Delay-Tolerant Network (DTN) – WS 16 2021

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30 June 2021 | 16:30-17:30 CEST | Studio Trieste | Video recording | Transcript
Consolidated programme 2021 overview / Day 2

Proposal: #53

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Session teaser

The current Internet protocols are inadequate to deal with situations in which substantial network delays are experienced. Initially thought for interplanetary communication, the delay-tolerant network (DTN) has interesting applications also on our planet.

The session will include information about the principles of the protocol, examples of applications, and the policy implications.

Session description

This session features a panel of experts who will address different aspects related to the Delay-Tolerant Network technology and applications. These are the points that we would like to cover:

What is the Delay-Tolerant Network (DTN) protocol and what are the problems that it addresses? Vint Cerf will present the bundle protocol and describe how it can be used in situations where there are substantial delays in the transmission and/or a large fault rate.

The Interplanetary Internet Communication in outer space experiences substantial delays and high risk of faults. Under these circumstances the current Internet protocols would be inadequate, while DTN will solve these problems. The Inter-Planetary Networking Special Interest Group (IPNSIG) was created for this purpose. Oscar García will present the work of IPNSIG.

Provide connectivity to the Sámi nomadic community The idea to make use of DTN for Sámi reindeer herding communities started twenty years ago within a university led constellation, with the basic notion of connectivity as such and focus on general services. Today a community initiative owns the process and the current focus is business intelligence. Maria Udén and Samo Grasic will present the evolution from 2003 to 2021.

Environmental monitoring and tourist protection in the Postojna caves In the Postojna caves there are several meteorological stations and other surveillance equipment that must provide the collected data to the base station. Boštjan Grašič will explain how DTN technology was used to vehicle the data to the base station via the tourist train that runs regularly in the caves.

Attendees are strongly encouraged to read the material referenced below under "Further reading" to have a better idea of the topics that will be discussed. During the session, the audience will be asked some questions via MentiMeter. You can see the results below and download them as pdf.

WS16-2021 menti-answer how-familiar-are-you-with-delay-tolerant-networks-dnt.jpg  WS16-2021 menti-answer do-you-believe-that-dtn-can-solve-some-problems-related-to-your-daily-routine.jpg


The session will be organised as a round table. Four experts will provide short presentations of different aspects of Delay-Tolerant Networks. The interaction with the participants will be ensured by asking questions to the audience and providing also time for questions by them to the panelists.

Further reading

These excellent - and short! - videos explain the principle of DTN and its advantage over plain IP:

For further reference, please see the Wikipedia page:

IPNSIG (InterPlanetary Networking Special Interest Group) uses DTN to realize a functional and scalable system of interplanetary data communications:

This is a paper about using DTN on mobile phones to improve communications in challenged areas:

This paper describes how DTN was used to provide connectivity to the Saami nomadic community:

This paper describes another DTN experiment, implemented at the Postojna caves to assist automatic environmental monitoring and tourist protection:


Focal Point Focal Points take over the responsibility and lead of the session organisation. They work in close cooperation with the respective Subject Matter Expert (SME) and the EuroDIG Secretariat and are kindly requested to follow EuroDIG’s session principles

Organising Team (Org Team) List Org Team members here as they sign up.

The Org Team is a group of people shaping the session. Org Teams are open and every interested individual can become a member by subscribing to the mailing list.

  • Roberto Gaetano, EURALO
  • Kris Shrishak, YouthDIG
  • Avri Doria, Technicalities
  • Vint Cerf, Google
  • Marco Zennaro, ICTP
  • Kristin Little, IEEE
  • Franci Gabrovšek, Karst Research Institute
  • Marija Zlata Božnar
  • Boštjan Grašič, MEIS
  • Maria Kristina Udén, Luleå University Of Technology
  • Oscar Garcia, IPNSIG
  • Samo Grasic

Key Participants

Key Participants are experts willing to provide their knowledge during a session – not necessarily on stage. Key Participants should contribute to the session planning process and keep statements short and punchy during the session. They will be selected and assigned by the Org Team, ensuring a stakeholder balanced dialogue also considering gender and geographical balance. Please provide short CV’s of the Key Participants involved in your session at the Wiki or link to another source.


The moderator is the facilitator of the session at the event. Moderators are responsible for including the audience and encouraging a lively interaction among all session attendants. Please make sure the moderator takes a neutral role and can balance between all speakers. Please provide short CV of the moderator of your session at the Wiki or link to another source.

