NASA DTN Protocol: Interplanetary Internet, How It Works, What LEGOS Have to
To With It
Author: Gina Smith
NASA is calling it the interplanetary Internet, and announcements have been
hitting in recent weeks regarding the sending of the first emails, voicemails
and, of late, news of an experiment that involved remote controlling of a
LEGO space robot with it. But what’s truly cool is the technology enabling it
— it’s a protocol called Delay-Tolerant Networking, better known as DTN.
At its heart is Vint Cerf’s Bundle Protocol (BP), a version of the IP
protocol he helped develop to pioneer the Internet decades ago.
In testing for several years, DTN got a major boost recently, says Badri
Younes, a NASA administrator in Washington. Astronaut Sunita Williams — she
commanded the International Space Station’s current Expedition 33 mission —
used NASA’s experimental Disruption Tolerant Networking (DTN) protocol to
drive a small LEGO robot at the European Space Operations Center in Germany
late last month.
That was big news for the DTN and BP protocols, developed jointly by Internet
pioneer +Vint Cerf and NASA’s Jet Propulsion Laboratory.
In a nutshell — we’ll get down and dirty with the tech lower in the piece —
DTN allows a standard method of communication over long distances and through
time delays, agency officials said. Its centering tech is similar to the IP
protocol (that is the TCP/IP protocol) that is the building block of the
Internet we use on Earth. That’s called the Bundle Protocol (BP).
The big difference between BP and IP is that, while IP assumes a more or less
smooth pathway for packets going from start to end point, BP allows for
disconnections, glitches and other problems you see commonly in deep space,
Younes said. Basically, a BP network — the one that will the Interplanetary
Internet possible — moves data packets in bursts from node to node, so that
it can check when the next node is available or up.
“The demonstration (of the DTN controlled robot) showed the feasibility of
using a new communications infrastructure to send commands to a surface robot
from an orbiting spacecraft and receive images and data back from the robot,”
Younes said. “The experimental DTN we’ve tested from the space station may
one day be used by humans on a spacecraft in orbit around Mars to operate
robots on the surface, or from Earth using orbiting satellites as relay
stations,” Younes added.
Credit: European Space Agency
The first thing to understand is that the DTN testbed with BP driving it is
in active testing now, NASA says.
Its first successful test was in 2008, when NASA announced that early DTN
software for the first time enabled the transmission of more than a dozen of
space images to and from a NASA science spacecraft located about 20 million
miles (32M KM) from Earth. In a statement then, NASA’s Jet Propulsion
Laboratory and Google’s +Vint Cerf said it kicked off the Interplanetary
Internet. But what is DTN?
“The experimental DTN we’ve tested from the space station may one day be used
by humans on a spacecraft in orbit around Mars to operate robots on the
surface, or from Earth using orbiting satellites as relay stations,” Younes
In a nutshell, says NASA, “The Disruption Tolerant Networking (DTN) program
establishes a long-term, readily accessible communications test-bed onboard
the International Space Station (ISS). Two Commercial Generic Bioprocessing
Apparatus (CGBA), CGBA-5 and CGBA-4, will serve as communications test
computers that transmit messages between ISS and ground Mission Control
Centers. All data will be monitored and controlled at the BioServe remote
Payload Operations Control Center (POCC) located on the Engineering Center
premises at the University of Colorado – Boulder,” reps said today.
According to NASA’s Delay-Tolerant Networking Research Group (DTNRG), ”the
DTN protocol is under active development.”
An experiment using DTN to control the LEGO robot is in the news today, but
NASA says there are real world, military and consumer applications that
affect Internet users worldwide.
“In addition to network security, research goals for the DTN activity will
focus on testing and evolving important network services including naming and
addressing, time synchronization, routing, network management and class of
service,” NASA reps add, saying that “the DTN experiments on the
International Space Station (ISS) consist of software which is to be placed
on both Commercial Generic Bioprocessing Apparatus (CGBA), CGBA-4 and CGBA-5,
and then tested from a ground operations center.
What’s going on? Researchers explain “the DTN activity will focus on testing
and evolving important network services including naming and addressing, time
synchronization, routing, network management and class of service. The DTN
experiments on ISS consist of software (that) is to be placed on both
Commercial Generic Bioprocessing Apparatus, CGBA-4 and CGBA-5, and then
tested from a ground operations center. This software is not in any critical
path of the CGBA operations and may be turned off at anytime. This software
does not preclude the use of the CGBA units for other purposes or research
DTN, say NASA reps, is “a networked architecture required to successfully
complete these missions. The experiments that will be performed are designed
to test the DTN protocol suite in an actual space environment, and to
determine how well the protocols perform and what improvements may need to be
made. The impact of the results of the research will help to advance the
technical maturity of the DTN communications technology so that it is
available for NASA use in both human and robotic Exploration missions.
The Delay-Tolerant Networking Research Group (DTNRG) is a research group
chartered as part of the Internet Research Task Force (IRTF). Members of
DTNRG are concerned with how to address the architectural and protocol design
principles arising from the need to provide interoperable communications with
and among extreme and performance-challenged environments where continuous
end-to-end connectivity cannot be assumed. Said another way, we are concerned
with interconnecting highly heterogeneous networks together even if
end-to-end connectivity may never be available. Examples of such environments
include spacecraft, military/tactical, some forms of disaster response,
underwater, and some forms of ad-hoc sensor/actuator networks. It may also
include Internet connectivity in places where performance may suffer such as
developing parts of the world.
DTNRG members research aspects of delay-tolerant networking in a number
of ways including academic publications, technical specifications, several
active mailing lists, and code (reference implementation) development. DTNRG
holds semi-regular teleconferences for software developers and occasional
face-to-face public meetings. The public meetings usually occur in
conjunction with an IETF meeting. The current co-chairs for DTNRG are Kevin
Fall (Qualcomm), Stephen Farrell (Trinity College, Dublin) and Jörg Ott
(Aalto University, Helsinki). Back in 2006 Stephen wrote a book on DTN.
Several of the members of DTNRG participated in the (highly-related) DARPA
Disruption Tolerant Networking program.
DTN research is necessary in space especially, NASA says, for the maturation
of protocols to enable Internet-like communications with space vehicles,
remote planetary habitats, rover vehicles and support infrastructure on a
planetary surface. “It is being tested for the first time on ISS Onboard
(local) ISS , ISS-to-ground, and NASA ground communications networks will
become DTN-enabled,” NASA says. “That is the key stepping stone to enabling
the Interplanetary Internet.