On Building an Internet Gateway for Internet Telephony

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 an increasing amount of attention for the reason that it has the potential to significantly reduce the cost of long distance voice communication. 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 also validate the gateway built by having fluent two-way communication between a PSTN phone and an H.323 terminal. A performance study on the sensitivity of the buffer size is also conducted. It is noted that the gateway devised is very versatile and can be easily extended to support various applications.