Research and Analysis of QoS in the Next Generation Network NGN (1)

1. Introduction
The evolution of network architecture and broadband technology have promoted and accelerated the evolution of traditional networks to the next generation network NGN. With the expansion of the network scale and the gradual expansion of applications, especially emerging businesses with real-time requirements, such as VoIP, video conferencing, multimedia remote teaching, and on-demand video streaming, communication networks are more and more required to provide efficient end-to-end service quality support. At the same time, users are increasingly demanding network service quality (QoS) and QualityofService. Therefore, how to provide end-to-end QoS is one of the core issues of NGN.
2. Architecture of NGN and QoS Problems
2.1NGN system organization
NGN is based on SoftSwitch and adopts an open and standard architecture to provide various services such as voice, video, and data.
As the core technology of the Next Generation Business Network, Softswitch is also one of the key technologies of NGN. The basic meaning of Softswitch is to separate call control from media gateway and implement basic call control functions through software on the server, including call routing, management control, Connection Control, session creation, and session removal) and communication. The main design concept of Softswitch is the separation of business/control and transmission/access. Each entity connects and communicates through standard protocols. Its main functions include the following parts: 1) call control function; 2) service provision function; 3) service exchange function; 4) Intercommunication function; 5) SIP proxy function; 6) billing function; 7) network management function; 8) routing, address resolution, and authentication functions; 9) control and management functions of H.248 terminals, SIP terminals, and MGCP terminals; 10) signaling 7 (MTP and Its Application); 11) (Optional ).
The function structure 1 of Softswitch is shown in.

Figure 1 Structure of the softswitch system

2.2qos problems in NGN
For QoS, there are two important differences between the softswitch network and the Internet. Firstly, the softswitch network is a multimedia communication network. It must not only support traditional data applications of IP networks, but also support high-quality real-time audio/video communication services. Secondly, the softswitch network is a commercial operation network that must provide users with the promised service quality and be charged based on the provided service quality. Therefore, QoS must be provided based on different application requirements.
Technically, the softswitch network is also very different from the traditional stns. The GSTN is a circuit switching network. When the network traffic reaches a certain level, the switch rejects subsequent call requests because all network resources are occupied. Rejecting a call affects only one user, but does not affect ongoing calls. The Softswitch Network is a group network for resource statistics reuse. When the network traffic increases, network resources are congested. Although subsequent calls can still enter the network, their QoS will decrease, qoS of ongoing calls will also be affected. Therefore, QoS Problems in the softswitch network are much more complex than those in the GSTN.
Implementing end-to-end QoS in NGN includes the following aspects: End-to-End meaning, boundary locating, and UNI scope; defining the end-to-end multimedia QoS level and the method for registering a single media stream QoS level; access Control and resource management, including interoperation between entities at the network layer and entities at the application layer. It indicates how to use the Low-layer QoS mechanism within the network to obtain high-level QoS and Low-layer intra-domain QoS control.
3. QoS framework model and Key Technologies
3.1QoS framework model
The core of the Framework Model Supporting QoS in NGN is a series of modules used to control network performance and prevent network resource contention. It can be summarized into a comprehensive technology designed for multiple planes: management plane, control plane, and data plane, as shown in figure 2.