ess), Internet draft draft-zangrilli- p2psip-dsip-dhtchord-00, February. [21] Rosenberg, J., J. Winberger, C. Huitema, and R. Mahy. 2003. STUN: Simple Traversal of User Datagram Protocol (UDP). RFC 3489, Internet Engineering Task Force, March. [22] Zangrilli, M., and D. Bryan. 2007. A bamboo-based DHT for resource lookup in P2PSIP. (work in progress), Internet draft draft-zangrilli- p2psip-dsip-dhtbamboo-00 February. [23] Bryan, D., and B. Lowekamp. 2007. Decentralized SIP: peer-to-peer SIP. ACM Queue Magazine 5(2): 34-41. [24] Harjula, E., J. Ala-Kurikka, D. Howie, and M. Ylianttila. 2006. Anal- ysis of peer-to-peer SIP in a distributed mobile middleware system. In IEEE Global Telecommunications Conference (Globecom06), San Fran- cisco, CA, USA, November 27-December 1. © 2009 by Taylor & Francis Group, LLC SIP Mobility Technologies and the Use of Persistent Identifiers to Improve Inter-Domain Mobility and Security Henry Jerez Corporation for National Research Initiatives Joud Khoury and Chaouki Abdallah The University of New Mexico CONTENTS 10.1 Introduction 10.2 SIP Inter-Domain Mobility 10.3 Host Identification and Mobility 10.4 Implementation 10.5 Future Work 10.6 Conclusion Acknowledgements References The original implementation of the Internet assumed a set of static nodes talking to each other. This approach sets clear boundaries between different network topologies and allows mobility only through patches and adaptations that make true seamless mobility very difficult. This is due to the use of IP addresses that contain geographic semantics and are inherently not mobile and domain names that are intrinsically linked to these static servers. In recent years, the total number of mobile devices has outpaced that of static ones and supporting mobility in Internet Protocol (IP) networks has become a a crucial step toward satisfying the nomadic communication paradigms on the current Internet. Session Initiation Protocol (SIP) presents one approach toward sup- porting IP mobility. Additionally, SIP is increasing