Interplanetary Internet

The Interplanetary Internet (IPN) is a conceived computer network in space, consisting of a set of network nodes which can communicate with each other. Communication would be greatly delayed by the great interplanetary distances, so the IPN needs a new set of protocols and technology that are tolerant to large delays and errors. While the Internet as we know it tends to be a busy network of networks with high traffic, negligible delay and errors, and a wired backbone, the Interplanetary Internet is a store-and-forward network of internets that is often disconnected, has a wireless backbone fraught with error-prone links and delays ranging to tens of minutes, even hours, even when there is a connection.

Development

Space communication technology has steadily evolved from expensive, one-of-a-kind point-to-point architectures, to the re-use of technology on successive missions, to the development of standard protocols agreed upon by space agencies of many countries. This last phase has gone on since 1982 through the efforts of the Consultative Committee for Space Data Systems (CCSDS), a body composed of the major space agencies of the world. It has 11 member agencies, 22 observer agencies, and over 100 industrial associates.

The evolution of space data system standards has gone on in parallel with the evolution of the Internet, with conceptual cross-pollination where fruitful, but largely as a separate evolution. Since the late 1990s, familiar Internet protocols and CCSDS space link protocols have integrated and converged in several ways, for example, the successful FTP file transfer to Earth-orbiting STRV-1b on January 2, 1996, which ran FTP over the CCSDS IPv4-like Space Communications Protocol Specifications (SCPS) protocols. Internet Protocol use without CCSDS has taken place on spacecraft, e.g., demonstrations on the UoSAT-12 satellite, and operationally on the Disaster Monitoring Constellation. Having reached the era where networking and IP on board spacecraft have been shown to be feasible and reliable, a forward-looking study of the bigger picture was the next phase.

ICANN meeting, Los Angeles, USA, 2007. The marquee pays a humorous homage to the Ed Wood film Plan 9 from Outer Space, while namedropping Internet pioneer Vint Cerf.

The Interplanetary Internet study at NASA's Jet Propulsion Laboratory (JPL) was started by a team of scientists at JPL led by Vinton Cerf and Adrian Hooke. Cerf is one of the pioneers of the Internet on Earth, and currently holds the position of distinguished visiting scientist at JPL. Hooke is one of the directors of the CCSDS.

While IP-like SCPS protocols are feasible for short hops, such as ground station to orbiter, rover-to-lander, lander-to-orbiter, probe-to-flyby, and so on, delay-tolerant networking is needed to get information from one region of the solar system to another. It becomes apparent that the concept of a "region" is a natural architectural factoring of the InterPlanetary Internet.

A "region" is an area where the characteristics of communication are the same. Region characteristics include communications, security, the maintenance of resources, perhaps ownership, and other factors. The Interplanetary Internet is a "network of regional internets."

What is needed then, is a standard way to achieve end-to-end communication through multiple regions in a disconnected, variable-delay environment using a generalized suite of protocols. Examples of regions might include the terrestrial Internet as a region, a region on the surface of the moon or Mars, or a ground-to-orbit region.

The recognition of this requirement led to the concept of a "bundle" as a high-level way to address the generalized Store-and-Forward problem. Bundles are an area of new protocol development in the upper layers of the OSI model, above the Transport Layer with the goal of addressing the issue of bundling store-and-forward information so that it can reliably traverse radically dissimilar environments constituting a "network of regional internets."

Bundle Service Layering, implemented as the Bundling protocol suite for delay-tolerant networking, will provide general purpose delay-tolerant protocol services in support of a range of applications: custody transfer, segmentation and reassembly, end-to-end reliability, end-to-end security, and end-to-end routing among them. The Bundle Protocol was first tested in space on the UK-DMC satellite in 2008.

An example of one of these end-to-end applications flown on a space mission is CFDP, used on the comet mission, Deep Impact. CFDP is the CCSDS File Delivery Protocol an international standard for automatic, reliable file transfer in both directions. CFDP should not be confused with Coherent File Distribution Protocol, which unfortunately has the same acronym and is an IETF-documented experimental protocol for rapidly deploying files to multiple targets in a highly-networked environment.

