensure that the distant correspondent’s level of quality meets other network providers’ needs.