On the Concept, features and functions of vswitches

Push forward networks with Softswitch Technology

Abstract: firstly, based on a brief analysis of some issues discussed in the current soft switch, this paper re-discusses the concept and features of the soft switch and Its Role in the Next Generation Network; clarified some of these fundamental concepts and put forward their further discussions concerning some of the popular ones. Finally, it provides telecom operators with strategic suggestions on the implementation of soft switch technology.

Introduction

With the increasingly sophisticated communication network technology, especially the increasingly mature IP technology in recent years, the application of end-to-end fusion of voice, data, and video through grouping networks has become increasingly competitive in the future market. At present, it has been recognized that the separated voice, data, and video networks will gradually evolve into a next-generation communication network (NGN) that integrates multiple services, grouped IP addresses, and is open ).

Over the past year, people have been paying attention to and discussing NGN in line with this market trend. Fortunately, although there are some differences in the expression of NGN, we already have the following common understandings in principle:

· NGN will be based on the grouped data network and Unified IP protocol, even those who have conservative opinions on IP grouping technology agree that the integrated data network technology will become the core network technology of telecom operators in the next few years, no one raised any objection to IP technology as the basic backbone service platform of the telecom operator NGN. NGN will mean that the transmission technologies of various services and applications are completely forward and integrated into grouping and broadband IP addresses. Smart light, DWDM, and high-speed routing and group switching technologies will be fully utilized.

· NGN will provide an integrated and open network architecture. Its development goal is to integrate various application networks with a unified network technology to achieve end-to-end multimedia service convergence. The NGN network will unify various service networks-wireless and wired networks, fixed networks and mobile networks, voice networks and data networks-on a common Transmission Basis and network application platform.

As a commercial hardware platform based on open, standard, multi-protocol, and operational management technology representative, soft switches will become one of the important and critical systems and equipment technologies in NGN. However, it must be seen that, due to the rare networking and practice of vswitches with a certain scale in China, the Discussion and Practice of vswitches only focus on the concept of local and individual technologies. Over the past one year, people have gained some practical knowledge about soft switches, starting to discover that building NGN with a single soft switch technology will face a series of challenges and some fundamental conflicts. The author believes that the core of some of the key issues may not be technology, but the concept, angle, and way of thinking of the problems. Therefore, the author believes that it is necessary to review the concept and features of the Soft Switch Technology and Its Role in NGN.

Basic concepts of vswitches

Although soft switches are currently a hot topic in the discussion of NGN, their concepts are still somewhat plausible. So is it a device concept? A System Concept? A technical architecture? What is the relationship between a soft switch and an IP address phone and an NGN ﹖

1. Origin of Softswitch

The term "Soft Switch" can be said to have been translated from foreign countries. Its concept is basically formed with the development of the functional hierarchy of the IP telephone technology system and the concept of control separation. As we all know, in the traditional PSTN switching network, business control, call control, and transmission load are all concentrated in switches, and various services of the PSTN must be implemented through the TDM switch. To meet users' demand for new services, a public service generation platform (Intelligent Network) appears in the PSTN network. The PSTN intelligent network proposed for the first time and implemented the separation of some all-network service generation and call control. Therefore, it improved the development of all-network services of the PSTN and improved the capability of centralized network service provision, this shortens the cycle for providing new services across the network. The IP telephone technology system not only further strengthens the idea of separation of service generation and call control, but also looks forward to the separation of Call Control and media transmission bearer. The goal of this separation is to allow the control and generation of IP phone services to be truly independent from the media transmission network facilities, so as to achieve more flexible and effective integration of IP Phone and its related services and multimedia applications. More importantly, this separation also facilitates telecom operators to implement centralized operation, management, maintenance and preparation of OAMP on the group network. Telecom operators and users can customize configurations and manage their own business features through IP connections in the local system, without worrying about the types and configurations of user terminals, in this way, the provision of business and application is more likely, flexible, and operable and manageable.

