What is Next Generation Networks (NGN)? Why NGN?
Next-Generation Networks (NGN):
NGN is about the network infrastructure that will enable the provision of the existing telecommunications services and innovative applications of the next generation. The term NGN refers to a converged network capable of carrying both voice and data over the same physical network, with all traffic (voice and data) carried as IP.
“IP networks are likely to be simpler and easier to run and maintain as compared to the existing legacy networks and provide the operators with sufficient flexibility in their cost base to reduce both OPEX and CAPEX. In addition, all IP networks allow for innovation in terms of new services and applications, with a truly converged product offering that bridges the current distinction between fixed and mobile networks.”
The process of realization of NGN will lead to a revolution in the design and build-up of telecommunications network architecture, which will result in a change in the way service providers offer their services and the way people communicate. Ultimately, NGN would phase out the existing legacy networks at a point of time in the future.
There are some practical factors that have collectively formed the key drivers for NGN migration. Firstly, the existing network operators are facing fierce competition in the market and they have to remain competitive to survive. In order to achieve this, operators are trying to build cost-effective businesses on the one hand and create new business models and generate new revenue streams on the other hand. The convergence of fixed and mobile networks and integration of voice and non-voice services are becoming their targets because such an approach would lower operational cost and allow greater flexibilities for service innovation and shorter time-to-market.
Secondly, the increasing service requirements from the end-users call for innovative applications/multimedia services, high flexibility of service access, high bandwidth, high quality of service and etc. Apparently, the operators’ need for remaining competitive and the end-users’ demand for increased service requirements are together forming a strong driving force pushing the development of NGN all over the world with characteristics and features that would fulfill the needs of network operators, service providers, and end-users.
NGN is as much about the easier provision of advanced services such as VoIP, Broadband, multimedia applications, etc. as it is about cost-saving through simplification of the network.
A migration to NGN will bring about a complete change in the existing business models which is a source of concern for both operators and regulators world over.
Introduction to the NGN concept
Historically, incumbent operators typically ran one network — the Public Switched Telephone Network (PSTN). The PSTN was designed to carry voice when the voice was the only communication carried. As demand for data communications developed the incumbents adapted their networks to also carry data traffic. However, typically, rather than replacing the PSTN operators typically built new networks that they ran in parallel – which is called the overlay network. These new overlay networks were designed specifically to carry data traffic.
As network technology continued to develop, the number of networks multiplied in step. As a result, today, many operators run typically 5-10 different network platforms (ATM, IP, Frame Relay, ISDN, PSTN, X.25, etc.). The problem with this multi-network approach is that it has created a web of complexity resulting in management complexity, operational inefficiencies, maintenance issues and duplicating CAPEX.
Next-Generation Networks aim to reverse the clock and go back to the simplicity of one single network. NGN is all about deploying one network platform capable of supporting all traffic types while facilitating service innovation (Fig. 1).
ITU defines Next Generation Network (NGN) as “a packet-based network able to provide telecommunication services and able to make use of multiple broadbands, QoS-enabled transport technologies and in which service-related functions are independent of underlying transport-related technologies.
It enables unfettered access for users to networks and to competing service providers and/or services of their choice. It supports generalized mobility which will allow the consistent and ubiquitous provision of services to users”.
Convergence between Telecom and Internet
It is believed that the rapid and widespread growth in the use of the Internet has become the catalyst to the fostering of such a concept of NGN. With Broadband access service becoming increasingly popular, easily accessible and more affordable to any corporate entity and individuals, more and more applications and services have been developed and evolved based on the IP technology of Internet, varying from narrowband voice telephony services (i.e. VoIP) to broadband applications such as high-speed Internet access, video conferencing, multi-casting of TV programs and etc. The increasing proliferation of IP-based services has in turn driven the rapid development of packet-based networks in the access, transport and core layers of the telecommunications infrastructure in order to cater to the drastic increase in the volume of IP traffic. Such a change in telecommunications services brought about by the Internet has paved the path and laid a foundation for the development of IP-based NGN.
From a high-level perspective, Next Generation Networks rely on three main principles. First of all, NGNs are implemented in such a way that the functions performed by the network are separated into functional planes. These functional planes include access, transport, control & intelligence, and service layers. Layers are independent in the sense that they can be modified or upgraded regardless of other functional layers. This layered architecture provides a flexible and scalable network, reducing time to market for the implementation of new services. Moreover, the functional planes are separated by open interfaces in order to facilitate the interconnection to other operators’ networks but also the integration of third-parties’ services and applications. Provided that commercial agreement is reached between the different parties, such a principle can widen the operator’s coverage and service scope and can also provide end-users with access to a greater number of services.
