Department of Technology Education, Korea National University of Education, San 7-1, Darakri, Chongwon-Gun, Chungbuk, 363-791, KoreaSummaryMobile IPhasbeendeveloped to handlemobility of Internet hosts at thenetworklayer.MobileIP(MIP),however,suffers from a number of drawbacks such as requirement of infrastructure change, high handover latency, highpacket loss rate, and conflict with network security solutions. In this paper, we describe and evaluate theperformance of SIGMA, a Seamless IP diversity-based Generalized Mobility Architecture. SIGMA utilizesmultihoming to achieve seamless handover of mobile hosts, and is designed to solve many of the drawbacks ofMIP, including requirement for changes in infrastructure. We first evaluate the signaling cost of SIGMA andcomparewiththatofhierarchicalMobileIPv6(anenhancementofMobileIP)byanalyticalmodeling,followedbycomparison of handover performance of SIGMA and Mobile IPv6 enhancements. Criteria for performanceevaluation include handover latency, packet loss, throughput, and network friendliness. Our results indicatethat in most cases SIGMA has a lower signaling cost than Hierarchical Mobile IPv6. Moreover, for a typicalnetwork configuration,SIGMA hasahigherhandoverperformanceoverMobileIP.Copyright#2005JohnWiley& Sons, Ltd.KEY WORDS: mobile handover; SIGMA; mobile IP; IP diversity; signaling cost1. IntroductionMobile IP (MIP) [1] has been designed to handlemobility of Internet hosts at the network layer tomanage mobile data communication. It allows aTCP connection to remain alive when a mobile host(MH) moves from one point of attachment to another.Several drawbacks exist when using MIP in a mobilecomputing environment, the most important onesidentified to date are high handover latency, highpacket loss rate [2], and requirement for change ininfrastructure. MIP is based on the concept of homeagent (HA) and foreign agent (FA) (which requiresmodificationtoexistingroutersinInternet)forroutingpackets from previous point of attachment to the newone. An MH needs to complete the following foursteps before it can receive forwarded data from theprevious point of attachment: (i) perform layer 2 (L2)handover, (ii) discover the new care of address (CoA),(iii) registering the new CoA with the HA, and (iv)