1 Introduction

The Point-to-Point Protocol (PPP), as specified in [RFC1661], provides a standard method for transporting multi-protocol datagram over point-to-point links. The point-to-point links mentioned here refer to the medium between two points (or parties) that can communicate using the medium. The medium could be dial-up media like Public Switched Telephone Network (PSTN) and Integrated Services Digital Network (ISDN).

The Callback Control Protocol (CBCP) defines an interoperable method for negotiating dial-up callbacks over point-to-point links in a secure and flexible manner. The callback negotiation in dial-up links is specifically useful for saving on toll charges.

Sections 1.5, 1.8, 1.9, 2, and 3 of this specification are normative. All other sections and examples in this specification are informative.