Analysis of NGN core Softswitch Technology

As the control entity of the Next Generation Network, Softswitch provides Call Control and Connection Control functions for businesses with real-time requirements for the Next Generation Network NGN. It is the core of the Next Generation Network call and control. Softswitch is located at the control layer of the Next Generation Network (NGN) and evolved from the call server CallServer proposed by some vendors) or the media gateway controller. China's Ministry of Information Industry, China Telecom transmission Institute, defines Softswitch as: "Softswitch is one of the core devices for network evolution and next-generation grouping networks. It is independent of the transmission network, it provides call control, resource allocation, protocol processing, routing, authentication, billing, and other functions. It also provides users with all the services available to existing circuit switches, it also provides third-party programmable capabilities." As the core of NGN, Softswitch is the coordination center between the Circuit Switching Network and the IP network. It controls various media gateways to achieve service layer fusion between different networks. The protocol used by SoftSwitch.

In the communication system, the control is solved through negotiation, and a protocol is required accordingly. In the NGN architecture, as the control center, Softswitch is implemented by supporting multiple protocols such as H.248/MEGACO, SIP, SIGTRAN, BICC, and H.323.

SIPSessionInitiationProtocol) Protocol: according to the definition of IETFRFC2543, SIP is an application layer control protocol used to create, modify, and end multimedia sessions or calls. These multimedia sessions include Internet Multimedia conferences, distance education, Internet telephones, and other applications. The SIP protocol can be transmitted over TCP or UDP. Because the SIP itself has a handshake mechanism, UDP is preferred. According to the survey, the number of vendors that support the SIP protocol has increased significantly. The SIP protocol is widely accepted as the core protocol for multimedia services and applications, including 3G mobile multimedia.

H.248/MEGACO Protocol: this protocol is a gateway control protocol jointly promoted by ITU and IETF. After resolving the complexity and poor scalability of H.323, H.248/MEGACO is widely supported by manufacturers and becomes a key media gateway control protocol for the Next Generation Network.

SIGTRAN protocol signaling Transfer Protocol): SIGTRAN is the protocol that transfers circuit exchange signaling in the IP network, mainly the No. 7 signaling), through the signaling gateway SG. In our country's specifications, the signaling gateway is used to connect the No. 7 network and the IP network, and relay, translate or terminate signaling information.

As the core of next-generation network control, Softswitch combines the advantages of traditional telephone network reliability, flexibility and effectiveness of IP technology, and is an important concept of the transition from a traditional circuit switching network to a segmented network. It is worth noting that the development of NGN lies not only in softswitch, but also in the overall technological progress at each layer. For example, DWDM, optical network technology, API interface technology on the business layer, and various wide and narrow band access technologies such as LMDS and XDSL on the access layer ). Problems with Softswitch

Although many manufacturers have released Softswitch solutions and operators are actively conducting relevant tests, the application of new technologies takes a long time to complete, from the solutions provided by the current manufacturers, the main problems are:

1. No experience in networking and operation of large networks in the world

After long-term operation and accumulation, traditional telecommunication networks have mature experience in network organization. However, Softswitch-based network organizations do not yet have mature experience at home and abroad, the use of fully-plane structure based on Softswitch or regional routing structure remains to be further explored in terms of technology and practice.

2. Protocol compatibility is not yet achieved, and standards are still under development

The Softswitch of different manufacturers is not compatible with each other in terms of technical standard selection and Protocol compatibility. BICC protocol, SIP-T protocol and H.248 protocol are also under development, protocol options require operators to further determine according to business needs.

3. No mature API Products

Based on an open business platform and standard API interfaces, this platform has created a bright future for network operators to provide new services. However, relevant products are still being explored and developed.

4. QoS has no final solution

5. Currently, the main solution only provides voice services, and new services are being actively developed and tested.

6. Further development of multimedia services is required

7. network security problems

8. Third-party business model issues

9. Manageable business issues

The existence of the above problems will not hinder the application of new technologies. On the contrary, the operator will calmly solve these problems with the equipment supplier, and actively conduct experiments and continuously improve them.