Last but not least, NGN is a multi-service network meaning that an NGN can be used to provide many services, as opposed to legacy networks that are only used for specific services. This multi-service network enables operators to implement converged and new services in addition to POTS. From the users’ perspective, the convergence of services will enable the emergence of seamless service concepts, where users can access their “desired” services from any type of access network.
The NGN architecture
Along with a new architecture, Next Generation Networks will bring an additional level of complexity over existing networks. The addition of support for multiple access technologies and for mobility results in the need to support a wide variety of network configurations.
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 a request from the applications, whether these be implemented by users, operators or service providers.
- The Service control not an integral part of the network is related to the final service provided for the user.
The NGN Architecture
The NGN transfer process can be divided into five main parts
- User facility: depends upon what type of types of equipment the 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 is 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 up to the 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 of 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 is expressed in terms of parameters that are independent of techniques and mechanisms implemented by the network. This makes it necessary to translate, for example, 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 was given a choice of commands for 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.
Service control is not part of the network but uses it so that the media component of the service transferred between the terminals and the servers with the expected quality of service and with a minimum of constraints regarding the location of customers and providers.
Control of resources and the transfer network
As described in previous sections control of the network includes a resource control function which has the objective of controlling, when requested by applications, the reservation and the configuration of all the resources needed for these applications to run smoothly, in accordance with the parameters that express the required QoS. These resources may be associated with information transfer: either directly (to attribute an address, establish a channel, reserve a transmission rate)or indirectly (via the intervention of a server, etc). These resources may also be linked, for example, with the dialogue between user and application (via the intervention of a voice server, etc.) or with security functions (implementation of a firewall, etc). It is noticeable that the control of resources comprises a “global” part, located in the network control, and a “decentralized” part, at the level of the network elements themselves.
As regards the control of transfer resources in the NGN, three main aspects should be mentioned.
-The consideration of differentiated QoS, which implies that the network elements know, flow by flow, which level of QoS to observe, in such a way as to be able to implement the appropriate mechanisms
-The possibility of modifications during a single session, which might mean a change of the bit rate allocated to a flow that has already been established, the processing of a complementary flow or the routing of a given flow via an intermediate entity such as a transcoding device.
-The convergence of transfer resources onto a single control interface whatever the applications involved. In conventional networks, the control of transfer resources uses one of two quite distinct channels according to the origin of the request: network operator for a management application or user for a communication service. This has led to the need to manage two different interfaces each with specific protocols: the “equipment-management” interface (considered a weak or average real-time constraint) and the equipment-call processing’ interface (a severe real-time constraint). However, in the NGN convergence between the fields of management and control of services(illustrated, from the end user’s point of view, by the fact that he will himself increasingly have direct access to management facilities) should also lead to the convergence of the control of resources towards a single interface at the equipment level.
From Service Control to resource control
With the aim of ensuring the connection between users and the terminals and servers involved in a telecommunications service, it is necessary to decide which paths the media flows between these terminals will be routed along. This may or may not mean building real new paths by manipulating addresses and indications of directions, and deciding whether or not to set aside network capacity, or establishing priorities between flows sharing the same path, according to the characteristics of the media flows that support the service requested. Establishing this ‘connectivity’ and managing its evolution comes under the title of “network control”, whose prime role is to give directives that will allow flows to follow the right paths under satisfactory conditions. This role is known more precisely by the term “resource control”. It must, of course, take into account the techniques used on the path being established. It is a different task to establish a path through a 64kbps switched digital network than to do the same through an end-to-end IP network, where it is enough to indicate to a SIP terminal, for example, which IP address should be used to reach the requested party, and perhaps to implement the appropriate mechanisms to guarantee the required level of QoS.
One of the features of NGN principles in network control is to distinguish between resource control and “call control” or “session control”. The aim here is to separate.
- The implementation of actual resources, specific to transfer techniques, that are necessary for establishing physical connectivity, with the required QoS, between network inputs and outputs, these being represented by physical addresses. This is the role of resource control.
- The actions, on a more generic level, ideally independent of transfer techniques, that manipulate the various possible representations of these addresses, and that determine the general characteristics of the connection to be made, particularly in terms of bit rate and QoS. This is the role of call control or session control.
