http://www.rfc-editor.org/rfc/rfc2458.txt
RFC 2458: Toward the PSTN/Internet Inter-Networking--Pre-PINT Implementations, H. Lu, M. Krishnaswamy, L. Conroy, S. Bellovin, F. Burg, A. DeSimone, K. Tewani, P. Davidson, H. Schulzrinne, K. Vishwanathan1998-11-01T23:00:00-00:00This document contains the information relevant to the development of the inter-networking interfaces underway in the Public Switched Telephone Network (PSTN)/Internet Inter-Networking (PINT) Working Group. This memo provides information for the Internet community.