Mobility and security are becoming dominant themes in the Internet of the new millennium. These factors present many challenges and many opportunities for healthy growth of the Internet. Mobility heightens the need for security, just as it brings into sharp focus the need for applying other technologies like service discovery, location management, tunneling, and remote data management. Taken together, these technologies represent a fundamental restructuring of previous approaches for continued growth of the Internet.

Tunneling alone is powerful enough to effect such a restructuring, but network designers rarely create solutions that involve pure tunneling. Instead, the tunnel management is equipped with many and sundry techniques for deciding when to enable, start, and stop the use of the tunnel. All of these techniques amount to an expression of some policies, which are motivated by the problem that the tunneling solution is intended to solve. Two very prominent tunneling policy regimes are Mobile IP and VPNs. The former is intended to create useful routes so that data can be delivered to whatever foreign domain the mobile node should visit. The latter is supposed to create useful routes so that data can be delivered securely to whatever foreign domain at which a portable device may become situated at.

When portable devices become wireless, they (and their users!) become much more mobile. Soon, traditional methods for managing VPNs will be viewed as inadequate. Mobility techniques, perhaps those derived from Mobile IP, or Mobile IP itself, will be adapted to fulfill the needs of devices whose communications are protected by VPNs. This will create the Mobile VPNs described in this book.

I believe this book will help the practitioner understand the many related wireless, mobility management, and security technologies that can be used to create MVPNs. Undoubtedly, there will be many ideas for solutions, depending on the background and goals of the designers. And yet, security is very tricky, so care and study are crucial for success.

Nothing beats experience, and it is important to learn from the experiences of others, understanding why their solutions succeeded or failed. Moreover, vendors for existing products that are related to MVPNs will surely try to take advantage of opportunities for extending their product lifetimes. Thus, we are likely to see many different variations upon the technologies and themes presented in this book.

My own work with Mobile IP has given me the opportunity to meet and work with Alessio Casati and Alex Shneyderman. Alessio and I made an initial effort to make more tunneling tools available to Mobile IP, namely GTP, the tunneling mechanism of choice within GPRS domains. That was after I had grown to enjoy Alessio's forthright assessments of various developments on the IETF mobile-ip mailing list. That same spirit of forthright assessment and technical presentation will make this book accessible and valuable for the many readers interested in solutions providing mobility and security. I wish them, and this book, the best of luck to find that readership.

Charles E. Perkins Nokia Fellow, Nokia Research Center
Mountain View, CA