Recommendation ITU-T Y.2015 begins with showing the limitations of the conventional IP architecture, which uses IP addresses as both node identifiers (IDs) and locators, on supporting mobility, multi-homing, fast endpoint renumbering, traffic engineering, and scalable routing. It then shows that ID/locator separation, i.e., the use of distinct sets of values as node IDs and locators, helps to overcome these limitations. This Recommendation provides general requirements for introducing ID/locator separation in NGN.