Creating value added services in Internet telephony: an overview and a case study on a high-level service creation environment

摘要

Value added services, or more simply - services, are the critical ingredient for the success and the survival of Internet Telephony. Services can be defined as anything that goes beyond two party voice calls. Some examples are multiparty gaming, customized stock quotes and call screening. This paper focuses on service creation in Internet Telephony. Service creation plays a major role in Internet Telephony because it enables openness and programmability by offering frameworks for the development of value added services. Two principal sets of standards have emerged for Internet Telephony: H.323 from the ITU-T and SIP from the IETF. No service creation framework comes with the H.323 set. Two frameworks come with the SIP set: the Call Processing Language (CPL) and the SIP common gateway interface (CGI). Besides the IETF, other forums such as Parlay and JAIN have proposed pertinent frameworks. The first part of the paper provides an overview of the service creation frameworks for Internet Telephony. A common characteristic of these frameworks is that they require knowledge that nonexperts may not have (e.g., scripts, programming languages). High-level service creation environments may help these nonexperts. The second part of the paper presents a case study on a high level service creation environment (SCE) where pre-defined graphical components are combined into services. The environment is discussed in detail along with the service logic execution environment (SLEE) where the services are executed. The SCE and SLEE make no assumption on the service creation framework supported by the network, and any of the standard frameworks could be used provided it offers the functionality abstracted in the graphical components. We have used the Parlay APIs as a framework and the prototype is built for a SIP environment. The prototype is described and the lessons we have learned are presented.