HSTCP-LP: A Protocol for Low-Priority Bulk Data Transfer in High-Speed High-RTT Networks

This work presents HSTCP-LP (High-Speed TCP Low Priority), a high-speed TCP stack whose goal is to utilize only the excess network bitrate (bandwidth) as compared to the ''fair-share'' of bitrate as targeted by other TCP variants. By giving a strict priority to all non-HSTCP-LP cross-traffic flows, HSTCP-LP enables a simple two-class prioritization without any support from the network. It enables large file backups to proceed without impeding ongoing traffic, a functionality that would otherwise require a multi-priority or separate network. One class of applications for HSTCP-LP is low-priority background file transfer over high-speed networks. Examples are bulk data transfers of huge scientific data across the Internet, database replication, or Internet content distribution. A second class of applications is available bitrate optimization (e.g., to select a mirror server with the highest available bitrate). Current techniques first estimate the available bitrate and then download data via a transport protocol. HSTCP-LP, since it only uses excess/available bitrate, is able to estimate available bitrate while doing a useful data transfer.