NGN and soft exchange technology
Gong Shuangqi
1.NGN and network evolution
1.1 overview
my country's telecommunications network has had a rapid development in recent years, and the continued growth of telecom traffic. The income and network size of telecommunications business have been greatly developed. They are in the world leading position in the development speed and scale, and the level of the network is very large. Improvement. my country's mobile communication network, data communication network and multimedia communication network has laid the foundation, intelligent network, all kinds of information desk, and public multimedia networks in China to provide a broad business platform. . Many new technologies are basically synchronized with advanced countries in the world. The main task of the past telecommunications network is to provide voice and transport data on the basis of voice transmission, and future telecommunications networks continue to transmit voice services more important to transfer data and multimedia business. From the situation of current telecommunications development, existing networks include telephone network, X.25 data network, DDN network, frame relay network, and the Internet, all of the telecommunications services, how the future network should develop ? About this problem industry has a variety of different views, more views that future networks are based on packet transfer. Especially with the development of a new generation of networks such as the next generation of Internet, IP will have greatly accelerate the penetration of traditional telecommunications services and the integration of traditional telecom business and IP. At present, both operators or equipment manufacturers are constantly discussing the characteristics and new growth points of the next generation network.
What is the next generation of online (NGN), the answer will be a five-flowers, it should be said that he is just a broad concept. First of all, he must meet more and more business and applications needed by users. From operators' views to provide simple business no longer produce enough benefits, to provide users with a wide range of, useful and convenient services . Therefore, the next generation network is driven by service, providing various means of opening new services. Looking at the next generation network has a large change in the network construction method, the structure of the NGN network is not only conducive to the convergence of voice and data, but also contributes to optical transmission and packet technology fusion, fixation and movement. Fusion, the most important is a safe and guaranteed quality network. At the same time, there must be cost efficiency, and the operating cost should be lower than the traditional network.
1.2 Main features of next-generation network
At present, ITU and other international standards are still in the research phase, not clearly and complete definitions, but there are some consensus for NGN's main features. According to the needs of the foreseeable future business development, the next generation network should have the following features:
1) The next generation network should support the diversification of the business, including voice, data, and multimedia services. Support wide range of business includes real-time / stream / non-real-time business and multimedia services, while supporting business, mobile mobility, openness, and flexibility.
2) The next generation of online will be based on the package transfer;
3) Separate carrying capacity and control function, call / meeting, application / business
The network system uses a hierarchical structure, ie, is divided into core media layers, control layers, and business strata.
- Core Media Layer: The media layer is responsible for passing the message from one end of the user to the other end. (
- Control layer: The control layer is the transfer, billing, management, and maintenance of the media layer completed message.
- Business Layer (Application Layer): Responsible for the provision of various additional services on the basis of basic business.
--- Access layer: The user is access to the core media layer by various access methods.
The layered system of the next generation network is a major feature of the next generation network. It avoids the shortcomings of the traditional circuit switched network to concentrate various functions in one contact, not only separate the service providing and call control. Moreover, the call control and bearer connection are separated, and the current conventional circuit switched network is changed, and the status of the bearing connection is tightly bundled, and the network can be flexible, and conveniently organizes the network and providing services.
4) Business and online release combination and open interface
Next-generation networks should provide an open business interface, which can be conveniently provided by third parties through various standard interfaces. In particular, the operation company, equipment manufacturing company, value-added business company, content providing company, system integration company, and communication software company have developed a variety of business.
5) The ability to have end-to-end broadband transfer. The physical bearer of the next generation network will mainly use WDM-based optical transmission systems. And gradually introduce an optical switching device in the optical transmission system. 6) The next generation network must be able to cooperate with the traditional network, as there is also a role in which the existing traditional Internet will continue, but also make full use of existing network resources so next generation network must Solve cooperation and interoperability with traditional existing networks.
7) Support the mobility of the terminal
The next generation of networks must support the mobility of the terminal to meet the needs of growing mobile services.
8) Generation network should be convenient to manage, scheduling and maintenance.
9) The next generation network should be guaranteed to ensure quality and sufficient security and reliability.
10) The next generation network should be sustainable.
Because there are many problems with the next generation network, ITU is expected to be related to NGN related advice in 2004.
2. About soft exchange technology
2.1 Soft Switch Overview
2.1.1 Soft exchange in the next generation network
Softswitch is currently universal view is a core device evolved from the network to the packet network. It is also one of the important equipment of the next generation of telecommunications network. It is independent of the underlying load agreement, mainly completed call control, media gateway access Control, resource allocation, protocol handling, routing, authentication, billing, etc., and can provide users with all business and diverse third-party services that can be provided by existing circuit switches. And it is also the concept used in the development of next-generation network. Its main feature is:
----- Business Provisioning and Call Control Separate;
---- Call control and bearer connection separation;
---- Open interface, easy to provide business;
Soft exchange is located in the control level in the next generation group network hierarchical structure, which can be illustrated by Figure 1. It provides various services to the carrier layer, signaling network, various access gateways, relay gateways, etc. to provide various services through corresponding protocols.
