International ISDN Packet Switching Capabilities, Applications, and Numbering Plan Considerations

ISDN has moved beyond the trial stages in the U.S., with more than 200,000 lines shipped by AT&T alone. At the same time sales of ISDN lines in many Pacific Rim countries are growing. Therefore the need for ISDN interworking across the Pacific Rim is going to be a customer demand in the near future. CCITT CCS7 standards will enable circuit switched 64Kbs clear transmission in the 1990-91 time-frame. However, the date for ISDN-PSPDN (Packet Switched Public Data Network) interworking remains unclear because of the different numbering plans used for ISDN packet switching and the existing PSPDNs. CCITT has set 1996 for a permanent solution to this interworking issue, which involves the use of the Numbering Plan Indicator (NPI) and Type Of Number (TON) facilities in the X.25 packet.