We propose the Robust Overlay Architecture for Mobility (ROAM) to provide seamless mobility for Internet hosts. ROAM is built on top of the Internet Indirection Infrastructure (i3). With i3, instead of explicitly sending a packet to a destination, each packet is associated with an identifier. This identifier defines an indirection point in i3, and is used by the receiver to obtain the packet. ROAM takes advantage of end-host ability to control the placement of indirection points in i3 to provide efficient routing, fast handoff, and preserve location privacy for mobile hosts. In addition, ROAM allows end hosts to move simultaneously, and is as robust as the underlying IP network to node failure. We have developed a user-level prototype system on Linux that provides transparent mobility without modifying applications or the TCP/IP protocol stack. Simulation results show that ROAM's latency can be as low as 0.25-40% of Mobile IP. Experimental results show that with soft handoff the TCP throughput decreases only by 6% when there are as many as 0.25 handoffs per second.
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