dy deployed from same states described in the BCSM model by IP client. It is very easy to APIs (Application Programming Interfaces) implementation for access to services used in the traditional PSTN model. Nevertheless there are some problems to resolve, such as the choice of SCP to put in communication with the SIP server and also the security problem in IN or more precisely, the authentification of the caller and the callee. With the introduction of intelligent functionality in telecommunications systems, the necessity for security functions is emphasized. Integrating the application of this functionality will be important to give a clear view to each user that information and orders are processed correctly, and that information is processed solidly in the system. Of course, there is a long list of functionality demands for services of security, but the main demand list is given from the user viewpoints. Therefore, in order to market IN as a technical and economic success, we have to make good work not only in our laboratory development and in the adminstration of telecommunications, but also to establish a level of human comprehension. References [1] Schulzrinne, H. 1998. Signalling for Internet Telephony, Columbia Uni- versity, Dept. of Computer Science Technical Report Number CUCS- 005-98 [2] Schulzrinne, H. 2001. The Session Initiation Protocol (SIP). Columbia University, New York, http://www.cs.columbia.edu/hgs. May 2001. [3] Johnston, A., A. Sparks, R. Donovan, S. Summers, K. 2002. SIP service examples. draft-ietf-sip-service-examples-03.txt, June. [4] Fondation internet nouvelle génération (FING). 2001. Principes et condi- tions de mise en oeuvre du standard ENUM en France. http://www.art- telecom.fr/publications/index-cp-enum.htm 18 June 2001. Huston, G. 2002. ENUM-Mapping the E. 164 Number Space into the DNS. The Internet Protocol Journal. Volume 5, number 2. Page 13-23, June. [6] Chapron, J., and B. Chatras. 2001. An analysis of the IN call model suitability in the context of VoIP. Computer Networks 3