This document defines the Call Processing Language (CPL), a language to describe and control Internet telephony services. It is designed to be implementable on either network servers or user agents. It is meant to be simple, extensible, easily edited by graphical clients, and independent of operating system or signalling protocol. It is suitable for running on a server where users may not be allowed to execute arbitrary programs, as it has no variables, loops, or ability to run external programs.Lennox, et al.

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A large number of the services we wish to make possible for Internet telephony require fairly elaborate combinations of signalling operations, often in network devices, to complete. We want a simple and standardized way to create such services to make them easier to implement and deploy. This document describes an architectural framework for such a mechanism, which we call a call processing language. It also outlines requirements for such a language.

Many approaches and topologies -including multicast and media mixing -have been proposed for distributed Internet conferencing. While existing solutions can work well for large or pre-arranged conferences, they can be less appropriate for smaller, impromptu ones. We present an alternative, full mesh conferencing, which allows any number of parties to communicate in a conference without a central point of control. The protocol allows parties to join and leave the conference at any time, and ensures that all members of the conference are always informed of new members. The paper gives an overview of the protocol, analyzes it, describes a simulation environment for it, and discusses its applicability to the Session Initiation Protocol (SIP) and to other forms of decentralized communication.

Internet telephony enables a wealth of new service possibilities. Traditional telephony services, such as call forwarding, transfer, and 800 number services, can be enhanced by i n teraction with email, web, and directory services. Additional media types, like video and interactive c hat, can be added as well. One of the challenges in providing these services is how to e ectively program them. Programming these services requires decisions regarding where the code executes, how i t interfaces with the protocols that deliver the services, and what level of control the code has. In this paper, we consider this problem in detail. We develop requirements for programming Internet telephony services, and we show that at least two solutions are required | one geared for service creation by trusted users such as administrators, and one geared for service creation by u n trusted users such as consumers. We review existing techniques for service programmability in the Internet and in the telephone network, and extract the best components of both. The result is a Common Gateway Interface CGI that allows trusted users to develop services, and the Call Processing Language CPL that allows untrusted users to develop services.