ISDN有很多服务提供商和交换类型-CCNA中文版PPT下载

ISDN有很多服务提供商和交换类型 服务类型根据国家和地区不一样 ISDN 交换类型 CO CO S S S S S S S S S S S S S * Purpose: The figure introduces an overview of ISDN switches. Emphasize: The figure shows two representations of the ISDN world. In the top image, the cloud represents the providers by using different colors for the various switches they use. An example of switch diversity occurs in Western Europe where all PTTs now offer ISDN. Despite efforts to adopt a common Euro-ISDN standard, switches in one nation may not easily interoperate with switches in another nation, Early adopters of ISDN, such as France, face major equipment upgrade efforts before they fully accommodate the European Telecommunication Standards Institute (ETSI) specifications. For the administrator, a key requirement is to configure for compatibility with the switch on the ISDN local loop—the end-user ISDN device connected to the ISDN switch in the provider’s central office. The lower image shows the globe and continental geographic representations to indicated the worldwide scope of ISDN standards-based networks. The bullet cautions that services and prices vary. ISDN coverage is not as seamless as it might appear on paper. Note: Switch variations complicating ISDN switch configuration occur because of the different approaches used by ISDN providers at the network-layer functions between the terminal and the switch. Q.931 is the most prevalent protocol used for this network-layer function.