Basics
Softswitch
Softswitch technology is the core technology of NGN network, which provides call control and control for the services of next generation network (NGN) with real-time requirements Connection control function. The softswitch technology is independent of the transmission network, and mainly completes the main functions of call control, resource allocation, protocol processing, routing, authentication, and billing. At the same time, it can provide users with all the services that existing circuit switches can provide and provide third parties Programmability.
Proposed
The concept of softswitch originated in the United States. At that time, in the enterprise network environment, users used Ethernet-based telephones to realize the PBX (Private Branch eXchange, user-level switch) function (IP PBX) through a set of PC server-based call control software (Call Manager, Call Server). For such a set of equipment, the system does not need to lay the network separately, but can realize the unity of management and maintenance only by sharing with the local area network, and the overall cost is much lower than that of a traditional PBX. Since the enterprise network environment does not require high equipment reliability, billing, and management, it is mainly used to meet communication needs, and the equipment threshold is low. Many equipment vendors can provide such solutions. Therefore, IP PBX applications have achieved great success. Inspired by the success of IP PBX, in order to improve the overall operating efficiency of the network, the development of the network tends to be more reasonable and open to better serve users. The industry has proposed such an idea: The traditional switching equipment is divided into call control and media processing. Standard protocols (MGCP, H248) are used between the two and pure software is used for processing. Therefore, Soft Switch (soft Exchange) technology came into being.
Development
Once the concept of softswitch was put forward, it was quickly recognized and valued by the industry. The establishment of ISC (International Soft Switch Consortium) accelerated the development of softswitch technology. At the same time, softswitch related standards and protocols have received the attention of IETF, ITU-T and other international standardization organizations.
According to the definition of the International Soft Switch Forum ISC, Soft Switch is a device and system that uses program-controlled software to provide separate call control functions and media processing based on a packet network. Therefore, the basic meaning of softswitch is to separate the call control function from the media gateway (transport layer), and realize the basic call control function through software, so as to realize the separation of call transmission and call control, which is the control, switching and software programmable functions. Create a separate plane. Softswitch mainly provides functions such as connection control, translation and routing, gateway management, call control, bandwidth management, signaling, security, and call detailed records. At the same time, the softswitch also encapsulates network resources and network capabilities, and connects to the service application layer through standard open service interfaces, which can quickly provide new services on the network conveniently.
Yin Kang, chief technical consultant for NGN/VoIP in Cisco Systems Asia Pacific, believes that although "softswitching" is a hot topic of NGN discussion, people still have a somewhat paradoxical concept of it. He said: "The term'soft switch' can be said to be derived from the translation of Soft switch. The term Soft switch borrows the concept of'hard' switch'switch' in the PSTN network of the traditional telecommunication field. The difference is that it emphasizes it. Based on the meaning of separation of call control and media transmission on the packet network. At the beginning, some people in China translated Soft switch as "softswitch". However, the translation term "softswitch" is not very clear enough, and it is difficult to make people look literally. Understand whether it is an equipment system concept or a system concept."
Yin Kang pointed out that China’s telecommunications industry has always translated the switch of the noun attribute and the equipment concept category as "switch", and the switch of the gerund attribute. Translated as "exchange". X25 switch is translated into X25 switch, ATM switch is translated into ATM switch, and L2/L3 switch is translated into Layer 2/Layer 3 switch. Therefore, he suggested that for the seriousness of academic research, soft switch should be more accurately translated as "soft switch." This is just a matter of translation concept. However, from a certain point of view, the vagueness of the concept of softswitch also reflects that the industry still has deviations in some aspects of softswitch understanding, and there is an overemphasis on a certain aspect of the ability, or excessive exaggeration of softswitch. Functional situation. It can even be said that for a long period of time, softswitch has been artificially "mythical". It is regarded as a technology that represents the future of the communications industry and seems to be omnipotent.
Softswitch is a developing concept that contains many functions. At its core is an open architecture that uses standardized protocols and application programming interfaces (APIs). This opens the door for third parties to develop new applications and new businesses. Other important features of the softswitch architecture include application separation (de-coupling of applications), call control and bearer control.
Basic elements
The most significant feature of softswitch technology that is different from other technologies, and the three basic elements of its core idea are:
Generate interface h3>
The main way for softswitches to provide services is to provide new integrated network services through APIs and "application servers". At the same time, in order to better take into account the existing communication network, it can also cooperate with the existing SCP in the IN to provide traditional intelligent services.
Access capability
Softswitch can support numerous protocols to control various access devices, maximize user investment and give full play to existing communications The role of the network.
Support system
The softswitch uses a policy-based implementation method that is completely different from the traditional OAM system to complete the function of the running support system. The strategy for real-time, intelligent, centralized adjustment and intervention of network characteristics to ensure the stability and reliability of the entire system.
