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 occur 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 performance of TCP Tahoe without considering packet buffering through the simulation. Our simulation result shows that in most cases, the smooth handoff by the route optimization extension of Mobile IP standard cannot prevent the degradation of TCP performance due to handoffs, although it is designed to reduce the number of packets dropped during the handoff. It also shows that in utilizing the route optimization extension, the TCP performance sometimes becomes worse even than the case of the base Mobile IP unless its smooth handoff makes less than four packets be dropped during the handoff. Such results mean that at least for TCP, the smooth handoff is not useful unless the route optimization extension supports the buffering method, which makes handoffs be transparent to transport layer protocols by recovering the packets dropped during the handoff. We then investigate the effects of packet buffering on the performance of TCP. We modify the route optimization extension 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 addressed to recover the packets dropped during the handoff by the buffering method without giving a worse impact on the performance of TCP, and propose our solution to solve those problems.