The NGN architecture supports different services including multimedia services and content delivery services such as video streaming and broadcasting. NGN provides support for PSTN/ISDN replacement (i.e. PSTN/ISDN emulation) as well as PSTN/ISDN simulation. In addition, the NGN provides infrastructure for Value Added Service addition by 3rd party.
The NGN reference architecture comprises three distinct levels:
- The transfer network carries out the transport in the form of packets, of information flows interchanged between peripheral units, user terminals and service provider servers:
- The network control includes the functions necessary to establish the links needed to transfer information in conformity with request from the applications, whether these be implemented by users, operators or service providers.
- The Service control not an integral part of network is related to the final service provided for the user.
The NGN transfer process can be divided into five main parts
- User facility: depends upon what type of equipments user is using.
- Connecting user facility: connection is hereby defined as the part of the network through which user facilities are connected to the first equipment unit from which user flows are multiplexed or concentrated onto shared transmission media. Customers may process their own connection resource (dedicated wire access) but the connection may also be shared at least partially as in the case of radio access or cable networks. The connection network will be considered to include the first network unit shared by several customers to be defined by the generic term connection unit (Access Node, Access Muxer, Access Gateway) and classified in terms of base stations and base station controller for radio access, DSLAM for ADSL access, distribution centre for cable network, etc.
- Aggregation: The aggregation functions in linking connection units to the peripheral units to the peripheral routing nodes at which level communication between users are setup. It is independent of connection technologies and is implemented in networks that each agglomerate flows originating from customer connections from one area and convey them to peripheral routing node managing several areas.
- Peripheral routing: It terminates customers virtual access and handles the elementary information flows they carry by sorting, classifying and finally routing them either individually to local customers (connected upto same routing node) or in groups to the network core. As well as handling information flows, routing extracts the control flows sent by customers and directs them to the network control.
- Transit : The functions of transit is carried out by the core network, a very high speed meshed network that handles the aggregated flows that are transported through various channels, giving priority to routing speed and economy rather than optimization of resources, which are a source of processing complexity and high costs. The NGN core network combines, then high transmission rates, long distance and low costs.
Controlling the NGN involves four main functions : mediation for access to the services, user mobility and presence management and control of resources.
- Mediation: Accessing services in a competitive environment:
The mediation function represents the interface between customers and service providers. It takes the form of a portal which will enable interchanges with the customer by calling on different technologies depending upon the terminal used : HTML pages on PC, WML on a mobile phone, audio on a fixed telephone, etc. through this portal customers can navigate among the components of their service package, either to use them or manage them.LIKDPGKPFDGPD
- Managing mobility
The aim of mobility management is to allow users to enjoy their services wherever they are. This involves maintaining a constant relationship ( necessary for the routing of information) between the address of the terminal used and the address of its active point of connection to the network, whether this connection is by wire or radio. The characteristics of the terminal and of the access to which it is connected must also be constantly available in order to be able to adapt services to their performance ( access speed, user dialogue mode, terminal operating system, etc.).
- Managing presence: in the network, in the services, or both?
In traditional telephone networks, the status of the user was simply ‘free’ or ‘busy’ and was supplied only after a call was made. Presence management, however, consists in permanently posting the status that the user of the network wishes to make known to others: ‘I can be contacted by members of my sports club’, etc. The concept ha the potential to transform the way people communicate, and theoretically could be applied to all forms of communications. It could also be shared by many services and thus become, at least in part, one of the generic control functions associated with the network.
- Controlling resources
Resource control consists essentially in the process of receiving a request of a given application, deciding on a route between two peripheral points on the network ( where the relevant terminals or servers are located ) and configuring or reserving resources along this route. Controlling I performed at two levels, that of the global network and that of the equipment, and corresponds to several entities: physical link, virtual circuit, address, transmission rate, memory capacity, etc.)
Request from services are expressed in terms of parameters that are independent of techniques and mechanisms implemented by the network. This makes it necessary to translate, for examples, the identifiers (URL, directory number, etc.) used by the service or the expression of the quality of the service expected into a language adapted to the equipment and to the resources themselves. Although it is an important characteristic of NGN, this ‘de-correlation’ is nevertheless difficult to apply, and this is one of the reasons for the continuing variations in vocabulary used to describe this function: ‘ Gatekeeper’, ‘Call Server’, ‘ Policy Server’, or ‘Session Server’ are all used for sets of functions that are not always identical.
Even though the above definition is evocative of information transfer in particular, the control of resources also concerns other types of equipment that may be used in applications ( voice servers, cache servers, transcoders, etc.)
Each service is controlled in a specific way. Algorithms and data are combined to enable the implementation of end services between two customers or between a customer and a server. For example , for a VoD service, the user I given a choice of commands foe selecting, then navigating within a movie supplied by a provider , using such command as fast forward, rewind, pause etc. which are commonly used on a VCR or DVD player.