ents 3323, IETF. November. [22] Marshall, W., K. Ramakrishnan, E. Miller, G. Russell, B. Beser, M. Mannette, K. Steinbrenner, D. Oran, F. Andreasen, J. Pickens, P. Lalwaney, J. Fellows, D. Evans, K. Kelly, and M. Watson. 2001. SIP Extensions for Caller Identity and Privacy. Internet Draft, IETF. November. [23] Castleman, M. 2001. Sipanon: A SIP Anonymizer CS W3998. Columbia University. © 2009 by Taylor & Francis Group, LLC Secure Intelligent SIP Services Handoura Abdallah Ecole Nationale Supérieure des Télécommunications de Bretagne CONTENTS 21.1 Background 21.2 Introduction 21.3 Implementing Intelligent Network in VoIP Applications with SIP 21.4 Telecommunications Services Security with SIP 21.5 Conclusion References 21.1 Background Intelligent network must become the standard of telephony services. However, the transition to Internet-based telephony services also provides an opportu- nity to create new services more rapidly and with lower complexity than in the existing public switched telephone network (PSTN) [1]. The Session Initiation Protocol (SIP) is a signaling protocol that creates, modifies and terminates associations between Internet end systems. The SIP uses DNS procedures to allow a client to resolve a SIP URI into the IP address, port, and transport protocol of the next hop to contact. Generally, these are the problems of mapping the name of a destination into an address, and to find the best route to the destination in a combined IP and PSTN network. Two protocols are being developed by the Internet Engineering Task Force (IETF) to solve these problems. The Telephony Routing over IP (TRIP) protocol solves the gateway location problem by distributing routing information between entities on the IP network. The tElephony NUmbering Mapping (ENUM) provides a solution to the terminal location problem based on DNS. The intelligent network is a basis to establish and commercialize the services of the telecommunication network. Selling services and information through a network does not define solely a cons