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Brief Overview of NGN
“Next Generation Network (NGN) is a packet-based network able to provide services including Telecommunication Services and Able to make use of multiple broadband, QoS-enabled transport technologies in which service-related functions are independent from underlying transport-related technologies; It offers unrestricted access by users to different service providers. It supports generalized mobility which will allow consistent and ubiquitous provision of services to users” 
Next Generation Networks are the networks of future. These are the networks based on emerging technology of IP which is leading to convergence of networks, services and markets and providing efficiency and flexibility. That means you can provide any service through NGN platform based on IP. In today's environment it is inevitable for Operators and ISPs to deploy a high speed packet switched network so that requirements for new, innovative and bundled services can meet. .NGN is such a network which provides benefits to operators, ISPs and end-users. 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. NGN with the help of soft switch can co-exist with the legacy PSTN networks and hence the existing investments of operators do not go waste. Many important countries like UK, Japan, Korea, Malaysia, Italy and China have decided to migrate to NGN. The incumbent operators there are going for NGN and replacing their existing networks to IP based in a time bound manner. This is being done to beat to competitors and new entrants on the technology front and being able to provide new value added services, cut down on OPEX as well as to make the network future proof.
NGN should be capable of providing seamless converge services from telecom, internet and broadcasting infrastructure at any time, anywhere to anywhere from any device to any device. The incumbent operators there are going for NGN and replacing their existing networks to IP based in a time bound manner. This is being done to beat to competitors and new entrants on the technology front and being able to provide new value added services cut down on OPEX as well as to make the network future proof.
NGN architecture is a four layered process, having several protocols, standards and to typical PATN networks, NGN is quite simple intoitsnature,implementation,operations and outcomes. Next Generation Network (NGN) is a service oriented network. Through the separation of service and call control, the service- independent architecture is implemented, which makes services independent of switching network.
NGN is a kind of open service architecture. It is a kind of brand- new network integrating voice, data, fax, and video services. Its architecture consist of four layers,
- Service Management
- Network Control
- Core Switch
- Edge Access 
Functions of each of these layers are
1 Service Management
This layer consists of applications programs e.g.
- Policy Server
2 Network Control
Network control layer consists of core of the whole NGN the SOFT SWITCH
3 Core Switching
Core Switching Layer contains clouds of networks, giving connectivity to between soft switch and components of edge access layer by using a set of appropriate protocol.
4 Edge Access
This layer is divided into three parts:
- Broad Band access
- Broad Band devices are
- IAD (Integrated Access Device)
- AMG(Access Media Gateway)
- PSTN Devices are
- SG(signaling Gateway)
- TMG(Trunk Media Gateway)
- UMG(Universal Media Gateway)
- PLMN/3G Devices are
- UMG(Universal Media Gateway) 
NGN Layered Approach
NGN Architecture components
Actually Next Generation Networks consist on multiple protocols and standards. These standards and Protocols are the key for an efficient network which can transfer a Bundle of services at the same time through single NGN connection. These protocols and standards are developed by international regulatory and control bodies of technology. Like
And several domestic bodies which are continuously working on how and what type of regulation should be developed for the control and to regulate networks with appropriate standards. Main components which carry NGN technology are
Core protocols in this hierarchy are
- Megaco (H.248)\MGCP
There are some other protocols for ALL-IP networks but these are basic and important components and are responsible for the efficient delivery of packets.
- Internet protocol (IP)
It is the base for NGN network. That's why NGN is also some times called an ALL-IP network. There are some other terms referred to NGN because of its dependence over IP protocol. Network layer of OSI model is the layer where IP works.
The Internet Protocol (IP) is a data-oriented protocol used for communicating data across a packet-switched internet work. IP protocol use packets to transfer information encapsulated with IP addresses for destination and source identification. Data from an upper layer protocol is encapsulated inside one or more packets/datagram. No circuit setup is needed before a host tries to send packets to a host it has previously not communicated with (this is the point of a packet-switched network), thus IP (Internet protocol) is a connectionless protocol. 
IPv6 (IP version 6) is the new development in IP protocol to overcome the increasing needs of IP addresses. It is also called IPng addressing scheme. The main improvement brought by IPv6 is the increase in the number of addresses available for networked devices. IPv4 supports 232 (about 4.3 billion) addresses. In comparison, IPv6 supports 2128 (about 34 × 1037) addresses or approximately 5×1028 addresses for each of the roughly 6.5 billion people alive today. It was not the intention of IPv6 designers, however, to give permanent unique addresses to every individual and every computer. Rather, the extended address length simplifies operational considerations including dynamic address assignment and router decision making, avoiding many complex workarounds that were necessary in IPv4. Its simplified packet header format improves the efficiency. 