As a new solution for the integration of packet switching networks and traditional PSTN networks, softswitching combines the reliability of PSTN with the flexibility of data networks. It is a new way for emerging operators to enter the voice market. Technical means is also a way for traditional voice networks to evolve to packet voice. Internationally, as the core component of the next generation network (NGN), softswitch has been accepted and adopted by more and more operators.
Architecture
Soft switch control device (Soft switch Control Device) This is the core control device in the network (also known as soft switch). It completes call processing control functions, access protocol adaptation functions, service interface providing functions, interconnection and intercommunication functions, application support system functions, etc.
Business platform
Complete new business generation and provision functions, mainly including SCP and application server.
Signaling Gateway
1. Signaling Gateway Device No. 7 The traditional No. 7 signaling system is based on circuit switching, and all application parts are carried by MTP. In the softswitch system, it needs to be carried by IP.
2. ISDN signaling gateway. It is an international standard for digital telephone networks and a typical circuit-switched network system. In the ITU proposal, ISDN is a communication network developed on the basis of the digital telephone network IDN. ISDN can support a variety of services, including telephone services and non-telephone services.
3. SIP signaling gateway. It is a multimedia communication protocol formulated by IETF (Internet Engineering Task Force). SIP based on the IP protocol utilizes IP networks, and fixed network operators will gradually realize the far-reaching significance of SIP technology to them.
Media Gateway
Complete the conversion processing function of the media stream. According to its location and the different media streams processed, it can be divided into: Relay Gateway (Trucking Gateway), Access Gateway (Access Gateway), Multimedia Service Access Gateway, Wireless Access Gateway, etc.
IP terminal
Mainly refers to two kinds of H.323 terminal and SIP terminal, such as IP PBX, IP Phone, PC, etc.
Other support
Such as AAA server, large-capacity distributed database, policy server, etc., which provide necessary support for the operation of the softswitch system.
Network structure based on softswitch technology Softswitch is one of the core equipment of the next-generation network. When constructing a network structure based on softswitch technology, operators must consider the intercommunication with other various networks. . In the next generation network, there should be a more unified network system structure.
The interface between the softswitch and the application/service layer provides access to various databases, tripartite application platforms, functional servers, etc., to achieve support for value-added services, management services, and tripartite applications. Among them: the interface between the softswitch and the application server can use SIP and API, such as Parlay, to provide support for tripartite applications and value-added services; the interface between the softswitch and the policy server can dynamically intervene in the work of network equipment, and can use the COPS protocol; The interface between the softswitch and the gateway center implements network management, using SNMP; the interface between the softswitch and the intelligent network SCP implements support for existing intelligent network services, and uses the INAP protocol.
Through the interaction between the core packet network and the media layer gateway, the processing call-related information is received, and the gateway is instructed to complete the call. Its main task is to establish relationships between points. These relationships can be a simple call or a more complex process. Softswitch technology is mainly used to process real-time services, such as voice services, video services, and multimedia services.
The interface between the softswitches realizes the interaction between different softswitches, and can adopt SIP-T, H.323 or BICC protocol.
Technical principle
Technical definition
The technical definition of softswitch can be described as:
·It is a kind of providing call control Functional software entity
·It supports all existing telephone functions and new conversational multimedia services
·It uses standard protocols (such as SIP, H.323, MGCP, MEGACO/ H.248, SIGTRAN and various other data and ITU protocols)
· It provides interoperability between equipment from different manufacturers
·It is compatible with one of the following or Multiple components are used in conjunction
· Media gateway
· Signaling gateway
·Characteristic server (for example, providing CLASS service)
· Application server (for example, providing multimedia services)
·Media server (for example, providing services such as data streaming media, conferences and advertisements)
·Management, supply and charging/billing interface.
Perhaps from a business perspective, a more vivid definition can be given:
Softswitch is a kind of network and business problems related to traditional telephone services and new multimedia services. Solution. It can reduce capital and operating expenses and increase revenue.
Principle and Objective
Softswitch technology is a distributed software system that can provide seamless interoperability between networks based on various technologies, protocols and devices. The basic design principle is to try to create a distributed software system with good scalability, interface standardization, business openness, etc., which is independent of specific underlying hardware/operating systems and can handle various services well. The required synchronous communication protocol pushes the architecture to the Moore curve track in an ideal position. And it should have the ability to support the following basic requirements:
(1) The development of call processing and/synchronous meeting management applications for call equipment independent of protocol and equipment.
(2) It can safely execute multiple third-party applications in its softswitch network without any harmful effects caused by malicious or erroneous applications.
(3) Third-party hardware vendors can increase the ability to support new devices and protocols.
