AN IMPLEMENTATION OF MOBILE IP WITHIN THE LINUX KERNEL

Abstract

Many efforts have been made to provide mobility support within the Internet and the relevant prototypes for the past five years. The Mobile IP Working Group of the Internet Engineering Task Force (IETF) has developed a few protocols, where IP Mobility Support, also called Mobile IP, is the base protocol. This protocol is primarily concerned with the maintenance of mobility bindings such that the mobile node is able to move around while still maintaining Internet connectivity. This thesis presents an implementation of Mobile IP within the Linux kernel. A few soft states are designed to reduce complexity, improve robustness and reduce wasted bandwidth. The system provides an application programming interface through the existing TCP/IP socket calls and users can monitor the Mobile IP kernel stack with these calls. This thesis addresses a problem with the ARP cache update on receiving gratuitous ARP messages, and another problem appearing around the edge of the mobile node's home subnet. This thesis proposes relevant solutions. The implementation is compliant with the standard Mobile IP protocol. Four releases were made freely available on the Internet. The implementation was successfully tested, in terms or interoperability, with a few other Mobile IP implementations. Presently, researchers in a few countries are using thi.s implementation for the purpose of teaching, research and development. This thesis additionally introduces a new model, proximity proxies for mobility agents and mobile nodes, which the author has developed separately as an Internet draft. This model is useful for Mobile IP interoperability testing across the Internet. It is also an alternative to solve a problem with frequent distant registrations or mobility bindings. This thesis proposes the concept of foreign agent system and home agent system to generalize the mobility agents in the existing protocol. This refinement can ease the painful key management among mobility agents and mobile nodes, and reduce distant registration frequency.