Softswitch and NGN-Overview of Softswitch

Since the successful launch of the first product in the telecom market, the concept of "Softswitch" has become a popular term in the telecom industry. Because it can implement the same functions as hardware-based traditional telephone switches and simultaneously process IP communication, the Softswitch technology promises to provide many advantages, for example, it is easy to integrate circuit switching and group switching, reduce network costs, and enable operators to earn revenue more quickly.

What is Softswitch?
What is Softswitch? When we ask such a question, we often get a series of characteristics: it is the core of NGN, it has an open architecture, it can achieve the separation of Call Control and media transmission ......
Yin Kang, chief technical consultant of Cisco Systems Asia Pacific NGN/VoIP, believes that although "Softswitch" is currently a hot topic in NGN discussion, its concept is still somewhat plausible. He said: "The term 'softswitch 'is translated from Softswitch. Softswitch refers to the concept of 'hard' switch 'in the PSTN network in the traditional telecom field, the difference is that it emphasizes the meaning of separation of group-based online call control and media transmission bearer. At the beginning, someone in China Translated Softswitch into 'softswitch '. However, the term 'softswitch 'is not very clear enough, so it is hard to understand whether it is a device system concept or a system concept ."
Yin Kang pointed out that China's telecom industry has always translated switch in terms of terms and concepts into "switch", and switching in terms of terms as "Exchange ". X25 switch is translated into X25 switch, ATM switch is translated into ATM switch, L2/L3 switch is translated into L2/L3 switch. Therefore, he suggested that softswitch should be translated into "soft switches" more accurately for the seriousness of academic research ". This is just a translation concept. However, the vague concept of softswitch also reflects that the industry still has deviations in some aspects of understanding of softswitch, and there are capabilities that emphasize one aspect too much, or, the softswitch function is exaggerated. It can even be said that for a long time, Softswitch has been artificially "mythical". It is regarded as a technology that represents the future of the Communication Industry and seems omnipotent.
Softswitch is a developing concept that includes many functions. Its core is an open architecture that adopts standardized protocols and application programming interfaces (APIS. This opens the door for third-party development of new applications and new businesses. Other important features of the softswitch architecture include application separation (de-coupling of applications), call control, and bearer control.
As a functional entity, Softswitch provides Call Control and Connection Control functions for businesses with real-time requirements for the Next Generation Network NGN. It is the core of next generation network call and control.
To put it simply, Softswitch is an entity that implements the "Call Control" function of a traditional Programmable switch. However, the traditional "Call Control" function is integrated with the business, the call control functions required by different businesses are different, while Softswitch is irrelevant to the business. This requires that the call control function provided by Softswitch is the Basic Call Control Function of various businesses.
The difference between Softswitch technology and other technologies is also the three basic elements of its core idea:
1) Open service generation interface.
The main way that Softswitch provides services is to cooperate with the "Application Server" through APIS to provide new integrated network services. At the same time, IN order to better balance the existing communication network, it can also use INAP and the existing scp in to provide traditional smart services.

2) Comprehensive device access capabilities.

Softswitch supports many protocols to control various access devices, protect user investment to the maximum extent, and give full play to the role of existing communication networks.
3) policy-based operation support system.
Softswitch uses a Policy-based implementation method that is completely different from the traditional OAM system to implement the functions of the operating support system, adjust and intervene network features in real time, intelligently and centrally according to certain policies to ensure the stability and reliability of the entire system.

As a brand new solution for integrating the group switching network with the traditional PSTN network, Softswitch combines the reliability of the PSTN with the flexibility of the data network, and is a new technical means for emerging operators to enter the voice market, it is also a way for traditional voice networks to evolve to grouped voice. As the core component of the Next Generation Network (NGN), Softswitch has been accepted and adopted by more and more carriers.
At present, it is widely believed that the softswitch system mainly consists of the following devices:
1) Softswitch Control Device is the core Control Device in the network (also known as Softswitch ). It provides call processing control, access protocol adaptation, business interfaces, interconnection, and application support system functions.
2) The Service Platform generates and provides new services, including SCP and application servers.
3) Currently, the Signaling Gateway mainly refers to the No. 7 Signaling Gateway device. The traditional No. 7 signaling system is based on circuit switching. All applications are carried by MTP, and IP addresses are required for the softswitch system.
4) Media Gateway converts a Media stream. According to their location and the different media streams they process, they can be divided into: Relay Gateway (Trunking Gateway), Access Gateway (Access Gateway), Multimedia Gateway (Multimedia Service Access Gateway) and Wireless Access Gateway.
5) IP Terminal (IP Terminal) currently mainly refers to H.323 terminals and SIP terminals, such as ip pbx, IP Phone, and PC.
6) Other Supporting devices. Such as AAA servers, large-capacity distributed databases, and Policy servers, which provide necessary support for the operation of the softswitch system.
"However, Softswitch is not just NGN. It can 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 layers: one is the bearer network layer, and the alternative core technologies include TDM, ATM, and IP. Softswitch is not in this layer; one is the service network layer, and the Softswitch technology will play a core role." In the future, the core technology of VoIP will be SoftSwitch. Softswitch is the core technology in the speech part of NGN, that is, the next generation telephone service network (including the fixed network and mobile network). However, the service model to be carried by NGN is not very clear today, it is hard to determine that VoIP is the core communication service of the future NGN. Therefore, some insiders believe that Softswitch is the core technology of NGN.
What are the consequences of considering that NGN is a Softswitch or that NGN is expected to be a single "Softswitch" Integrated Device? Yin Kang believes that this will inevitably lead to the lack of feasible overall system network benefits and objectives of the NGN solution, this makes the thinking and Discussion of NGN confined to the local structure system and category of a single category of devices and related technologies. More seriously, the features and technical features of the "Softswitch" device can only provide very limited "network" concepts and functions, it is likely that the networking mode of NGN and its overall network architecture become unsolved.

