Users often use a dial-up connection, such as a modem or Integrated Services Digital Network (ISDN), to access the Internet or a corporate network in order to use resources on these networks. The Internet service providers (ISPs) that provide Internet access or the administrators of a corporate network may 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 may change over time and, when they change, the most current POP information must be published to users in a reliable and cost-effective manner. The Connection Point Services (CPS) phonebook file specifies a format for documenting POP entry information.
Because there may be multiple POP entries in a geographic location or area, in order to supply multiple connection options to users (for example, an ISDN number that provides higher bandwidth for users who have an ISDN connection), the CPS phonebook file also provides a logical grouping of POPs information based on the geographic location or area. (In this document, geographic locations or areas are called regions.) Each POP has the information about the region it serves, and 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 may select one local POP entry when they are in India and use another local POP entry if they visit the United States.
Sections 1.7 and 2 of this specification are normative and can contain the terms MAY, SHOULD, MUST, MUST NOT, and SHOULD NOT as defined in RFC 2119. All other sections and examples in this specification are informative.