The conceptual model of NGN architecture consists of four layers : access layer, transport layer, control layer and service layer. Their functions are different. The access layer provides the infrastructure, i.e. the access network, between the end-user and the transport network. The transport layer provides transport between network nodes to which the access networks are connected. The control layer is responsible for the control of communication sessions, e.g. establishing or disconnecting voice etc..The service layer offers elementary service functions that can be used by service providers to build more complex or comprehensive