- MPLS (multi-protocol label switching)
It is the key protocol used on Network layer in Routing protocols Group. It works with IP to efficient delivery and routing of packets. MPLS gives network operators a great deal of flexibility to divert and route traffic around link failures, congestion, and bottlenecks. Multi Protocol Label Switching (MPLS) is a data-carrying mechanism that belongs to the family of packet-switched networks. MPLS operates at an OSI Model layer that is generally considered to lie between traditional definitions of Layer 2 (data link layer) and Layer 3 (network layer). It was designed to provide a unified data-carrying service for both circuit-based clients and packet-switching clients which provide a datagram service model. It can be used to carry many different kinds of traffic, including IP packets, as well as native ATM, SONET, and Ethernet frames. MPLS works by packets with an MPLS header, containing one or more 'labels'. This is called a label stack. 
These MPLS labeled packets are switched after a Label Lookup/Switch instead of a lookup into the IP table. As mentioned above, when MPLS was conceived, Label Lookup and Label Switching was faster than a RIB lookup because it could take place directly within the switching fabric and not the CPU.
MPLS has certain advantages which make it more desirous and demanding for a Next Generation Network, these are.
- Provides QoS support
- Fast, consistent forwarding.
- Provides traffic engineering support
- Different routes can be assigned to flows at ingress routers.
- Provides multi-protocol support
SIP stands for “Session Initiation Protocol”. It is an application-layer control protocol which has been developed and designed within the IETF. The protocol has been designed with easy implementation, good scalability, and flexibility in mind. The specification is available in form of several RFC; the most important one is RFC3261 which contains the core protocol specification. “The protocol is used for creating, modifying, and terminating sessions with one or more participants”. By sessions we understand a set of senders and receivers that communicate and the state kept in those senders and receivers during the communication. Examples of a session can include Internet telephone calls, distribution of multimedia, multimedia conferences, distributed computer games, etc.  The main Characteristics of this protocol are
- Transport-independent, because SIP can be used with UDP, TCP, ATM & so on.
- Text-based, allowing for humans to read SIP messages.
- SIP makes use of elements called proxy servers to help route requests to the user's current location, authenticate and authorize users for services, implement provider call-routing policies, and provide features to users
- SIP also provides a registration function that allows users to upload their current locations for use by proxy servers 
In a traditional telephone network, the infrastructure consists of large telephone switches which interconnect with each other to create the backbone network and which also connect to customer premise equipment (PBXs, telephones). While the internal network today is based upon digital communication, links to customers may be either analog (PSTN) or digital (ISDN). The links to customers are shared between call signaling (for dialing, invocation of supplementary services, etc.) and carriage of voice/data. In the backbone, dedicated (virtual) links interconnecting switches are reserved for call signaling (de-facto creating a dedicated network of its own) whereas voice/data traffic is carried on separate links. The Signaling System No. 7 (SS7) or variants of it are used as the call signaling protocol between switches; this protocol is used to route voice/data channels across the backbone network by instructing each switch on the way which incoming "line" is to be forwarded to which outgoing "line" and which other processing (such as simple voice compression, in-band signaling detection to customer premise equipment, etc.) is to be applied. Voice/data channels themselves are plain bit pipes identified by roughly a trunk and line identifier at each switch.
- Soft switch(MGC)
- Media Resource Centre
- Media gateway
- Signaling gateway
A soft switch 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. The Call Agent takes care of functions like billing, call routing, signaling, call services and so on and is the 'brains' of the outfit. A Call Agent may control several different Media Gateways.
MRS (Media Resource server)
Under the control of SoftX3000, MRS600 provides medium resource to packet network. Unlike the traditional packet peripherals (IP) based on circuit technology, MRS6000 is directly based on packet technology and eliminates the coding/decoding conversion from TDM to IP, resulting in high quality. .
Functions of MRS:
- Collecting and decoding DTMF signal
- Generating DTMF signal to test and support various PSTN application equipment
- Storing and playing back the static audio clips such as announcement which has been recorded in advance
- Recording and playing back various temporary audio clips
Signaling gateway: A Signaling Gateway is a network component solely responsible for translating signaling messages (i. e. information about call establishment and teardown) between one medium (usually IP) and another (PSTN).
The 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. Locating at the edge access layer, TMG8010 acts as media gateway to enable inter-working between PSTN and NGN network with outstanding QoS guarantee
1 www.itu.int/ITU-T/ITU-T RECOMMENDATION Y.2001 (STUDY GROUP 13) PAPER
2 Nguyen T.H, Sadiku M.N.O, ” Next generation networks”,Potentials IEEE, Volume 21, Issue 2, Apr-May 2002 Page(s):6 - 8
3 Knightson, K.; Morita, N.; Towle, T.; “NGN architecture: generic principles, functional architecture, and implementation”, Communications Magazine, IEEE , Volume 43, Issue 10, Oct. 2005 Page(s):49 - 56
4 ITU_T NGN TECHNICAL WORKSHOP 14-15, JEJU ISLAND, KOREA
8 NEXT Generation Networks 2004 project www.itu.int/ITU-T/STUDYGROUPS/COM13NGN2004
9 Next Generation Networks Global standards initiative, research paper http:// www.itu.int/ITU-T/NGN/
10 PTCL NGN exchange