The objective of Recommendation ITU-T Y.2012 is to describe the functional requirements and architecture of the next generation network (NGN), taking into account the requirements and capabilities for ITU-T NGN as described in Recommendation ITU-T Y.2201. The functional architecture provided in this Recommendation allows a clear distinction between the definition and specification aspects of services provided by the NGN, and the actual specification of the network technologies used to support those services. In line with Recommendation ITU-T Y.2011 principles, an implementation-independent approach is adopted.