Remote Moderator

Trained remote moderators will be assigned on the spot by the EuroDIG secretariat to each session.


The Reporter takes notes during the session and formulates 3 (max. 5) bullet points at the end of each session that:

  • are summarised on a slide and presented to the audience at the end of each session
  • relate to the particular session and to European Internet governance policy
  • are forward looking and propose goals and activities that can be initiated after EuroDIG (recommendations)
  • are in (rough) consensus with the audience

Current discussion, conference calls, schedules and minutes

See the discussion tab on the upper left side of this page. Please use this page to publish:

  • dates for virtual meetings or coordination calls
  • short summary of calls or email exchange

Please be as open and transparent as possible in order to allow others to get involved and contact you. Use the wiki not only as the place to publish results but also to summarize the discussion process.


  • DTN networks on Earth are an example of an early entry into the community network trend that is now becoming so important. There are unexplored uses for DTN in emergencies and even under conditions of network shutdown by repressive governments.
  • We need to pay attention to the underserved communities and find the solutions to offer them services.
  • We might need to consider regulation about the use of frequencies for applications on Earth as well as in space.
  • The Solar System Internet effort is a serious attempt to plan for a real network to support manned and robotic exploration of the Solar System.
  • The DTN technology and the bundle protocol, originally developed for space exploration, can be used by applications on Earth. Applications on Earth can be used as test bed for space applications development, as is the case for the Sámi reindeer herd tracking and for Karst cave meteorological data collection.

Find an independent report of the session from the Geneva Internet Platform Digital Watch Observatory at

Video record


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This text, document, or file is based on live transcription. Communication Access Realtime Translation (CART), captioning, and/or live transcription are provided in order to facilitate communication accessibility and may not be a totally verbatim record of the proceedings. This text, document, or file is not to be distributed or used in any way that may violate copyright law.

>> ROBERTO GAETANO: Good afternoon. Let’s start this session. We will be talking about delay-tolerant network. As a first thing, I would like to propose a poll, a question to all participants. And I will share the screen, actually. Let me do this. It’s a bit – I’m not expert of these tools, and you can clearly see that.

So here we go.

So this is – the first question for the audience, I have no idea besides the experts that here how much the delay-tolerant networks are well known. So in order to have an assessment of this, I would like to have this – to launch this poll to you. I will put an instruction in the chat if you don’t see it. And you need to go to, and use the code 10890356, in order to answer this poll. You can start when you want. I think that we can have an indication of what kind of audience we do have. So the plan, while you are answering this question, I will explain a bit the plan of the session.

We would like to start with an introduction by Vint Cerf that will explain to us what is the delay-tolerant network – what this is all about, what this technology, the delay-tolerant network is about.

Unfortunately, I don’t see Vint yet. I’m told he’s coming. So in the meantime, while you continue the poll, then we will have – we will have Oscar Garcia who is in the board of the interplanetary network, if I did remember that right.

That will talk about the interplanetary for interplanetary communication.

Then we are going back to the earth with an example of application of the delay-tolerant network on the earth, with the nomadic population in northern – in – well, actually, Northern Scandinavia.

And then we will close because after having been in the sky and on the surface, we go underground, to talk about another application that is in the caves. I will introduce then the speakers when it’s their turn.

So I see Vint in the room. I have Vint. Good afternoon. I made you cohost.

Let me just summarize the result of this slide and then I will relinquish the screen so that you can share your screen with your presentation.

So what I get here is the model value is some basic knowledge. So we have a couple of experts that will be some of the presenters. One absolute beginner. Welcome to the world of delay-tolerant networks and a couple of people with advanced knowledge. But the model value is some basic knowledge. So we will keep that also in mind for the presentation. I think I have spoken too much I stop my sharing and Vint, you have the floor.

>> VINT CERF: Okay. I will see if I can get my presentation up. Let’s see. We want to get to window, and we want to get to – there we go.

And share.

And let’s see, I hope that you are seeing what I’m seeing. What you should be seeing, though is this slide and I will go full screen. So let me ask, can you see that correctly?

I’m not hearing anybody. Can you hear me?

>> Yes, we can hear you.

>> VINT CERF: You should see a slide that says “Pathfinder, Reconnaissance Orbiter.” The Problem Is I Can’t See You Any More.

