A Scheme for Adapting TCP to Drastic Changes in Link Characteristics

The mobile environment has been improved in this decade with technologies of mobility transparency such as mobile IP (MIP) and network mobility (NEMO), plus there has been progress in wireless and device technologies. Mobility transparency makes it possible for a mobile node to change its upstream data-link without any disruption of existing TCP connections. However, these technologies do not suffice for TCP to retain its performance, since they do not hide any changes in link characteristics. In this paper, we propose a scheme which adapts TCP congestion control to link characteristics after the upstream data-link changed. This scheme is based on a (re)setting of the parameters used for TCP congestion control after a upstream data-link changed. Some strategies of how parameters are derived, and when they are set, are discussed and examined here. We also implemented the scheme and carried out emulation experiments, the results of which demonstrated the scheme can avoid a adverse affect caused by a changes in the upstream data-link and make the TCP congestion control to adapt the changes in link characteristics.