Abstract

Internet telephony — voice transmission and call signalling over IP networks — can pro-vide services far beyond those of the circuit-switched telephone network. This thesis discusses Internet telephony services in four broad areas: user-location services; multi-party conferenc-ing; the interworking of Internet telephony and mobile telephony; and Internet telephony feature interaction. User-location services are services which modify how a telephony server locates a user. Service authors need a way to control this process; this thesis presents two of them. The SIP Common Gateway Interface (SIP CGI) is a low-level server interface which allows fine-grained control of message processing in Session Initiation Protocol (SIP) servers. The Call Processing Language (CPL) is a protocol-independent, inherently safe high-level language for describing services in a way that is easily created and edited. The thesis also describes a general service framework providing a straightforward and powerful API atop which these and other service execution environments can be implemented, and an event thread architecture that makes imple-mentation of transaction-based protocols such as SIP efficient and scalable. Multi-party conferencing involves calls in which three or more people communicate si-

Citations