2 NGN architecture evolution towards Future Network architectures
2.1 NGN concepts and architectures

The main principles of the NGNs (Next Generation Networks) were formed when the idea of NGN itself emerged. The next two definitions from ETSI and ITU-T describe NGN in substance.

ETSI describes NGN as a concept for the defining and establishing of the networks, allowing a formal distribution of functionalities into separate layers and planes by using open interfaces. The NGN concept provides new conditions for creation, implementation and effective management of innovative services. ITU-T describes NGN as a network based on packet transfer, enabling to provide services, including telecommunication services, and is capable of using several broadband transmission technologies allowing guaranteeing QoS. The functions related to services are at the same time independent of the basic transmission technologies. NGN provides unlimited user access to different service providers. It supports general mobility providing the users with consistency and availability of services.

That is what definitions say, but probably eventually NGN advantages are of bigger importance. Worth mentioning are some requirements for NGN it should conform to:

Within the NGN concepts the standardisation institutions are solving the following issues and problems:

  • existing networks migration towards NGN,
  • development in the field of access technologies,
  • connection of other networks to IP networks,
  • provision of services and development of new ones,
  • interworking in the area of addressing,
  • interworking of signalling systems,
  • roaming and mobility.

There are many conceptual models and reference architectures for both the converged networks and VoIP architectures. Therefore, we have tried to find common features and to define a suitable conceptual model for NGN. An objective of the conceptual model is to determine functional layers (covering similar functionalities), their entities, reference points (interfaces) and information flows between them. Such a model then can be mapped more easily into the physical reference architecture (and it is independent of the physical entities, i.e. components of the architecture).

In most analyzed cases the NGN conceptual model layers are from the point of view of functionalities divided into independent parts as follows (Fig. 2): access (some reference architectures do not include it directly into the NGN model or replace it by the adaptation one), transport (transmission, switching), control (call/sessions control) and application (services).

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Fig. 2 - NGN conceptual model and its functional layers