The performance of TCP in wide-area networks (WANs) is becoming increasingly important with the deployment of computational and data grids. In WAN environments, TCP does not provide good performance for data-intensive applications without the tuning of flow-control buffer sizes. Manual adjustment of buffer sizes is tedious even for network experts. For application scientists, tuning is often an impediment to getting work done. Thus, buffer tuning should be automated.

Existing techniques for automatic buffer tuning only measure the bandwidth-delay product (BDP) during connection establishment. This ignores the large fluctuation of the BDP over the lifetime of the connection. In contrast, the dynamic right-sizing algorithm dynamically changes buffer sizes in response to changing network conditions.

In this paper, we describe a new user-space implementation of dynamic right-sizing in FTP (drsFTP) that supports third-party data transfers, a mainstay of scientific computing. In addition to comparing the performance of the new implementation with the old in a WAN-emulated environment, we give performance results over a live WAN. In this particular WAN environment, the new implementation produces transfer rates of up to five times higher than untuned FTP.