Thank You for Giving Me the Opportunity to Tell You About this. This starts with a series of missions from Mars and most recently, of course, China, for example and the United Arab Emirates and the Russians have made a number of attempts as well. So this series of successful missions have driven a group of us to believe that we should be developing an interplanetary extension of the Internet. The initial work was done with the help of the NASA jet propulsion laboratory in particular and also Miter corporation. So we have successfully made a number of landings on Mars as you all know. The most recent – the most important one after the Pathfinder which landed in 1996 is – or actually, it launched in ’96 and landed in ’97, which was spirit and opportunity which landed many January of 2004. The plan was to deliver this at 28 kilobits, and they reduced the duty cycle and made the scientists very grumpy.

There were X band radios on both the spacecraft on Mars and the orbiter to map the surface of Mars and figure out where the orbiters should go. So they were reprogrammed with a version of the CCSDS file delivery protocol which is a store and forward protocol, which all of you will recognize as packet switching, in order to push the data up to the orbiter when it got overhead, and then the orbiter would hang on to that data until it got to the right place in its orbit to deliver the data to what’s called the deep space network. These are three 70-meter dishes that are on earth looking out towards the solar system, with a great deal of sensitivity so they could pick up even weak signals in order to receive the data.

So since 2004, all of the missions that the US has sent to Mars have been delivering the messages through the store and forward relay system. So in ’98, right after the Pathfinder mission landed successfully for the first time, in ’97 on Mars after a 20-year gap. In ’76 we had the two Viking landers successfully arriving on Mars and then nothing worked for 20 years.

So the path finder arrives and in 2004 – and in 1998, we get together at JPL and we say, hmm, why don’t we do an interplanetary backbone to support man and robotic space exploration, why don’t we use TCP/IP, it works on earth and why don’t we do it on Mars?

Then we did the math and we looked at the variable distance between earth and Mars the round trip could be 70 to 40 minutes and TCP flow control does not work very well with a 40-minute round trip time and DSL doesn’t work. You request an IP address while you are on Mars, and you get an answer back if you are lucky 40 minutes later, by which time the IP address may actually have changed on earth because the target was mobile.

So we needed to do some very different architectures in order to accommodate a range of parameters that were pretty different from the ones that made TCP/IP work well on earth.

So we explored this idea of delay and disruption tolerant networking. You can see the delay, obviously, but the disruption is there too. The planets are rotating and we don’t know how to stop that. So if there’s something on the surface that you are talking to and the planet rotates, you have to wait until it comes back around again. The same thing with the orbiting satellites.

So NASA along with the European space agency, the Japanese, the Korean, and the consultation system, began working on the delay and disruptant tolerant.

We created the bundle protocol. It does a delay name resolution so that first you figure out which planet you are going to and you get there before you ask where on that planet do I find the destination. So it’s in the two-step DNS lookup. The second thing and the very important aspect of the bundle protocol, unlike TCP/IP, we actually store data in the network. If you are going from earth to say Jupiter, and you are stopping by way of a relay that’s in orbit around Mars, you don’t want to throw the data away just because the Mars relay doesn’t have the Jupiter relay and contact and at the moment when it receives data. Unlike TCP/IP which says if I don’t have a path to the destination, I’m throwing the information away back then. Memory was expensive back then. Now it’s not as expensive. So the idea is to transmit the links when it comes back. And so that’s a different architecture than TCP/IP.

The other problem we ran into because of the variability and the length of the delay, latency in the system, network management in an interactive way. Ping is not your friend. If you ping something and it takes 40 minutes to a day to get an answer back, you are north getting the kind of interaction that you have become accustomed to in the Internet.

So we have a very new network management philosophy, which is more like remote execution, where you send, you know, a set of things to be done and it goes once and lands and then stuff comes back. And so that’s a very different mechanism.

Now, at the beginning of this program, the first thing that I told my team there is I did not want a headline that says 15-year-old takes over Mars Net. It’s bad enough that we have attacks against things right now on the earthbound internet, but I didn’t want that to happen on Mars or any place else.

So we built in to the bundle protocol being strong authentication and encryption in order to protect against abuse and so that’s a fundamental, you know, core part of the design.

And then in terms of routing, it turns out that for many of these architectures, since we can compute the orbits of the various spacecraft or at least the trajectories of spacecraft, we can know when contacts are possible.

And so we can create a contact graph which basically says, this is when these two things can talk to each other.

And that helps us figure out how to route traffic through the network.

So I’m not going to go into great detail here, except to just convey you to all the stuff that’s gone on with the space agencies, especially within NASA, but also with the others. So we did some direct testing of the protocols, the prototypes, protocols with the deep space impact – or the deep impact spacecraft that was used in the EPOXI mission, and we tested this in situ with the EPOXI spacecraft and then we have been testing, since 2009 on the International Space Station. So the bundle protocol is supporting crew interactions with earth.

