Jim,
In contrast, I came across one of the themes in this white paper - wireless mobility vs. portability - yesterday (as you may have, yourself), in the Sun Microsystems article posted by Rob on the 4G thread:
"All Wireless, All the Time"
research.sun.com
A sidebar from the above: "Mobile or Portable?"
research.sun.com
I've copied the sidebar, below.
FAC
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Mobile or Portable?
Well before the attacks on the World Trade Center, millions of people depended on wireless networking to connect to their work environments while travelling or working remotely. The events of September 11 and their aftermath deepened our dependence on mobile networking, and made clear the distinction between mobile and portable computing.
During and shortly after the attacks, cellphones and air interface communications emerged as our only links to the tragedy that unfolded. In the days that followed, tens of thousands of officeless workers scrambled to get re-connected, many of them working from home and makeshift workplaces, all of them suddenly "mobile."
Observers agreed that September 11 drew attention to a trend that had been gathering steam for some time. "I think it makes lots of sense for people with critical jobs to have lots of ways to communicate, and it's a no-brainer to have at least two devices, such as a Research In Motion [RIM] e-mail device and a voice cell phone," Alan Reiter, an analyst at Wireless Internet & Mobile Computing in Chevy Chase, Md. told Computerworld.
Ken Dulaney, an analyst at Gartner Inc. in Stamford, Conn., predicted that there will be more demands to stay connected and said that "the use of an adjunct to the notebook will become more popular, not only for disaster but to keep connected continuously."
Keeping connected continuously suggests the distinction between mobile and portable computing. "Mobile computing and networking should not be confused with the portable computing and networking we have today," says former Sun Microsystems Laboratories engineer Charles Perkins. "In mobile networking, computing activities are not disrupted when the user changes the computer's point of attachment to the Internet. Instead, all the needed reconnection occurs automatically and noninteractively." [http://www.computer.org/internet/v2n1/perkins.htm]
Staying connected is the goal of the Mobile IP technology being designed by the IETF's Mobile IP working group. James Kempf and Jonathan Wood have been deeply involved in working with the Mobile IP working group to design and implement a virtual tunnel technology that keeps IP-based wireless communications clear and connected.
Taking Care of Address
A breakthrough in "fast handoff," Kempf and Wood's virtual tunnels keep wireless devices connected as they physically move between different radio access points. In the world of Mobile IP, each mobile device maintains an extra IP address. The spare IP address, known as a care-of-address, changes whenever the device moves from one subnet to another. The device also has its address on the home network, called the home address. The problem: delays associated with changing the care-of-address can result in connection disruption, especially for delay-sensitive real time traffic such as voice. "The delay can put people off. We wanted to make it better," recalls Kempf.
The design breakthrough involved reducing this delay by devising an implementation that tunnels. Rather than have the care-of-address change, you fix it at an anchor router, and it forms a tunnel, passing the mobile's packets to the router where the mobile is located. This router then delivers the data packets to the mobile under the old care-of-address. At a pause in the real time conversation (cellphone) or data traffic (mobile Internet device), the router updates the care-of-address.
Thanks to Kempf and Wood's work, the wireless world may soon be less glitchy. Kempf and Wood's work is currently being specified by the IETF for the current version of IP (IPv4 ), and a variation is also being done for IPv6.
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