Application viewpoint: basic concepts of vswitches

Many people regard the IP telephone technology and soft switch technology as independent, but we all believe that they will play a very important role in the next generation network technology. Over the past few years, with the rapid popularization and maturity of domestic IP phone technology and successful market operation practices, people have been paying more attention to and enthusiastic about China Telecom's next-generation network. Few people raise objections to IP technology as the basic backbone service platform of the next-generation Telecom Network of telecom operators.

However, when people talk about the next generation network, they often concentrate on the soft switch technology. It seems that the soft switch technology is all discussed in the next generation network technology. However, the soft switch technology itself can only provide very limited "network" Concepts and functions, let alone provide the overall network architecture of the Next Generation Network. This makes the thinking and Discussion on the Next Generation Network Limited to the local structure and scope of the soft switch technology. At the same time, this also makes the practice and goal of the Next Generation Network appear blind and confused for technology. Logical conflicts in some basic concepts have caused many people to be still confused about the relationship between the soft switch technology, IP phone technology and the Next Generation Network; some people also regard the IP telephone technology and the soft switch technology as isolated and opposite. Therefore, the author believes that it is necessary to review the concepts of soft switch technology and IP phone technology and their roles in the Next Generation Network.

Concept of soft switches in the Next Generation Network

Although Softswitch is currently a hot topic in the next generation network, its concept is still somewhat plausible. So what is the concept of a device? System Concept? System Concept? Or technical architecture? What is the relationship between a vswitch and an IP address and the Next Generation Network?

According to the definition of isc in the international Softswitch Forum, Softswitch is a device and system that uses program-controlled software to provide call control functions based on the sub-network. According to this definition, we can clearly see that Softswitch is a typical technical practice method designed for the speech purpose of the sub-networking. It focuses more on the devices and systems of call control functions. It cannot constitute a special overall networking technical mechanism and network architecture. But why is such a simple concept confusing? One of the reasons for this problem may be that many people in China translate Softswitch into "Softswitch ". The term "Softswitch" is not clear enough to give it a logical illusion. From a literal perspective, it is difficult to distinguish whether it is a device system concept or a system concept. China's telecom industry has always translated switch as switch, while switching as "switch ". So why are we making an exception here? Even more troublesome, it is difficult to identify the differences between "softswitching" and "softswitch" in Chinese. Therefore, the author believes that for the seriousness of academic research, we should translate Softswitch into soft switch more accurately. In the formal written language, "Softswitch" should be avoided as a short name for soft switches.

There have been a lot of discussions about vswitches, and people have basically agreed on the technical characteristics of vswitches. Vswitches use MGCP/H.248 media control protocol technology to separate call control from media bearer. Therefore, some foreign scholars refer to soft switches as call proxy CA or media gateway controller MGC. The concept of a soft switch not only makes the voice service function of the Next Generation Network completely transparent and compatible with the switch function of the traditional PSTN network, but also fundamentally ensures that the IP phone technology can completely replace the PSTN network. Vswitches are basically designed to implement the functionality of the PSTN vswitch on the IP network. In traditional PSTN networks, switches are vertical, closed, and private system structures. Soft switches are standard and open system structures separated by call control and media. In addition, the soft switch and the PSTN "hard" switch have some common features. For example, they are system devices that are relatively centrally controlled and managed, and all user-oriented data and call status information are stored in the system. This makes the soft switch very important to telecom operators, because only in this way can it meet telecom operation requirements, implement effective call service control and O & M management for IP point network endpoint access and PSTN interconnection.

It is particularly worth mentioning that, in order to support multimedia smart endpoint access, soft switches may also support the H.323 protocol and the SIP protocol to control and manage H.323 and SIP endpoints. In this way, the soft switch itself cannot completely implement call control and media bearer separation for all the endpoints under its control and management. In addition, the soft switch must also support H.323 and SIP protocols in the "inter-office" to connect to the H.323 network, the SIP network, and other soft switches. However, MGCP/H.248 media control protocol technology is always the basic feature of vswitches. If a call control device system does not support MGCP or H.248 media control protocols, it cannot be called a soft switch. Call control devices that feature H.323 protocol are usually called keeper, and call control devices that feature SIP protocol are called ProxyServer ). Therefore, judging from the telephone services provided by soft switches and their technical features, soft switches are an important part of the next generation network system, but do not provide any fundamental innovation in network architecture.

A soft switch is an implementation method of the Next Generation Network IP phone technology.

Some may say that the IP phone technology is H.323, and the soft switch technology is the next generation network technology. They are not the same thing. So what are the fundamental challenges of the next generation network? The goal of the next-generation network is to gradually integrate voice, data, and video services and integrate multiple services on the IP network. Voice is the most popular, basic, and important service for carriers. Its market covers the widest range, and its business income has a greater impact than other businesses. After nearly a hundred years of development, the traditional PSTN technology and TDM network provide mature business models and quality standards for carrier speech services. Data IP networks were originally designed for data services, while voice is a time-sensitive service, the IP telephone technology that provides large-scale voice services in data IP networks is the primary challenge for any operator in the transition to the next generation network.

The IP telephone technology demonstrates that the traditional PSTN service can evolve into a group IP network. It is useless for any next-generation network architecture to better adapt to the IP phone service. At the same time, the call control architecture of IP phones is also the basis of any multimedia business. Therefore, the research and practice of the IP telephone architecture system naturally become the core and fundamental research in the next generation network architecture system.

Any tests on the next generation network will become meaningless if there is no IP phone, and the small-scale or laboratory tests on the next generation network have very limited significance. Because the small network test mode is not necessarily suitable for the big network of IP Telecom, the test results of the small network test in the laboratory do not necessarily fully explain the problems of the big network of IP Telecom. Therefore, only the test results of IP Phone applications in large production networks can fundamentally Promote the Development of the Next Generation Network. There is no doubt that the IP phone technology is always closely related to the technology and development of the next generation network. The IP phone technology that provides the Call Control Function in the Next Generation Network will play an extremely important role.

In the discussion of the next-generation network architecture system, there have always been two very different strategies. One is to emphasize smart endpoints and edges and simple network facilities. Because the driving force of end-to-end multimedia converged services comes from endpoints and edges, the flourishing innovation and prosperity of next-generation network services are dependent on this. The success of the Internet also proves the importance of this idea to multimedia services. Another idea is to propose simple endpoints and edges, and smart network facilities. This is because only uniform endpoints and edge devices are conducive to the management and control of large-scale business. The speech service provided by the PSTN network has verified the reliability of this business practice. ITU-H.323 protocol and IETF-SIP Protocol are the technical system that reflects the first strategic thinking to some extent. The soft switch characterized by IETF/ITU-MGCP/H.248 protocol is the implementation means of the second strategy. As mentioned above, in order to achieve the telecom operation goal of end-to-end IP phones to a greater extent, people have designed a soft switch technology mechanism for telecom operators. The IP telephone voice service is the most important and fundamental service function in the soft switch. It is worth mentioning that the soft switch itself does not directly provide IP data services. Vswitches support video and multimedia endpoint services through call control mode and Function Extension. Vswitches still need to collaborate with other key technologies and devices to provide more comprehensive video and multimedia services.