(4) Service and application providers can increase the ability to support system-wide strategies without compromising their performance and safety.
(5) Have the ability to perform synchronous communication control to support various post-business office systems including billing, network management and other operational support systems.
(6) Dynamic topology of synchronous communication control network that supports runtime bundling or contributes to structural improvement.
(7) Network scalability from small to large and support for complete failure recovery capabilities.
The realization goal of softswitch is to realize the protocol conversion of various media streams through the way of computer software programming under the cooperation of media equipment and media gateway, and is based on the packet network (IP/ATM) The architecture realizes the interconnection of IP networks, ATM networks, PSTN networks, etc., to provide equipment that has the same functions as circuit switches and facilitates business value-added and flexible expansion.
Exchange protocol
The main protocol used by the softswitch The softswitch system involves many protocols, including H.248, SCTP, ISUP, TUP, INAP, H.323, RADIUS, SNMP, SIP, M3UA, MGCP, BICC, PRI, BRI, etc. Internationally, organizations such as IETF, ITU-T, and Soft Switch Org have been playing an active and leading role in softswitch and protocol research, and many key protocols have been completed or tend to be completed. These agreements will standardize the entire softswitch research and development work, so that the products will enter the industry common standard agreement stage from the stage of using each manufacturer’s private agreement. The interoperability of products between each manufacturer will become possible, and the original intention of softswitching will be truly realized—providing a standard, With an open system structure, each network component can be developed independently. In terms of the research progress of softswitch, our country is at the same level in the world. The "Network and Switching Standards Research Group" of the Ministry of Information Industry started the research on the softswitch project in the second half of 1999 and has completed the "General Technical Requirements for Softswitch Equipment." Here is a brief introduction to several major protocols.
248/MEGACO
H. Both 248 and MEGACO protocols are called media gateway control protocols, which are used in media gateways and H． Between 248/MEGACO and soft switch equipment. The contents of the two agreements are basically the same, except that H. 248 was proposed by ITU, and MEGACO was proposed by IEFT, and it is an agreement recommended by both parties. They introduce the two abstract concepts of Termination and Context. In Termination (terminal), the media stream parameters, MODEM and bearer capacity parameters are encapsulated, while Context (association) indicates the interconnection relationship between some Terminations (terminals). H. 248/MEGACO completes the operation between Termination (terminal) and Context (association) through 8 commands such as Add, Modify, Subtract, Move, etc., thus completing the establishment and release of the call.
Control Protocol
Media Gateway Control Protocol (MGCP) was proposed by IEFT and is a combination of Simple Gateway Control Protocol (SGCP) and IP Device Control Protocol (IPDC) . The MEGACO protocol is a further improvement, perfection and enhancement of the MGCP protocol. The MGCP protocol can be said to be a relatively mature protocol, and the content of the protocol is relatively similar to the MEGACO protocol. Most of the softswitch system equipment supports this protocol, and its shortcomings are slowly showing up. In the future, it may be subject to H． Replaced by the 248/MEGACO agreement.
In the softswitch system, the MGCP protocol and H. Like the 248/MEGACO protocol, it is applied between the media gateway and the MGCP terminal and the softswitch equipment. Through this protocol, the connection, establishment and release of the media/control flow on the media gateway and the MGCP terminal are controlled.
Initial Protocol
Session Initiation Protocol (SIP) is an application layer control protocol proposed by IETF for multimedia communication on IP networks. Based on the Internet Protocol (HTTP), following the design principles of the Internet, based on a peer-to-peer working mode. SIP can realize the connection, establishment and release of sessions, and support unicast, multicast and mobility. In addition, if SIP is used in conjunction with SDP, it can dynamically adjust and modify session attributes, such as call bandwidth, transmitted media type, and codec format. The specific content can be found in IETFRFC 2543bis.
In the softswitch system, the SIP protocol is mainly used between the softswitch and the SIP terminal, and some manufacturers apply the SIP protocol between the softswitch and the application server to provide value-added services based on the SIP protocol. . In general, the SIP protocol is mainly used in services that combine voice and data, as well as the establishment and release of calls between multimedia services.
Message mechanism
Command: It is the main content of H.248 message, which realizes the control of association and terminal attributes, including the designated terminal to report detected events and notify the terminal What signals and actions to use, and specify the associated topology, etc. The H.248 protocol defines eight commands:
–ADD: Add a Termination to a Context. When the Context ID is not specified (or a Termination is added for the first time), a Context will be generated, and then Join Termination.
–MODIFY: Modify the properties, events and signal parameters of a Termination. Such as: modify the coding type of the terminal, notify the terminal to detect off-hook/on-hook events, modify the topological structure of the terminal (two-way/one-way/isolation, etc.).
