Let Freedom Ring

Can IP mobility be the foundation on which the "mobile enterprise" is built?

By Fred Baker

To most business users, the "IP Internet," as we have known it over the past decade, looks like nothing more than a computer exchanging or accessing information on other computers via email and the World Wide Web. Under the covers, however, the network connecting those computers has continually evolved. Internet technology originally consisted of desktop LAN-attached computers at work connected by simple routers. These computers migrated home with the deployment of dial-up facilities, and into the road warrior's hotel room with the development of laptop computers. The palmtop consumed the functions of a meeting planner and a pager, making Internet technology something we could begin to call "convenient."

Some people in the Internet Engineering Task Force (IETF), which develops the protocols used in the Internet, envision a different world. They imagine one in which the computer does not simply connect at various times from various places in the network, but one in which it remains continuously in motion and in communication. In 1989, Charles E. Perkins, then at IBM Thomas Watson Research Center, and subsequently at Sun Microsystems and Nokia, suggested a model that overlaid address spaces. Why does a computer, he wondered, always have to be physically where its IP address says it is? Could we arrange a scenario in which it retains the appearance of being on a stationary desktop, but is in fact anywhere its user has carried it to? Could the network provide plumbing that made this not only possible, but easy to accomplish?

Research started by Perkins, John Ioannides, and Gerald Maguire at Columbia University, Dave Johnson at Carnegie-Mellon University, and several others, resulted in an IETF Proposed Standard in 1996, which has been continuously improved since then. We call that specification IP Mobility.

The Concept of IP Mobility

IP Mobility is conceptually simple, although (as is often true in technology) the details can be quite complex. You could compare it to the way a busy executive uses an assistant to maintain a presence in the office while traveling. If someone wants to reach her, that person calls the number on a business card. Her assistant answers and connects the caller with the executive. The fact that she is physically somewhere else - at home, driving, or at another facility - is invisible to the caller; the executive appears to be behind her desk. IP Mobility, in an analogous manner, frees the computer user to be anywhere at any time and maintain both continuous access and continuous accessibility regardless of physical location.

Being out of telephone contact is an opportunity cost for the busy executive. As our dependence on Internet technology grows, being out of digital contact is equally an opportunity cost for a real estate agent en route to an open house, for example. If another house comes on the market - or the target house is sold - a real estate agent who is in touch can change plans. The executive, in the same way, can have the latest information available at her request, rather than hoping someone will keep her informed. The deployment of IP Mobility means that we can put the Web in an ambulance or an airplane - in motion - and give emergency medical personnel greater access to life-saving information while they have a patient in transit. It means an engineer can use his laptop as he walks around a building or between buildings, reviewing or changing documents at that time rather than "taking an action item" to change them later. It means, in short, that we can be free of the computer as an anchor that constrains the way we live, work, and play by its own limitations. We can instead begin to use it to simplify the way we live, work, and play on our own terms.

Various vendors are now developing the technology for two primary applications (although others are possible): Wireless LANs and third-generation mobile telephones. In addition, airlines are slowly deploying the technology in their aircraft in order to offer passengers services such as email and Web access. Experiments are also being conducted using the technology to connect IP devices in satellites in the earth's orbit. Some companies are considering whether Mobile IP might viably support national IP Internets that use a common infrastructure to connect users in arbitrary places with arbitrary service providers.

Wireless LANs use a combination of IP Mobility technology and mobile LAN technology (which is analogous to Mobile IP, but connects the computers using a small number of radio systems called "base stations") to enable a computer to remain connected while moving around a campus. This campus is not limited in size technically; wireless service providers may enable such connectivity over a major part of a city or across a small country. However, as the wireless LAN grows to those sizes, it becomes a set of small radio networks connected by a more traditional backbone. It is here that IP Mobility comes into play: IEEE 802.11b mobile LANs implement the radio networks, and those radio regions are connected using Mobile IP.

Similarly, third-generation mobile networks (3GPP and a variety of related efforts) overlay the GSM, PCS, or CDMA telephone networks with an IP Internet whose end stations are telephone handsets. NTT DoCoMo in Japan deployed such a network, called "I-Mode," which has seen surprisingly rapid acceptance. Such networks enable users to go beyond using their telephones as voice instruments and pagers to using them much as they do PDA-limited Web access, email, calendaring, and other convenience functions. Some next-generation cell phones now combine the PDA and the handset into a single device.