Enabling Traffic Prioritization for Space Communications Over DTNs

The growing number of space missions planned in the near future has created a need for a robust communication infrastructure. Such an infrastructure is being developed in the frame of lunar communications by ESA (2023) and NASA (2022) using Delay- and Disruption-Tolerant Networking (DTN) and Bundle Protocol (BP). While their characteristics have made them the standard for future space communications, some areas such as Quality of Service (QoS) or quasi-real-time communications are still to be further developed. This study emphasizes the benefits of using traffic prioritization as a mechanism to enhance QoS and enable quasi-real-time communications between Earth and space. Through a three-state Markov Chain model, the specific channel between Earth and the Moon is modelled realistically, and the impact of traffic prioritization on bundle transmissions is analyzed for several types of transmitting sources. When looking at the amount of high-priority bundles arriving within the 2.5s mark set by ESA for it to be considered quasi-real-time communications, it is shown that there is a significant improvement of up to 23%. This feature is crucial for DTN BP to be able to support the requirements of the upcoming lunar missions, especially those involving extended astronaut stays. Moreover, a priority grid taking into account all the current requirements expressed by both ESA and NASA is presented, as well as implementation proposals to include traffic prioritization in BP as an extension block. Lastly, the need for a common policy for all DTN nodes in order to allow interoperability is highlighted. Therefore, this work contributes to the advancement of DTN BP, bringing it closer to the requirements ahead of us, and paves the way for the needed mechanisms to be implemented.