On Inter-network Handover Performance using Mobile IPv6

In this paper, we report on our practical experiences using the Mobile IPv6 protocol in an integrated LAN-WLAN-GPRS testbed. Through detailed analysis from packet traces of inter-network (vertical) handovers conducted over the testbed, we examine the performance of transport protocols such as TCP during such handoffs. The considerable differences in link-layer characteristics between the different networks reveal a number of performance issues. We show how inter-network handovers can have significant impact on TCP performance, causing connections to timeout and leading to severe underperformance. We highlight several such problems that seem inherent in providing transparent mobility in a heterogeneous environment. From practical experimentations over our testbed, we discuss how some of these problems can be addressed through exploiting knowledge of the link-layer conditions to improve the handover process. We propose and evaluate schemes such as Fast Router Advertisements (RA), RA Caching, Binding Update (BU) simulcasting to aid Mobile IPv6 protocol during inter-network handovers. We show how a proxy installed in GPRS network for smart buffer management, can improve TCP performance during handovers involving GPRS, and also use of soft handovers to improve TCP performance. We demonstrate the benefits from each of these schemes, and conclude with our experiences using Mobile IPv6 to successfully migrate TCP connections during inter-network handovers in an overlay environment.