NGN Core Analysis Development Status of Softswitch Technology

We all know that the Softswitch technology supports many different protocols from different standardization organizations. Here we analyze the next generation radio/TV Network Technology Based on the Softswitch technology. How to build a sustainable network, integrate data and voice services, speed up user-oriented business development, and improve its flexibility, to ensure that carriers can gain their expected market share in the future data multimedia business, this is the fundamental starting point for proposing the NGN network.

Network Features of NGN

NGN is the next generation network. From the perspective of development, NGN is evolving from a traditional PSTN network dominated by circuit switching to a group switching. It carries all the services of the original PSTN network, unmount a large amount of data to an IP network to reduce the heavy load on the PSTN network, and add and enhance many new and old services with the new features of IP technology. In this sense, NGN is the product of TDM-based PSTN voice network and IP/ATM-based grouping network convergence, it makes it possible to integrate voice, video, and data services on the next generation network. From the perspective of network functions, NGN is not a simple development and extension of which network is today, but a product of triple play. It not only has all the functions of today's various networks, but also has new functions generated after network convergence. The NGN technology enables business convergence and intercommunication between networks (PSTN/ISDN, PLMN, IN, and Internet) to quickly provide new voice, data, and images over the entire network, integrates the strengths of IP, ATM, IN, and TDM to form a layered and open system architecture. In addition, the integration of fixed networks and mobile networks will be realized in NGN. In terms of network architecture, NGN will evolve from today's IP network. The first is the IP address of the network. All access networks from terminals, man networks, and wide area networks are IP-oriented. Further evolution is to improve the structure of the IP network and develop new protocols to meet the requirements of NGN.

NGN is a business-driven network and a network independent from the network. It is not a day to transform an existing network into a next-generation network, the coexistence of the original network and the new network takes a long time, so the new network needs to be able to communicate with the original network, which requires the new network system to complete the following functions: the TDM transmission network and SS7 signaling network are used to interconnect with existing services (such as services provided by the Intelligent Network) and the existing PSTN network system. NGN can communicate with existing networks, such as PSTN, ISDN, and GSM Through gateway devices. At the same time, NGN also supports existing terminals and smart IP terminals, it includes analog phones, fax machines, ISDN terminals, mobile phones, GPRS terminals, SIP terminals, H.248 terminals, MGCP terminals, Ethernet telephones through PCs, and cable modems.

NGN is a new type of target network that integrates multiple services. Its outstanding advantages are guaranteed by a series of key technologies, it is bound to involve a considerable number of traditional technologies and new protocols, such as Softswitch, digital processing, digital transmission, routing, and IP-based communication protocols. Many technologies and protocols will continue to emerge and need further improvement. Therefore, research and construction of NGN is an exploratory, phased, and arduous process. However, the open service platform of NGN provides a broader space for its own development, which is the focus of operators.

Core Technology of NGN-Softswitch

Softswitch technology is the core technology for implementing the next-generation voice communication and multimedia and data interaction. In terms of applications, Softswitch is mainly applied on the IP network. The Softswitch technology is very natural in IP networks, because the call control and bearer connections required by the IP networks are separated. As the core of next-generation network call and control, Softswitch is a key technology in the NGN architecture. Its core idea is to implement hardware software-based functions such as switch control connection and service processing through software, various entities connect and communicate with each other through standardized protocols, facilitating the implementation of various complex protocols in NGN and providing services more conveniently. It is the core device provided by the Voice/Data/video service call, control, and service in NGN. Currently, Softswitch provides the following functions: media Gateway access function, call control function, service provision function, interconnection function, support for open business/application interface function, authentication and authorization function, billing function, resource control function and QoS Management functions, protocols, and interfaces.

To put it simply, Softswitch is an entity that implements the "Call Control" function of a traditional Programmable switch. However, the traditional "Call Control" function is integrated with the business, because different services require different call control functions, the call control function provided by the Softswitch technology is the Basic Call Control Function of various services. One of the important features of Softswitch is to provide a platform for third-party applications, allowing users to program the system and create new businesses, which not only increases the service types, but also speeds up service applications. In addition, the Softswitch technology uses open application interfaces (APIS), allowing flexible introduction of new services in the exchange mechanism. The Softswitch technology embodies the idea of separation of business/control and transmission/access. In the entire softswitch system, the signaling protocol that completes connection and control functions plays a core role, determines the strength of the service provision capability. The separation of transmission and call control establishes a separate plane for control, exchange, and software programmable functions, allowing service providers to freely combine transmission services with control protocols, service Transfer is realized, so that Softswitch can be seamlessly integrated into multimedia services such as communication data, fax, and video.

