The public telecommunications carriers don't understand the data communications business and couldn't market modems to PC users if their lives depended on it.
-W. Frezza, "Going the Way of Wireless," Network Computing, October 1, 1995.
The most ubiquitous internetwork is called the Internet. Routing in the Internet is based on the Internet Protocol (IP). In the late 1970s and early 1980s when the IP was developed, mobility of hosts was never considered. At that time most hosts were simply physically too large to move around.
The explosive growth of the Internet combined with the widespread availability of highly mobile small hosts in the form of laptop and palmtop computers, and personal digital assistants, has created a big demand for the concept of Mobile IP. The current trends point clearly towards further miniaturization and greater mobility. It is not unreasonable to expect many of tomorrow's hosts to be in the form of pagers, cell phones or even wrist watches. Transparent mobility is a major requirement for the next generation IP (IPv6).
For the Internet to support global transparent mobility, a new set of mobility management protocols that accommodate roaming among different subnetworks and different media types is required. None of the technologies discussed thus far completely addresses this requirement.
However, significant efforts are presently underway to develop a comprehensive solution for transparent mobility in the Internet. In this chapter we discuss two such efforts. First, we survey the so called "Mobile IP" effort which enhances the current Internet Protocol (IPv4) to support mobility. Next, we discuss the next generation of Internet Protocol (IPv6), which is being designed to address the mobility requirement. We then compare and contrast CDPD mobility with Mobile IP. Table 10.1 provides a comparative glossary of CDPD and Mobile IP, which those familiar with CDPD may choose to review prior to reading the chapter.