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The TCP/IP Guide  9  TCP/IP Lower-Layer (Interface, Internet and Transport) Protocols (OSI Layers 2, 3 and 4)       9  TCP/IP Internet Layer (OSI Network Layer) Protocols            9  Internet Protocol (IP/IPv4, IPng/IPv6) and IP-Related Protocols (IP NAT, IPSec, Mobile IP)

IPSec Key Exchange (IKE) 1 Mobile IP Overview, History and Motivation

The Internet Protocol (IP) is the most successful network layer protocol in computing due to its many strengths, but it also has some weaknesses, most of which have become more important as networks have evolved over time. Technologies like classless addressing and Network Address Translation combat the exhaustion of the IPv4 address space, while IPSec provides it with secure communications it lacks. Another weakness of IP is that it was not designed with mobile computers in mind.

While mobile devices can certainly use IP, the way that devices are addressed and datagrams routed causes a problem when they are moved from one network to another. At the time IP was developed, computers were large and rarely moved. Today, we have millions of notebook computers and smaller devices, some of which even use wireless networking to connect to the wired network. The importance of providing full IP capabilities for these mobile devices has grown dramatically. To support IP in a mobile environment, a new protocol called IP Mobility Support, or more simply, Mobile IP, was developed.

In this section I describe the special protocol developed to overcome the problems with mobile computers attaching to IP internetworks. I begin with an overview of Mobile IP and a more detailed description of why it was created. I discuss important concepts that define Mobile IP and its general mode of operation. I then move on to some of the specifics of how Mobile IP works. This includes a description of the special mobile IP addressing scheme, an explanation of how agents are discovered by mobile devices, the process of registration with the device's home agent, and how data is encapsulated and routed. I discuss the impact that Mobile IP has on the operation of the TCP/IP Address Resolution Protocol (ARP). I end the section by examining some of the efficiency and security issues that come into play when Mobile IP is used.

IPSec Key Exchange (IKE) 1 Mobile IP Overview, History and Motivation