Analysis of softswitch network protocols

In the continuous learning of vswitches, we know that the important role of vswitches cannot be replaced. One type is SoftSwitch. For Softswitch, we will not go into details here. We will mainly explain about the softswitch network agreement and standards in the switch. human communication includes three multimedia contents: voice, data, video and audio, the above three types of communication services are carried and dredged by different communication networks respectively. Telephone networks carry and dredge voice services, data networks carry and clear data services, and multimedia networks carry and clear multimedia services ｡

With the further deepening of social informatization, communication has become an indispensable tool for people's life and work, people's requirements for communication are no longer just basic voice communication services and simple WWW browsing and sending and receiving E-mail, people need to be able to obtain the required information at any time, anywhere, and flexibly. Therefore, telecom operators are required to provide users with a wide range of telecommunication services flexibly, however, the operation modes based on different communication networks that provide different services are difficult to meet users' demands for "flexible access to required information, only by building a "full-service network-that is, a network capable of simultaneously carrying and dredging voice, data, and multimedia services" Can users meet their increasing needs for communication services ｡

The telephone network has a long history. Its core is a telephone switch. The telephone switch has gone through 5 stages of development, including magnet, shared battery, step-by-step, vertical and horizontal, and process control, the difference is that the implementation of vswitches has changed. The emergence of remote control telephone switches is a historic change. It adopts an advanced architecture, its functions can be divided into three parts: call service access, route selection (switch), and call service control, the switching and call business control functions are mainly implemented through program software. However, they adopt an exclusive Circuit Switching Mode for resources, and the peer-to-peer bidirectional 64 kbit/s fixed bandwidth channel provided for both parties of the communication is not suitable for data services with large burst data volumes and large differences in upstream and downstream data traffic ｡

The wide area network (WAN) protocol can be divided into DDN, X.25, frame relay, and IP network, because the IP network has simple protocols, low terminal device prices, and the development of WWW services based on the IP protocol, the Internet based on the IP protocol is booming, once became synonymous with the data network, the IP network requires the user terminal to encapsulate all user data in the IP packet, the core device of the IP network-the router is only a simple task of "best effort" to forward IP packets, it uses the packet exchange mode of resource sharing and dynamically occupies the upstream and downstream transmission channels according to the business volume needs. Therefore, the IP network is actually only a data transmission network, and it does not provide any high-level service control function, if the voice service is enabled on the IP network, additional phone service control devices must be added. It is worth mentioning that IP packets transmitted in the IP network can carry any user data information, it creates conditions for transmission of voice, data, multimedia streams, and other information in a bearer network, both the telephone network and the data network have some inherent defects and cannot be transformed into a "full-service network" through simple transformation. Therefore, to enable Simultaneous Delivery of voice, data, and multimedia services on the same network, that is, the convergence of communication services, softswitch technology is developed ｡

Core transfer layer

The core transport layer is actually the Bearer Network of the softswitch network, its function and function are to connect various softswitch network elements, such as various media gateways in the edge access layer, soft switches in the control layer, and various server platforms in the business application layer ､ data, video, and other media information, at the same time, it has the advantages of simple protocols, good support for protocols by terminal devices, and low costs, therefore, the softswitch network uses the IP network as the bearer network. In the softswitch network, various network elements encapsulate various control information and service data information in IP data packets and communicate with each other through the IP network of the core transport layer ｡

Softswitch Network Agreement and standards

In Softswitch networks, network elements at the same layer and network elements at different layers communicate through standard protocols defined by Softswitch technology. International organizations engaged in softswitch standards are mainly IETF and ITU-T. starting from the standpoint of the computer and telecom respectively, it has contributed to the softswitch protocol ｡

Protocols between media gateways and vswitches

The protocols between media gateways and vswitches except SG are MGCP and MEGACO/H.248. MGCP is a version earlier than MEGACO/H.248, its flexibility and scalability are not comparable to MEGACO/H.248, and its support for multiple carriers is not as good as MEGACO/H.248 ｡

MEGACO/H.248 is actually the name of the same Protocol, jointly developed by IETF and ITU, IETF called MEGACO, ITU-T called H.248. MEGACO/H.248 called Media Gateway Control Protocol, it has simple protocol, powerful functions and excellent scalability. The SIGTRAN protocol is used between SG and the soft switch, and SCTP protocol is used at the lower layer of SIGTRAN to provide reliable connections for the No. 7 signaling to be transmitted over TCP/IP networks; the high-level layers include M2PA, M2UA, and M3UA, therefore, it is widely used at present. The fundamental function of SIGTRAN/SCTP protocol is to transmit TDM-based signaling in the PSTN to a soft switch through SG using the IP network as the bearer, the soft switch completes the handling of the No. 7 signaling ｡

Protocols between vswitches

One of the situations in the softswitch network protocol is that when the media gateways controlled by different soft switches need to communicate, the related soft switches need to communicate, BICC protocol is a standard protocol recommended by SIP-T, which is mainly to encapsulate the ISUP protocol in the original signaling 7, SIP-T is a standard protocol recommended by IETF, which is mainly used to expand the original SIP protocol. It belongs to an application layer protocol and adopts the Client-Serve structure, the support for multimedia data services is good, it is easy to add new businesses, and the SIP-T is simple and flexible, easy to achieve, good scalability. At present, BICC and SIP protocol has a lot of international applications ｡