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DTN and the IoT

DTN and the IoT

Increasingly, communication over the Internet is not facilitating communication between human beings, but between things. In fact, it’s estimated that by 2022, 45% of the traffic over the Internet will be between and amongst things, rather than people. By 2020, 212 billion “Things” will be connected to the Internet.

While this is impressive, it should also be somewhat alarming. Using the Internet as the glue to facilitate all of these machine-to-machine interactions necessarily assumes that the end-to-end continuous data flow that allows TCP/IP to work for the traditional Internet exists in the machine-to machine environment. And that’s often not true.

Let’s think about the kinds of devices being connected, why they’re being connected, where they’re being connected, and what their capabilities are. Many people might assume that the largest market for IoT would be retail. After all, we’re bombarded by commercials pushing the latest home security systems—or even home management systems that integrate voice-activated power and HVAC controls with advanced security systems that not only arm alarm systems, but also physically secure the home. Retail IoT systems like these are only forecasted to reach 1% of the total value of the IoT market by the year 2025

The biggest potential market for IoT appears to be in the health care industry. Connected devices can play a significant role in healthcare applications through embedding sensors and actuators in patients and their medicine for monitoring and tracking purposes. IoT is already in wide use in clinics to gather and analyze data from diagnostic sensors and lab equipment. There is an increasingly large movement towards embedding devices in patients themselves to monitor health and/or actuators implanted in the patients’ bodies. These are necessarily small, low power devices that are unpredictably mobile—all factors contributing to disruption or delay.

The second largest market for IoT is forecasted to be industrial manufacturing. Not only have robotics been widely deployed to reduce human labor costs, but there has also been an explosion of sensors that can detect errors immediately and generate repair requests complete with necessary maintenance and repair information. Except for certain environments, traditional Internet infrastructure is readily available.

Third place in the forecasted IoT market is monitoring the production and distribution of electrical power. This means placing devices in many locations far removed from traditional Internet infrastructure, or even cellular infrastructure. Maintenance and repair vehicles are mobile. Again, an environment in which network connectivity is not guaranteed end-to-end.

These are just a few of the emerging markets, use cases and environments in the IoT field. Most of the standards work in these areas have addressed the need for low power wireless communications for different applications. Efforts to deal with disruption and delay have been proprietary, and do not have the foundational assumption that the network will be partitioned in some way that disrupts end-to-end communication. As an emerging IETF standard, DTN presents an opportunity to provide consistent network automation enabling the expansion of the IoT into constrained network environments.

Our next blog will dive a little deeper into the IoT, highlighting how DTN could facilitate the communication between the edge of the Internet and the often network-constrained “Things” that need to connect with it.

This blog is a product of the usual suspects: Scott Burleigh (NASA/JPL); Keith Scott (Mitre Corp./CCSDS); E. Jay Wyatt (NASA/JPL) and Mike Snell (IPNSIG)

How humans will bring the Internet to space

IPNSIG board member Vint Cerf brought this nice article about DTN to our attention…

It’s slanted towards a general audience, and provides some historical background of DTN development. It emphasizes the need to maintain the open architecture of DTN, and stresses the importance of the security features being built into the protocol suite (for more information about the Bundle Security Protocol and how it works, see the security section of the DTN Primer at: DTN_Tutorial_v3.2). The article also features excerpts of interviews with long-time IPNSIG friends Leigh Torgerson (NASA/JPL) and David Israel (NASA Goddard SFC).

TCP/IP for Gateway

TCP/IP for Gateway?

We’ve been hearing that there are some within NASA advocating for the use of TCP/IP for space data communications on the Gateway lunar missions. At first glance, this might seem to make sense— after all, the Near-Rectilinear Halo Orbit planned for Gateway would guarantee that its line-of-sight with earth would never be interrupted. While it would seem that RTT between ground stations on earth and Gateway’s communications relay module would be problematic for latency-sensitive applications, TCP/IP would probably work. Kind of.