2. Definition of vswitches

So what is a soft switch? 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, Softswitch is a typical technical practice designed for the speech purpose of the sub-networking. This definition also indicates that Softswitch borrowed the concept of "hard" switch in the PSTN network in the traditional telecom field, the difference is that it is based on the meaning of separation of sub-networking and call control and media transmission bearer. Softswitch is an important component of NGN, but 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 this simple concept confusing? One of the reasons may be that many people in China translate Softswitch into "Softswitch ". The definition of the term "Softswitch" is not clear enough to give it a logical illusion. It is literally difficult for people to understand 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? What's even more troublesome is that it is difficult for Chinese to distinguish between "softswitching" and "softswitch. Therefore, I believe that we should translate Softswitch into soft switches more accurately for the seriousness of academic research. In the formal written language, "Softswitch" should be avoided as a short name for soft switches.

3. Significance of the technical basis and concepts of vswitches

The technical basis of the soft switch is the MGCP/H.248 media control protocol. Media control protocol, also known as Device Control Protocol, is a so-called master-slave relationship control protocol. Generally, a simple device or device that is not in the Smart State is not included in the prosecution. All status events and changes must be reported to the master device. Therefore, media control protocols should not be considered call signaling and can only be used to control endpoints, including user terminals and relay endpoints. The Inter-board call signaling protocol of the soft switch cannot use MGCP/H.248, but must use the existing Multimedia International Standard, namely, ITU's H.323 Protocol and/or IETF's SIP protocol.

Vswitches use media control protocol technology to separate call control from media transmission. 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 enables the voice service function of NGN and the switch function of the traditional PSTN network to be completely transparent, but also fundamentally ensures that the IP telephone technology can completely replace the PSTN network.

Technical Features of vswitches

The technical features of vswitches are basically consistent. According to the concept of vswitches, the technical characteristics of vswitches are the idea of separating call control from media transmission based on MGCP/H.248 media control protocol.

Although the goal of NGN is to gradually integrate the voice, data, and video services into a collection of multiple services over the IP network, however, it still faces the fundamental challenge of finding a mature IP phone technology that can be used for large-scale operation management. Voice is the most popular, basic, and important service for carriers. It covers the widest range of the market and has a greater impact on business revenue 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 the operator's voice business. A Data IP network was originally designed for data services, while a speech 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 NGN.

Vswitches are basically designed to implement the functionality of the PSTN vswitch on the IP network. Vswitches of the traditional PSTN network are vertical, closed, and private system structures. Soft switches are standard-based and open system structures separated by call control and media. In addition, the "hard" switch of the soft switch and the PSTN has many common attributes. 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 we meet the telecom operation requirements to implement effective call service control and O & M management for the access of IP network endpoints and the interconnection with PSTN. Therefore, soft switches are an important implementation method of IP telephone technology in NGN.

It is particularly worth mentioning that, in order to support access from smart endpoints, video endpoints, and multimedia endpoints, a soft switch may also support H.323 protocol and SIP protocol to control user endpoints for managing H.323 and SIP. In this way, the soft switch itself cannot completely implement call control and media transmission separation for all the endpoints it controls and manages. In addition, as mentioned above, the soft switch must also support the H.323 and SIP protocols in the "inter-office" to interconnect with 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 generally cannot be called a soft switch. Call control devices that are characterized by H.323 protocol are usually referred to as the Gatekeeper keeper, and call control devices that are characterized by SIP protocol are called the proxy server ProxyServer.

In addition, although the soft switch supports the access of smart endpoints, video endpoints, and multimedia endpoints, it does not mean that all voice, data, and video services must be centrally implemented on the softswitch machine. Theoretically, even the possibility of such a device is completely unnecessary, because such a system does not have any advantages but has a series of overall architecture defects. In fact, the core design of the soft switch is focused on the Call Control Function of various businesses and the management of the terminal capability to a certain extent. For example, a soft switch does not directly provide any form of IP data service. A soft switch can support the video endpoint service, but the video conferencing control function is not provided directly by the soft switch, it is achieved by connecting to other application servers.