The first distinction, proposed within the framework of NGN, has never really been implemented before. In telephone networks, for example, resource control and call control are integrated into the “call-processing” of the switches.,
A second distinction, also included in the NGN, separates everything to do with network control, i.e. the more or less simple connection (in a session) of terminals, from everything to do with the control of the services provided during these sessions. Control of services here can be extended to include even the consideration of complex information necessary for the complete establishment of the session. This may concern the identification and authentication of the users, their presence and availability, network and even geographic localization, their means of payment (especially in the case of prepayment), etc. This distinction may be considered as an extension of the IN (Intelligent Network) concepts but experience shows it to be difficult to define and even more difficult to stabilize, In fact, certain services can be processed only at the level of call control. This is the case, for example, for a simple telephone or videophone communication. For other services, the definition may appear to be quite a simple matter, as in the case of a pre-paid multimedia messaging service. However, it is easy to imagine that this distinction between network control and service control would be less easy to define in complex applications involving several actors, network operators and service providers. The availability of open interfaces, which has not been achieved in the IN context applied to telephony, can be seen to be even more necessary in multi-service networks like the NGN.
It will also be noted that, according to this principle of separation, the network becomes, in a sense, unaware of the application that is actually being implemented once the session is established, which is different from the traditional context of telephone networks. For example for a terminal that connects to a web server in normal (best efforts) mode via an ADSL link, the NGN network control will set up a link to the internet access provider (identification of access, allocation of an IP address, session initiation, routing), then will supervise the connection, but it will not “see” which services the user is actually using during the session. Depending on how the application proceeds, the network controller may be solicited to set up a new telephone or videophone call.
The Network Control
NGN Control Functions
The Control functions presented here are not new and are already being used in today’s telecommunications networks. However, evolving from a context of dedicated networks to a potentially multi-service one implies a rethinking of these control functions in terms of their application, no longer to a determined set of services, but rather to the whole range of services accessible through the NGN. This analysis does not take into account any particular implementations, which might be very heterogeneous, as indeed has been proved by the variety of initial commercial products ( ‘ Softswitch,’ call server, ‘ application server, etc.) These functions should be seen as being interdependent, and their implementation can use common resources, notably databases.
- Identification and authentication
The identification function consists in establishing the link between a terminal that accesses a network, the user of such a terminal and a customer who has a contract with a network or service operator. This customer may be represented by an anonymous account. Such is the case, for example, with anonymous pre-paid communications, where the contract is implicit.
This identification may be authenticated in order to reduce the risk of forgery and to ensure the identification of a terminal matches its associated physical address and its user. In conventional telephony, for call set-up purposes, identification is deduced from the address of the subscriber’s copper line and no authentication is performed. On GSM and UMTS mobiles, identification is carried out through the SIM card and authenticated through the PIN code. For Internet applications, including access, the still prevalent, simple pair of operations ‘ login/password’ gives an authenticated identification. During a single access session that supports different services, several identifications might have to be made, and it could be useful to try and join them in order to avoid duplication or, conversely, to distinguish between them. An identification function is usually one of the first functions to be used, at least when it comes to finding an address or giving one to a terminal.
- service mediation
A characteristic function of the NGN is the mediation of access to services. From a single terminal or from several terminals, a user can launch successively or simultaneously different access and communication session. This may also occur during an active service session. For example, on a GSM terminal it is possible to choose a mobile access network from among those available at a given place. In a wider sense, it is possible to imagine that a wide range of interpersonal communication services ( voice or videophone combining several media), mixing direct interaction with the distribution of shared information, might be accessible via an advanced control interface that would prompt for call and resource controls in order to set up new sessions (or sub-sessions). This control interface would already be part of another third party communication session. The important joint here is that communication services can be started from an active service session. For example, during a best effort IP session, it could be requested to set up a videophone session from a web page between two terminals on the network Such access to services through mediation is characterized in the Internet sphere, at least in part, by the concept of ‘ portals’, with the added possibility of managing one’s own session parameters or personal preferences.
- presence management and indication of Availability
Presence management originated on the Internet. As the presence of a person on the network could not be detected, because he was not associated with a fixed network address, and as machines could also be connected in the absence of their users, it became useful to know if a potential communication partner could be ‘ reached’ on the Internet. Presence management was initially used in instant messaging, which is different from conventional asynchronous messaging in that an ‘ instant’ reply is expected to a short message. It is also now seen as a potential delayed trigger for interpersonal relations, where information is sought regarding the manner in which parties can and wish to be contacted before they are actually contacted. It is even possible for net surfers to cause other people to contact them by prior posting of their availability. The combination of presence management and mediation in portals will be one of the major developments of the future in interpersonal relations. It will lead to the registration and management of the information provided by users on the conditions under which they would wish to set up a communication with ( or be reached by ) specific people or groups by means of such and such a session type. This is related to the discussion on ‘self-management’. Furthermore, this same information will be accessible to the network control in order to set up ( or not) the sessions requested , taking into account conditions named by the users.