However, we think it would be ill advised for reasons other than interactive voice and video performance issues: the whole point of Gateway is to meet the objectives laid out in Space Policy Directive-1:

Beginning with missions beyond low-Earth orbit, the United States will lead the return of humans to the Moon for long-term exploration and utilization, followed by human missions to Mars and other destinations.

If the reason for Gateway is to support eventual human missions to Mars and other interplanetary destinations, it makes no sense to use anything other than the communication protocols designed to support those missions: in particular the DTN suite. Benefits resulting from the use of DTN for Gateway include:

  • Gaining experience with a protocol suite suitable for further exploration beyond lunar orbit.
  • Built-in resilience to communications disruptions that do occur, e.g. due to weather effects on Earth if Ka-band or optical links are used.
  • More efficient use of the Gateway-to-Ground links, since Bundle Protocol convergence layers can be tuned for the characteristics of the links (e.g. using alternate congestion control mechanisms and hence avoiding the issues with running TCP over high bandwidth-delay-product paths).
  • Flexibility in the use of ground stations to communicate with Gateway, especially when humans are not present.  DTN’s store-and-forward capability will enable more flexible allocation of ground stations to communicate with Gateway, since data will be stored if all available ground stations need to be used for other tasks.

Because so many operational benefits accrue from the use of DTN vs. TCP/IP, and because DTN aligns with the overall objectives specified in Space Policy Directive-1, we at IPNSIG highly recommend that NASA elect to use DTN for all space data communications on the Gateway missions.

Webinar: Hacking the Extraterrestrial Internet

Webinar: Hacking the Extraterrestrial Internet - Where Fiction Meets Reality


IPNSIG Vice Chair Scott Burleigh will be featured in an Ethical Hacking webinar this Thursday, June27th, starting at 1:00 p.m. Eastern Daylight Time. Here’s the blurb from the Ethical Hacking website:

Normal SciFi glosses over a glaring problem with comms through the vastness of space… The Internet and TCP/IP suffer a massive self-imposed DOS attack with any disruptions for more than a few seconds. Ignoring that fact doesn’t cut it for bestselling author, Daniel Suarez. How do we hack it to make it work for a realistic, near future novel on mining asteroids? Enter Scott Burleigh and an international team from NASA, other national space agencies and industry. They already did it! It’s called DTN. Join them for details, security considerations and how to get involved in this FREE EH-Net Live! webinar on Thurs June 27, 2019 at 1:00 PM US Eastern.

The webinar is free, but you must register to attend. Here’s the link:


Motivation for DTN: Terrestrial Use Cases

Many people new to InterPlanetary Networking are surprised to discover that DTN is also considered effective for many terrestrial use cases. That’s because the same kind of constraints exist in many networking environments right here on planet earth. These primarily include disruptions and delays—or perhaps even the absence of traditional Internet infrastructure that would make network communications via TCP/IP unfeasible or prohibitively expensive.

It’s not too difficult to envision some of those environments. Some constraints are inherent in the communication environment itself:

  • Like water as a communication medium. RF waves do not propagate well, but sound waves do, which are incredibly slow and whose speed varies unpredictably with the density of the water column.
  • Or think of underground applications like mining. Cable can be expensive to lay and subject to disruption through unintentional damage by mining equipment. RF does not penetrate the earth.
  • First responders searching through rubble are subject to unpredictable disruptions caused by loss of LOS with wireless signals.
  • Battlefield sensors cannot maintain constant RF contact for security reasons.
  • Finally, many regions that would benefit from Internet services find them unavailable (or prohibitively expensive) simply because they are not located where traditional Internet infrastructure exists. A look at any light pollution map shows you how much of the world does not have ready access to traditional Internet infrastructure.

