Application Perspective: main functions and multi-service features of the network Softswitch Technology

With its excellent multimedia service, the network Softswitch technology can provide new services on various application servers to the public clients based on different users' needs. With the continuous development of computer and communication technologies, more and more operators and equipment manufacturers have recognized the voice, data, and images carried in a public group network. Under this trend of business-driven and network convergence, the next generation network model of NGN was born. In a group network, a distributed network structure was used to effectively carry voice, data, and multimedia services.

At present, Softswitch has been recognized as the core technology of NGN networks, and its development has received more and more attention. As the control function module 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. 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."

At present, China has completed and issued the "General Technical Requirements of softswitch Equipment" YDC003-2001 ), the positions, functional requirements, business requirements, Operation Maintenance and network management requirements, protocols and interfaces requirements, billing requirements, and performance indicators of softswitch in the network are clearly standardized, the interconnection requirements with IP phones and intelligent networks are also stipulated. It is particularly worth mentioning that, on the basis of the fixed network, the technical requirements of mobile Softswitch equipment and the approval of Device specifications have also been completed recently, it mainly expands the features of the network Softswitch technology in mobility management and authentication in mobile networks. It is not hard to see that, in the case of increasingly common group exchange, the network Softswitch technology plays an important role in the development and integration of fixed network and mobile network, as the core technology of the network. The Network Softswitch technology is embodied in physical nodes, that is, "soft switches" or "Communication servers ", the so-called "soft" is relative to the traditional TDM circuit switching devices of the telecom network that mostly use dedicated hardware platforms.

Vswitches of the traditional PSTN network adopt a vertical, closed, and dedicated system structure, while vswitches implement separation of Call Control and media, mostly based on standard and open system structures. The reason for this development trend is that the design of traditional telecom equipment is experiencing a process of changing from a dedicated design method to an open modular design. At first, all the hardware circuits and software code design models independently implemented by various equipment providers, with the increasing competition in the telecom industry, the cost-saving requirements and the pressure on shortening the development cycle are gradually changed to the outsourcing method, that is, the open commercial products provided by third parties should be used as much as possible, this includes commercial hardware platforms, software operating systems, and database management systems. The competition of equipment providers is gradually shifting to the competition of corresponding software functions.

At present, the development of the hardware platform of the soft switch conforms to this trend. The open computer hardware platform mostly adopts industry-standard, enabling operators to flexibly develop new businesses, it also makes full use of the rapid development of computer technology to bring about a rapid improvement in its performance. For example, the SUN server platform, multi-processor mechanism, the software is based on the Solaris operating system, and the system is extended through the unique Cluster technology of SUN, it meets the requirements for system processing capability and reliability in telecom-grade applications.

According to different network conditions and business needs, the current Softswitch applications mainly focus on the following four aspects: group relay, local access, multimedia services, and 3G core network. The software functions of softswitch are mainly reflected in media gateway access, call control, service provision, interconnection, network management and billing. According to different network conditions and business needs, the current Softswitch applications mainly focus on the following four aspects: group relay, local access, multimedia services, and 3G core network. Compared with the call control module of a traditional Programmable switch, the software functions of softswitch inherit and implement the following five functions.

1. Media Gateway access function. This function can be considered as an adaptation function. Softswitch can connect to various media gateways, such as PSTN/ISDNIP relay media gateway, ATM media gateway, user media gateway, wireless media gateway, and Integrated Access Gateway; supports the H.248 Media Gateway Control Protocol or MGCP protocol to control, access, and manage media gateways.

2. Call control function. The call control function is one of the important functions of SoftSwitch. It establishes, maintains, and releases basic calls, including call processing, Connection Control, Intelligent Call trigger detection, and resource control.

3. The service provides functions. In the evolution from circuit switching to group switching, end users should have full inheritance of services. Therefore, Softswitch must be able to implement all services provided by the PSTN/ISDN switch, including basic services and supplementary services, as well as to provide intelligent service in combination with the existing intelligent network. In addition, as an indispensable part of the NGN network, Softswitch must provide programmable and open api interfaces for interworking with external application platforms, this makes it easy to introduce and develop new businesses.

4. interconnection functions. The next generation network is not an isolated network, especially in the evolution of the existing network to NGN, it is inevitable to achieve interconnection with multiple existing networks, including the PSTN network, PLMN network, SS7 signaling network, VoIP network, intelligent network, and other Softswitch networks ). Therefore, the softswitch device must support relevant signaling and protocols, such as ISUP, INAP, PRI, V5.2, and MAP in China, to achieve interconnection with the above networks.

5. Network Management and billing functions. Local maintenance management and communication with the network management center through the SNMP protocol; maintenance, configuration, business statistics, alarms, and billing information collection. According to different network conditions and business needs, Softswitch applications are mainly concentrated in the following four aspects.

Group relay: The group relay stack network is constructed by using the network Softswitch technology to address the surge in the number of users and the increase in transmission bandwidth, media Gateway directly provides high-speed grouped data interfaces, greatly reducing the number of low-speed cross-connection devices in the transmission network, suppressing voice mute, compressing voice, and variable rate adaptation of AAL 2/ATM, reduces network transmission costs and bandwidth requirements, and saves nearly 60% of transmission resources) to meet the expansion requirements of existing long-distance bureaus and settlement bureaus.

Local access: local access to group voice is achieved by using the network Softswitch technology in various access methods, such as DSL, Ethernet, Cable, WLAN, and twisted pair wires, in a sense, it not only replaces or creates a Class5 terminal board, but also provides end users with a comprehensive business of data and voice.

Multimedia services: to meet the needs of users' multimedia services, the network Softswitch technology is used to control new services on various application servers under centralized call control of softswitch devices, various gateway devices are finally provided to end users. Softswitch directly controls the issuance and implementation of various new services, ensuring the timeliness of the services across the network.

3G core network: The network Softswitch technology is not only applicable to fixed networks, but also in the 3G wireless core network defined by 3GPPR4, it also uses the network Softswitch technology to achieve separation of Call Control and media bearer.