A sender-based TFRC for Saratoga: A rate control mechanism for a space-friendly transfer protocol

Saratoga is a protocol for fast file transfers across dedicated links in private networks, using small amounts of feedback for loss recovery. It is in use to download large amounts of imaging data from remote-sensing satellites, where the link environment is highly asymmetric and up-links are constrained. However, Saratoga lacks a rate-control mechanism to allow fair share with co-existing flows for simultaneous competing transfers, or for across the congested Internet where it must coexist fairly with TCP. TFRC, a self-and TCP-Friendly Rate Control mechanism, can be adopted for Saratoga and leverage its existing protocol information. Use of TFRC normally requires significant changes in protocol operation, including additional data in feedback. We design a sender-based TFRC for Saratoga, needing only simple modifications within the sender and using only existing feedback information. This sender-based TFRC is shown to share the bottleneck-bandwidth fairly under various network conditions, allowing Saratoga to be adapted for shared links or for the congested Internet, while still supporting the asymmetric environments that Saratoga was originally developed for.