A Next Generation Networks (NGN) is a packet-based network able to provide Telecommunication Services to users and able to make use of multiple broadband, QoS-enabled transport technologies and in which service-related functions are independent of the underlying transport-related technologies. It enables unfettered access for users to networks and to competing service providers and services of their choice. It supports generalised mobility which will allow consistent and ubiquitous provision of services to users. [ITU-T Recommendation Y.2001 (12/2004) - General overview of NGN]

The NGN is characterised by the following fundamental aspects:

• Packet-based transfer 
• Separation of control functions among bearer capabilities, call/session, and application/service
• Decoupling of service provision from transport, and provision of open interfaces
• Support for a wide range of services, applications and mechanisms based on service building blocks (including real time/streaming/non-real time services and multi-media)
• Broadband capabilities with end-to-end QoS and transparency
• Interworking with legacy networks via open interfaces
• Generalised mobility
• Unfettered access by users to different service providers
• A variety of identification schemes which can be resolved to IP addresses for the purposes of routing in IP networks 
• Unified service characteristics for the same service as perceived by the user
• Converged services between Fixed and Mobile networks
• Independence of service-related functions from underlying transport technologies
• Support of multiple last mile technologies
• Compliant with all Regulatory requirements, for example concerning emergency communications and security/privacy, etc.