–SUBSTRACT: Delete a Termination from a Context and return the statistical status of Termination at the same time. If there is no other Termination in the Context, this Context will be deleted.
–NOTIFY: Allow MG to notify MGC of detected events. For example: MGW reports the detected off-hook event to MGC.
–MOVE: Transfer a Termination from one Context to another Context.
–AUDITVALUE: Return the current Properties, Events, Signals, Statistics of Termination.
–AUDITCAPABILITIES: Returns the capability set of the Termination feature in the MG.
–SERVICECHANGE: Allows the MG to notify the MGC that one or more terminals will leave or join the service. Used for MG to register with MGC and restart notification. The MGC can use ServieceChange to restart the MG. The MGC can use ServiceChange to notify the MG to cancel one or part of the Termination.
NGN
Wei Leping, chief engineer of China Telecom Corporation, pointed out that NGN in the broad sense encompasses all new-generation network technologies, and NGN in the narrow sense refers to softswitching. In China, people often associate NGN with softswitch, or even equate them. In fact, it can be seen from international research and actions on NGN that NGN contains a very wide range of content.
Origin
In 1996, the US government and universities respectively took the lead in proposing the Next Generation Internet Action Plan (NGI) and Internet2. In addition, many government departments, industry groups, standardization organizations and other organizations participate in NGN action plans in the world, such as IETF's next-generation IP, 3GPP and UMTS forum's next-generation mobile communications, Canada's CANET3, EU's NGN action plan, etc. . Many of these NGN plans and actions have nothing to do with softswitching. Some of them specialize in the development of network technology in this field (for example, the IETF's "Next Generation IP" studies how to transition from IPv4 to IPv6), and some are more inclusive. A comprehensive research project of network technology and application.
Of course, there are some special researches on next-generation networking technologies for voice networks in the world, such as the softswitch-based NGN solution proposed by Telcordia (formerly Bellcore). However, it is undoubtedly questionable to say that NGN is a softswitch. According to the NGN solution proposed in China, as one of its most important features, the openness of the softswitch platform can provide operators with a flexible and fast new business development model, allowing NGN to truly become a business-driven network.
"But softswitch is not NGN. It can even be said that softswitch is not necessarily the core technology of NGN." Jiang Lintao, chairman of the National IP and Multimedia Standards Research Group, pointed out. He believes: "The core technology involved in NGN has two levels: one is the bearer network level, alternative core technologies are TDM, ATM, IP, etc., softswitch is not among them; the other is the service network level, softswitch technology will play The core role." The core technology of VoIP in the future will be softswitching. Softswitch is the voice part of NGN, that is, the core technology in the next-generation telephone service network (including fixed network and mobile network). However, the business model to be carried by NGN is not very clear today. It is difficult for us to conclude that VoIP is the core of NGN in the future. Communication business. Therefore, some people in the industry believe that it cannot be simply concluded that softswitching is the core technology of NGN.
Then think that NGN is a softswitch, or NGN hopes that a single "softswitch" comprehensive device will bring about what consequences? Yinkang believes that this will inevitably result in the lack of feasible overall system network benefits and goals for NGN solutions, making NGN thinking and discussion limited to a single category of equipment and the partial structure and scope of related technologies. What's more serious is that the equipment characteristics and technical characteristics of "softswitch" can only provide very limited "network" concepts and functions. This may cause the NGN networking mode and its overall network architecture to become unsolvable.
Development
According to data, many operators in the United States, such as Bell Atlantic, Level3, British Telecom, Great East, Deutsche Telekom, and NTT of Japan, have carried out NGN trials and achieved Some phased results. Due to the maturity of the softswitch itself, most of their experiments are limited to the tandem function of the softswitch, which can provide some simple multimedia services, but most of them are single-domain small-scale networks.
Yang Jing, chief scientist of UT Starcom, believes that the core of NGN should be embodied in cross-network services, rather than open service interfaces. He said: "NGN is not so much a switching network as it is a business network based on IP infrastructure." ) All implement the soft switch mechanism.
"The soft switch embodies the idea of separating call control and media transmission through the media control protocol MGCP/H248 technology. The concept of the soft switch makes the voice service function of NGN and the traditional PSTN network compatible. The switch function can be completely transparently compatible, which fundamentally ensures that IP telephony technology can completely replace the switch in the PSTN network," Yin Kang said, "Soft switch is an important part of NGN, but it is more focused on IP networks. The equipment and system of the call control function in itself cannot constitute a special overall networking technology mechanism and network system architecture. The networking mode that completely revolves around the soft switch as the core to interconnect with each other does not have much test and discussion value. It limits NGN can only be statically configured by soft switches and connected to each other, which is the so-called "non-network mode" of the so-called full-plane network."
