Along with the fast development of the internet , the main technology used in the communication network is changing from circuit - switched technology to the packet - switched technology , especially to the connectionless ip technology 随着互联网的迅速发展、以网络为中心的计算时代的到来,通信网正在完成从电路交换技术转向分组交换技术,特别是无连接ip技术的战略性转型。
While ss7 deals with non - circuit switched data ( messages are transported without a dedicated circuit established for that purpose ) , the function of the isdn - up ( isup ) is to control the circuit - switched voice or data connection services Ss7是处理非电路交换数据(传输消息时,没有建立用于该目的的专用电路)的,而isdn - up ( isup )则实现控制电路交换语音或数据连接业务的功能。
But in the process they have also lost a degree of control . in circuit - switched environments network managers always knew exactly what paths , or routes , their network traffic would take - because they set up those fixed paths themselves 在电路交换的环境中,网络管理人员总是很准确地知道其网络话务将由哪一条路径或哪一条路由负载,因为这些固定的路径是由他们自己建立的。
In recent years , the rapid development of the computer networks has brought the enormous change for the global development of various fields . among them , multimedia communications technology which based on ip network offers a convenient and low - priced way to shorten the distance among the people , and gives an end to traditional circuit - switched communication 近年来,计算机网络的迅速发展给全球各个领域的发展都带来了巨大的变化,其中基于ip网络的多媒体通讯技术为人们的远距离交流提供了一个既方便又廉价的途径,结束了传统电信领域中电路交换一统天下的局面。
However , compared with developed nations , we still have large room for development in voice service . thus , it is of realistic significance for us to transform the legacy switches by replacing the 2 mbits trunk interfaces with stm - 1 trunk interfaces ( 155 mbits ) in the legacy circuit - switched switches 17亿门,但比起发达国家的水平,我国的话音业务仍然有很大的发展空间。因此对传统交换机的改造仍具有现实意义。在传统的电路交换机中用stm - 1 ( 155mbits )中继接口取代2mbits中继接口,意义重大。
The limited number of sites and unattractive charges are problems arose in the process of operators and icps deploying the service and the restrictions on the terminals mostly refer to the small - sized displays of the handsets and the inconvenience of entering characters through the keyboard , which are manufacturers problems . as to slow connectivity , it seems to be the weakness of wap . however , the fact is that there is a limit of 9600 bits on the circuit - switched data services provided by the gsm network and this is the very bearer mode that is currently selected by wap established on the network layer . this only means that people do not accept wap over csd 站点少、资费并不具吸引力等缺点是运营商与icp在对该业务推广的过程中所显现的问题;来自于终端的限制则是手机制造商的问题,虽然各大厂商都推出了支持wap的手机,但用户的批评大都集中在手机屏幕太小及输入不方便;至于连接速度慢,这似乎是wap本身的缺陷,但事实是gsm网络所能提供的基于电路交换的数据业务存在9600bits的限制,而建立在网络层之上的wap目前选择的恰恰是这种承载方式,因此只能说wapovercsd这种业务提供模式人们不能接受。
The 3g mobile communications system took into account the support to packet - switched data service from the stage of establishing standards . however , gsm as the 2g mobile network began to develop in order to support voice service and circuit - switched data service . the growing demand for packet data service has required the gsm network to add the corresponding functions 第三代移动通信系统( 3g )从标准制订开始就考虑到对分组数据业务的支持,而gsm作为第二代移动通信系统( 2g )的网络,主要是为支持话音业务和电路交换方式的数据业务而发展起来的,随着对分组数据业务需求的增大,要求gsm网络增加相应的功能。