Bridging Space and Earth with Delay Tolerant Networking (DTN), a Workshop on Empowering Connectivity

At the end of September this year, speakers from IPNSIG travelled to the Abdus Salam International Centre for Theoretical Physics (ICTP), in Trieste, Italy. The first leg of my journey was from SEA-TAC to Heathrow, a flight with an average duration of 9 hours and 45 minutes, easily divided between two movies, several lukewarm coffees, the hallmark half-sleep of a man who has forgotten his neck pillow, and a brief (if uneasy) truce with the in-flight “meal”.

If I had sent a message to Voyager 1 before boarding that flight, at light speed, that message would still need about 12.05 hours to arrive at the time I walked off the plane. Moving at the maximum speed of any object in the universe, the time required for a transmission to reach Voyager 1 from Earth is more than double the time of my transatlantic hop. When the fastest rate of transmission in the universe waits nearly a day to be received, you stop designing for “always-on” and start designing for delay. That’s the mindset behind DTN - and the throughline of ICTP’s Workshop on Empowering Connectivity: Bridging Space and Earth with DTN, organized by Samo Grasic, the head of IPNSIG’s Pilot Projects Working Group.

Now, let’s imagine you are sending a message Earth to a rover on Mars, and let’s assume that Mars is at its closest approach to Earth, and that you can instantly send this message at the speed of light with no atmospheric or solar interference. Ideal conditions!

Message Sent…

Back to the shore of the Adriatic and into the classroom. IPNSIG members were present to speak, mentor, and host a lab that put Delay/Disruption-Tolerant Networking (DTN) into the hands of attendees. Attendees were similarly diverse, representing innovation in the most remote regions of the world, solving problems ranging from monitoring flooding rivers in Malaysia to creating new, sustainable education opportunities in underdeveloped regions of Kenya to advancing federated machine learning in UAVs for biosphere monitoring.

By week’s end, attendees had booted Raspberry Pi 5s as Internet Overlay Network (IONe) nodes, seen bundles move, sent multi-hop messages and files to their fellow students, and left with a working IONe-compatible node and, more importantly, a mental model of how to design for disruption - on Earth or in space.

The workshop gathered a rare cross-section: space-mission veterans, ground-network practitioners, and researchers focused on underserved regions. All were unified in the purpose of bringing communications to the edge of human habitation and exploration, and focused on one question: how do we make connectivity work when links are intermittent by design?

The Internet is for everyone – even in space.

                                                          -Vint Cerf

The program paired in-depth talks with hands-on lab blocks: learn the logic of store-and-forward transmission, scheduled contacts, and IONe, then build.

The workshop was organized by:

Samo Grasic (IPNSIG Pilot Projects lead) designed the lab, kept the week on rails, and connected space-first thinking to real terrestrial deployments.

Marco Zennaro (ICTP) organized the workshop with Samo Grasic and was the liaison between the ICTP and IPNSIG.

Vint Cerf (Google, IPNSIG/ISOC founder) opened with the why and the where-to-next, reminding us that resilient networking is as much a public good as a technical craft.

Along with guest speakers and technology pioneers from around the world:

Nii Narku (University of Cape Coast, University of Ghana) brought his experience as the father of the African internet to contextualize the efforts of communications innovators and provide a vision of the connected world.

Scott  Burleigh (JPL, ret., IPNSIG Board Member), co-author of the Bundle Protocol (RFC 5050) and Licklider Transmission Protocol (RFC 5326), walked us through first principles and how they map onto today’s missions.

Keith Scott (CCSDS DTN WG, IPNSIG Board Member) brought the pragmatic routing and operations lens: when to lean on CGR, when opportunistic paths win, and how to make real links behave.

Leigh Torgerson (JPL PTL; IPNSIG) laid down the historical arc and timeline of DTN and ION, then dove deep into ION’s internals and the decisions that shaped it in flight and on the ground.

Roberto Gaetano (ICANN veteran) added the governance and standards view, revealing what it takes to align multi-stakeholder realities with DTN’s promise.

Laura Chappell (Chappell University, IPNSIG Academy Lead) translated theory into packet-level intuition, using traces to make custody, timers, and convergence layers visible.

Life in the Lab

We started in the classroom each day. After primers from the experts - why DTN is scheduled-first, how plans/ranges/contacts interlock, why we make the routing choices we do, and how to account for the speed of light just being too slow- we moved to the lab benches to make those ideas real. 

My Echo, My Shadow, and Me

Before touching the network, attendees launched two IONe instances on a single Pi and passed a bundle between those instances via loopback. A quick bping (and bpecho) confirmed custody and contact graphs were working; logs and (optional) packet captures made the bundle lifecycle visible. No cables, no surprises. This is a simple and direct way we like to start our DTN labs.

