Integration of Circuit Switching Technology and group Switching Technology

Source: Internet
Author: User

1. Integrated switch technology 

Although the ATM technology does not enable people to achieve the dream of "integrated business", people have been looking for a way to provide various services on a single network, telecom operators also hope to make full use of existing network resources to provide users with a wide range of services. The first technology proposed is the integrated switch technology. It is mainly through the transformation of the existing circuit switching network to support both circuit switching and broadband switching, including ATM switching and IP switching. Many manufacturers have also developed integrated switches, and the related industry standard comprehensive switch technical specifications has been formulated and promulgated. A comprehensive switch provides the functionality of a narrowband switch and a broadband switch. The current integrated vswitch can be implemented in two ways: one is to use a hybrid switching node, and multiple independent switching matrices are configured inside the vswitch, that is, the circuit switching matrix, the ATM and IP group switching modules. The traditional PSTN calls are mainly handled by the Circuit Switching Module, And the broadband-related services are handled by the broadband group processing module, protocol conversion is required when two modules need to interact with each other. The other is to use a converged switching node. The integrated switch has only one single ATM or IP address switching matrix, for example, Shanghai Bell's broadband switch S12 P3S directly uses the ATM technology as the core exchange technology, and all media information is converted into ATM cells for processing inside the switch, circuit Switching Network, ATM network, and IP network are also supported. Because the integrated switch has been changed to a unified exchange platform internally, it has great advantages in flexible and fast business deployment. Because of the various functions, the cost of the integrated switch is also relatively high. It is mainly used in customs bureaus and end Bureaus with a large business volume and is not suitable for implementation across the network.

2. IP phone technology

The integrated switch mainly adopts the transformation of Circuit switches to support group switching. In the process of exploring the integration of Circuit Switching Technology and group switching technology, at the same time, people also hope to use a group network to send voice services. In the emergence of Web applications, Internet networks have developed at an astonishing speed and eventually become a global network, people use the Internet to get various services. The Internet network is based on IP technology and is a group exchange technology. It uses the best effort to transmit and select routes for each group based on the routing information and network conditions. Internet networks are mainly used to transmit data services. With the great success of the Internet, IP technology has become the pillar Technology of future information networks, TCP/IP-based network technology is not only the dominant technology for data transmission, but also the traditional telecom operators are trying to use IP technology to send voice services. Currently, traditional telecom operators generally set up their own IP networks. In addition to providing data services with relatively low profits on IP networks, operators hope to make full use of existing resources to provide users with a wide range of services, most of which are voice services. Currently, voice services are still the most important sources of revenue in operation, the first application of the group-based online speech delivery service was the IP phone technology.

Currently, IP telephone technology has become a familiar service, mainly using H.323 series protocols, including the signaling protocol H.225 for call establishment and the H.245 protocol for media channel establishment, voice services are transmitted in the IP network using RTP grouping. Although the voice quality of IP phones is not as high as that of traditional circuit exchange networks, however, the H.323 protocol is widely recognized as the most mature protocol that supports voice, image, and data services on the group network. It is widely used in the IP Phone field. Many VoIP networks created using the H.323 protocol are operating in the world. But some shortcomings of H.323 are also obvious. First, the call control signaling in the H.323 protocol is based on Q.931. The Q.931 protocol is a UNI-based protocol. It is simple and has no NNI interface definition. There is no problem in implementing computer-to-computer calls within a dedicated network, but NNI interfaces must be required to provide nationwide services and PSTN-to-PSTN connections. Secondly, a centralized gateway is used in the H.323 network. The gateway must simultaneously process media streams and signaling streams, which also limits the development of the H.323 network in terms of processing capabilities. At present, ITU-T draws on the experience of IETF related norms to further expand and revise the H.323 series protocol. In addition, compared with SIP, the H.323 protocol has poor scalability. In order to provide services similar to those provided to users on the circuit switching network in the H.323 network, many manufacturers have extended the H.323 protocol, therefore, the interconnection between H.323 devices from different manufacturers is also an important issue facing the development of the H.323 network.

However, the successful application of IP phones and a considerable market share make people see the dawn of business integration, and people gradually know that voice services can be transferred on the group network, and can achieve better communication performance. In addition, group exchange has many potential performance advantages. One advantage is the efficient use of the communication capabilities of transmission channels, especially for burst transmission. Although the burstable voice data is not as prominent as interactive data, it is still abrupt in the form of emergency/mute. The average duration of a burst is determined by the mute detector used. In typical phone conversations, a single voice source is active for only about 35-45% of the time. Another advantage is statistical reuse. In this way, call congestion requires an average bandwidth, rather than a function of peak bandwidth. Therefore, it can be more flexible in Transmission Control and billing. Thanks to these advantages, Internet voice applications, especially IP phones, have become one of the most striking applications in the "three-in-one" tide.

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