Improving TCP handoff performance in Mobile IP based networks

Mobile IP has been designed to support host mobility over the Internet. In this paper, we show that in most cases the smooth handoff by the route optimization of the Mobile IP standard cannot prevent degradation of TCP performance in events of handoffs, although it was originally intended to reduce the number of packets dropped during a handoff. We also show that in utilizing the route optimization extension, the TCP performance sometimes becomes worse even than the case of the base Mobile IP, if its smooth handoff fails to avoid losses of four or more packets during a handoff. To resolve such problems without sacrificing the scalability in Mobile IP based networks, we propose a buffering of packets at a Base Station (BS). We modify the route optimization extension in order to support packet buffering at the BS, which only requires minor changes. Finally, we discuss some problems occurring when recovering the packets dropped during a handoff by the buffering method, and propose our solution. The proposed buffering method makes handoffs be transparent to transport layer protocols by recovering lost packets during a handoff.