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.