Experience with Delay‐Tolerant Networking from orbit

Abstract

We describe the first use from space of the Bundle Protocol for Delay‐Tolerant Networking (DTN) and lessons learned from experiments made and experience gained with this protocol. The Disaster Monitoring Constellation (DMC), constructed by Surrey Satellite Technology Ltd (SSTL), is a multiple‐satellite Earth‐imaging low‐Earth‐orbit sensor network in which recorded image swaths are stored onboard each satellite and later downloaded from the satellite payloads to a ground station. Store‐and‐forward of images with capture and later download gives each satellite the characteristics of a node in a disruption‐tolerant network. Originally developed for the ‘Interplanetary Internet,’ DTNs are now under investigation in an Internet Research Task Force (IRTF) DTN research group (RG), which has developed a ‘bundle’ architecture and protocol. The DMC is technically advanced in its adoption of the Internet Protocol (IP) for its imaging payloads and for satellite command and control, based around reuse of commercial networking and link protocols. These satellites' use of IP has enabled earlier experiments with the Cisco router in Low Earth Orbit (CLEO) onboard the constellation's UK‐DMC satellite. Earth images are downloaded from the satellites using a custom IP‐based high‐speed transfer protocol developed by SSTL, Saratoga, which tolerates unusual link environments. Saratoga has been documented in the Internet Engineering Task Force (IETF) for wider adoption. We experiment with the use of DTNRG bundle concepts onboard the UK‐DMC satellite, by examining how Saratoga can be used as a DTN ‘convergence layer’ to carry the DTNRG Bundle Protocol, so that sensor images can be delivered to ground stations and beyond as bundles. Our practical experience with the first successful use of the DTNRG Bundle Protocol in a space environment gives us insights into the design of the Bundle Protocol and enables us to identify issues that must be addressed before wider deployment of the Bundle Protocol. Published in 2010 by John Wiley & Sons, Ltd.

A Task-Driven Updated Discrete Graph Assisted Minimum Delivery Delay Routing for Remote Sensing Disruption-Tolerant Networks

“…To cope with such challenge in RSNet caused by time-varying and divisional topology, Remote Sensing Disruption-Tolerant Network (RS-DTNet) is proposed [14], with specific-designed store-forward and retransmission mechanism. In [15], large image file transfer experiments for the remote sensing satellites were performed, with Bundle Protocol (BP) overlaying different sub-networks. Particularly, the performance of BP and convergence layer adapter (CLA) protocols is evaluated in [16], which highlights the advantage of Licklider Transmission Protocol (LTP) for space communication environment with long link delay and lengthy link disruptions.…”

“…Due to the restricted resource, such as contact capacity and storage onboard, delivery delay is identified as important metric for RS-DTNet, in consideration of the high request on timeliness of remote sensing image data. As mentioned above, the delivery delay D m for multi remote sensing task RI is defined as (15) where D j f is the delay for task ri j , and can be further expressed as…”

Applying autonomy to distributed satellite systems: Trends, challenges, and future prospects

“…The coordination mechanisms are very much intertwined with the networking characteristics of DSS. The literature in ISL and Intersatellite Networks is extensive and has been looking at several aspects, such as: the limitations of small satellite platforms; the adoption of ground Internet standards for space; the design of new network protocols for specific DSS architectures; or the exploration of delay‐tolerant network concepts in Earth‐imaging constellations …”

“…The coordination mechanisms are very much intertwined with the networking characteristics of DSS. The literature in ISL and Intersatellite Networks is extensive and has been looking at several aspects, such as: the limitations of small satellite platforms 44 ; the adoption of ground Internet standards for space 45 ;the design of new network protocols for specific DSS architectures46 ; or the exploration of delay-tolerant network concepts in Earth-imaging constellations 47. Many networking characteristics may influence the design of coordination mechanisms in DSS, since these are the foundations of the decentralized interactions envisioned in many cases.Likewise, the design of autonomous DSS, needs to cope with the technological constraints in small spacecraft technologies.…”

Taking Saratoga from space-based ground sensors to ground-based space sensors

“…Saratoga has also enabled delivering data as large 'bundles' for the first in-space tests of the 'Bundle Protocol' and 'Interplanetary Internet' from the UK-DMC satellite [7]. Acting as a 'bundle convergence layer' was proposed as an optional feature for Saratoga for delay-tolerant networking scenarios where the Bundle Protocol might be used [8].…”