Light Pollution



Examples of experimental implementations of DTN to overcome these constraints include:

  • Providing basic Internet services to reindeer herders in the Arctic Circle in Sweden.
  • Monitoring air quality in a karst cave in Romania.
  • Monitoring the cardiac health of first responders during emergency operations
  • Providing basic Internet services to remote villages in Africa that had no access to traditional network infrastructure

An area of particular interest to the DTN community is the Internet of Things (IoT), where communication is primarily amongst things and not people: sensors in buildings, roadways, on farms and even in our bodies. Because of the mobility of many of these Things, and limitations in power and signal strength, continuous end-to-end connectivity is either not achievable at all, or not maintainable. Since DTN assumes that such continuity does not exist, it can perform a valuable function in the world of IoT (sometimes call the “DTN of Things”)

Our next blog will dive into DTN’s potential role in IoT in more detail.

This blog is a product of the usual suspects: Scott Burleigh (NASA/JPL); Keith Scott (Mitre Corp./CCSDS and Mike Snell (IPNSIG)


DTN Motivation for Space Communications

As NASA contemplated longer space missions involving multiple spacecraft, they foresaw the need for network automation, much the same as exists on the terrestrial Internet. Missions had to include not only coding for the applications to perform navigation and scientific observations—they also had to support communications with earth. NASA wanted to standardize and automate network communications in space, and at interplanetary distances.

Network automation is a huge advantage of the terrestrial Internet. Application developers in general do not have to worry about the performance of the network, and TCP/IP requires relatively little centralized administration. The Transmission Control Protocol (TCP) in particular, assures reliable communication for applications (almost anything of significance on the Internet uses TCP). TCP does this through a series of exchanges back-and-forth between the sending and receiving hosts in order to establish a communication session; establish communication speed and verify that all of the disparate pieces of a message have been properly received and reassembled at the destination in the right order. If anything is missing, it gets retransmitted.

All of these behind-the-scenes messages between sender and receiver assume that a communication pathway exists between the two that is almost instantaneous in nature. If that assumption breaks, TCP breaks. The session times out and must be re-established.

TCP works relatively well on planet earth because the velocity of light provides almost instantaneous bidirectional communication speeds given the relatively short distances involved (after all, a photon could circumnavigate the globe about 7.5 times a second). However, NASA was contemplating traveling very long distances indeed. The minimum distance from Earth to Mars is about 54.6 million kilometers (about 33.5 million miles). The farthest apart they can be is about 401 million km (about 350 million miles). The average distance is about 225 million km (about 140 million miles). This means round trip times for radio frequency communications ranging from a minimum of about 7 minutes to a maximum of about 40 minutes.

Not only would communications at interplanetary distances involve many, many times the signal delay experienced on earth, but they would also experience significant periods of disruption. Planets have this pesky habit of rotating. Anything on the surface of Mars would experience long periods of communication blackouts while the planet Mars itself blocked line of sight with the earth.

While other factors also constrained data communications at interplanetary distances, delay and disruption were the two primary limitations preventing the architecture of the terrestrial TCP/IP Internet from working in that environment. Which is how Delay/Disruption Tolerant Networking (DTN) got its name.

How to deal with this extreme environment? Change the store-and-forward (albeit for only a few milliseconds) architecture of the Internet to what has come to be called a “store-carry-and-forward” architecture. This uses local storage in network devices themselves to hold onto a much larger “bundle” of data (than an IP packet), and only forward that packet onto its target destination when an opportunity to do so presents itself.

We’ll be explaining this architecture in more detail in future blogs, but first, we’ll explain how DTN, which was designed for use in outer space, has very useful applications in network environments displaying very similar constraints right here on planet earth. That will be the topic of our next blog…

This blog is a product of the usual suspects: Scott Burleigh (NASA/JPL); Keith Scott (Mitre Corp./CCSDS and Mike Snell (IPNSIG)



IPN Video Resources


As promised, here are a number of short videos (none over 7 minutes) that explain basic elements of DTN. Some also include historical information and explanations of the problems DTN solves in constrained environments.

IPNvideo1 Short (slightly under two minutes) simple animation developed by JPL to explain the basic problems that DTN solves and the basic store-carry-forward architecture.