We did a METERON experiment with the ESA team in order to show that we could do realtime control if the latencies were low. So there’s a little robot that was controlled directly with a crew member on the International Space Station so that we have the ability to do realtime, if, in fact, the latencies are low.

We also did a high bandwidth test, using a lunar laser communication system which was bouncing a laser off of an orbiting spacecraft around the moon and we did that, demonstrated to 622 megabit second capabilities using optical coms which is of great interest to everyone, in order to increase data rate to achieve and pull data back from the various exploratory spacecraft.

We did interoperability testing of ION, and NASA and JAXA. There was an IETF Working Group set up to standardize the bundle protocols and the transmission protocols of Licklider and that’s been going on since 2014. The conative committee on space data systems has been working in parallel with IETF on standardization of the bundle and the JSON protocols that are part of that protocol suite. And we also had a wonderful project at the Lulea University in Sweden, way up in the north to use DTN techniques in order to allow the Sami people to track their reindeer. This is just a demonstration of an opportunistic connectivity in the system.

We have implementations from Android, from Braunschweig. NASA did a 90-day test and decided to go to implement rather than research and development mode. So we are in the process at NASA in doing implementation of the bundle protocols.

The software for this is open source. It’s available at GitHub for both the ION implementation from NASA and the IBR-DTN from Braunschweig. We are working on getting DTN on it the TDRSS system and the deep space network. And at the moment, we are looking forward to DTN for Artemis and Gateway. There’s a difference between the people that do the work at NASA and IPNSIG, and a lot of people from IPNSIG are working on this, including the vice chairman, and so there’s an overlap.

But IPNSIG is an interest group. It’s not responsible necessarily for doing all the stuff that I just described. That’s being done by the space agencies, and eventually he will buy the private sector that is engaged now in supporting space exploration.

So I think that’s my last slide and I will stop sharing because I think you want to hear now from some the other speakers.

>> ROBERTO GAETANO: Yes, thank you very much, Vint. And I – before going to the next speaker, while I introduce the next speaker, let me share the screen for the second question. You have been talking about the protocol, and defining what was the original problem. Now the question is whether people believe that the delay-tolerant network can solve some problem related to our daily routine, things that have an impact on our daily life.

And while this is – while you vote, I’m introducing the next speaker that is Oscar Garcia. That is in the board of the interplanetary network special interest group. I will give just another few seconds and then I will stop my screen to let Oscar – I think we have a sufficient sample. The vast majority, almost everybody thinks it will provide solutions to some problem with one person that thinks it’s going to be a game changer. And I wonder whether that is Vint.

Anyway, I’m – but – so people believe that it will have an impact and there’s going to be interest in this, which makes me think that we should already start thinking about another session on this in 2022.

So I will stop sharing my screen and give the floor to Oscar. Oscar, please you have the floor. Just one other thing, I think that it’s better if we – if we have the – all the questions at the end, because otherwise, we maybe a lot of people will ask questions to Vint and then there’s not enough time for the rest.

Oscar, please go on.

>> OSCAR GARCIA: Thank you, Roberto. Thank you very much. Are you getting me well?

>> Yes.

>> We can hear you.

>> OSCAR GARCIA: Thank you. Thank you, for also the presentation of the protocol and the development about all of this.

Well, my name is Oscar Garcia. I am the pilot project Working Group lead of the interplanetary network special interest group. And I’m going to start sharing my screen so you can follow. Can you see there?

>> VINT CERF: It’s blank right now. There we go.

>> OSCAR GARCIA: Great. I’m going to make it full screen. Well, the mission of the interplanetary network and the IPNSIG is to realize functional assistance for interplanetary communications as Vint has been explaining.

Our group, the IPNSIG started in 2002, it was some years but not so much five years after the first discussions about the interest planetary network and we are nearly 20 years now of development. We are divided in several work groups that are strategy, outreach, documentation, technical documentation specifically, and pilot projects that I linked.

We have a global participation of 787 members that are distributed all around the world in all the continents as you can see.

We have been working in several developments over the years, but in the last – I will mention some developments of members of the IPNSIG that are from the last year. In November 27 last year, 2020, we developed the first DTN communication in cloud servers with Dr. Larisa Suzuki, myself, Oscar Garcia, and with Vinton helping us and – and he sponsored this – this project.