In addition to reliably copying a file from one entity (i. e., a spacecraft or ground station) to another entity, the CCSDS CFDP has the capability to reliably transmit arbitrary small messages defined by the user, in the metadata accompanying the file, and to reliably transmit commands relating to file system management that are to be executed automatically on the remote end-point entity (i. e., a spacecraft) upon successful reception of a file.

At the 2020 Lunar Development Conference Surrey Satellite Technology discussed their plans for a commercial lunar relay mission.

Implementation

The dormant InterPlanetary Internet Special Interest Group of the Internet Society has worked on defining protocols and standards that would make the IPN possible. The Delay-Tolerant Networking Research Group (DTNRG) is the primary group researching Delay-tolerant networking. Additional research efforts focus on various uses of the new technology.

Template:As of, NASA has canceled plans to launch the Mars Telecommunications Orbiter in September 2009; it had the goal of supporting future missions to Mars and would have functioned as a possible first definitive Internet hub around another planetary body. It would use laser communication using laser beams for higher bandwidth. "Lasercom sends information using beams of light and optical elements, such as telescopes and optical amplifiers, rather than RF signals, amplifiers, and antennas"

NASA JPL continued to test the DTN protocol with their Deep Impact Networking (DINET) experiment on board the Deep Impact/EPOXI spacecraft in October, 2008.

In May 2009, DTN was deployed to a payload on board the ISS. NASA and BioServe Space Technologies, a research group at the University of Colorado, have been continuously testing DTN on two Commercial Generic Bioprocessing Apparatus (CGBA) payloads. CGBA-4 and CGBA-5 serve as computational and communications platforms which are remotely controlled from BioServe's Payload Operations Control Center (POCC) in Boulder, CO. These initial experiments provide insight into future missions where DTN will enable the extension of networks into deep space to explore other planets and solar system points of interest. Seen as necessary for space exploration, DTN enables timeliness of data return from operating assets which results in reduced risk and cost, increased crew safety, and improved operational awareness and science return for NASA and additional space agencies.

DTN has several major arenas of application, in addition to the Interplanetary Internet, which include sensor networks, military and tactical communications, disaster recovery, hostile environments, mobile devices and remote outposts. As an example of a remote outpost, imagine an isolated Arctic village, or a faraway island, with electricity, one or more computers, but no communication connectivity. With the addition of a simple wireless hotspot in the village, plus DTN-enabled devices on, say, dog sleds or fishing boats, a resident would be able to check their e-mail or click on a Wikipedia article, and have their requests forwarded to the nearest networked location on the sled's or boat's next visit, and get the replies on its return.

• Latency. One specific particularity on an Internet between Mars and the Earth is the communications latency. Due to speed of light limitation, there is necessarily a lag of 4 to 15 minutes in one direction and 8 to 30 minutes in bi-directional communications. This means it is impossible to get quick information from a central server on Earth, and that much of the Internet's data will need to be replicated on Mars. This will require large amounts of data storage and access protocols.

Transmission rates

The transmission rate of data for the deep space network is extremely low compared to current communication systems on Earth. This is looking to be superseded though laser communication with relay satellites, allowing for faster and more reliable communications from Mars to Earth.

• A single high resolution video channel with encoding may require a 5 Mbit/s Bitrate. High quality scientific video might require 50 Mbit/s. A link with ten to twenty Gbit/s, similar to the one that can be provided by the most recent telecommunications satellites, could transmit video information from a Martian settlement to Earth, and supply the vast amounts of bandwidth that are likely to be needed in order to transmit scientific and other data from Mars, or to provide entertainment or education to Martians from Earth.

External links

• The Consultative Committee for Space Data Systems (CCSDS)
• The InterPlaNetary Internet Project IPN Special Interest Group
• The Delay-Tolerant Networking Research Group (DTNRG)
• NASA video: DINET-DTN w/Vint Cerf (requires Flash)
• wikipedia:Interplanetary_Internet
• wikipedia:List_of_interface_bit_rates