First, the origin
The concept of soft exchange originated from the US enterprise network application. In a corporate network environment, users can use Ethernet-based calls, and then implement PBX function (IP PBX) through a set of PC servers, Call Manager, Call Server. For such a set of equipment, the system does not need to be laid separately, and through the sharing of management and maintenance through the sharing of local area network, the integrated cost is much lower than the traditional PBX. Since the enterprise network environment is highly reliable, billing and management requirements are not high, it is mainly used to meet communication needs, and the equipment threshold is low. Many device companies can provide such solutions, so IP PBX applications have achieved great success. Traditional circuit swap equipment is mainly provided by a few equipment vendors, and the price is generally hundreds of thousands to millions of dollars, and the version upgrade may spend a few months and hundreds of thousands of dollars. Network integrated operation cost is very high. Operators are very hoped to seek an alternative product and technology. Enconsprected by IP PBX, the industry puts forward the idea: the traditional exchange equipment components are divided into call control and media processing, and the standard protocol (MGCP, H248) is used between the two, and the call control is actually running. In the generic hardware platform, media processing converts TDM to IP-based media streams. So, SoftSwitch (soft exchange) technology came into being, because this system has the characteristics of strong telescopic, interface standards, business openness, etc., the development is extremely rapid.
Second, what is soft exchange
The basic meaning of soft exchange is to separate the call control function from the media gateway (transport layer). Basic call control functions are implemented by software, including call selection, management control, connection control (establishment / demolition session) and signaling intercom. Thus, the separation of call transmission and call control is achieved, and separate planes are established for control, switching, and software programmable functions. Softswitch mainly provides functions such as connection control, translation, and selection, gateway management, call control, bandwidth management, signaling, security, and call detailed record. At the same time, softswitch also encapsulate network resources and network capabilities, which can easily provide new services on the network through standard open business interfaces and business application layers.
Soft switching is located in the network control layer, through the call related information in the interaction of the media layer gateway, the call related information in the reception process, indicating the gateway to complete the call. Its main task is to establish a relationship between points, which may be a simple call or a more complex process. Soft switching technology is mainly used to deal with real-time business, such as voice services, video services, multimedia services, etc., and some basic supplementary services are provided, which is very similar to traditional exchange call control and basic business.
Once the soft exchange concept, it quickly got a wide range of identity and attention. The establishment of ISC (International SoftSwitch Consortium has concluded the development of softswitch technology, soft exchange related standards and protocols have been IETF, ITU-T, etc. The attention of international standardization organizations. After several years of development, soft exchange technology has made great progress in standardization and industrialization, and some agreements such as H.323, MGCP, etc., new agreements such as BICC, SIP / SIP-T continue to launch, some softswitch technology The product is gradually moving toward the practical phase, making softswitch into the topic of NGN's most active and popular.
Third, the meaning of introducing soft exchange
1. What is the soft exchange to the user? Softswate can implement cross-domain control, can control and manage the access levels, and provide voice, data, and video services for users, and other fusion services. As the development trend of communication networks has gradually become focused focus from the transformation of technology drivers to business drivers. Soft exchange provides an open service interface Open API to ISV (Independent Software Developer), ISP, ICP, ASP (Application Business Provider), and ISV / ISP / ICP / ASP often more familiar with end users more than soft exchange providers. Demand, therefore the business provided by the ASP / ISP / ICP is closer to the user, close to life. In addition, a large number of ASP / ISP / ICP participates in the results of competition, speeding up the rhythm of diverse, advanced, economic and practical business. 2, what is the soft exchange to the business? As the NGN core component, soft exchange can be developed independently, production and procurement, its development cost, production cost, and procurement costs are relatively low, thereby reducing the investment of operators. The appearance of soft exchanges can enable the three network to realize network interconnection between the network level, realize the penetration and crossing of the business level, so that a variety of business based on the unified grouping network becomes possible. Operators can end the situation of the three networks, through a fused network to provide voice, data and multimedia business, and implement the ITU's "telecommunications network, computer network and TV network and other network resources). Seamless fusion constitutes a high efficiency network with unified access and application interfaces, enabling humans at any time and place, with an acceptable cost and quality, safe enjoyment of various ways aims. For data networks, network foams have led to excessive investment, with redundancy, while soft exchange technology can quickly deploy NGN businesses, while softswitch Open API can provide operators with powerful business generation capabilities. . Fourth, soft exchange technology reference model
Figure 1 is a softswitch reference model recommended by the ISC, which involves five planes such as transmission plane, control plane, application plane, data plane, and management planes. The transmission plane is in the bottom, responsible for the transmission of specific bearing data such as speech and video, including switching functions, logical port functions, adaptable functions, physical signaling functions, etc., the reference points related to the transfer plane are A, B, C. Among them: A is the signaling channel, using the IETF IPS7 protocol; the B reference point is between the logical port function and the device control function, using the protocols such as MGCP, Megaco, IPDC, Q.931; C-reference adopts vsi, GSMP and other protocols. The transmission plane and the external interface 1 use TDM channels or packet links, including band signaling.