Hello Neighbor

Each pair then got to dive into the config files and define their first neighbor node. This gave attendees a hands-on experience manually configuring the trifecta of range, contact, and plan that underpins the Contact Graph Routing (CGR) in ION.

A Skip, Hop, and Jump

With confidence up, it was time to introduce a third hop, creating a network rather than a single link between two nodes. This involved creating contacts, plans, and ranges for each attendee’s two closest neighbors. With all nodes on Tailscale VPN, participants were now able to form multi-hop links between nodes.

To the Ends of the Earth

Finally, Samo federated everyone into the IPNSIG Pilot Projects Working Group (PWG) network, so class nodes could participate in larger, scheduled paths beyond their table. This network is shown on the IPNSIG PWG home page (https://www.ipnsig.org/ipnsig-pilotprojects-wg) and includes many participant nodes, now in their home countries, along with two emulated nodes: the Moon and Mars.

What We Learned

Our time at the ICTP in Trieste confirmed what we hoped and revealed what we hadn’t planned for. On the expected side, seeing contact graphs operate in real-time – windows of contact open, custody shift, bundles advance - reinforced how powerful scheduled paths are when the plan is predictable.

On the surprising side, the diverse focus of attendees in the room surfaced new routing needs and unanticipated use cases that don’t fit neatly into fixed schedules. We saw an emerging demand for opportunistic approaches alongside CGR, plus a clear signal that ION must become more user-friendly to cast a wider net to bring in fresh challenges, new contributors, and broader deployment.

The future of DTN, space communications, and ION will hinge on participation: lowering the on-ramp, inviting more hands to experiment, and letting practitioners bend the stack to challenges we haven’t imagined yet. Adoption drives innovation. If we can make ION and IONe easier to learn, easier to run, and easier to extend, DTN and many other components of space communication, such as network architecture, varieties of link-layer, federated learning or other automation advances, and much more, will all benefit from the innovative community that already exists just waiting to be tapped into.

Even as IPNSIG members helped attendees configure their nodes and join the PWG network, it was clear that the education was flowing both ways. The challenges that ION was designed to overcome may not be the only challenges that it can overcome, especially given the transmission-layer agnosticism that is central to the Bundle Protocol upon which ION and IONe rely.

Ensuring that “The Internet is for everyone – even in space” will be no simple or straightforward task. Questions of budget (both financial and power/resource), pace of innovation, ease of onboarding, clarity of communication and purpose, and the ever-looming aspect of governance are all being tackled by IPNSIG as an organization, and the buy-in from communities and organizations represented by the attendees at the ICTP’s Workshop on Empowering Connectivity: Bridging Space and Earth with DTN is critical to its success.

Message Received!

Assuming you read at an average (or just slightly above average) speed, your message to Mars from the start of this post has just arrived. Communication that goes beyond classical internet architecture is the consequence of a space-bred discipline. ION was built for predictable passes, long RTTs, and tight power, storage, and memory limits. That heritage gave us habits that matter: treat the contact plan as topology, design for store-and-forward custody, and accept that waiting on purpose is a feature, not a failure.

Labs like the one in Trieste build a bridge. In the lab, we mapped those space-hardened patterns directly onto terrestrial reality without diluting them: the same IONe stack, the same scheduled-first mindset, the same discipline around custody and timers - now running on Pi-based nodes, classroom sensors, and the PWG network. The payoff is a shared goal of bending the capabilities of ION and DTN in general to fulfill the needs of humanity in a myriad of environments.

In developing DTN technology, reaching the stars may be the guide, but serving humanity will always be the goal.

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With thanks to the IPNSIG members who turned principles into practice:

Samo Grasic – Lab and event architect and lead

Vint Cerf - Opening frame and north star

Nii Narku - Vision for connecting underserved communities

Scott C. Burleigh - BP/LTP first principles, logic, and vision

Keith L. Scott - Routing & operations pragmatics

Leigh Torgerson - DTN/ION timeline, deep dives, and details

Roberto Gaetano – Guidance on governance and vital stakeholders

Laura Chappell - packet-level intuition and visibility

And all speakers who participated in bringing ION to Earth to help foster stakeholder communities and support the human endeavors that benefit from DTN technology.

Special thanks to the Abdus Salam International Centre for Theoretical Physics (ICTP), our liaison and facilitator, Marco Zennaro, and all attendees at the Workshop on Empowering Connectivity: Bridging Space and Earth with DTN.