The Interplanetary Overlay Network (ION) software distribution is an implementation of Delay-Tolerant Networking (DTN) architecture as described in Internet RFC 4838. It includes implementations of the DTN Bundle Protocol, the Licklider Transmission Protocol, most of the Bundle Security Protocol, and two CCSDS application protocols that have been adapted to run over the BP/LTP stack: the CCSDS File Delivery Protocol and Asynchronous Message Service.
If you're interested in the use of Delay-Tolerant Networking in space flight operations, check out the Interplanetary Networking Chapter of the Internet Society: ipnsig.org.
