Dynamic TCP Proxies: Coping with Disadvantaged Hosts in MANETs

Applications in mobile ad-hoc networks can suffer from poor link quality and degraded network services. In particular, standard TCP over low-quality, long routing paths, can have disproportionally low throughput as the result of a double penalty:long end-to-end round-trip time-due to long path length, and frequent congestion window back off due to packet losses that could not be masked by the link-layer retransmissions. To address this problem, we leverage a well-known concept of dynamic TCP proxies but propose to dynamically install these proxies along a routing path based on the quality of the links comprising the path. By enclosing poor quality path segments between a pair of TCP proxies, we isolate the effect of these segments on the rest of the network and improve the overall performance. We further utilize cross-layer optimization to select proxy locations without a separate signaling protocol, by leveraging existing messages in the underlying routing protocol. We demonstrate the potential benefits of this dynamic TCP proxies mechanism, and illustrate the relevance of host mobility level on this design choice.