DESIGN AND IMPLEMENTATION OF THE MOBILE INTERNET PROTOCOL ON THE LINUX KERNEL TO SUPPORT INTERNET MOBILITY A Thesis Presented to The Faculty of the Fritz J. and Dolores H. Russ College of Engineering and Technology Ohio University In Partial Fulfillment of the Requirement for the Degree Master of Science Radha Thothadri November 1999 OHIO UNIVERSITY Contents 1 Introduction 1 1.1 Internet Protocol Architecture ....................... 3 1.1.1 OSI Model ............................. 4 1.1.2 TCP/IP Protocol Suite ...................... 5 1.2 Motivation for Mobile IP ......................... 8 1.3 Organization of Thesis .......................... 9 2 Internet Mobility 10 2.1 Internet Addressing Scheme ....................... 10 2.2 Mobility Problem ............................. 11 2.3 Mobility Support Requirements ..................... 12 2.4 Proposals to Address Internet Mobility Issue .............. 13 2.4.1 Columbia Scheme ......................... 13 2.4.2 Sony ................................ 14 2.4.3 Loose Source Routing ...................... 15 2.5 Overview of Mobile IP .......................... 17 2.5.1 Mobile IP Terminology ...................... 18 2.5.2 Operation of Mobile IP ...................... 19 3 Concepts of Mobile IP Protocol 21 3.1 Agent Discovery .............................. 21 3.1.1 Agent Advertisement Message .................. 22 3.1.2 Mobile Host Migration Detection ................ 23 3.1.3 Agent Solicitation Message .................... 23 3.2 Mobile Node Registration ........................ 23 3.2.1 Role of the h4obile Host ..................... 23 3.2.2 Mobility Agents' Role ...................... 24 3.2.3 Registration Message Format .................. 24 3.2.4 Registration Reply from Home Agent ............. 25 3.2.5 Security Concerns for Registration Mechanisms ........ 26 3.3 Routing and Packet Redirection Mechanisms .............. 28 3.3.1 Intercepting Mobile Host Packets ................ 28 3.3.2 Tunneling Packets to Mobile Host ................ 28 3.3.3 Security Concerns for Tunneling ................. 30 3.3.4 Other Security Schemes for Mobile IP .............. 31 3.4 Implementations with a Foreign Agent ................. 32 3.5 Design without Foreign Agent ...................... 32 4 Implementation of Mobile IP on Linux 36 4.1 IVhy Linux? ................................ 36 4.2 Mobile IP Installation .......................... 37 4.2.1 Physical Setup of the Hosts ................... 37 4.2.2 Kernel Modification ........................ 37 4.2.3 Kernel Compilation ........................ 38 4.3 Mobility Support on the Mobile Host .................. 39 4.3.1 Migration of the Mobile Host .................. 39 4.3.2 Mobile Host Configuration .................... 40 4.3.3 Role of the Mobile Host Daemon ................ 42 4.3.4 Routing Management for Mobile Hosts ............. 45 4.3.5 Summary ............................. 49 4.4 Mobility Support on the Home Agent .................. 49 4.4.1 Home Agent Configuration .................... 49 4.4.2 Role of the Home Agent Daemon ................ 50 4.4.3 Summary ............................. 53 4.5 Problems and Limitations ........................ 54 4.6 Conclusions ................................ 55 5 Performance Analysis of Mobile IP Implementation 56 5.1 Description of test-bed .......................... 56 5.2 Experiments with ping .......................... 57 5.2.1 Observations I ........................... 58 5.2.2 Observations I1 .......................... 61 5.2.3 Conclusions from the ping Test ................. 62 5.3 Client-Server Program for TCP Packets ................. 63 5.4 Performance Measurements for Routing Optimizations ........ 64 5.5 Performance while Switching Networks ................. 65 5.6 Summary ................................. 65 6 Conclusion 66 Bibliography 69 Appendix A 72 Appendix B 75 Appendix C 82 List of Tables 4.1 A sample Mobile Policy Table ...................... 47 5.1 Observations of ping requests from Mobile Host ............ 59 5.2 Observations of ping requests from remote hosts to mobile host ... 61 5.3 Observations from the Client-Server Model . The mobile host is the client .................................... 64 5.4 Comparison of Bidirectional Tunneling and Triangular Routing ... 65 List of Figures Overview of Internet ........................... 3 OSI reference model ........................... 4 TCP/IP suite ............................... 7 Addressing scheme in TCP/IP Internet ................ 11 IETF Mobile IP Protocol ......................... 19 Mobility Agent Advertisement Message ................ 22 Mobility Node Registration Request Message ............. 25 Mobile IP Tunneling using IP-in-IP ................... 29 Mobile IP protocol without foreign agent ............... 