NASA Delay Tolerant Networks: Operational, Evolving, an Ready for Expansion

The future of humanity’s presence beyond Earth depends on the successful commercialization of space. For
commercialization to succeed, companies need cost-efficient architectures to support their business models and
minimize risks for human capital, design, development, and operations. An ongoing challenge to any space enterprise
is the reality that terrestrial network technologies are insufficient to provide reliable communications between assets
in space. Whether you need to ensure your valuable data is safely transmitted to the ground or reliably delivered
between platforms in orbit, ensuring data integrity over intermittent communication links is a necessity. Current
solutions to space communications rely heavily on manual recording, storing, and retrieval of data from spacecraft.
The current standard in space communication protocols, Consultative Committee for Space Data Systems (CCSDS)
Space Packet standard, is reliant on inflexible network architectures based around mission-critical infrastructure to
ensure data delivery. However, by automating the recording, storing, retrieval, and verification of data with Delay
Tolerant Networks (DTN), the operator is freed from the dependence on manual data management and expensive
mission critical infrastructure.

NASA has been developing delay tolerant systems since the late 1990’s. Multiple DTN implementations
have been established during that time, each suited to different use cases. Most notably, the DTN deployment for the
International Space Station (ISS) includes demonstration of two DTN technologies: Interplanetary Overlay Network
(ION) and Delay Tolerant Network Marshall Enterprise (DTNME). Beyond ISS, there are even more NASA DTN
deployments being considered. Now that DTN implementations are maturing, it is appropriate to reflect upon these
decades of work, review the integration and performance of the existing ISS deployment, and explore the future
possibilities for DTN deployment industry-wide.

The ISS DTN deployment is a complex architecture consisting of different DTN implementations for the
onboard and ground network environments. The ION DTN implementation is being used in the on-board network.
The Huntsville Operations Support Center (HOSC) DTN implementation, DTNME, is used by the ground network
supporting ISS and will soon be a second onboard gateway too. The two implementations work cooperatively to
provide high fidelity data services to flight operations users and payload developers across the globe. Though the two
implementations yield a quality service, limitations are evident. Data rate, data storage, and device management are
constrained by the services themselves and the complex nature of the deployment. Evolution of operations concepts
will improve system capabilities and stability, but significant improvement will require additional development to the implementations themselves and to the overall deployment architecture. Taking advantage of the ongoing
development and operation of the ISS DTN service will be central to the success of the future evolutions of NASA
DTN deployments while demonstrating the benefits of DTN’s low-cost reliable data communication protocols for the
growing commercial space industry.

A broad effort on DTN integration and support is necessary to promote expansion beyond existing
applications. NASA is developing several useful DTN implementations across a number of different systems: ION,
DTNME, High-Rate DTN (HDTN), Bundle Protocol Library (BPLib), and others. To prevent fragmentation, DTN
implementation teams need to communicate, collaborate, and integrate with one another to build a solid operational
foundation for new DTN deployments. The establishment of a group that can assist new DTN users with understanding
the purpose of each DTN implementation, provide best practices, and serve as a general knowledge base is paramount.
Potential use of DTN on Gateway and other future NASA missions further drives the need for streamlined
communication between DTN implementation teams. A well-integrated and highly engaged NASA DTN working
group should help provide system architects the best DTN solutions for future commercial space efforts.

This paper will first review the history of DTN implementations, explore the shortcoming of current space
networking solutions given available limits in technology, and therefore establish the need for Delay Tolerant
Networking in space communications. Secondly, the authors will explore NASA’s array of DTN implementations and
highlight their usefulness to space applications. Thirdly, this paper will establish general DTN implementation
distinguishing factors. Fourthly, the authors will discuss attempts to create a generic DTN comparison matrix, and the
authors will review potential future topics in DTN innovation and collaboration, highlighting several key future
efforts. Finally, this paper will describe how the institution of a NASA DTN Working Group will benefit DTN
adoption across the governmental and commercial space sector. The goal of this paper is to encourage enthusiasm for
DTN, share strategies for improving DTN on both current and future applications, promote the collaboration of DTN
implementation groups within the international space operations community, and open the conversations about DTN,
priorities, complexities, and innovation to the wider spaceflight industry.