IPNvideo2 A slightly longer (about 5 minutes) and slightly more technical animation developed by JPL to illustrate how DTN store-carry-forward approach and custody transfer work. Basically audio playing against a simple (and non-changing) background with an animated speaker. Good verbal content, but in the later portions, it presupposes a level of computer networking knowledge that would probably make the content difficult for a newbie to absorb.


IPNvideo3 Another simple NASA video that should be useful for the newbie. This one graphically demonstrates how DTN significantly increases throughput compared to traditional IP in a space data communications environment.






IPNvideo4 Another pretty simple JPL animation that should be easily understood by the newbie. This one graphically compares the throughput of TCP, UDP and DTN—particularly emphasizing the difference in data throughput between TCP and DTN and the difference in data loss between UDP and DTN.






IPNvideo5 NASA Jet Propulsion Laboratory. Disruption Tolerant Networking Summary comprised of video clips and animations. Vint Cerf is prominently featured, but if you look carefully, you can spot other IPNSIG board members (Scott Burleigh and Jay Wyatt) and friends (Leigh Torgerson)..

This is the first of a number of blog entries designed to help newbies come up to speed on Delay & Disruption Tolerant Networking. If you find an online article you think others would be interested in, or if there is a topic you would like to see covered in future blogs, drop a note to

What if I don’t know anything about IPN?


Many members of IPNSIG may be familiar with the technologies behind the traditional Internet, but be completely new to the domain of Interplanetary Networking and DTN (Delay & Disruption Tolerant Networking). While there are hundreds of technical articles available about different aspects of DTN, these articles typically assume previous knowledge of the technical foundations of the protocols and the problems they are attempting to solve. One can always turn to RFC’s… but they also assume the reader is “in” on the technical context.

What is a newbie to do?

There are a number of terse introductory videos and online documents available to help newbies come up to speed, and some on them are available on the website. Here’s a couple:

A short TED Talk by Vint Cerf explaining the very basic challenges IPN presents and DTN’s approach to addressing them:

A terse technical introduction to DTN, covering most major topics. Many thanks to Forrest Warthman of Warthman Associates) for authoring this latest version (and Scott Burleigh of NASA/JPL for technical consultation and review).

However, if you really want to understand Interplanetary Networking and DTN, we’d suggest you investigate a couple of recently published books that provide both a solid overview of the history, architecture and technologies involved in DTN:

  • Delay and Disruption Tolerant Networks: Interplanetary and Earth-Bound — Architecture, Protocols, and Applications CRC Press – Aloizio Pereira da Silva (Editor), Scott Burleigh (Editor), Katia Obraczka (Editor) – 2018
  • Delay-Tolerant Satellite Networks (Space Technology and Applications) Artech House – Juan A. Fraire (Author), Jorge M. Finochietto (Author), Scott C. Burleigh (Author) – 2017

While books like these represent an investment in time and money (there is a Kindle edition available at deep discount for Delay and Disruption Tolerant Networks: Interplanetary and Earth-Bound — Architecture, Protocols, and Applications), there is much to be gained by plowing one’s way through them. Both contain excellent introductory content that lays a good foundation for the reader in understanding later technical topics.

As the title indicates, Delay-Tolerant Satellite Networks (Space Technology and Applications focuses almost exclusively on DTN in space data communications. The more limited scope allows the authors to explain not only DTN, but also the existing and planned space communications infrastructure upon which it operates.

Delay and Disruption Tolerant Networks: Interplanetary and Earth-Bound — Architecture, Protocols, and Applications expands the arena for DTN to include the many, many terrestrial applications for addressing constrained network environments. These run the gamut from enabling email delivery for reindeer herders in the Arctic Circle to providing basic Internet services to villagers in rural Africa. There’s an entire chapter devoted to DTN’s usefulness in the burgeoning world of the Internet of Things (IoT).

There is also the first book-length treatment of DTN from back in 2006:

  • Delay- and Disruption-Tolerant Networking - Artech House Publishers – Stephen Farrell, Vinny Cahill – 2006

Stephen Farrell was the co-chair of the DTN Research Group. This book is most useful for an understanding of the history of DTN development and why it is so necessary for both interplanetary and constrained terrestrial networking environments.

