The main goal of this project is to develop efficient path probing and topology management schemes for overlays that support mobile users. Overlays facilitate the deployment of functions not available from the commercial Internet (e.g., multicasting, QoS-aware routing etc.). While conventional overlays so far have connected stationary users, the overlays of the future must support also mobile customers. There is need for hybrid wired and wireless overlays that include wireless segments and even "opportunistic" ad hoc networks (e.g., networks of cars in an urban environment). To respond to such needs, this project develops OverProbe, a new toolkit that includes the innovative probing technique CapProbe and works for both wired and wireless overlay links. OverProbe evaluates "virtual link" quality very rapidly. Speed is critical in wireless since the user at the end of the path may move across different type of wireless media (e.g., 3G, 802.11, Bluetooth, CDMA, etc.) within minutes. Besides frequent monitoring of wireless connectivity, the toolkit assists mobile users in soft handoff without breaking TCP connections. The research also includes the design and evaluation of scalable, hierarchical overlay structures (using "backbone overlays"). The results of this research will help promote new services among the mobile community, from telecommuting, to e-commerce and entertainment. Key results include: (1) A set of path probing methodologies and tools (Over-Probe toolkit). (2) A two level overlay and proxy architecture. (3) OverProbe implementation in PlanetLab and WHYNET.
