Internet Protocol (IP)-based networks were recognized by the Plenipotentiary Conference of Minneapolis, 1998, in its Resolution 101, as an issue of crucial importance to the future, as an important engine for growth in the world economy in the twenty-first century, stressing the need to identify the implications of the development of such networks in ITU Member States, and this to include interoperability issues between IP-based networks and other telecommunication networks as well as how to provide the quality of service required by the users. Data traffic is growing rapidly compared to voice traffic and consequently, the past concept of telephone networks that also carry data might be replaced (when and how?) by the concept of data networks that also carry voice. By Decision 498, the 2000 session of the ITU Council decided to convene the third World Telecommunication Policy Forum (WTPF-01) in Geneva, from 7 to 9 March 2001, in order to discuss and exchange views on the theme of Internet Protocol (IP) Telephony. Having in mind the "IP telephony" challenges in developing countries, Opinion D was adopted by the Forum. Opinion D was supposed to answer many challenges and issues facing developing countries, in particular those facing many public (or privately dominant) telecommunication operators when "IP telephony" is introduced, such as: – its impact on their revenue streams, resulting from lower-priced "IP telephony" tariffs compared with their PSTN tariff schemes – how not to place any additional requirements on PSTN networks when interconnected to IP based networks – how to meet the performance metrics, and traffic identifications when IP-based networks interwork with PSTN – how to generate the necessary funds to invest in IP-based networks – how to deal with numbering and addressing issues The conclusions and main issues on "IP telephony" derived from this report represents the answers to many of these challenges as well as the answers to the tasks enumerated in Part 3 of Opinion D.