Yin Kang believes that the "non-network mode" NGN architecture It can only support one or a few soft switches, with no scalability or flexibility, and it is not suitable for large-scale operations. The soft switch must have the ability to connect with the "network". This "network" is the multimedia signaling network of NGN. He said: "NGN multimedia signaling between soft switches can not only guarantee unlimited scalability, dynamic and flexible routing structure, but also truly achieve the goal of'network is the switch'."
"The networking of the next-generation network adopts a layered multimedia signaling network and a flat media stream structure. The multimedia signaling network is realized through the multimedia signaling protocol system and multimedia signaling transfer point network elements. Because the multimedia signaling network The main function does not involve media control, so it is generally not composed of soft switches, but is composed of specialized multimedia signaling servers.” Yin Kang said, “The true meaning of next-generation networks requires both the innovation and prosperity of intelligent endpoint services, but also The system needs to be managed on a large scale. From the perspective of current technology maturity and development, the three technologies of ITU-H323 protocol, IETF-SIP protocol and soft switch characterized by MGCP/H248 protocol are all IP telephone communications and next-generation networks. The three technologies have their own differences and their specialties need to be complementary. Only the use of a network architecture system and implementation methods that integrate the three technologies is the best policy."
Many scholars pointed out a long time ago, The soft switch can also be regarded as the result of the decomposition of the intelligent gateway under the H323 and SIP system. It assumes the important task of regional or end office system platform in the next generation network, and shoulders the functions of simultaneously controlling network access traffic and controlling PSTN network edge interconnection traffic. However, soft switches still need other key technologies and equipment to work together to ensure viable QoS and network security solutions. Soft switches provide various voice services of existing circuit switches, and support new multimedia endpoint services that integrate voice, data, and video and diversified third-party services (including video telephony, video teleconference, PC-Phone), but soft switches It should not be regarded as a general control platform for data and video services and applications. Therefore, only the proper positioning of the soft switch in NGN to make it play an appropriate role is the correct way to play its important and key functions in NGN.
Driving advantages
Cost reduction
Most network operators today are most concerned about ensuring the security of their existing services. Voice and dial-up services are still their main sources of income, and traffic will continue to grow. Although broadband access is growing, it is still very limited in most markets. At the same time, deregulation and competition have led to lower prices and eroded the profits of operators. These factors, coupled with limited funds, force operators to reduce operating and capital expenditures (OPEX and CAPEX).
However, in the process of realizing these savings, it is obviously better for operators to invest in future technologies than to optimize the network using existing technologies, although in many cases the latter can also achieve similar savings. This decision is mainly based on business rather than technical considerations.
New revenue
It is not enough to reduce costs. Although reducing costs by providing traditional services can bring about protecting the profits of operators, the creation and deployment of new services that can generate revenue is the key to the survival of fixed telephone service providers. As can be seen from the chart in Figure 1, fixed-line telephone revenue is "shrinking."
Basic services (such as adding/removing media, presentation, messaging, and media combination, etc.) will be integrated to provide end users with conversational multimedia services that can be accessed in any form of access. These services may include video conferencing, video telephony, voice-enhanced games, and user-controlled call processing.
Improved method
The general view is that: the development direction of network operators will be based on a packet-switched multi-service network environment, with softswitching to provide call and session control.
However, under the commercial situation, there are huge challenges in integrating into the softswitch environment. If the existing infrastructure cannot effectively meet the needs of its target applications and customers, it simply cannot exist. Any alternative technology must be able to handle a certain application as or better than existing solutions-with more advantages in terms of functionality and/or price. In addition, the new business model must prove to be able to meet the needs of the business supported by the existing technology. However, since telephones are still the main source of revenue for operators, alternative PSTN solutions that cannot provide a full set of PSTN services and carrier-class quality of service (QoS) cannot be adopted. Operators can't take their phone customers and revenue to risk.
Communication service providers need to adopt a gradual development approach and deploy softswitch technology as part of a cost-effective broadband multi-service network.
Softswitch
From a technical and commercial point of view, it can be seen that softswitch still faces many complex requirements. Obviously, as mentioned above, softswitch is still in the development stage. Ericsson proposes a terminology framework so that we can discuss its evolution.
Softswitch is actually a call or session controller separated from the softswitch system.
Softswitch systems are usually built on traditional call control platforms (with appropriate media gateways that support traditional telephone services). It is based on a commercial platform and is an appropriate media gateway supporting multimedia and basic voice services.
The multifunctional softswitch solution meets the two needs of operators: supporting traditional telephone services and any combination of multimedia services. The specific solution depends on the specific situation and needs of the customer.
The softswitch network architecture includes a general architecture foundation. Including the deployment of network elements (such as media and signaling gateways, service creation environment); interaction and signaling transfer between network elements; relationship with edge nodes and broadband access; quality of service (QoS) for IP infrastructure Requirements; and safety, operation, maintenance and supply.
