ITU-T Y.2325: NGN Evolution Towards Future
International Telecommunications Union (ITU) defined Next Generation Network (NGN) underlies most wireline and wireless packet-based telecommunications networks. A key design principle of NGN is decoupling of service-related functions from the underlying transport stratum, making user services independent of transport technologies. Interestingly, the NGN architecture, as defined in ITU standards, did not follow this design principle for internal network services, e.g., mobility, or authentication though adhering for external user services like IPTV or Multimedia services. These internal services are handled by the NGN transport control plane, making them an intrinsic part of the transport stratum, resulting in a tightly coupled service and transport functionality as opposed to the proclaimed design goal. This design choice may force each transport technology to support internal services individually, e.g., separate authentication service for each transport, leading to duplication. Since the NGN architecture is the base underlying architecture for most packet-based telecommunications network including advanced cellular networks like 4th/5th Generation cellular networks, the limitation persists in these cellular networks as well. To remedy the situation, the decoupling of service and transport can be generalized to include internal services like mobility and authentication also. In this context, the recently published ITU Y.2325 recommendation, defines an evolved NGN architecture, wherein all services, including internal network services, are decoupled from the transport stratum. The proposal results in a more scalable and modular evolved NGN architecture that can be used as a template for all future telecom networks including IMT-2030 (6th generation mobile networks). In this article, we review the evolved NGN architecture, as proposed in ITU-T Y.2325.