Mobile multicast with routing optimization for recipient mobility

This paper explores the issues of multicasting for mobile hosts using IETF Mobile IP. Mobile IP suggests two approaches for mobile multicasting, namely, remote subscription (MIP-RS) and bi-directional tunneling (MIP-BT). While having the advantage of optimal routing efficiency, MIP-RS uses a naive join-and-leave policy for mobile hosts to participate in the groups of interest and causes serious packet losses while roaming. MIP-BT is free from packet losses due to roaming; however, MIP-BT and its modification MoM suffer from the triangle routing problem, resulting in inefficient routing and wastage of system resources. We propose a new mobile multicasting protocol called mobile multicast with routing optimization (MMROP) that employs a modified join-and-leave mechanism, and routes the missing data sequence due to the "out-of-synch" problem to other agents in the adjacent networks via tunneling for roaming terminals. With MMROP, the mobility agent (foreign or home agent) in Mobile IF, in addition to mobility management, is extended to assist multicasting for mobiles. The mobility agent is not necessarily a multicast router. From the perspective of the multicast router, the mobility agent is a group participant, and from the mobiles, the agent serves as the proxy of multicast services. As a result, MMROP enjoys no packet losses from roaming as in MIP-BT, and optimal routing efficiency as in MIP-RS. We also conducted a simulation study and developed a cost analytical model to evaluate the performance of MMROP, in comparison to MIP-RS, MIP-BT, and MoM. The results demonstrate that MMROP has optimal routing efficiency, low delivery cost and high robustness, as compared to other approaches.