Through a Unified IP-based transmission infrastructure, call control devices can be dominated by soft switches ), build a system with other IP technology and data application technology to support multimedia and other smart services. We can call such a system a soft switch system. In a broad sense, a soft switch system is a collection of multiple logical functional entities for call, media, and business control. It provides Call Control, connection, and some other functions for telephone terminals, smart terminals, and multimedia terminal services. Such a soft switch system can be used to control, manage service access, and manage local devices at the edge of the PSTN network. In this way, a variety of call control-related businesses can be integrated into the system for management and operation. However, such a soft switch system will still adopt multiple distributed subsystem models to flexibly provide intelligent and multimedia business applications including voice in the integrated system.

Therefore, from the telephone service provided by the soft switch and its technical features, the soft switch is an important component of the NGN system, but it does not provide any fundamental innovation of the entire network architecture.

Role of soft switches in NGN

Soft switches are important devices and systems that provide call control in various services of the Next Generation Network. However, soft switches are not all about the next generation network. As an important part of next-generation network call control, soft switches still need to complement other key technologies and devices to collaborate in carrying out richer video and multimedia services.

1. Thoughts on popular soft switch ideas

At present, one popular term in the discussion of soft switches is "Softswitch is the core of the Next Generation Network". I think this term is worth further consideration and discussion.

The soft switch technology is one of the most important and critical speech service aggregation node technologies in the Next Generation Network. There is no doubt that we should pay special attention and attention to it. However, the technical features of vswitches do not provide the only direct core network technology.

In addition, the concept that "Softswitch is the core of the Next Generation Network" will bring about confusion in some basic propositions and logical confusions. The core technologies of the Next Generation Network should fundamentally include various network technology systems that support voice, data, and video services. The soft switch itself is only a local device system and does not have the characteristics of a comprehensive network architecture. Vswitches do not directly provide IP data services. Vswitches support video and multimedia endpoint services through call control mode and function extensions. However, vswitches still need to collaborate with other key technologies and devices to develop more video and multimedia services. The soft switch technology is mainly designed for centralized call control functions. In addition to the soft switch technology, the next generation network will also rely on a series of other existing IP technologies and other application technologies to support voice, data, video, and other services.

In terms of policy, the phrase "Softswitch is the core of the Next Generation Network" often leads to the assumption that the soft switch technology is equivalent to the next generation network technology, in this way, the focus of research and practice is only on a single soft switch technology and its surrounding areas. The future investment will only be considered for devices and systems related to vswitches. This leads to short-sighted strategic thinking that only looks at trees and does not look at forests.

In terms of technology, "Softswitch is the core of next-generation networks" often lead to the expectation of all next-generation networks on soft switch devices, then, we thought about constructing the so-called next-generation network with soft switches as the core, so that the discussion and practices on next-generation networks remain at the conceptual level of basic, local, small-scale, and individual device system technologies for a long time, as a result, the local structure of the soft switch is the overall network architecture of the Next Generation Network.

In practice, it is very easy to test and explore the networking mode around soft switches as the core. As a result, the practice and discussion of other next-generation network technologies are ignored, which limits that the next-generation network can only be connected by soft switches. the "no-network" mode of the full flat network ". Obviously, the "no-network" next-generation network architecture can only support one or several soft switches, which is not suitable for telecom operators to operate on a large scale. This phenomenon is called the "island phenomenon" of the soft switch technology practice ".

In terms of network structure, "Softswitch is the core of next-generation networks" cannot answer questions such as the need for next-generation networks without core network technologies. If not, how can we avoid the "island phenomenon" of soft switches ", if necessary, what is the core network technology of the Next Generation Network, how to solve the coordination and interconnection between soft switches, how to carry out the next generation network-wide business and other basic issues.

