The migration of the traditional Time Division Multiplexed (TDM) telephony networks to a packet-based network for carrying voice is moving out of the early adopters phase into the mainstream production phase. All aspects of the telephony infrastructure from the telephone on the desktop to the Central Office switches that route millions of calls a day are being effected. Since this transition will take many years, there is a need for gateways that interface between the traditional telephone equipment and the packet networks. Voice over IP is rapidly becoming the protocol of choice in this transition because of its ubiquity and the rapid evolution of the Internet.

This paper will examine two key issues in effectively realizing Voice over IP gateway systems that are used in a wide variety of applications: scalability and flexibility.