Based on this framework, the softswitch system will form two major branches, which will develop along two different tracks: one for processing new multimedia services; the other for processing and controlling complete PSTN services.
Choose
Svante Bjorklund, senior strategist for Ericsson's multi-service network, pointed out that softswitch is actually a call or session controller separated from the softswitch system. He said: "From a business perspective, softswitch can be given a more vivid definition: it is a solution to network and business problems related to traditional telephone services and new multimedia services."
The softswitch with "separation of switching and control" as the core idea has broken the old telecommunication network structure, and has made sufficient preparations for the integration of data and voice and the creation of a large number of new services. This is also widely regarded as "NGN Core” reason.
In addition to technical factors, industry insiders believe that the openness and competition of the telecommunications market is the most fundamental reason for operators to accept softswitches. Since 2001, domestic operators have started commercial experiments on softswitches. China Telecom's north-south split and the formation of a new "5+1" pattern have provided opportunities for the development of softswitches. Both China Telecom and China Netcom need to build networks in each other's "territories". The traditional PSTN is undoubtedly not the best choice. All-IP packet switching networks including softswitch technology will become the operators' first choice. For operators lacking fixed network resources and emerging telecom operators, they can only win in the fierce market competition with networks that can provide novel and rich types of services. Softswitch networks are also a good choice.
Since the beginning of 2002, the broadband telephone project of Netcom has been carried out in 8 cities across the country at the same time. At the end of 2002, the typical model of operation, management and commercialization represented by Ningbo Netcom has been recognized. Officially entered large-scale commercial use. By 2002, five of the six major operators had already invested in substantive testing and commercial use of softswitches.
On the one hand, the long-term rapid development of the telecommunications industry has made the existing and mature PSTN technology and traditional VoIP technology unable to keep up with the increasing business needs of users, business and terminal equipment customers Integration and individualization, and the unified and convenient management and maintenance have become important conditions for operators to increase revenue. On the other hand, the softswitch technology has absorbed the advantages of both the intelligent network and the Internet, and has embodied the maturity and advancement of its technology from the beginning. The layered network model is used to effectively solve the evolution and evolution of the existing communication network. The issue of convergence conforms to the two major trends in network construction and development: one is the convergence of different forms of communication networks, and the other is the gradual separation of business operations and network operations. The above factors have all promoted the development of softswitch in China.
Evolution
Although operators and vendors are very optimistic about softswitches, they have also begun to look at how softswitches can enable existing single-switches from a more realistic and practical perspective. The business network is transplanted to the future all-IP network. The development of softswitch technology must meet several conditions: It does not affect the development of the existing network, and provides operators with a practical and feasible solution with lower investment costs and higher cost-effectiveness.
The softswitch system can be carried on data networks such as LAN, WLAN, CATV, ATM, and even DDN, microwave network, 3.5G, etc. It enables operators to make full use of existing network resources; terminal The access methods are flexible and diverse, and can provide various accesses such as TG/SG, AG, IAD, MSAG, Cable IAD, etc., and intercommunication with existing fixed, mobile, and multimedia terminals; especially for ADSL, PHS, and WLAN users , Has a strong competitiveness for users of existing networks; the miniaturization and diversification of the terminal equipment of the softswitch system greatly improves the actual installation rate of the project, saves a large amount of working capital for the operator, and significantly shortens the equipment recovery time . According to market estimates, the payback period for the softswitch system is within 3 years, compared to 8 years for 3G.
The softswitch system also provides a brand-new operating model. In the early stage, it can be carried out in multiple areas at the same time, using a unified softswitch core control device. When the number of users in a certain area has grown to a certain number, the corresponding control equipment and operation support system can be separately configured to form an independent operational system. Some regional operators and corporate users are also very interested in the characteristics of unified services such as voice, data, and multimedia provided by softswitch networks. In particular, local broadband operators can only provide data services when building broadband networks in the past, while traditional Voice telecommunication services are also provided by telecommunication bureaus, which greatly reduces their market competitiveness. The new softswitch-based broadband network can provide users with all the telecommunication services they need at the same time.