Figure 1 Soft switching device and various gateways and the connection network connection
In FIG. 1, it is an architecture of a network of a soft exchanged to core, including various access gateways, relay gateways, signaling gateways, service application planes, and the like in this architecture. Soft exchange provides a variety of access to access, access, wireless access, etc. of V5.1. Softswate mainly completes various call controls and is responsible for the transmission of the corresponding business processing information. Business application planes are mainly providing a variety of value-added services.
2.1.2 Main features of soft exchange
The main features of soft exchange include the following parts:
- Call control function
- Business provides functionality
- Business Switching Function
- Interoperability
-SIP proxy function
- billing function
- Net management function
- Routing, address resolution and authentication
-H.248 Terminal, SIP terminal, control and management functions of the MGCP terminal
- Seventh signaling (ie MTP and its application part) function
-H.323 terminal control, management function
The functional structure and protocol system of soft exchange is shown in Figure 2.
Figure 2 Structure of Softswitch System Structure
2.2 Maturity analysis of soft exchange
Since the Bell Laboratory of Soft Switch, in just a few years,
International has experienced the three development phases of the laboratory stage, market promotion phase and application phase. Under the common promotion of numerous manufacturers and operators, Soft Switch products are gradually mature, and the features are increasing, and the standardization process is steadily advanced, so that Soft Switch technology begins to go to the market.
Currently, Softswate is hotter than the world, and is generally believed that this is the core part of the next generation network, and it is desirable to gradually replace the existing circuit switched network with soft exchange and provide new business growth points below. Analyze soft exchange maturity
2.2.1 Functional maturity
Soft exchange (some vendors also call it a call server, or performance server), many vendors started to start based on:
- Popular existing circuit switches to the IP network, replace the traditional circuit switched network;
- The existing H.323-based IP telephone service is a single one. It is hoped that the implementation of softswitch can provide more business to users, at least the same as the traditional circuit switched network can be provided. business. Such as calling numbers display, call transfer and other services. Alternatively replace existing telephone networks.
In Internet evolution, more and more operators and vendors are aware of despite the rapid development of data services, the voice business is still the main business volume, and is the main body of telecommunications revenue. Therefore, the manufacturer's attention is still intended to provide voice. Although everyone talks about softswitch is the core of the next generation, the current soft exchange mainly considers the following: - Provide soft-swap control devices on IP / ATM to pass existing long-distance traffic through softswitch Road bypass. In fact, it is actually a relay exchange of the telephone.
- The second step in soft exchange is to bypass the entire telephone network, allowing the user to provide voice traffic over the network of softswitch through the access network or through the terminal access device. That is to offer local telephone services.
The above two aspects should be said to be soft exchanges. It is also a problem that requires key considerations, especially for new operations when building a telephone network, it is hoped to use new technologies to build a network. Soft exchange is undoubtedly some operators' choices.
The positioning of each manufacturer's softswitch is the control section of the next generation network, that is, it not only provides the currently required telephone service, but also provides data services and multimedia services on the basis of providing voice. To provide new business creative conditions, soft exchange should be:
--- Provide a variety of services to the user directly under soft exchange by various IP terminals (H.323 terminals, SIP terminals).
- Can provide mobile phone services through a wireless access gateway,
- Get the data and multimedia services of the IP network through various access gateways;
- Provides more services through the intelligent network and a third-party application server.
In the above-mentioned soft exchange functions, mature is to provide a fixed telephone service, in particular a transfer service of a fixed telephone. In terms of providing a number of supplementary services, it is necessary to provide support with the need to provide a number of supplementary services, and some softswitch devices must have corresponding functions but are not very wide. Its maturity is There is still a difference compared to the traffic.
The supply of soft exchange functions is more difficult than fixed networks. First introduced mobile softswitch concepts, which will then define mechanisms that use SIP signaling on the packet domain to control multimedia services. Mobile network is the same for the 3GPP or 3GPP2 network evolution, and step-by-step implementation is taken according to the characteristics of mobile networks. At the same time, in order to support global mobility in various environments, it is necessary to develop corresponding network functions in the control layer. especially:
--- Identify and demonstrate mechanism
---- Access control and authentication control
---- Location Management
---- Terminal and Meeting Address Assignment and Management
---- Support the management of the user environment
---- Management of User Performance
---- Access to user data
etc.
