[tt] interplanet approaching maturity

[Eugen Leitl]

http://www.internetevolution.com/author.asp?section_id=562&doc_id=159862&

Mary E. Shacklett

Scientists Plan Interplanetary Internet Protocol

Written by Mary E. Shacklett

7/24/2008 1 comment

The Internet's TCP/IP protocol could be headed for outer space.

For the last several years, Vint Cerf, co-creator of TCP/IP and now a VP at
Google (Nasdaq: GOOG), has worked with colleagues from NASA and elsewhere to
extend Internet connectivity to deep space.

If their work succeeds, astronauts on manned missions to Mars and other
distant locations could keep in touch with researchers worldwide (while
maintaining their Twitter links). (Notably, Cerf's work began prior to his
start at Google and continues independently of that company.)

Deep space presents daunting challenges to Internet communications. These
include distance; line-of-sight obstructions (like meteors); weight issues
(high-powered antennas are often too heavy to send on a space mission); and
the need for specialized "hardened" equipment that can automatically heal
itself or be fixed via remote (very remote) network management.

Cerf and others are engaged in several efforts to address these challenges.
One approach is to modify the satellite payload design now used to link IP
routers with Ka-band satellites in government and business networks. Some
researchers think an adjusted satellite-based IP would work fine, as long as
links were made to planets or highly concentrated communities in space,
mimicking the successful one-to-many transmission patterns of today's
high-powered Ka-band gear.

"One could envision using IP to connect a fleet of rovers operating in close
proximity on Mars, or among members of a spacecraft constellation in deep
space, or orbiting Earth or another planet," says Keith Scott, principal
engineer at The Mitre Corp.

In the future, Scott envisions routers afloat in deep space: "Some spacecraft
might operate as a router as we think of Internet routers, autonomously
responsible for forwarding data received from some external source."

NASA is investigating the potential for a group of six circling satellites to
establish communications for Mars one day. According to Scott, the NASA
Constellation program will advance the use of IP in continuously connected
near-Earth environments.

Researchers from NASA and Mitre also have been working with Vint Cerf on
delay-tolerant networking (DTN) to solve the shortcomings of pure IP in
space.

"There are sometimes long periods of disconnection in such networks, so DTN
uses a store-and-forward model where DTN messages may be stored at
intermediate nodes while waiting for a communication link to become
available," says Scott. "Reliability in DTN is provided by a mechanism called
custody transfer, where nodes in the network can assume responsibility for
retransmitting lost messages. This allows for retransmissions from inside the
network rather than having to retransmit data from the source, as is the case
with TCP."

NASA has initiated a new program designed to bring DTN to a state of flight
readiness by 2010. "This will involve a number of flight demonstrations on
deep-space spacecraft and the international space station to test the
protocol's performance and capabilities," Scott notes. "The 2010 goal is
designed to bring DTN to a sufficient level of maturity to incorporate it
into designs for robotic and human lunar exploration. This effort also
supports the international standardization of DTN as the space
internetworking layer supported by the major space agencies."

As deep space Internet initiatives intensify, both commercial and social
opportunities will open up -- virtual interplanetary space tours, for
instance. "There will be more demonstrations of IP in space over the next
five years," says Rick Skinner, VP of Strategic Planning in Global
Communications Systems for Lockheed Martin Space Systems Co. "This will
further work to define the business case for commercial Internet in space
systems."

Mitre's Scott agrees, but he adds that there is also a cultural issue with
space networking that could keep it out of the range of public use, for
awhile at least. "The culture of space missions is understandably
conservative, leading to the desire to manage all aspects of spacecraft
operation... Some operations will be out of the direct control of ground
operators. Conversely, it takes a large degree of trust to design a
spacecraft, such as the Phoenix lander, that is dependent on relay satellites
to operate."

— Mary E. Shacklett, President of Transworld Data