This was first time that this DTN communications at least publicly has been used to make connections in the cloud.

Also last February, a DTN network management system was developed for one of the members of our group, the Spatiam Corporation. Also, you can see that we have in development a test bed of 100 servers that work by Dr. Ronny Bull in the Utica College in the state of New York in the United States.

We can also mention that Dr. Larissa Suzuki is working with artificial intelligence and transferring images on DTN and making interpretation of them with this technology about artificial intelligence and routing clouds and multitasking.

Vint also is the DTN for reindeer has been – well, Maria, are going to make a deeper explanation all of this.

And in my group, and team, we have developed the unified medical records for space exploration that connects the health records on earth with possibly organization of this technology in space. So the medical records could be available on space exploration.

And this is a new project that we are launching very soon. It’s a testing plan for interplanetary Internet so most – some volunteers on earth can be of the testing plan from their personal computers, even testing the DTN protocols if you are interested, you can send an email to I will refer to this later, and we will contact you. And this is a project that very – very new that was development with the offset that this is the space lab of Europe, European Space Agency allowing the connection between different implementations of DTN protocol. This was developed by 3DTN Gmbh, from Germany and the ION protocol developed by JPL, and connecting also with interpretation of images with artificial intelligence as I commented before.

So this is a very, very interesting element that was highlighted also by the ESA, the European Space Agency Twitter.

Well, in other areas that are related too, the Internet Governance, we set up a space Internet Governance webinar. Vinton was there, and Scott Burleigh was the moderate and Scott Pace. It’s online and you can review it.

Today is the publishing date of the strategy Working Group report talking about the development of the solar system Internet and Vinton, would you like to make some comments on this to – before I make a closing of my presentation?

>> VINT CERF: Yes, thank you so much, Oscar.

We are all very excited about offering this document. We’re very humble about this. We know that the IPNSIG, although there’s almost 800 of us, are not necessarily capable of building and operating the solar system internet, but we would like to get there. We would like people to think their way through what is going to be needed in order to achieve the objective. And you might ask, why would we want to do that at all? And the answer is we want to support space exploration with man and robotic instruments, and that a number of those devices, including people will be increasing over time.

And so having a backbone network in the – in the solar system serving in the same way that the Internet does on earth, seems like a very important objective and so we have laid out our thoughts on how to get there to help us refine these ideas and so there are ways of getting in touch with us after you get a copy of this report.

It will be available in soft copy form. Thank you.

>> OSCAR GARCIA: Thank you very much for allowing us to show all of our developments. You have there our web – our website and my email there is Thank you, Roberto for the invitation.

>> ROBERTO GAETANO: Thank you, Oscar. I’m also being reminded of two things. One, that, you know, we need also to somehow address policy issues that are related to the European Internet Governance. I think it’s a little bit difficult in the session like this, and we knew that already on the start. The second thing I’m reminded that we have a plenary starting at 17:30 local time and that’s 15:30 UTC and we need to close on time and give also the time to the – to the reporter to draw some messages from – as a result from this session.

So without further ado, I would introduce the first speaker. I believe it’s Samo Grasic, with Maria and also Avri Doria was involved in that project. And provided the project to provide connectivity using DTN to the nomadic population of Sami. That has already been mentioned by Vint. Please Samo, go ahead with your presentation.

>> SAMO GRASIC: Thank you, Roberto. Can you hear me all?


>> SAMO GRASIC: And you see my slides.


>> SAMO GRASIC: Thank you. I would like to thank you for inviting me. As you can see this photo kind of in the background shows and illustrates well the conditions that we are facing on – out on the field, and it was taken from this spring maintenance time when we maintain most of the base stations.

So I would like to start to say a few words first about the project that we work right now. So current work is conducted under the project that aims to provide safer work environments for reindeer herders. It’s hosted by Annelie Paivio, with the Dalvvadis Economical – association. It involves almost 200 individual reindeer herders. We are located in this yellow area on this small map that I show. Yeah.

So throughout the yearly seasons, reindeer herders are moving their herds through different pasture lands. A rather large month in there, approximately 200 by 200 kilometers big, close to the Norwegian border and lacks any type of Internet or Internet policies and this challenges the reindeer herders work environment and their safety as they have troubles to communicate.

So if I return a bit to the idea of using DTN for extraterrestrial use. The idea was first introduced by Avri Doria, and Anders Lindgren and it was later on implemented in the project that Maria Uden. And it was to use hikers, helicopters and snowmobiles as data mules. There’s 20 to 30 kilometers distance between them.

