Saratoga: a Delay-Tolerant Networking convergence layer with efficient link utilization

Abstract

Saratoga is a lightweight transport protocol based on the user datagram protocol (UDP/IP). Saratoga was developed by Surrey Satellite Technology Ltd (SSTL) for file transfers of imaging data recorded onboard the Internet-Protocol-Based Disaster Monitoring Constellation (DMC) satellites, and has been in operational use from low Earth orbit since 2004. Saratoga focuses only on efficient communication to the next hop when link connectivity is available, by filling the link with packets sent at line rate. This ensures that as much data as possible is transferred to the peering node during a twelve-minutes-or-less pass over a satellite ground station. Saratoga uses a minimal bandwidth-efficient negative acknowledgement mechanism to ensure reliable data transfer. We examine how Saratoga can be adapted to serve as an efficient convergence layer for delay-tolerant networking (DTN), by transferring DTN bundles as well as files. This will allow DTN networks to increase efficiency of communication across briefly-available disrupted links -for long-distance deep space links as well as for short-distance terrestrial mobile ad-hoc networks.