Design and Implementation of A PSTN/Internet Gateway for Internet Telephony

Abstract

In recent years, the Internet has emerged as an important collaborative platform, Many applications utilize the Internet to provide new kinds of services. Among others, Internet telephony is attracting and increasing amount of attention for the reason that it has the potential to significantly reduce the cost of long distance voice communication. Moreover, Internet telephony gateways, or PSTN/Internet gateways, extend the cost saving benefits of Internet telephony to any one with phone connected to the PSTN. In view of this trend, it is very important to construct a PSTN/Internet gateway for further experiments and developments. In this paper, we explore several methodologies for the implementation of a PSTN/Internet gateway. Based on these methodologies, we devise the corresponding architecture and implement a PSTN/Internet gateway. Following the ITU H.323 Recommendation, the gateway built is interoperable with other H.323 compatible terminals. We have validated the gateway built by having fluent two-way communication between a PSTN phone and a Microsoft NetMeeting terminal in our laboratory. A performance study on the sensitivity of the buffer size has also been conducted. It is noted that the gateway we devised is very versatile and con be easily extended to support various applications.