Figure 1 Soft exchange reference model (click to enlarge)
The control plane is in the second layer, providing control functions, such as signaling processing, carrying connection control, device control, call leg (LEG) control, gatekeeper, and proxy signaling. Where: reference point D is located between signaling processing functions and database functions, using TCAP signaling; reference point E between signaling processing functions and session control functions, using TCAP signaling, used for transmission, business logic of IN request Transfer of messages such as calls for calls; reference points F1, F2 use call control API and carrier connection control API, such as TAPI, JTAPI, etc. Control plane and the outside interface 2 use protocols and signaling such as H.323 (H.225 / H.245), SIP, TCAP (TCAP / SCCP / M3UA / SCTP / IP). The upper application plane provides services and application control functions, including session control, business logic, translation, routing and policies. Where: h reference points are between session control functions and business logic functions, using Jain, Parlay and other public APIs; G-reference points and I reference points adopt TCAP, LDAP and other protocols; J reference points have not been defined. Application plane and the outside interface 3 uses H.323 (H.225), SIP, JCAT and other protocols. Data planes provide database functions, such as billing services, specific features, reference points, and interfaces still to be studied. Management plane provides management capabilities, including management of network operations / control, network authentication, network maintenance, and network entities, and management interfaces use protocols such as SNMPv2, CMIP. V. Function Description of Soft Switch
Softswate is a collection of multiple logical functional entities, providing call control, connection, and partial business features of integrated services, is the next generation of telecommunications network voice / data / video service call, control, and service providing core devices. The main design ideas of soft exchange technology are connected and communicated between business, control, transmission, access separation, and entities, through standard protocols, and focus on the function of softswitch:
1, call control and processing
Provide control functions for basic calls, maintenance, and release, including call processing, connection control, intelligent call trigger checkout, resource control, etc., receive monitoring requests from service exchange functions, and process the events related to the call, receive Call control related information from service exchange, supports the establishment and monitoring of calls; support two or more call control functions, providing multi-party call control functions, including multi-party call special logic relationship, calling members, exit, isolation, side listening, and mix Sound control, etc.; the user pick, dial, and hang up the media gateway report, control the media gateway to send audio signals to the user, such as dial tone, ringing tone, ringing tone, etc., meet the operator's dial plan.
2. Soft exchange of protocols is an open and multi-protocol entity that communicates with various media gateways, terminals, and networks using standard protocols, including H.248, SCTP, ISUP, TUP, INAP, H.323, RADIUS, SNMP. , SIP, M3UA, MGCP, BICC, PRI, BRI, etc.
3, business
Provide PSTN / ISDN switch service, including basic business and supplementary services; with existing smart networks, providing existing intelligent networks can provide with a third party, providing a variety of value-added services and intelligence services.
4. Business Exchange Service Exchange is combined with call control functions, providing a set of functions required to communicate between call control functions and service control (SCF).
5, interworking
The interoperability of the package network and the existing seven signaling network can be implemented by signaling gateways; multi-intelligent services can be provided through signaling gateways and existing intelligent networks; allowing SCF to control VoIP calls, and operate call information ( Number display, etc.); can achieve interworking with the IP telephone network with the existing H.323 system, can be implemented by interworking module, using the SIP protocol to implement interoperability with the SIP network system; mutual communication with other softswitch Even, use SIP, BICC protocol; available interoperability between the IP network H.248 terminal, the SIP terminal, and the MGCP terminal. 6. Resource management provides resource management functions, centralized management, such as resource allocation, release, and control. 7. The billing function has the functions of collecting detailed bills and complex, which can be transferred to the billing center according to the operational needs. For billing card billing business, there is real-time disconnection function. 8. Certification / Authorization Softswitch and Certification Center Connection, you can send users, media gateway information within the jurisdiction to the certification center, certification and authorization to prevent illegal users or equipment access. 9, address parsing completes E.164 address to the IP address, alias address to the IP address conversion, while the redirection is completed. 10. Voice handling soft exchange control media gateway can select a voice compression algorithm, including G.729, G.723, etc .; soft exchange provides a voice block buffer to the media gateway to reduce jitter's impact on voice quality.
Six, soft exchange of external interface
The interface between soft exchange and the media gateway is used to soft exchange to the carrier control, resource control / management, and the media gateway control protocol (mgcp), the Internet device control protocol (IPDC), the Internet Device Control Protocol (IPDC), SIP Protocol, H.323 and H.248 protocol. The interface between soft exchange and signaling gateway is used to pass signaling information between softswitch and signaling network, which can use Signaling Control Transfer Protocol (SCTP) or other similar protocols. The interface between soft exchanges achieves interaction between different soft exchanges, which can be used with SIP-T, H.323 or BICC protocol. The interface between soft exchange and application / business layers provides access to various databases, triplicate application platforms, functional servers, and implement support for value-added services, management services, and triplicate applications. Among them: The interface between soft exchange and application servers can use SIP, API, such as PARLAY, providing support for tripartite application and value-added services; soft exchange and policy server intervening network equipment work, can adopt a COPS protocol; The interface between soft exchanges and gateway enables network management, using SNMP; the interface between soft exchange and intelligent network SCP implements support for existing intelligent network services, using the INAP protocol.
Seven, conclude
The next network is a business-driven network, providing business open capabilities with SoftSwitch as the core, in line with the trend of fixed network and mobile network integration, providing voice, data, video services, and multimedia integration services to meet communication personalization, mobility And obtain the development goals of information anytime, anywhere.
