Precautions for Softswitch networking (1)

This article first analyzes the causes of the Softswitch technology, then briefly introduces the Softswitch technology, and proposes the application of the softswitch network for the services currently provided by the softswitch device. Finally, the problems that should be paid attention to in the Technical Group network using Softswitch are analyzed.

Background of Softswitch Technology

Human Communication includes voice, data, video and audio multimedia. For a long time, the above three types of communication services are carried and dredged by different communication networks. The telephone network carries 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. What people need is the ability to obtain the required information anytime, 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 business network-that is, a network that can simultaneously carry and clear voice, data, and multimedia services" can we meet the increasing needs of users for communication services.

The telephone network has a long history. Its core is a telephone switch. The telephone switch has undergone 5 stages of development, namely, magnetic stone, shared battery, step-by-step, horizontal and horizontal, and process control, the difference is that the implementation of vswitches has changed. The emergence of the telephone switch 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, it adopts an exclusive circuit switching mode, 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 bursts of data 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, since the IP network has simple protocols, low terminal device prices, and the development of WWW services based on the IP protocol, the IP-based Internet has exploded and became synonymous with the data network. The IP network requires the user terminal to encapsulate all user data in the IP package. The core device of the IP network-the router is only a simple task of "best effort" for IP packet forwarding, 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 the IP packet transmitted in the IP network can carry any user data information, which creates conditions for the transmission of voice, data, multimedia streams, and other information in one bearer network.

It can be seen that both the telephone network and the data network have some inherent defects and cannot be simply transformed into a "full-service network". 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 introduced.

Core transfer layer

The core transport layer is actually the Bearer Network of the softswitch network, its function is 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.

In view of the fact that the IP network can carry multiple types of media information such as voice, data, and video at the same time, it also has the advantages of simple protocols, good protocol support for terminal devices, and low price, therefore, the softswitch network selects the IP network as the bearer network.

In the softswitch network, various network elements encapsulate various control information and business data information in IP data packets and communicate with each other through the IP network at the core transport layer.

Protocols and standards in Softswitch networks

In a softswitch network, network elements of the same layer communicate with each other through standard protocols defined by the Softswitch technology. International organizations engaged in the establishment of softswitch standards mainly include IETF and ITU-T. They contributed to the softswitch network protocol from the standpoint of the computer and telecom respectively.
1. protocols between media gateway 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. It is not as flexible and scalable as MEGACO/H.248. It is also inferior to MEGACO/H.248 in terms of support for multiple carriers.

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 is called the media gateway control protocol, which features simple protocols, powerful functions, and good scalability.

The SG and the vswitch adopt the SIGTRAN protocol. The lower layer of the SIGTRAN uses the SCTP protocol to provide reliable connections for the No. 7 signaling to be transmitted over the TCP/IP network. The higher layers include M2PA, M2UA, and M3UA. M3UA is widely used because of its great flexibility. The basic function of the SIGTRAN/SCTP protocol is to transparently transmit TDM-based signaling on the PSTN to the soft switch through SG using the IP network as the bearer, and the soft switch completes the processing of the signaling on the 7.

2. protocols between vswitches

When media gateways controlled by different soft switches need to communicate with each other, the related soft switches need to communicate with each other. The protocol between soft switches and soft switches includes BICC protocol and SIP-T protocol.

BICC protocol is a standard protocol recommended by ITU-T. It is mainly to encapsulate the ISUP protocol in the original No. 7 signaling, and the support for multimedia data services is insufficient. SIP-T is a standard protocol recommended by IETF, which is mainly to expand the original SIP protocol, belongs to an application layer protocol, using the Client-Serve structure, the multimedia data business support is good, easy to add new businesses, while SIP-T has simple and flexible, easy to achieve, good scalability characteristics. Currently, BICC and SIP protocols are widely used internationally.