Background
With the rapid development of communication network technology, people’s requirements for broadband and services are also growing rapidly, in order to provide users with more flexible and diverse existing services and new additions. Business, to provide users with more personalized services, puts forward the concept of next-generation networks, and major telecom operators have begun to experiment with next-generation communication networks. Softswitch technology is one of the focal points in the next-generation communication network solutions, and has become a hot topic discussed in the industry in recent years. my country's network and switching standards research group has completed the overall technical requirements framework for the softswitch system, and the 863 plan has also established projects for the softswitch system in multimedia and mobile communication and wired communication systems.
The origin of the concept
The concept of softswitch originated in the United States. At that time, in the corporate network environment, users used Ethernet-based telephones to realize the PBX function (IPPBX) through a set of PC server-based call control software (CallManager, CallServer). 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, and standard protocols (MGCP, H248) are used between the two and pure software is used for processing. Therefore, SoftSwitch (soft switching ) Technology came into being.
Once the concept of softswitch was put forward, it was quickly recognized and valued by the industry. The establishment of ISC (InternationalSoftSwitchConsortium) has accelerated the pace of development of softswitch technology. Softswitch related standards and protocols have been approved by the IETF. , ITU-T and other international standardization organizations.
According to the definition of the International Softswitch Forum ISC, Softswitch 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.
Network structure
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 interaction with other various networks. Of interoperability. In the next generation network, there should be a more unified network system structure. The softswitch is located at the network control layer, which better realizes the separation of call control function and media processing function based on the packet network and the use of program-controlled software.
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 softswitches realizes the interaction between different softswitches, and SIP-T, H. 323 or BICC agreement.
Design principles and goals
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 The synchronous communication protocol required by the business 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) Protocol and device-independent calls, device call processing and synchronous meeting management application development.
(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.
Detailed explanation
What is a soft switch? When asking such questions, we often get descriptions of a series of characteristics: it is the core of NGN, it has an open architecture, it can realize the separation of call control and media transmission......
Cisco Systems Asia Pacific Yin Kang, chief technical adviser of NGN/VoIP in the district, believes that although "softswitching" is currently a hot topic of NGN discussions, people still have a somewhat paradoxical concept of it. He said: "The term'softswitch' can be said to be translated from Softswitch. The term Softswitch borrows the concept of'hard' switch'switch' in the PSTN network of the traditional telecommunication field. The difference is that it is based on packet The meaning of the separation of online call control and media transmission bearer. At the beginning, some people in China translated Softswitch as "softswitch". However, the meaning of the translation term "softswitch" is not very clear enough, and it is difficult to make people understand it literally. Is it the equipment system concept or the 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 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, softswitch 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. Function
Softswitch technology (7 photos)
. 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.
Softswitch is a functional entity that provides call control and connection control functions for the next-generation network NGN with real-time requirements. It is the core of the next-generation network call and control.
In a nutshell, the softswitch is an entity that implements the "call control" function of traditional program-controlled switches, but the traditional "call control" function is combined with the business, and calls required by different services The control function is different, and the softswitch has nothing to do with the business. This requires the call control function provided by the softswitch to be the basic call control for various services.
The basic elements of thought
The most significant feature of softswitch technology that is different from other technologies, and the three basic elements of its core idea are:
1) Openness Business generation interface.
The main way for softswitch to provide services is to provide new integrated network services through API and "application server". 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.
2) Comprehensive device access capabilities.
Softswitch can support numerous agreements, in order to control various access equipment, protect user investment to the maximum extent and give full play to the function of existing communication network.
3) Operational support system based on strategy.
Softswitch uses a policy-based implementation method that is completely different from the traditional OAM system to complete the function of the operation support system, and performs real-time and intelligent network characteristics according to certain strategies. , Centralized adjustment and intervention 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. At present, as the core component of next-generation network (NGN) internationally, softswitch has been accepted and adopted by more and more operators.
Architectural composition
Currently, a relatively common view is that the softswitch system should mainly consist of the following devices:
1) Softswitch Control Device (Softswitch Control Device) ) This is the core control device in the network (also known as softswitch). It completes call processing control functions, access protocol adaptation functions, service interface providing functions, interconnection and intercommunication functions, application support system functions, etc.
2) The service platform (Service Platform) completes the function of generating and providing new services, mainly including SCP and application server.
3) Signaling Gateway (Signaling Gateway) currently mainly refers to the No. 7 signaling gateway equipment. 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.
4) Media Gateway (Media Gateway) completes the conversion processing function of the media stream. According to its location and the different media streams processed, it can be divided into: Trunking Gateway, Access Gateway, Multimedia Service Access Gateway, Wireless Access Gateway, etc.
5) IP terminal (IP Terminal) currently mainly refers to two kinds of H.323 terminal and SIP terminal, such as IP PBX, IP Phone, PC, etc.
6) Other supporting equipment. Such as AAA server, large-capacity distributed database, policy server (Policy Server), etc., they provide the necessary support for the operation of the softswitch system.
Technical definition
The technical definition of softswitch can be described as:
· It is a software entity that provides call control functions;
·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 devices of different manufacturers
·It is used in conjunction with one or more of the following components< /p>
·Media Gateway
·Signaling Gateway
·Characteristic server (for example, providing CLASS service)
·Application server (for example, providing multimedia Business)
·Media server (such as providing data streaming media, conferences and advertising services)
·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.
Relationship with NGN
Softswitch and NGN (1)
Wei Leping, chief engineer of China Telecom Group Corporation, pointed out that the universal NGN embraces all new generations Network technology, NGN in a narrow sense refers to softswitch. 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.
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 currently proposed in China, as one of its most important features, the openness of the softswitch platform can provide operators with a flexible and efficient new service development model, allowing NGN to truly become a service-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.
Softswitch and NGN (2)
Then think that NGN is a softswitch, or NGN hopes that a single "softswitch" comprehensive device will bring about The 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.
According to data, many operators such as Bell Atlantic, Level3, British Telecom, Great East, Deutsche Telekom, and NTT in the United States 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.” At present, the technology of China Telecom’s softswitch trial network also requires CLASS4 (long-distance link) and CLASS5 (connections). Into the layer) 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 the IP network. 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
Reduce costs
Today's most network operators are most concerned about ensuring the security of their existing services. In the near future, 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.
An improved method
Currently, 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, in the current business 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.