But they are frequently visited by hikers and there’s many helicopter flights scheduled in. And we equipped – we hand out the various devices to these people that were involved in this test, and they were transferring data back and forth to the field, using these small devices.

The goal of the current project is to build a reliable reindeer tracking service, provide short messaging community service to reindeer herders and extend the current network coverage with a drone that can hover and collect the data.

And this is, I think, quite a bit – this is a difference between the work that we have done before, where we kind of ran full – fully bundled stack protocols that ran on the Linux machines and current platform that I will talk about right now that it’s much, much more constrained. And it doesn’t provide as large bandwidth as we did.

So this is tailor made nor any herders and it’s made to with stand the harsh winter conditions. There’s a larger – a large market of GPS tracking devices but none of them is actually suitable for our scenario. For instance, even rather governmentally GPS tractors that uploads are not applicable as you need the Internet connectivity to show the GPS positions of reindeer on actual phone.

So the platform is designed for highly power constrained environment. And base stations are equipped with solar panels in order to charge them, all the way during the long arctic winter conditions, we do not get basically any solar power for three to four months.

In addition, harsh cold affects the battery chemistry and significantly reduces the battery capacity.

LoRa-DTN is ail light weight store-and-forward. I do need to mention that thanks to the IPNSIG support, the entire system was built around the DTN architecture which is important as it allows later on to extend the GPS tracking service to other services such as short messages and we can carry any pay load over this network.

We are using on the shelf, lower radios on, 433 megahertz, with high gain antennas. This gives us a good range, 60 kilometers despite the low powered transmissions.

The entire Internet is synchronized to save the bandwidth. And they go in sleep time and wake up four times on average to exchange the data.

In order to save the development time, the entire system was built on the Arduino development boards and all the plastics are freely printed in order to adapt to various conditions and development phases.

So now I will present the LoRa-DTN. It’s a rather large battery to give us one to five years battery life. It’s quite important as these collars can be accessed only once per year when the reindeer herds are gathered. The second components are base stations. Most of them are actually mobile. We have a couple of fixed ones, and the reason why we made them mobile is so that we can deploy them where and when we actually need them. So they are actually built on this sleds so they can be moved around with the snowmobiles in the winter.

The crucial part, I think of this latest deployments are actually pocket nodes. These small devices are carried around by the reindeer herders and with the DTN. It’s done over Bluetooth. In case you are out of the lower DTN range, they can also be attached to the drone and fly higher up and until you actually get access to the network. By doing this we manage to significantly extend the range of the already deployed network. And as the lesson, I think quite a vital part of this network is actually our mobile application called Nomo track. And its function is to show GPS tracking of reindeers and it provides short messaging functions and most important feature of that app is it’s fully functional even without Internet connectivity. All data is actually locally buffered and then synchronized as soon as you reach any kind of internet connectivity.

I would like to conclude with a couple of challenges that we’re still facing. We are still assessing what type of economic model can be applied to this network. It deals with the governance issue as well. We believe that in order to keep this network alive, it’s quite important that the reindeer herders own and maintain this network. And this is particularly important because in order to access one of these remote base stations, it’s rather costly to send an external actor to the field.

We are also working on a LoRa-DTN. We were able to exchange the messages between our high lye constrained LoRa-DTN region and ION-DTN that IPNSIG is building. Routing of the traffic is slowly becoming an issue as our network is less partitioned as we expected or anticipated due to the rather long radio links. And then it is classical snow and ice formations that are damaging our antennas. We are still trying to solve this in some way. At the moment, it seems like the wind turbulences are actually causing the biggest damages, actually.

And then at the end, I would look to mention as well the radio interference problems that we have with commercial drones and that’s due to the highly powered video transmitters on the DTN drones. Our lower radios are very, very sensitive and they operate on very low powers and it’s very important not to have a strong transmitter. We try different filters and different methods. We hang maybe 1.5-meter – hang the pocket nodes 1.5 meters under the drone to get a bit of distance from the drones themselves.

With this, I would like to thank you all for your attention and close my presentation.

>> ROBERTO GAETANO: Thank you, Samo. That was extremely interesting. And I have to make a comment. Internet is for everyone. And we have situations in which we need to apply new technologies and normative solutions to bring the Internet to populations that would be otherwise not well served. This happens with community networks and that happens with DTN. So maybe one of the – one of the points that we can draw from your presentation is exactly that we need to pay attention to the underserved community and find the normative solutions to cover that.