According to some materials, many carriers in the United States, including Bell Atlantic, level3, British Telecom, British dadong, German Telecom, and Japanese NTT, have carried out the NGN test and achieved some phased results. Due to the maturity of softswitch itself, most of their tests are limited to the softswitch function, which can provide some simple multimedia services, but most of them are single-domain small-scale networks.

YANG Jing, chief scientist at UT yunkang, believes that the core of NGN should be reflected in cross-network services, rather than opening up business interfaces. He said: "NGN is not so much an exchange network as a service network based on IP infrastructure ." Currently, China Telecom's Softswitch test network technology also requires that both class4 (long-distance link) and class5 (access layer) Implement the softswitch mechanism.
"The soft switch embodies the idea that call control and media transmission are separated through the media control protocol MGCP/h248 technology, the proposal of the concept of a soft switch enables completely transparent compatibility between the voice service function of NGN and the switch function of the traditional PSTN network, and fundamentally ensures that the IP telephone technology can completely replace the switch in the PSTN network, "Yin Kang said," a soft switch is an important part of NGN, but it focuses more on the devices and systems of the Call Control Function in the IP network, it cannot constitute a special overall networking technical mechanism and network architecture. It is of little value to test and explore the networking mode that completely centers around soft switches. It limits that NGN can only be statically configured and interconnected with soft switches, that is, the so-called "no-network mode" of the flat network '."
Using NGN multimedia signaling between vswitches not only guarantees unlimited scalability, but also ensures the dynamic and flexible routing structure. In addition, the goal of "network is vswitch" is realized ."
However, soft switches still require other key technologies and devices to work together to ensure feasible QoS and network security solutions. The soft switch provides various voice services of existing circuit switches, and supports new multimedia endpoint services and a variety of third-party services (including video calls, video teleconference, PC-phone), but the soft switch should not be regarded as a general control platform for data, video services and applications. Therefore, it is the correct method to give full play to the important and key functions of a soft switch by positioning it appropriately in NGN.
What is the status of relevant international organizations?
1) InternationalSoftswitch Consortium, an internationally recognized authoritative international organization specializing in research on the softswitch system. It advocates applying open structures and multi-vendor interoperability to next-generation speech, image, and data solutions. There are eight working groups, including Application, Architecture, Carriers, Device Control, Legal Intercept, Marketing, Session Management, and SIP. As of the end of 2000, there were 195 members. At present, major international equipment manufacturers and operators are involved.

2) ITU-T's work in Softswitch
In order to meet the requirements of the transition from the circuit network to the branch network, the BICC protocol for intercommunication between Softswitch control devices is developed on the basis of ISUP, at the same time, the H.248 protocol for controlling the relationship between Softswitch control devices and MG is completed.

3) IETF's work on Softswitch
IETF formulates the Megaco Protocol Based on the MGCP protocol that describes the control relationship between MGC and MG. To port SS7 signaling to the IP network, SCTP and M3UA are developed. The control protocol SIP is developed for the intercommunication between Softswitch control equipment and data terminal equipment, as well as the SIP BCP-T protocol for intercommunication between Softswitch control equipment.
Ideally, the multimedia softswitch system is built on the same architecture as 3GPP (3rd generation mobile network standard) and uses the Session Initiation Protocol (SIP ). As an emerging Internet standard, SIP can flexibly integrate messaging, services, Multimedia conferences, and real-time communication (such as telephone ). It has been carefully designed and adopts a modular structure. It integrates applications with innovative methods and can be expanded to support new technologies.
Using SIP and Building the architecture on the 3GPP standard has many important advantages.
First, SIP is an ideal choice for the Internet community. The simple text-based format enables application developers to get started quickly (for example, it is easier to use than the binary format H.323 ). This means that SIP can support more applications.

Second, it is built on the 3GPP architecture that supports 3G mobile networks. This allows you to use a platform to provide general multimedia applications for fixed and mobile users.

Third, SIP uses existing protocols that support Web applications (such as email and Web browsers), and H.323 can be used to process these applications more or less. This means that you can easily and smoothly communicate with each other in the SIP environment.

Ericsson believes that SIP is an outstanding protocol for session control over session-based multimedia communication. Compared with the current multimedia service solution, the new multimedia softswitch system can provide multimedia services with higher security and higher quality of service (QoS), and flexible billing.

Open APIs (such as SIP plug-ins and Parlay) have opened up a new market with huge business opportunities for application service providers and third-party application developers. The large-scale application development industry can ensure rapid and cost-effective application development and provide more innovative applications for the market. This will help operators enrich their business products, reduce the loss of customers, attract more users, and increase usage and revenue.
If you have doubts, I always think that the network is a vro. Now, achieving the goal of "Network is a vswitch" is achieved. In reality, the network is always a terminal user. It is transparent to us. In our mind, we are still "not aware of the network! In terms of big trends (to be continued)