Softswitch combines the reliability of traditional voice networks and the flexibility, validity, and openness of IP technology, so that traditional telecom operators and emerging operators are very optimistic about the development prospects of this technology. The primary challenge facing the Softswitch technology is the multi-protocol, which supports many protocols, and these Protocols come from different standardization organizations, this brings many coordination difficulties for technical research, equipment production, and communication operations. Softswitch technology has become a new hot spot in the industry, and its emergence has made voice networks open to new architecture. As the core of next-generation network switching, SoftSwitch combines the reliability of traditional telephone networks and the flexibility and effectiveness of IP technology. It is a new technical means for emerging operators to enter the voice market, it is also a way for traditional voice networks to evolve to group voice. The series of network devices formed by these networks will play an important role in the evolution of China's telecom networks and the use of IP networks to provide a wide range of services, it has broad development prospects. In the communication system, the control is solved through negotiation, and the corresponding protocol is required. In the NGN architecture, as the control center, Softswitch is implemented by supporting multiple protocols such as MGCP, H.248, MEGACO, and SIP.

1. MGCP

MGCP is a media gateway control protocol defined earlier by the ietf megaco Working Group. In the softswitch system, MGCP is mainly used to define the behavior between Softswitch, media gateway, or SoftSwitch and MGCP terminals from the functional perspective, softswitch uses this Protocol to control the connection, establishment, and release of the Media/control flow on the media gateway/MGCP terminal. Its implementation is relatively simple. Without the detailed definition of packages and attributes like H.248, the event interaction mechanism is also relatively simple. Therefore, MGCP is easy to implement, but its interconnectivity and support capabilities are limited.

2. H.248/MEGACO

The H.248/MEGACO Protocol was developed by the ietf megaco Working Group and was later adopted by the ITU-TSG16 to form a ITU-TH.248 proposal, based on the MGCP (Media Gateway Control Protocol) protocol (RFC2705, developed based on the features of other media gateway control protocols. This Protocol provides a mechanism to control the creation, connection, and release of the Media/control flow on the media gateway/H.248 terminal and to ensure the execution of these commands, it can also carry some along-the-way call signals. After resolving the complexity and poor scalability of H.323, H.248/MEGACO has been paid attention to its flexible functions and strong support business capabilities, and is constantly providing new accessories to supplement its capabilities, it is widely supported by manufacturers and is the mainstream protocol between media gateway and Softswitch technology. At present, H.248 protocol is recommended between Softswitch technology and media gateway in China.

3. SIP

SIP is an application layer protocol based on UDP/IP technology. The RFC2543 protocol only describes the application layer of the SIP protocol, and stipulates that the SIP protocol can be carried on UDP/IP, so you do not need to care about the specific underlying implementation technology. SIP is a text-based plain text protocol. All control packages can be understood manually without specialized and expensive decoding instruments. The SIP protocol is very simple. There are only six commands (INVITE, ACK, BYE, CANCEL, OPTION, and REGISTER), and the return code is basically the same as that of the HTTP protocol. The biggest feature of SIP is that you only need to use the defined message header fields to easily support various new and intelligent services by simply and necessary expansion, strong flexibility and scalability. Because the implementation is very convenient, efficient, and the maintenance cost is relatively low, according to the survey, in the development plans of major equipment manufacturers, vendors that support the SIP protocol are increasing. The SIP protocol has been widely accepted as the core protocol for multimedia services and applications, including 3G mobile multimedia. Currently, the main Protocol of SIP (RFC2543) has been completed, and most of the multimedia call control functions can be completed. The draft supplementary protocol of SIP is being formulated and discussed.

Problems to be concerned during NGN network construction

Any new technology is not perfect at the beginning of application. problems need to be found and improved through tests. As a brand-new network, NGN must have some problems in its construction: these technical problems need to be further studied. The operation modes of the NGN network are also very different from those of the existing network, which is very important. Operators and equipment suppliers should work together to calmly solve these problems and actively conduct tests to continuously improve them. The IETF organization has put forward multiple models. We believe that the open network architecture and flexible business platform will be the development direction.

Conclusion

With the emergence of NGN technology, operators have begun to invest in research and testing on next-generation networks. A number of domestic carriers are actively conducting NGN network experiments and trial operations. Currently, many equipment suppliers, such as Siemens, Alcatel, Nortel Network, and ZTE, have released solutions for the Next Generation Network. It can be said that NGN has a huge commercial interest. The transformation of NGN to the existing network will greatly enhance the competitiveness of the network. At the same time, the multimedia services in NGN will be the profit growth points of major operators. With the continuous maturity of products, technologies, standards and network operations, we believe that in the near future, NGN will inevitably become the mainstream of network construction.