Next generation networks




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5.3NGN Functional Architecture


One of the biggest challenges of the NGN is the separation between services from underline transport technologies. The basic reference model of the NGN is shown in Figure 6 (ITU-T Recommendation Y.2011) [8].

In general, any and all types of network technologies may be deployed in the transport stratum indicated as "NGN transport", including connection-oriented circuit-switched (CO-CS), connection-oriented packet-switched (CO PS) and connectionless packet-switched (CLPS) layer technologies according to ITU T Recommendations G.805 and G.809. Until today it is considered that IP is the preferred transport protocol used to support NGN services as well as supporting legacy services. The "NGN services" provide the user services, such as a telephone service even and Web services and others. Therefore "NGN service" may involve a complex set of geographically distributed services platforms or in the simple case just the service functions in two end-user sites.





Figure 6 – Basic NGN Architecture

  • NGN service stratum: provides the user functions that transfer service-related data and the functions that control and manage service resources and network services to enable user services and applications. The NGN service stratum is concerned with the application and its services to be operated between peer entities. User services may be implemented by a recursion of multiple service layers within the service stratum. From an architectural perspective, each layer in the service stratum is considered to have its own user, control and management planes;

  • NGN transport stratum: provides the user functions that transfer data and the functions that control and manage transport resources to carry such data between terminating entities. Dynamic or static associations may be established to control and/or manage the information transfer between such entities. An NGN transport stratum is implemented by a recursion of multiple layer networks. From an architectural perspective, each layer in the transport stratum is considered to have its own user, control and management planes.

Based on the above basics of the NGN architecture, ITU-T developed the NGN functional architecture model with detailed functions and published by ITU-T Recommendation Y.2012 as shown in Figure 7.



Figure 7 – NGN Reference Architecture

NGN Architecture in ITU-T Recommendation Y.2012 has been developed to incorporate the following principles:



  • Support for multiple access technologies: The NGN functional architecture shall offer the configuration flexibility needed to support multiple access technologies;

  • Distributed control: This will enable adaptation to the distributed processing nature of packet based networks and support location transparency for distributed computing;

  • Open control: The network control interface should be open to support service creation, service updating, and incorporation of service logic provision by third parties;

  • Independent service provisioning: The service provisioning process should be separated from transport network operation by using the above-mentioned distributed and open control mechanism. This is intended to promote a competitive environment for the NGN development in order to speed up the provision of diversified NGN services;

  • Support for services in a converged network: This is needed to generate flexible, easy-to-use multimedia services, by tapping the technical potential of the converged, fixed-mobile functional architecture of the NGN;

  • Enhanced security and protection: This is the basic principle of an open architecture. It is imperative to protect the network infrastructure by providing mechanisms for security and survivability in the relevant layers, and;

  • Functional entity characteristics: Functional entities should incorporate the following principles:

  • Functional entities may not be distributed over multiple physical units but may have multiple instances;

  • Functional entities have no direct relationship with the layered architecture. However, similar entities may be located in different logical layers.

5.4Service aspects of NGN


“Decoupling of service provision from transport operation” is one of key features of the NGN greatly impacts to service aspects of the NGN. Before the NGN, service provisions are tightly coupled with underline transport technologies, in general called silo-effect, as shown in left hand of Figure 8. These couples are caused by different transport technologies are developed and used for different specific services. Therefore different network infrastructures have been required to support various multiple services; consequently different systems and user devices have been also used as well as different providers are required. These difficulties have been resolved using such feature of the NGN as shown in right side of Figure 8. Thus the NGN looks like providing integrated services same as what ISDN objected but, major difference, using IP.



Figure 8 – Change of service environments of NGN

NGN enhances service aspects of telecommunications in two different angles: coverage and quality. Coverage of services using the NGN is largely widened than legacy telecommunication networks as well as traditional Internet. This caused by the NGN’s powerful transport capabilities supporting real-time and non-real-time of not only narrowband but also broadband services including one-to-one and any-casting (multicasting, broadcasting etc). These powerful capabilities support the NGN transport as an infrastructure for integrated services covering from simple text to multimedia including voice and TV.

In addition, ubiquitous networking capability of the NGN contributed to widened service coverage as shown in Figure 9 [19] extending of users, not only for persons (using attached devices such as PC, PDA, mobile phones) but also objects (such as remote monitoring and information devices, contents). Ubiquitous networking supports three types of communications [19]:


  • Person-to-Person Communication: persons communicate with each other using attached devices (e.g. mobile phone, PC);

  • Person-to-Object Communication: persons communicate with a device in order to get specific information (e.g., IPTV content, file transfer);

  • Object-to-Object Communication: an object delivers information (e.g. sensor related information) to another object with or without involvement of persons.

Ubiquitous networking of NGN aims to provide seamless communications between persons, between objects as well as between persons and objects while they move from one location to another.



Figure 9 – Service coverage of NGN with ubiquitous features

Regarding the quality aspect, the NGN has been equipped with more powerful capabilities addressed on the QoS, Mobility and Security aspects, even though NGN use of IP same as Internet. Followings are brief summary how the NGN support enhanced capabilities of QoS, Mobility and Security:



  • Quality of Service: NGN provides various classes of QoS which identified by ITU-T recommendation Y.1541 [10]. RACF (Resource Admission and Control Function) is the key functions for this QoS arranging transport resources to meet various QoS collaborating with service stratum as well as end user equipments. Through this RACF, the NGN provides guaranteed services when end user needed with their services such as guaranteed voice, multimedia and video conference services. NGN also provides general IP based services such as “Best Effort” and other existing services are also available through interworking with existing networks;

  • Mobility: NGN does not have dependency with underground transmission technology, so the NGN services are available whether fixed or mobile or wireless (e.g., WiFi and WiMAX) environments. Thus the NGN has a capability to support mobility of services in various ways such as service mobility, terminal mobility and user mobility. These different types of mobility have been supported by MMCF (Mobility Management Control Functions) identified in ITU-T Recommendation Y.2018. MMCF in NGN functional architecture has a key role to support the mobility. This function collaborates with NACF and RACF providing different levels of mobility such as normadism, handover and seamless handover;

  • Security: NGN provides much stronger security capabilities than other IP based networks such as Internet. For supporting of security, NACF (network Attachment Control Functions) and IdM functions take key roles. NACF identifies end user service requirements as well as their security preferences based on the subscription and service features. IdM function handles various identifications used for identifying end users, terminal devices, service providers as well as services and contents. Based on that information, security features have been identified and supported by the NGN.



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