NGN - Next Generation Network

             The general idea behind NGN is that one network transports all information and services (voice, data, and all sorts of media such as video) by encapsulating these into packets, like it is on the Internet. NGNs start making sense when voice, data, video are all in IP format.

              Basically, the core network should have a common service delivery architecture, with any access network hanging off the core.
Some important service characteristics for NGN would be real-time, multi-media communications, more personal intelligence, more network intelligence, more simplicity for users, personal service customization and management.

             It will benefit from its advanced control, management, and signaling capabilities, enabling a much broader array of service types, such as  

• Specialized resource services (provision and management of transcoders, multimedia multipoint-conferencing bridges, processing and storage services),  
• Middleware services (brokering, security, licensing, transactions),  
• Application-specific services (business applications, e-commerce applications, supply-chain management applications, interactive video games), 
  
• Content-provision services (electronic training, information push services).

             Next generation IP networks or NGN IP will be the key enabler of mobility and convergence. This would mean that convergence would not just be limited to wired networks. WLAN too can run voice, data, & video.
            NGN IP would help organizations achieve new levels of enhanced productivity, reduced operational costs, increased operational efficiency and better overall profitability.
            NGN IP would also support new levels of personal mobility, allowing for seamless integration of fixed and mobile networks. And, for enterprises it helps to scale their network architecture and prioritize bandwidth usage, and reduce network management complexities.
           In an NGN environment, almost 60–70% bandwidth would be reserved for data, and as voice would be on the same pipe, it would come almost free. With no additional costs for using voice, the usage of voice services would increase. And it is voice over IP (VoIP) that would be the killer application for NGNs.

Fundamental to Next Generation Networking :-

• Packet-Based Data Transfer.
• Separate control functions for bearer capabilities, calls/sessions and applications/services.
• De-coupling of service provision from the network, and provision of open interfaces.
• Support for a wide range of service applications and mechanisms based on service building blocks (including real-time/streaming/non-real-time services and multi-media).
• Broadband capabilities with end-to-end QoS and transparency.
• Interworking with legacy networks via open interfaces.
• Generalized mobility.
• Converged services between Fixed and Mobile networks.

Issues to be kept in mind while planning for NGN deployment :-

1. Latency (Delay)
2. Jitter
3. Bandwidth
4. Packet Loss
5. Reliability
6. Security
7. Inter-operability

NGN involves three main architectural changes that need to be looked at separately :-

• In the Core Network, NGN implies a consolidation of several (dedicated or overlay) transport networks each historically built for a different service into one core transport network (often based on IP and Ethernet). It implies amongst others the migration of voice from a circuit-switched architecture (PSTN) to VoIP, and also migration of legacy services such as X.25, Frame Relay (either commercial migration of the customer to a new service like IP VPN, or technical emigration by emulation of the "legacy service" on the NGN).
• In the Wired Access Network, NGN implies the migration from the dual system of legacy voice next to xDSL setup in the local exchanges to a converged setup in which the DSLAMs integrate voice ports or VoIP, making it possible to remove the voice switching infrastructure from the exchange.
• In Cable Access Network, NGN convergence implies migration of constant bit rate voice to PacketCable (CableLabs standards that provide VoIP and SIP services).

PacketCable Networks use the Internet Protocol (IP) to enable a wide range of multimedia services, such as Voice over IP (IP telephony), multimedia conferencing, interactive gaming, and general multimedia applications.

NGN Technology Components :-

• NGNs are based on Internet technologies including Internet Protocol (IP) and Multiprotocol Label Switching (MPLS). At the application level, Session Initiation Protocol (SIP) seems to be taking over from ITU-T H.323.
• For voice applications, one of the most important devices in NGN is a Softswitch - a programmable device that controls Voice over IP (VoIP) calls. It enables correct integration of different protocols within NGN. The most important function of the Softswitch is creating the interface to the existing telephone network, PSTN, through Signalling Gateways and Media Gateways.
• Gatekeeper - This was originally a VoIP device, which converted (using gateways) voice and data from their analog or digital switched-circuit form (PSTN, SS7) to the packet-based one (IP). It controlled one or more gateways. As soon as this kind of device started using the Media Gateway Control Protocol, the name was changed to Media Gateway Controller (MGC).
• IP Multimedia Subsystem (IMS) is a standardized NGN architecture for an Internet media-services capability.

SoftSwitch :- It's a central device in a telecommunications network which connects calls from one phone line to another, entirely by means of software running on a computer system. This work was formerly carried out by hardware, with physical switchboards to route the calls.
             It is typically used to control connections at the junction point between circuit and packet networks. A single device containing both the switching logic and the switching fabric can be used for this purpose. however, modern technology has led to a preference for decomposing this device into a Call Agent and a Media Gateway.
            Call Agent takes care of functions like billing, call routing, signalling, call services and so on and is the 'brains' of the outfit. A Call Agent may control several different Media Gateways in geographically dispersed areas over a TCP/IP link.
            Media Gateway connects different types of digital media stream together to create an end-to-end path for the media (voice and data) in the call. It may have interfaces to connect to traditional PSTN networks like DS1 or DS3 ports (E1 or STM1), it may have interfaces to connect to ATM and IP networks and in the modern system will have Ethernet interfaces to connect VoIP calls. The call agent will instruct the media gateway to connect media streams between these interfaces to connect the call.
              In more recent times (i.e., in IP Multimedia Subsystem or IMS), the Softswitch element is represented by the Media Gateway Controller (MGC) element, and the term "Softswitch" is rarely used in the IMS context, but another word of AGCF(Access Gateway Control Function).
             Feature Server, often built into a call agent/softswitch, is the functional component that provides call-related features. Capabilities such as call forwarding, call waiting, and last call return, if implemented in the network, are implemented in the feature server. The feature server works closely with the call agent, and may call upon the media server to provide these services. These features do not require the subscriber to explicitly request them but tend to be triggered within the call handling logic.


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