Still daunted?

We are all newbies at some point in understanding any topic in depth. It can be overwhelming. We encourage you to take advantage of some of the resources highlighted in this blog posting. We’ll be focusing on online video resources introducing you to the world of DTN in our next blog entry.

This blog is a product of the usual suspects: Scott Burleigh (NASA/JPL); Jay Wyatt (NASA/JPL); Keith Scott (Mitre Corp./CCSDS) and Mike Snell (IPNSIG)


DTN Content from JPL/NASA







Some new content has recently become available that I believe IPNSIG members would find interesting.

Leigh Torgerson, IPNSIG member and Space Communications Networking Architect from JPL/NASA, has posted some useful animations explaining Delay and Disruption Tolerant Networking concepts. It’s available for viewing at:

Leigh also recently made a presentation that was even more recently released for publication. It’s available here: 332-Section-DTN-Seminar-2019-for-Public-Release–final

The presentation provides fairly detailed historical background, an explanation of why Internet protocols do not work in space, and a picture of where DTN is going in the near future.


Announcing IPNSIG Blog

Welcome to the InterPlanetary Networking Blog! We intend to make this a weekly publication of interest to everyone interested in InterPlanetary Networking (IPN), Delay & Disruption Tolerant Networking (DTN), and computer networking in general.

Since this is the inaugural blog entry, we thought it would be useful to back up a bit and answer some basic questions:

What is IPN?

It is a solution to the constrained network environment present in space data communications and, more generally, in the emerging Internet of Things.

TCP/IP, the core technology [BSC(1] running today’s Internet, assumes essentially instantaneous, continuous end-to-end connectivity, and fails when it encounters delay or disruption of any significant length (about 4 seconds).

However, delays and disruptions are inherent in data communications at interplanetary distances, with the shortest Round Trip Time (RTT) for a radio signal to travel to Mars and back being about 7 minutes. Other factors contribute to the network constraints existing in interplanetary communications, but delay is the most significant factor making existing Internet protocols impractical for use.








Enter DTN:

Adrian Hooke (Sr. Technical Director with the Jet Propulsion Laboratory, NASA) meets Vint Cerf (co-author of the TCP/IP protocols and one of “Fathers of the Internet”) in the late 1990’s. They discover they both want to provide the same kind of network communications automation in space networking that works so well on the Internet.

Vint Cerf gets to work. A terse history follows:

  • DARPA funds work at JPL.
  • Core experimental “delay-tolerant networking” protocols developed by JPL, MITRE, Sparta researchers.
  • ION implementation of DTN developed at JPL for use by NASA.
  • DTNRG established to mature the protocols.
  • ION demonstrated on the EPOXI spacecraft in deep space.
  • ION deployed for all science payload communications on ISS.

Where is IPN today?

  • IETF DTN Working Group formed to establish DTN protocols as Internet standards.
  • Consultative Committee for Space Data Systems (CCSDS—a global standards setting organization for civilian space flight) standards adoption well underway.
  • Security Protocols maturing (including Public Key Infrastructure—PKI).
  • Dr. Scott Pace (White House Space Policy Director) challenges NASA to use DTN for all space communications (see for Dr. Pace’s presentation at our 2015 IPN Speakers Conference).
  • NASA integrating DTN into ground networks and future spacecraft.

IPN’s bright future

  • Increasing standardization amongst civilian space agencies.
  • Increasing international research into DTN for constrained terrestrial as well as space networking environments.
  • Coming adoption as internet standards.


What’s next for the blog?


Each week, we will post news about the exciting world of IPN, or summaries of academic research, or links to IPN in the mainstream media. We’ll also be announcing upcoming IPNSIG events and activities. We hope you enjoy the blog.


This blog is a product of the usual suspects: Scott Burleigh (NASA/JPL); Jay Wyatt (NASA/JPL); Keith Scott (Mitre Corp./CCSDS) and Mike Snell (IPNSIG)

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