1.3 Overview

Users often use a dial-up connection, such as a modem or Integrated Services Digital Network (ISDN), to access resources on the Internet or on a corporate network. The Internet service providers (ISPs) that provide Internet access or the administrators of a corporate network can provide several local access numbers in the geographic areas where they provide service so that users need not pay long-distance charges. These geographic locations with their local access numbers are called points of presence (POPs).

The POPs of an ISP or corporate network can change over time and, when they change, the most current POP information has to be published to users in a reliable and cost-effective manner. The Connection Point Services (CPS) phonebook file data structure specifies a format for documenting POP entry information.

Because there can be multiple POP entries in a geographic location or area, and to supply multiple connection options to users, the CPS phonebook file provides a logical grouping of POPs information based on the geographic location or area. For example, an ISDN number that provides higher bandwidth for users who have an ISDN connection may be included. In this document, geographic locations or areas are called regions. Each POP has the information about the region it serves. The list of regions is stored in a separate file known as a region file.

The dial-up networking (DUN) client allows the user to select the POP entry of their choice and connect to the network. For example, users can select one local POP entry when they are in India and use another local POP entry if they visit the United States.