In-depth discussion on NGN-Softswitch Technology

The solution based on Softswitch technology has many advantages, but do not forget that everything is a double-edged sword. From the solutions provided by current manufacturers, there are still many problems. As the control function 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. The Softswitch technology is located at the control layer of the Next Generation Network (NGN) and evolved from the call server or media gateway controller originally proposed by some vendors.

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.

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 technology is implemented by supporting H.248/MEGACO, SIP, SIGTRAN, BICC, H.323 and other protocols.

SIP (SessionInitiationProtocol) 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 a protocol that transmits circuit exchange signaling (mainly No. 7 signaling) in an IP network and is implemented 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 and optical network technologies on the transport layer, API interfaces on the service layer, and various wide and narrow band access technologies (such as LMDS and XDSL) on the access layer, including wireless ). Problems with Softswitch technology. At present, although many manufacturers have released solutions for Softswitch technology, operators are also actively conducting relevant tests, but the application of new technologies needs to be improved for a long time, from the solutions provided by the current manufacturers, the main problems are:

1. there is no experience in networking and operation of large networks in the world. After Long-Term Operation accumulation, traditional telecommunication networks have already gained considerable experience in network organization; however, the network organization based on Softswitch technology has no mature experience at home and abroad. It adopts a fully-plane structure based on Softswitch technology, the regional Routing Structure and other aspects of technology and practice need further exploration.

2. Protocols have not yet been compatible, and standards are still under development. It is difficult for different manufacturers to choose the softswitch technical standards and to make the protocols compatible with each other. 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. APIS do not have mature products. They are based on open business platforms and adopt standard API interfaces, which opens a bright future for network operators to provide new services, however, the corresponding products are still under exploration and R & D.

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.