Numbering, Routing, and Networks
Roger L. Freeman · 2002
Abstract Nearly every telephone subscriber in the world can access every other subscriber. Such calls are routed over a vast international network based on direct/high‐usage routing and, in some cases, third country transit exchanges, connecting one or more international switching centers (ISCs) in each country. Each nation has its own national network that is a functional part of the international network. This chapter provides design data and standards material on those networks. A telephone call is routed to its destination over the network [variably called the PSTN or public switched telecommunications (telephone) network] based on the telephone number provided by the calling subscriber. Thus, the first section of the chapter deals with numbering, the ITU‐T world numbering plan, and the North American plan. There is a brief section on international routing. This is followed by a section on the North American network and routing. Digital network management and quality of service (QoS) are briefly discussed.