2. Analysis of Two policies for the NGN network architecture system

In the discussion of the next-generation network architecture system, there have always been two different strategies: one is to emphasize smart endpoints, 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 advocate simple endpoints and edges and smart network facilities, because only simple and unified endpoints and edge devices are conducive to the standardized management and control. The speech service provided by the PSTN network has verified the reliability of this business practice. ITU's H.323 protocol and IETF's SIP Protocol reflect the technical system of the first strategy to some extent. A soft switch characterized by the IETF/itu mgcp/H.248 protocol is a means to implement 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.

Obviously, the true meaning of the next generation network requires both the innovation and prosperity of smart endpoint businesses and the scale-up management of its systems. The difficulties discussed in the next-generation network architecture system are how to comprehensively balance multiple technologies. I believe that, as far as the current technology is mature and evolving, three technologies, namely, the H.323 protocol, the SIP protocol, and the MGCP/H.248 protocol, which are characterized by soft switches, are the implementation methods of IP phones and next-generation networks. These three technologies have their own differences and expertise that need to complement each other. The best strategy is to adopt a network architecture system and implementation means that integrate the three technologies.

In fact, the system of the Next Generation Network should be composed of the core network and the local soft switches located in the next generation network access and edge locations. The core network of the Next Generation Network is a backbone communication network that covers the service scope of operators. It is used to achieve interconnection between soft switches, between multiple operators, and between different networks, implement network-wide traffic control and scheduling; Share the network-wide services of centralized database retrieval, share the business creation environment, and provide network management across the network. The core network of NGN provides functions such as networking, routing policies, traffic control, network-wide service creation and management, and network-wide maintenance and management. Obviously, among the three main technologies implemented by the next generation IP phone, the network technology of the H.323 protocol and the network technology of the SIP protocol will play a major role in the core network. Many telecom operators in the world have used H.323's Internet guard or SIP proxy servers and other network application servers to achieve networking, networking, and network-wide business and O & M.

This does not mean denying the importance and critical position of the soft switch technology in the Next Generation Network. The next-generation network architecture is determined by the H.323 and SIP network systems, however, the access and convergence of the most popular and basic IP phone service in the next generation network mainly relies on the soft switch technology characterized by MGCP/H.248 protocol. As many scholars have already pointed out, soft switches can also be seen as the result of smart gateway decomposition under the H.323 and SIP systems. In this way, the network architecture of the three technologies may be more clear. In fact, a true soft switch should be a general-purpose classless soft switch which undertakes the important responsibilities of regional or local system platforms in the Next Generation Network, it is capable of simultaneously controlling network access traffic and controlling edge interconnected traffic of the PSTN network. Regional general-purpose soft switches and National Core backbone networks can build a complete next-generation network communication system.

Knot
To sum up, soft switches are an important part of the call control, media control, and service provision and distribution systems for Voice/Data/video services in the next generation network. Next-generation networks require not only soft switches as technical labs with local structures and categories, it also needs to be part of the entire IP telephone network architecture and business practices that integrate with multiple technologies such as H.323 and SIP. Many other problems related to the Operation Management of soft switches also need to be verified through the operation and implementation of the IP telephone network. Small-scale or laboratory tests of soft switches are of limited significance. Because the small network test mode is not necessarily suitable for the big network of Telecom IP, the small network test results in the laboratory do not necessarily fully explain the problems of the big network of Telecom IP. Therefore, only the test results of IP Phone applications in large production networks can fundamentally Promote the Development of the Next Generation Network.
Soft switches face challenges in the process of large-scale integration with IP telephone networks and making them scalable, reliable, and operable. Telecom operators and equipment vendors should have reached a consensus on vision and cooperation, so as to work together to promote the depth and popularization of the correct concept of soft switches, we encourage you to explore innovative models of soft switches from different perspectives and advocate soft switches as new tools and means to drive new business models and create new market mechanisms. However, at the same time, it is necessary to solve the problems and challenges faced by technology moving towards the market so that technology can serve the business needs and business motivations of telecom operators, this will guide the entire industry to always adhere to the principles of business-oriented technology, user-oriented and business-oriented, so that the soft switch technology can provide the most comprehensive and systematic assurance for China Telecom operators to move towards the next generation network and enhance their competitiveness.