Currently, commercial mobile switching systems are currently based on R99. After the end of 2002, some manufacturers can provide R4, and the concept of soft exchange is started in R4 products. At present, R4-based products should be more mature, but there is no experience in interconnecting between various manufacturers. Therefore, applications currently softswun in mobile networks are also limited to providing telephone services and assumes relaying. Still do not have a function of mobility.
The introduction of the software exchange in the mobile network is also the first one of the development of steps:
--- TANDEM function
In this case, he is basically the same as the softswitch of the fixed network, the media gateway application mode is basically, mainly solves the IP interchange between mobile network and fixed network. Softswate has not yet mobilized functionality and cannot support business-oriented business.
--- GMSC (GATEWAY MSC)
The status of soft exchange is equivalent to the Gateway MSC, with mobility concepts, and HLR via the MAP / IS41 interface, positioning mobile users, supporting new mobility services.
--- VMSC (VMSC (Visited Or Serving MSC)
The third step is true to provide softswitch in VMSC.
Therefore, soft exchange is the same as the fixed network, which is mainly alternative to the traditional assembly network portion to provide IP phones.
2.3 Ripeness of the protocol
2.3.1 Soft Switching Protocol System
Soft exchange protocol requirements include:
--- H.248 protocol between the relay gateway,
--- SigTran protocol with NO.7 interoperability
--- SIP, H.248, MGCP protocol with IP terminals
--- INAP, CAP, MAP protocol with existing intelligent network --- H.323 protocol with existing H.323IP telephone network
--- SIP-T / BICC protocol with other soft exchanges
--- Agreement with access to the gateway
--- Open API agreement
For the standards of softswitch, the protocol is the key to network integration. The industry, including equipment manufacturers, business providers, is now working hard for standard development, hoping to introduce advanced services, voice applications into the data network, and can be fused with traditional networks. The current standard work is mainly involved in: interoperability; media control protocols (such as MGCP, H.248), communication between Softswun (such as SIP-T, BICC), protocol and API of the business platform; in line with international telephone connection Standard; safety standard; use soft exchange transfer advanced business and other aspects. The relevant standards mainly include H.323, MGCP, SIP, etc. However, the relevant softswitch standards have to be improved, unified and widely accepted. The primary and main challenges faced by soft exchange are multi-protocols, that is, there are many protocols supported by soft exchange, and these agreements come from different standardized organizations, which brings all aspects of technical research, equipment production and communication operations. A lot of difficulties in coordination. At present, there are many work in China in the standardization of agreements, and some agreements have been standardized and some are being developed.
At present, the relevant agreements that have been developed in China have been developed as shown in the following table:
2.4 Soft exchange network maturity
There are still many problems that need to be studied from the network's perspective.
---- Multiple soft exchange of collaborative work
At present, the experiment of softswitch is basically on the basis of soft exchange. Now some operators have also begun to carry out multiple soft exchange tests, from the perspective of the network, using a single softswitch program only suitable for small operations Commercial, rapid implementation in small networks, but for large telecom operators, we must build a softswitch network throughout the country, regardless of the extensibility to interconnection, and the capacity provided by the business. However, when using more than two softswitch networks, communication between softswitch systems will be involved in the softswitch system, which is not standardized enough, and the agreement can be provided by each manufacturer is different, so there is a different manufacturers. The mating and interoperability of soft exchange is not mature enough.
---- Soft exchange classification problem
If the soft exchange can solve multiple softswitch work, what should I use? Is it possible to use a level or a multi-level, some manufacturers also believe that even when using a plurality of softswitch schemes, the program is only implemented in medium-sized networks. For large telecom operators, because the program is built a flat network, its scalability is equally difficult to meet the needs of telecommunications operators in the country. Therefore, some vendors even propose soft exchanges to be divided into terminals level and coincident. If the end office is provided through the unified business point of the whole network, the efficiency of the business is low due to too complex process interaction and media streaming, which may damage part of the business characteristics and reduce business improvement flexibility. There is also a network system that proposes a multi-level position server in a soft exchange in the network. So softswitch network organization issues are not mature. There are still some problems to be studied.
2.5 Third Party provides business maturity
Since the standardization of open interfaces has not been completed, although some manufacturers can provide some third-party business, they are limited to the equipment of the same manufacturer. The cooperation of different manufacturers equipment and the provision of business is not mature.
3. Currently some problems in China's soft exchange development needs
At present, various operators have begun to test and test SoftSwitch technology. With the gradual improvement of performance and implementation of softswitch equipment, how to fully operate across the telecommunications network, but also solve the following problems:
3.1 address problem
