NASA has successfully tested the first deep space communications network modeled on the Internet. Working as part of a NASA-wide team, engineers from NASA's Jet Propulsion Laboratory in Pasadena, Calif., used software called Disruption-Tolerant Networking, or DTN, to transmit dozens of space images to and from a NASA science spacecraft located about more than 32 million kilometers (20 million miles) from Earth."This is the first step in creating a totally new space communications capability, an interplanetary Internet," said Adrian Hooke, team lead and manager of space-networking architecture, technology and standards at NASA Headquarters in Washington. NASA and Vint Cerf, a vice president at Google, Inc., in Mountain View, Calif., partnered 10 years ago to develop this software protocol. The DTN sends information using a method that differs from the normal Internet's Transmission-Control Protocol/Internet Protocol, or TCP/IP communication suite, which Cerf co-designed.
The Interplanetary Internet must be robust enough to withstand delays, disruptions
and disconnections in space. Glitches can happen when a spacecraft moves behind a planet, or when solar storms and long communication delays occur. The delay in sending or receiving data from Mars takes between three-and-a-half to 20 minutes at the speed of light. Unlike TCP/IP on Earth, the DTN does not assume a continuous end-to-end connection. In its design, if a destination path can't be found, the data packets are not discarded. Instead, each network node keeps custody of the information as long as necessary until it can safely communicate with another node. This store-and-forward method, similar to basketball players safely passing the ball to the player nearest the basket, means that information does not get lost when no immediate path to the destination exists. Eventually, the information is delivered to the end user.
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