- mobility and nomadism
One characteristic of NGN networks is the consideration given to the management of all forms of mobility and nomadism. Under the concept of mobility, the most obvious aspect is radio access networks allowing users to communicate from wherever they happen to be through a terminal they carry with them, and to move about during the communication. However, another form of mobility, established at about the same time, developed on fixed networks, first with post-paid cards linked to a contract, allowing the user to adopt provisionally a fixed access in order to make available from there some of his personal services, such as a directory. This is referred to as nomadism, mobility is a term reserved for the ability to move around during a single session.
Nomadism means a user being able to get through to his communication and information retrieval services from different physical accesses, whether they be different terminals with different identifications and capabilities or different network access interfaces and local loop operators. Yet nomadism, unlike mobility, is not really concerned with the continuity of an access or communication session. By combining mobility and nomadism it would become possible to suspend and resume communication sessions ( i.e. with the same context of communication and the same initial identification) on different access sessions.
To this extent, mobile networks already offer the user a combination of mobility and nomadism through the possibility of establishing access to the networks of different operators ( usually those having roaming agreements) and of accessing his own services. In the standardization of UMTS, there is a definition of the concept of ‘VHE’, or Virtual Home Environment, that has the objective of giving the user a consistent impression of the execution, the presentation and the management of his services, no matter where he may be located, no matter what type of access and terminal he is using and no matter which network is being visited. Implementing mobility and nomadism requires a combination of control of services, networks, and resources according to the type of session that needs to be established and maintained, and will usually require the co-operation of several different actors.
Firstly, the relationships between different addresses will have to be established and developed, implying the designation of the user, connection to a terminal and connection to network access. Any matches between addresses that may be made inside each of these domains will have to be ignored, and the fact that these addresses that may be made inside each of these domains will have to be ignored, and the fact that these addresses may be under the control of different operators must be taken into account Next, the information must be found and exchanged between these domains and between operators, making sure that it is not attached to a physical location, as was the case in the PSTN.
- Metering and monitoring
Making resources available is a part of the contract between the actors, and it is, therefore, necessary to check that these contracts are being respected. Providing means to control and count the resources used in an access or service session is the business of service and network control, and the existence of this metering and monitoring has strong consequences for the service and network architecture.
The distribution of control and the possibility of establishing different qualities of service at the same interfaces seriously complicate the implementation of this monitoring and metering as well as the possibility of forwarding the related data without any distortion up to contractual points of reference. In the conventional circuit or packet networks, local contractual metering was considered sufficient, as long as what passed for a contract could be deduced from what actually happened on that access.
In the simplest cases, the local exchange of a PSTN measures the duration of the communications, and billing then depends on this duration and on the number dialed. The circuit-mode structure of the network automatically ensures that the service contract is respected and no other verification is necessary.
The situation became more complicated once rerouting mechanisms were introduced and the metering was effectively distributed. Signaling was used to trace the metering information back to the origin of the call, but disruptions can upset this process and can lead to the need to abandon the service.
In routed packet (IP) networks, it is also at access that either the time or the number of packets transmitted can be measured , but it is very difficult to check that an end-to-end quality of service contract has been strictly respected, and it comes back to ensuring beforehand, through the resource control, that the architecture will guarantee that the contract is respected In fact, it is easier today to establish contracts making available large capacities of resources between network or service operators than to verify the dynamic and distant consumption of such resources by individual users. This situation may be improved by distributed metering and post hoc verification or payment, but the major difficulty, between integrating control and metering, remains the generalization of pre-payment possibilities to all types of services.
- terminals in the control
A further feature of NGN will be the very great variety of terminals with widely differing characteristics ( type of codec, window size, storage and display capacities, etc.) that must be known to applications servers, but also that must be accessible to the network controller so that the service required can be adapted to the terminal used. This may require the use of intermediate transcoding devices, for example, between communicating terminals. These terminals will be in part, manageable by or via the network, Software could be downloaded onto them and updated, data could be synchronized, etc. This will not be developed in the short-term, as it has as yet rarely been put into practice, but it seems sure that terminals equipped with ever increasing capacities ( for processing and storage) will be integrated totally into the handling of network and service control functions.
