RFC 2824 (rfc2824) - Page 2 of 25
Call Processing Language Framework and Requirements
Alternative Format: Original Text Document
RFC 2824 CPL-F May 2000 9.2 Script-to-script interactions ....................... 14 9.3 Server-to-server interactions ....................... 15 9.4 Signalling ambiguity ................................ 15 10 Relationship with existing languages ................ 15 11 Related work ........................................ 17 11.1 IN service creation environments .................... 17 11.2 SIP CGI ............................................. 17 12 Necessary language features ......................... 17 12.1 Language characteristics ............................ 17 12.2 Base features -- call signalling .................... 19 12.3 Base features -- non-signalling ..................... 21 12.4 Language features ................................... 22 12.5 Control ............................................. 23 13 Security Considerations ............................. 23 14 Acknowledgments ..................................... 23 15 Authors' Addresses .................................. 23 16 Bibliography ........................................ 24 17 Full Copyright Statement ............................ 25 1 Introduction Recently, several protocols have been created to allow telephone calls to be made over IP networks, notably SIP [1] and H.323 [2]. These emerging standards have opened up the possibility of a broad and dramatic decentralization of the provisioning of telephone services so they can be under the user's control. Many Internet telephony services can, and should, be implemented entirely on end devices. Multi-party calls, for instance, or call waiting alert tones, or camp-on services, depend heavily on end- system state and on the specific content of media streams, information which often is only available to the end system. A variety of services, however -- those involving user location, call distribution, behavior when end systems are busy, and the like -- are independent of a particular end device, or need to be operational even when an end device is unavailable. These services are still best located in a network device, rather than in an end system. Traditionally, network-based services have been created only by service providers. Service creation typically involved using proprietary or restricted tools, and there was little range for customization or enhancement by end users. In the Internet environment, however, this changes. Global connectivity and open protocols allow end users or third parties to design and implement new or customized services, and to deploy and modify their services dynamically without requiring a service provider to act as an intermediary. Lennox & Schulzrinne Informational
