Introducing Gateway Timeout Control in Wireless TCP Module

Many today TCP modules are derived from the BSD implementation which handles packet loss as signal of congestion. While in the wireless networks, the non-congestive packet losses can be frequent and shall be handled differently. In this paper we apply the Visualized IP-based Network Simulator (VINS) to study the differences between packet losses due to congestion and that due to link disruption, and propose a new scheme to handle the non-congestive losses. The new scheme comprises of two parts: introducing Gateway Timeout (GTO) control in the host’s TCP module on which host may switch its gateway; relocation within the domain if a host changes its gateway, especially on the border node. On GTO, if a new gateway is found available, TCP may silently shift the existing connections onto the new path in its sequencing context. Meantime the involved nodes shall be advertised to update their routing states so that the incoming packets can be forwarded to the right subnet. We implement this scheme in VINS and test it under varying background traffic. In comparison with the tunneling scheme employed in Mobile IP, the GTO scheme exhibits averagely better performance, especially when the domain is congestive.