The traditional fixed telecommunications networks operate with a very high level of quality, and this value is noticed by users. Their handling of emergency calls is viewed with a high degree of confidence and they offer relatively good protection against intrusions. This is not the case with the Internet, where users do not always find their services are available and are sometimes victims of unwelcome, or even malicious intrusions. It is, therefore, of particular importance to bring the same performance levels of these conventional networks, in terms of availability and security, to packet-mode networks like the NGN. Network control through its many links with a very diversified environment ( of users, other networks, service providers, etc.) will obviously be an active participant in this process.
User Profile and Customer profile
The implementation of all the functions mentioned above requires the management of data related to terminals, users and contracts if the required communication sessions are to be set up. Instrumental to this is the concept of a user profile, linked to the activation of services, and that of customer profile linked to contracts and payment. The customer profile can be defined in abstract terms as the set of customer-related data that correspond to the ‘User-Agent’ as defined in TINA and the user profile as the set of user-related data, whether it be for access to communication services or for the use of these services, Several user profiles can fit a single customer. For example, in a company or in a family there are usually several service users for a single customer. Moreover, several user profiles can fit a single person. These are often related to different customer profiles, often concerning the contract or to different types of access concerning usage ( e.g. mobile and ADSL access for the same person).
Conventional telecommunications developed without making a distinction between these two types of profile, Normally, access is associated with an identifiable customer and anonymous user at a given moment, and the data are distributed all over the network and the Information System. However, it could be considered that this type of approach already exists, either in the Information System (a single invoice containing the billing information of several users for example) or in the network (by using the intelligent network to distinguish between users in, for example, virtual private networks).
The GSM mobile networks already have a real profile base too, thanks to the use, in the terminal, of the SIM card, and in the network, of a database holding the authorization and usage profile of a mobile number ( the HLR). The network also has access to information concerning location, which is therefore related to the temporary situation of a terminal and to its actual access. But all the service data needed by the person who uses the terminal carrying the contract-related SIM card are not present in the HLR and there remains a certain association between customer and user. In a way, the user is equated with his SIM card and is authenticated thanks to a PIN code. The UMTS networks will build their architecture around an extension of HLR, the HSS ( ‘Home Subscriber Server’), which includes more service data, particularly related to the packet network. These are databases that are used as a model for profile aspects but are extended by user information and preferences such as those stored in the portals of the Internet.
A lot of different types of information are needed to implement these control functions. Here are just a few examples.
- access- related information: identification of the access address, of the address linked to a service ( which may be different from the former, e.g. the ATMVC address for an ADSL access, the IP address for services arriving at the terminal). Features of the terminal used. Characteristics of the type of access;
- user-related information ( at the network or service level) : identification of the user, the associated method and means of authentication, services that can be activated by the user according to the access selected, preferences, user’s rights, location data, data related to presence and to the ability to be reached, credit remaining, etc.;
- customer-related information delegation of rights to other users, contract validity, billing information or pre-payment accounts, etc.
These data may be static, changing very slowly, and be modified by explicit acts of management; they are above all contractual data. They may also be temporary and dependent on active sessions. But their static, manageable and temporary nature does not always remain stable in the evolution of networks and services. A typical example is that of a terminal’s IP address that has been attributed in a fixed manner through the contract, then attributed by an address server at the set-up time of an access session, and which may be allocated in a fixed way again, e.g. by using Ipv6.
The data will be accessible to and modifiable by a large number of people (network operators, service operators, customers, users), by network servers and by terminals during access or service sessions. Conceptually speaking, it would be easier to store all data needed for communication in a single database, indexed with a single identifier related, for example, to the user. However either for reasons of time of access to the data or for reasons of ownership and confidentiality, this is not possible, and the data will have to be distributed over bases which might need to be dedicated.
The profile of a user will, in fact, be made up of a series of profile fragments, located in the various domains, and featuring a certain degree of redundancy or replication. The bases of profile fragments will be an important part of the NGN economy. For the moment, in the definition of the profile bases, two approaches can be identified. Whose principles are, for the most part, agreed upon; one, the previously mentioned HSS within the framework of 3G mobile networks; the other having the objective of forming profile bases of identified and authenticated users on the Internet with, as the first type of application, simplification, and increased security for e-commerce applications.