Maybe another point could have some regulation about the use of frequencies so that different applications can coexist, but that’s a wider – that’s a wider issue.

So let me go to the last presentation that as I said will move us underground and exactly in the caves that are not far away from Trieste, although they are in a different country now. You know, here in this area, borders change quite often. So you never know what’s happening tomorrow. So I understand that that is Bostjan Grasic who will do the presentation.

We are in the Guinness of records for having two presenters with the same last name in the same session.


Bostjan, you have the floor.

>> BOSTJAN GRASIC: Thank you. Yeah. Well, we are also relations.



So hello to everyone. I hope you can see me, and you see my presentation, please.


>> BOSTJAN GRASIC: My name is Boštjan Grašič, and I come from MEIS research oriented company from Slovenia. I would also like to acknowledge the authorship of this presentation by my colleagues Primož Mlakar, Marija Zlata Božnar, Darko Popović and prof. Franci Gabrovšek from Karst Research Institute from Postojna.

So Postojna Cave is actually a large cave. It’s a cave system over 20 kilometers long. There’s five tourist routes and during this 2.8 kilometers is a railway. It’s taking tourists inside the cave to see the most beautiful part of the cave and then it brings them also out.

So to protect our cave, we installed inside the Postojna meteorological stations. You can see this on the left map. They are denoted with red dots.

And on the next slide, you can see that we have our Postojna Cave, one of these stations, this one in the middle is also connected to the legacy Internet. So it’s perfectly suited to bring the data out of the cave, but we have a problem, how to get the data from other two stations. One is at the entrance, and then the second one is Pisani Rov inside the cave because they are not connected to the legacy Internet and we do have any other means how to transfer data.

So we got during the – we needed to transfer the data from the cave to our office’s databases. So this train that is going through the cave has known driving schedule, except during corona, we didn’t have any data during that time.

So the idea for the detail and design was to – I will repeat it so to transfer data from these two meteor stations by train mule to the Kongresna station to the Internet.

For the implementation of the DTN, we used the prophet implement which was primarily developed in the project that was started in 2008. This implementation was also developed in years after the N4C ended. And I would like to emphasize that we didn’t go directly to the Postojna cave. We started to test it in our private cars.

So my colleague and I, we have meteorological stations in our home, and we collect data there and we put these mules first into our private cars and we bring the data from our homes to offices every day in cars. And when the technology was enough, mature to be put in testbed in Postojna cave, then we implemented that.

So the hardware used in our Postojna network was the meteorological stations that are installed inside the Postojna cave. It runs the line U system for the connection between the data on the trains and the station nodes. We used ad hoc WiFi. You can see how we mounted the data mules on top of the train. And the inside of the data, equipped with battery pack that can last approximately two or in best case three weeks.

And then we actually took two more so that we can exchange it. So when one is empty, we put another one on the train.

So since 2014, we are also collecting long-term database of all the meteorological data and also all the data about our DTN network and so we have a full database of locks, when the connections were made between the mules and the stations and what were delivery delay times. So the delivery delay time, this is the time it was measured and the time it arrives to our database.

So in the meteorological data, it’s not as in legacy in milliseconds. We are fine if the meteorological data is delivered 5 to 10 minutes after it’s measured.

So on the lower figure, you can see also the graph of data delays of all of our measured data. So we have – for every ten minute data we have a database how long was the delivery delay? And this graph is presented here and represents two weeks of data. And we can see that we have the delays up to, let’s say 30 hours.

So for the – then we decided to put this data on the delivery delay times to our analysis. We wanted to see them another way. So we used sunflower diagram. You can read and see more about this diagram in the paper that is described on the bottom of this presentation – on this slide. But the main idea of this sunflower diagram is that we have a radio frequency diagram, and you can see on this, it’s especially suitable for the variables that have delivery cycle. On the outer circle, you see that there are hours of the day. So we have midnight, with the moon and we have sun at 12:00. It’s going in the same direction as the regular clock, but we have 24-hours on this diagram instead of classical clock that has 12 hours.

And when we put the data of the delivery delays on this graph – oh, maybe I should mention that we also have a legend here that each spike that is made for each hour, it’s a segment – it’s segmented in several segments, where we have in the middle, we have the delays that are lower than one hour, and the second segment is the percentage of data that – the percentage of delivery delayed took from one to two hours and the magenta color shows more than 24 hours. So we can see that in the afternoon, and in the night, we have longer delivery days and during the daytime or when the train is passing by the stations, we have lower delay times.