At the same time, experts such as Svante Bjorklund also pointed out that under the business situation, there are still some challenges in the evolution to the softswitch environment.今天的大多数运营商最为关注的是保证其现有业务的安全。话音和拨号业务仍是它们的主要收入来源，且流量还会继续增长。任何替代技术都必须能够与现有解决方案一样，或更出色地处理某一应用——在功能和/或价格方面更具优势。
Svante Bjorklund说：“解除管制与竞争都将导致价格下降并侵蚀了运营商的利润。这些因素，再加上资金有限，都会迫使运营商不得不降低运营和资本开支。只降低成本还远远不够。虽然通过提供传统业务来降低成本可以保护运营商的利润，但是创造和部署能够增加收入的新业务才是固定电话业务提供商得以生存的关键。运营商投资于未来技术显然比利用现有技术优化网络更好一些。”
他认为：“网络运营商的发展方向将是基于分组交换的多业务网络环境，由软交换提供呼叫和会话控制。”
过渡
基于上面的观点，Svante Bjorklund认为，他认为，真正使得软交换业务与众不同的特点是存在管理（presence management）功能，它允许用户通过软交换系统进行自主控制并轻松使用所有通信业务。他说：“由于在开始时极少使用新特性，对于大多数用户而言服务似曾相识，因此用户更容易接受新系统。随着时间的推移，用户将发现越来越多的新特性，而且很快就会离不开这些特性。”
“开放API（如SIP 插件和Parlay）为应用服务提供商和第三方应用开发商开辟了蕴藏巨大商机的新市场。大规模应用开发行业能够确保快速而经济高效地开发应用，并为市场提供更多创新应用。这将帮助运营商丰富其业务产品，减少客户的丢失，吸引更多用户，以及提高使用率和增加收入，”Svante Bjorklund说，“随着新业务的开发和在用户群中的部署，运营商可以在传统电话业务的收入基础上获得额外的收入。”
他认为，软交换的发展就是平衡早期市场占有率与新老业务采用率。将“达到极限”的传统电话业务与支持窄带和宽带SIP业务的平台组合起来，有助于自始至终优化运营商的收入结构。不过他也特别指出，必须认识和考虑到创新性新业务使用率增长缓慢的现状。
其与3G
上海贝尔阿尔卡特副总裁谢铁林认为，3G网络的发展在很多方面应用了NGN下一代网络的技术。从网络结构、接口协议，业务以及业务开发各方面，3G与NGN的发展是协调一致的。在网络结构方面，NGN和3G中都提出了分层的网络结构；在接口协议方面，3G网络与NGN所采用的协议许多都是一致的，包括H.248/MEGAO协议、BICC协议、SIP协议、SIGTRAN协议；在业务方面，3G和NGN不仅提供的业务种类是相似的，例如各种多媒体业务，而且在业务的实现方式上也是类似的，3G和NGN都支持开放业务接口，所以二者在业务层面上是统一的，架构上也是一致的，也就是说，对于相似的业务，可以同时构建在NGN固定网和3G移动网络之上。软交换与3G网络的核心结构和业务模型十分吻合，为未来网络的完全融合提供了可能。 Svante Bjorklund也指出，最理想情况是，多媒体软交换系统是构建在与3GPP相同的体系结构之上，并使用会话始发协议（SIP）。 SIP是一种新兴的互联网标准，能够灵活地集成消息传递、存在业务、多媒体会议和实时通信。
很多厂商提供软交换解决方案时，都考虑了遵从3GPP体系架构设计，在多媒体域可以与3G核心网共享。中兴通讯网络事业部严华认为，软交换在国内的发展应该是：从语音业务着手，争取广泛的用户群；逐步发展多媒体业务，以提高用户附着力；然后适当引入移动业务，实现与现有移动业务的互通，扩大用户范围；最终实现移动多媒体综合业务，以及更多的未来网络新业务。
许可证
2003年春节前后，UT斯达康、爱立信、大唐都拿到了信息产业部颁布的软交换设备入网的试用许可证；在2002年，北电与华为获得了同样的入网试用证；中兴通讯更是在2001年就得到了信息产业部颁发的这张试用许可证。尽管只是试用的许可证，这些设备商还是非常高兴地宣扬了一把。因为这个许可证对于它们非常重要，国内运营商在进行NGN（下一代网络）试验以及试商用时，这张许可证就是它们进入的“门票”。
交换系统
多媒体软交换是为提供以下类型的业务和应用而设计的：
· 会话式多媒体－－在两方或更多方之间同时使用多种媒体进行的实时、延迟敏感的多向通信，如可视电话或视频会议。视频会议可以轻松处理媒体，在会话过程中添加或删除媒体
· 组合业务－－会话业务结合信息相关应用，如目录信息或基于位置的业务（例如业务和白板的存在调用）
·会话业务与其它多媒体业务组合－－如在线游戏结合可视电话或3D电话会议，组成包含社交活动的有趣而丰富多彩的业务。
