High Performance DTN Using Larger Packets and Kernel Resident Convergence Layers

This paper concerns the Delay Tolerant Networking (DTN) Internetworking overlay service that supports communications over paths with links that may introduce significant delays and/or disruptions. The service is therefore essential for air/land/sea/space mobility use cases, where delay and/or disruption can interfere with traditional interactive communications. 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 then show that for the Licklider Transmission Protocol (LTP) over Internet Protocol (IP) network paths increasing the LTP segment size results in better DTN performance even when IP fragmentation is invoked. We further establish that by moving the LTP segmentation and reassembly functions into the operating system kernel or even the network hardware that still greater performance is possible beginning with conventional packet sizes and increasing with still larger sizes. These results indicate an unfulfilled need for larger packets in the Internet as well as new approaches that relocate the LTP segmentation and reassembly functions to lower layers of the architecture.