Performance improvement by packet buffering in mobile IP based networks

It is well-known that TCP often experiences severe performance degradation in mobile networks since packet losses not related to network congestion oc cur frequently due to host mobility. In this paper, we propose a new packet buffering method to address such a problem without the scalability problem in Mobile IP based networks. For this purpose, we first investigate the pe rformance of TCP Tahoe without considering packet buffering through the sim ulation. Our simulation result shows that in most cases, the smooth handoff by the route optimization extension of Mobile IP standard cannot prevent t he degradation of TCP performance due to handoffs, although it is designed to reduce the number of packets dropped during the handoff. It also shows t hat in utilizing the route optimization extension, the TCP performance some times becomes worse even than the case of the base Mobile IP unless its smo oth handoff makes less than four packets be dropped during the handoff. Suc h results mean that at least for TCP, the smooth handoff is not useful unle ss the route optimization extension supports the buffering method, which ma kes handoffs be transparent to transport layer protocols by recovering the packets dropped during the handoff. We then investigate the effects of pack et buffering on the performance of TCP. We modify the route optimization ex tension in order to support packet buffering at the base station, but it is a very minor change. Finally, we discuss some problems that should be addr essed to recover the packets dropped during the handoff by the buffering me thod without giving a worse impact on the performance of TCP, and propose o ur solution to solve those problems.