支持这些类型的业务需要开放体系结构、API和协议。系统必须能够处理多媒体，包括实时视频、视频数据流、三维环绕立体声、数据（包括文本）、图像（如相片和图片）、以及传统但可以选择质量等级的话音。
由于在开始时极少使用新特性，这样，就没有必要在这种平台上重复提供PSTN业务，事实上那样做是一种倒退。
此外，还需要通过互联网上的应用开发商社区以低成本进行应用开发和部署；同样还需要为新用户设备提供多种能力以进行媒体播放和用户输入。
理想情况是，多媒体软交换系统构建在与3GPP（第3代移动网络标准）相同的体系结构之上，并使用会话始发协议（SIP）。 SIP是一种新兴的互联网标准，能够灵活地集成消息传递、存在业务、多媒体会议和实时通信（如电话）。它经过精心设计，采用模块化结构，以创新方法集成应用，可以扩展，从而支持新的技术。
使用SIP并在3GPP标准上构建体系结构具有许多重要优势。
首先，SIP是互联网社区的理想选择，基于文本的简单格式使应用开发商能够很快上手（例如，它比二进制格式的H.323更容易使用）。这意味着SIP能够支持更多的应用。
第二，在支持3G移动网络的3GPP体系结构上构建，这就可以使用一个平台为固定和移动用户提供通用的多媒体应用。
第三，SIP使用支持Web应用（如电子邮件和Web浏览器）的现有协议，同时H.323也可以或多或少地重新用于处理这些应用。这意味着在SIP环境中可以更轻松和平滑地进行互通。
爱立信确信SIP是对会话式多媒体通信进行会话控制的一种出色协议。与多媒体业务解决方案相比，新型多媒体软交换系统能够以更高的安全性和更优异的服务质量（QoS）提供多媒体业务，并灵活地进行计费。
传统电话软交换系统
100多年以来，传统电话一直是大型运营商的核心业务，而且电路交换机也在有线和移动网络中得到广泛部署。时分复用（TDM）交换技术是网络中最核心的技术之一，它具有集成应用、控制和连接平台，并且与接入和传统运营支持系统（OSS）密切相关。如果运营商大规模更换他们的TDM交换机，则不但可能失去收入丰厚的本地和汇接电话业务，而且还有为分离接入和OSS付出高昂成本的风险。
最近的标准化工作规定使用H.248和BICC等新信令协议把传统电路交换网络融合到分组交换网络。 TDM交换机被撤销，连接平台也从中央处理器和应用软件中分离出来。连接主要由分组基础设施（ATM或IP）来执行，其余的交换机则变成了电话服务器。电话服务器解决方案重新使用电话应用软件和处理器在多业务网络上无逢提供传统电话业务。
多功能软交换解决方案
软交换主要针对特定用户需求，并仅限于满足当前的运营商要求。因此为了充分利用新的市场机遇，需要提供多功能软交换解决方案。
随着新业务的开发和在用户群中的部署，运营商可以在传统电话业务的收入基础上获得额外的收入。
但是，必须认识和考虑到创新性新业务使用率增长缓慢的现状：移动电话和文本消息传递业务经历了5-10年之久才被大众市场广泛接受。包含更多功能的新业务将最终取代传统的电话业务；并且如上所述，个性化的存在管理将会加快这些新业务的流行。因此，在新平台上重新实施所有传统电话业务没有经济价值。此外，这将为现有业电话业务的服务透明度、服务质量以及收入带来风险。
另一方面，使用同一多功能软交换解决方案在彼此独立的呼叫或会话控制平台上分别实施传统电话业务和新型多媒体业务，这意味着可以在避免突然改变收入来源的同时迅速融合所有的传统业务。这还意味着拥有足够的时间等待从软交换系统的各个方面获得回报。此外，在QoS分组骨干上进行构建还意味着这种投资可以使OPEX和CAPEX降至最低，而不会失去任何新的多媒体商机。
采用多功能软交换解决方案，运营商们可以确保现有传统业务的总体透明度；同时获得一个通过全新业务实现收入增长的稳定平台。
有关情况
软交换国际论坛ISC（International Soft switch Consortium）专门从事软交换体系研究的公认的权威性国际组织。倡导将开放的结构和多厂商互操作性用于下一代的语音、图像和数据解决方案。分为Application、Architecture、Carriers、Device Control、Legal Intercept、Marketing、Session Management和SIP等8个工作组。截至2000年底，已有195个成员。国际上的主要设备制造商和运营商都参与进来。
ITU的工作
ITU－T为了满足电路网向分组网过渡的需要，在ISUP的基础上制订了用于软交换控制设备之间互通的BICC协议，同时完成了软交换控制设备和MG之间控制关系的H.248协议。
IETF的工作
IETF在描述MGC和MG之间的控制关系的MGCP协议基础上制订Megaco协议。将SS7信令移植到IP网上，为此制订了SCTP和M3UA。制订了用于软交换控制设备和数据终端设备之间的控制协议SIP，以及软交换控制设备之间互通的SIP BCP－T协议。