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The TISPAN NGN Architecture

The TISPAN High Level Architecture is closely aligned with that of 3GPP, but adds some elements to replace the inherited GSM components...


With respect to the network elements, both architectures have adopted the decomposed switch architecture for legacy services and PSTN interworking (based on H.248 control), and the IMS session control architecture for new services (based upon SIP).

The main elements of the TISPAN architecture not seen in its 3GPP counterpart are the RACS and the NASS. In 3GPP networks, the functions performed by these subsystems are already provided by existing GSM and/or GPRS functions; for example IMS in the 3GPP architecture uses the existing Home Subscriber Server (HSS) for user authentication and service profiles; the TISPAN architecture must invent this afresh for NGN.

The Network Access Support Subsystem (NASS) is responsible for:

  • Dynamic provision of IP address and other user equipment configuration parameters (e.g. using DHCP);
  • User authentication, prior or during the IP address allocation procedure;
  • Authorization of network access based on user network profile;
  • Access network configuration, based on user profile;
  • Location management (e.g. for emergency call, );
  • CPE configuration;
  • NASS provides support for temporary moves and roaming and can be distributed between a visited and home network.

The Remote Access Control Subsystem (RACS) is responsible for:

  • Authorization of QoS requests and definition of the polices to be enforced by the bearer service network elements.
  • Support for Application Functions (AF) including QoS support over multiple access networks
  • Applying Admission control to resource reservation requests according to network policies.
  • NAPT/Gate Control, which controls near-end and far-end NAPT and FW functions, when required, between two core TISPAN NGN networks, or at the border between core and access TISPAN NGN networks.

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