Delivery delay times. And so we go further with the analysis of our DTN network and we also put on this sunflower diagrams also the data – the amount of data that has been exchanged between the data mule and each station inside the cave. And so we have three stations, and we can see it’s been transferred from 7:00 in the morning to 18 hours in the afternoon. And from the legends below, we can see that we – and from the colors of these spikes, we can see that we can transfer during each encounter of the date mule up to 2 to 5 megabytes of data.

On the next slide, final, I would like to conclude that we found out the DTN technology is very useful for the cases without existing – with – sorry with existing schedule and known routes and also where legacy Internet infrastructure is not available.

On this slide, you can see the reference to detailed – to the paper where our DTN network is described in details. I would like to also acknowledge the current support by the Slovenian research agency.

I can show you the online data that is currently coming from the cave. I will put it here. On this page, you can see the data measurement for the station. You can see the data delivery times again. This is – this is the typical shape and the sunflower.

Unfortunately today, the train didn’t pass by the station. I guess it’s in the MEIS – how do we say it’s filling the battery.

>> Enlarge the graph.

>> ROBERTO GAETANO: We are really getting short in time, because I thought we could have some interesting questions. For instance, whether – whether the fusion of applications with DTN will create some governance issues in the same way as in the beginning of the Internet, we didn’t think about some of the governance issues that would have taken place afterwards.

So I see one hand from Vint Cerf. I will give you the floor, Vint, but let me remind that we also need to close with the reporter that tells us what were the messages that she gathers from – from this session.

So Vint, you have the floor. Please be brief.

>> VINT CERF: If we want to have a discussion, IPNSIG could schedule a webinar environment where EuroDIG audience, and we could explore what the outcome could be for the interplanetary network.

>> ROBERTO GAETANO: Thank you, Vint. That will be good. I will figure out how we can put this information in the follow-up of this session so that people who eventually join afterwards can.

So without losing more time, can I give the floor to the reporter and Diana, you have the floor.

>> Thank you very much. I’m your rapporteur and your absolute beginner which is an interesting contrast. We don’t encourage wordsmithing but for this particular session, I would be grateful for your help. I hope you can see the first message. It says DTN networks on earth, and one example of one of the early entries into the community network trend that is becoming important now. There are unexplored uses for DTN in emergencies and even under conditions of network shutdown by repressive governments.

I will give you a few seconds to react to this one.

>> ROBERTO GAETANO: Let me also remind that we will have time when those messages will be published to fine tune the messages on the net.

>> Okay. I hear no objections. So I will consider this message to be a rough consensus with the audience. And there are two points, Roberto brought up, but I think there might be a bit too vague. We need to pay attention to the underserved communicates and the normative solutions to offer them services. And we might need to consider regulation about the use of frequencies so that different applications can coexist.

Would someone like to tweak this message to better connect it to DTNs? Or are we fine with the way they are?

>> VINT CERF: I think these are fine, but I would like to ask if you could include a message that says that we’re serious about the solar system Internet, and that this is an attempt to look forward into the future to build it. That’s well outside of the scope of what you have been mentioning in your WS16 messages.

>> All right, I will pick up what you said transcript. I did see some nods as you were talking and that will be fine, as long as – as long as it is within consensus, then that’s fine.

Is someone writing in the chat something about messages because I can’t see. I’m sharing my screen. Could someone read it out?

>> ROBERTO GAETANO: Well, it – the message is about the regulation, and probably that point about the regulation a bit also – I don’t know. It can become controversial.

We can discuss that on the –

>> On the platform.

>> ROBERTO GAETANO: Definitely, I’m looking forward to the – since we gathered some interest to include this in the program of 2022, and I’m a bit too late in the game. Thanks you to Oscar, he made contact with the European Space Agency who may have a big interest in joining a session like this.

This was just to give you a taste of the – of the topic and spawn enough interest and see everybody in Trieste with a visit in person of the Postojna caves which are incredibly interesting!

So with this, I’m afraid that we need to – yeah. It’s – I’m getting reminders that we should stop.

Thank you all for participating. And this has been a great session and – and I’m looking in order to continue the – this discussion also with the webinar that Vint suggested to do. Thank you, in particular to Adrijana who was a complete beginner has done a great job of getting the essential out of this.

And with this we need to go to the plenary.

>> MARCO ZENNARO: Thank you very much.

>> Thank you to all the speakers.

>> Thank you.