At the interplanetary level communication delays are huge, and variable because the planets are in orbit around the sun. Existing communication protocols like the TCP/IP breaks down under such conditions. NASA has been performing tests on more robust network technologies, called Delay Tolerant Networking, or DTN, protocols, the second test of which was successfully conducted on the International Space Station.
The DTN protocols will extend the terrestrial Internet into space by overcoming a number of obstacles, including the extraordinary length of time it takes packets to move between separate hops in a deep-space network, the intermittent nature of network connections, and bit-scrambling solar radiation. On Earth, packets move from source to destination in milliseconds. By contrast, a one-way trip from Earth to Mars takes a minimum of 8 minutes. The constant motion of celestial bodies means that packets have to pause and wait for antennas to align as they hop from planet to probe to spacecraft.
Work on DTN began as early as 1998 and one of the co-inventor of the Internet's TCP/IP protocol, Vint Cerf, is also a key member of the group of scientists working on it.
