1. HOST MOBILITY SUPPORT BAOCHUN BAI

2. Outline Characteristics of Mobile Network Basic Concepts Host Mobility Support Approaches Hypotheses Simulation Conclusions

3. Characteristics of Mobile Networks High bit error rate and low bandwidth. Mobile networks are composed of a group of cells. A base station connects a cell with other parts of global network by wired media. Mobile hosts communicate with the base station to exchange information with their correspondent hosts.

4. Basic Concepts Home Agent –A router on a mobile host's home network. Foreign Agent –A router on a mobile host's visited network. Care-of Address –The termination point of a tunnel toward a mobile host.

5. Home Address –An IP address that is assigned to a mobile host. Home Network –A network having a network prefix matching that of a mobile host's home address. Foreign Network –Any network other than the mobile host's Home Network. Handoff –Mobile hosts migrate from one cell to the other cell while connectivity is still maintained. –Soft handoff and hard handoff

6. Host Mobility Support Methods Two-address methods –Mobile IP Hierarchical mobility management approach –Cellular IP One-address methods –Multicasting-based approach

7. Hypotheses redirect Local handoff Global Internet with Mobile IP Wireless access network Global mobilit y Mobile IP Cellula r IP Mobility Support Architecture

8. Hypotheses Route optimization –Using binding update to eliminate triangular route. Retransmission buffer mechanism –Adding buffer in base station to decrease the number of lost packets and improve the performance of local handoff

9. Simulation Simulation Model and Method –Discrete-event simulator –Two phases Handoff phase Retransmission phase –Events –Metrics the lost packet rate the duplicate packet rate OBS MH NBS

10. Simulation Results Analysis the lost packet rate in the case of soft handoff the lost packet rate in the case of hard handoff

11. Simulation Results Analysis the duplicate packet rate in the case of soft handoff the duplicate packet rate in the case of hard handoff

12. Conclusions Retransmission buffer mechanism can effectively to reduce the lost packets during a handoff. In the case of soft handoff, as the number of lost packets decreases, the number of duplicate packet increases. The retransmission buffer size should be no more than the average number of packets sent to the mobile host during a handoff. The decreased number of lost packets is gained at the cost of the increased number of duplicate packets and additional memory consumption for the retransmission buffer in the old base station and the complexity of local handoff protocol.