Design, Implementation and Evaluation of a Storage System for Delay-Tolerant Networks

Simple applications of networked information technology have been shown to have an impact in the developing regions in the areas of health care, education, commerce and productivity. However, use of information technology in developing regions setting is hampered by a lack of inexpensive reliable telecommunications infrastructure. In particular, existing applications relevant to this space are built using software architectures which assume always-on, low-latency, end-to-end connectivity. One potential connectivity solution is the Delay-Tolerant Networking (DTN) stack, an overlay network protocol that can route across network partitions and heterogeneous forms of network infrastructure. However, the DTN message-based interface is a poor fit for many applications as they are more naturally structured in terms of shared state. To address these issues, we present TierSync, a distributed eventually-consistent shared-storage synchronization primitive for DTNs. TierSync enables applications to share persistent data among TierSync nodes in an efficient and flexible manner. Novel features of the TierSync protocol include efficient support for fine grained partial sharing and the ability to arbitrarily order updates for data prioritization. We demonstrate an implementation of the TierSync protocol as a file-system and show useful applications can be easily ported to the TierSync system.