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Telecommunication networks started with the telephone. Later, Cable TV (CATV) networks appeared, and then mobile networks. All those networks were dedicated networks, all independent one to each other.
In the last decade the telecommunication panorama changed. At first, the tremendous amount of data traffic, which overtook the voice traffic, lead network operators to more differentiation, and large-scale economy. From a technical point of view, the all-purpose network paradigm emerged from the following: the fixed-mobile convergence, the emergence of new transport technologies, the maturity of IP, and the concept of ambient networks. This meant that different networks of the operators (xDSL, FTTx, etc.) were no longer seen as a set of disjoint networks with limited gateways, but as a unique shared infrastructure for voice and data.
Due to both the economic and technical aspects, the all-purpose networks paradigm lead to the concept of Next-Generation Networks (NGN), in which multimedia sessions, fixed-mobile convergence, generalized mobility, end-to-end Quality Of Service (QoS) are the main characteristics.
ITU-T in their recommendation Y.2001 (ITU-T, 2005) defines a Next Generation Network (NGN) as 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 generalized mobility which will allow consistent and ubiquitous provision of services to users.”
The fundamental stakes and issues in NGN are the following:
In networks, the term QoS refers to the capacity in satisfying and guaranteeing a certain amount of packets delivery, in a given timeframe, over a network. Modern networks are heterogeneous. There are composed of different segments and technologies: each segment is under a dedicated authority (local ruler) and may implement his own QoS solution. An utmost issue for an NGN implementation is to provide a unified QoS over a network, which is a composition of network segments.
In this context, the ITU-T identifies two QoS topics:
These topics cover different aspects such as class of QoS, the achievement of QoS for upper layers within a network, the QoS between domains and the end-user perception.
An NGN implementation is a unique network made by an interconnection of partitioned network segments. These segments use different transport technologies and can be under different authorities. They use the same signaling protocol and architecture to provide QoS along the network path (Figure 1). Typically a NGN is composed of Costumer Premises Network (CPN), Access Network (AN), Core Network (CN), Transit Network (TN) and Service Provider Network (SPN) (Manchese, 2007).
In order to provide an end-to-end approach, the QoS must be applied equally on each segment. For example, in a Terminal Equipment to Service Provider communication, QoS must be guaranteed in both Costumer Premises Network, Access Network, Core Network and Service Provider Network.