Next-generation e-Science applications will require the ability to transfer information at high data rates between distributed computing centers and data repositories. To support such applications, lambda grid networks have been built to provide large, on-demand bandwidth between end-points that are interconnected via optical circuit-switched lambdas. It is extremely important to develop an efficient transport protocol over such high-capacity, dedicated circuits. Because lambdas provide dedicated bandwidth between endpoints, they obviate the need for network congestion control. Consequently, past research has demonstrated that rate-based transport protocols, such as RBUDP, are more effective than TCP in transferring data over lambdas. However, while lambdas eliminate congestion in the network, they ultimately push the congestion to the endpoints — congestion that current rate-based transport protocols are ill-suited to handle. In this paper we introduce a “Rate-Adaptive Protocol ...