33 Experimental testbed on the ece.ohiou.edu network .......... 37 Representation of mobile host migration ................ 40 A sample file for mobile host configuration ............... 41 A sample file configuration for Mobile Policy Table .......... 41 Triangular routing ............................ 46 Bidirectional tunneling .......................... 47 Routing with link-layer virtual interface ................. 48 A sample file for home agent configuration ............... 50 Chapter 1 Introduction Personal computing devices including desktops and workstations are becoming in- creasingly popular with the fall in their prices and the increasing dependence on their computing and organizational capabilities. The spectacular progress in the computer industry over the last few decades, with the continuing revolution in the microproces- sor technology is facilitating the shrink in the physical size of the computing devices to palm tops, notebooks and laptops. These are as powerful, in terms of memory, storage and computing power, as some desktop and workstations. The proliferation of the powerful portable computers, the increasing availability of wireless network interfaces and products assures users network access at all times. There has been an explosive growth in the Internet, which is a global network con- necting various computers, hosts and networks across the world. The Internet that existed in 1990 was barely 5% of the current Internet [Com95, Sur]. The fundamen- tal technology of the Internet has adapted well to the exponential growth and the corresponding increases in the traffic. With the advent and popularity of online businesses, financial transactions and mar- keting, adopted by every commercial venture, continuous connectivity to the Internet is in great demand. The number of online users has increased from 26 million in 1995 to close to 172 million worldwide as of May, 1999 [Sur]. Thus mobility and portability are essential and crucial in the next generation computers and network protocols. The mobile devices in the existing Internet infrastructure can connect to the Internet using wireless interfaces just as the desktops are connected using Ethernet, token- ring etc. But when the mobile host migrates it changes its point of attachment to the network. This is a change in the network topology. The Internet and the OSI network architecture design is based on the fundamental assumption that the end users are stationary. Thus movement by the end systems leads to loss of existing connection. Replacing the existing Internet protocols to support mobility is infeasible considering the huge investments in the existing infrastructure and the corresponding changes and updates to support over 40 million hosts on the Internet. The challenge, thus, lies in providing mobility on the Internet with considerations to existing infrastructure, backward compatibility and avoiding excess overhead. In this thesis, we address our implementation of Mobile IP on the Linux platform to support Internet mobility for mobile hosts with a brief outline of the history of the approaches to resolve this mobility issue. Internetworking technology specifies procedures to accommodate diverse hardware technologies, software architecture and to interconnect heterogeneous networks. The underlying hardware and implementation details of each interconnected physical net- work is hidden, permitting computers in different networks with diverse architecture to communicate. These individual networks are connected to other networks by de- vices called routers to constitute a much wider internetwork. These routers have some methods or protocols to communicate the data between the source and destina- tion hosts which could belong to distinct and potentially incompatible networks (see Fig. 1.1). As a background to the Mobile IP protocol, we will be looking at the Internet protocol architectures and especially the TCP/IP protocol suite and its limitations. This will lead us to the motivation for Mobile IP and its operations. Our implementation on the ece.ohiou.edu subnet will be discussed in detail. Figure 1.1: Overview of Internet 1.1 Internet Protocol Architecture To minimize the inherent complexity, network protocols are organized as a series of layers or levels. The number and functionality of these layers differ with networks but with the common concept that each layer offers certain services to higher layers hiding the low level implementation details. The rules or conventions that each layer has to conform with, while exchanging information or data with peer entities are collectively termed protocols. Thus a protocol refers to the implementation of service or operations and is hidden from the users and higher layers. The two important network architectures,