Next Generation Network (NGN) architecture

The converged world of next generation networks (NGN) brings with it the promise of voice,video and data over a single broadband netwrok.This transition from the traditional circuit switched to packet switched networks has been underway for many years and Voice Over IP (VoIP) is now leading the transition

One NGN architecture for VOIP with centralised call processing decomposes the functional elements of a traditional circuit switch into specialized componnect with open interfaces.
Following are the key logical element of this reconstruction are the following:

1. THe MG handle the media or beared, interface.It converts media from the format used in one network to the format required in the another network.For example it can terminate the TDM trunk from the PSTN,packetize and optionally compress the audio signals an then deliver the packet to the IP network using real time protocol (RTP)

2. The MGC (also known as a call agent) contains the call processing.In addition it manage the resource of the MGs that it controls.The MGC controls the MG using a control protocol to set up the RTP connections and control the analog or TDM end point in the MG

3. THe SG sits at the edge of an IP network and terminates circuit-switched network signaling such as SS7 or ISDN from the circuit switched network.It transport or backhauls, this signaling to the MGC or other IP based application endpoint

MGCP can also be used as a control protocol between an MGC MGCU (TG) and an MG. While MGCP is defined by an informational (versus standard track) RFC, it is commonly used in many product today because the specification was available before Megaco and H.248 were finished.Both MGCP and Megaco/H.248 assume that the call control intelligence is outside the MGs and that the MGC handles it

Closely related to the MGCP protocol are the Packet Cable protocol, network based call signaling (NCS) and PSTN gateway call signaling protocol (TGCP).These protocol provide functionality similat to MGCP for cable based network


Sigtran

The IETF SigTran working group was founded after a Bird of a Father (BOF) session which was held at he Chicagi 1998 IETF meeting, to discuss transport of telephony sigaling over packet networks.The SigTran working group define the framework architecture and perfomance require in RFC 2719(126).The framework include the conceptof the reconstructing the traditional circuit switch into MGC,MG nad SG elements, thereby separating the signal and the media control plane

The framework document identified three necessary components for the SigTran protocl stack:

1. A set of adaptation layes that support the primitice of SCN telephony signaling protocol

2.A common siganling transport protocol that meets the requirement of transporting telephony signaling

3.IP network protocol

The three layers of the protocol stacks are:

1.Adaptation layer

2.Common Transport protocol

3.Internet protocol (IP)