Interplanetary and space communications (like to Mars) are inherently subject to significant delays and disruptions (i.e. we can’t go faster than the speed of light, and space is a rather hostile and unpredictable environment!). Interplanetary networking falls under the umbrella of Delay-tolerant networking, or DTN. DTN is an approach to network architecture that seeks to address the technical issues in heterogeneous networks that may lack continuous network connectivity. Traditional transport protocols including TCP don't fare well in the presence of long delays, so alternative protocols are needed. The Licklider Transmission Protocol (LTP) is designed for DTN and is principally aimed at supporting “long-haul” reliable transmission in interplanetary space, but also has applications in mobile or extreme terrestrial environments.

In this paper we discuss the architectural considerations of DTN. We specifically focus on performance aspects of DTN implementation architectures, including domains of application such as the International Space Station (ISS) where DTN experiments with both traditional radio frequency and high data rate laser links are underway. We provide an overview of LTP and show that increasing the LTP segment size results in better DTN performance even when Internet Protocol (IP) fragmentation is invoked. We also show how network services and service differentiation with FAST can be applied to optimize interplanetary communications.