Contact-Aware Dual-Layer CHORD for Peer-to-Peer Distribution in Integrated Satellite-Terrestrial Networks

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Integrated satellite-terrestrial (IST) networks will play a promising role in future peer-to-peer (P2P) distribution by bridging multiple isolated P2P sub-networks to provide real-time cross-regional file access in certain scenarios. However, due to the periodic orbital movements of satellites, highly time-varying visibility among peer nodes in IST networks imposes significant challenge on file lookup and retrieval, which is difficult to be solved with current methods in terrestrial P2P networks. Therefore, in this paper, we propose a contact-aware dual-layer Chord (DL-Chord) lookup mechanism for P2P-based IST networks by carefully considering link contacts among satellites and terrestrial P2P nodes. In the proposed DL-Chord mechanism, we develop a group of novel algorithms, comprising an orbital parameter-based dual-layer identification mapping scheme, a contact-based dual-layer finger table, an efficient file lookup algorithm, and a node updating scheme. Furthermore, a theoretical analysis is conducted based on the visibility of satellite constellations to evaluate the lookup performance of the proposed DL-Chord mechanism, i.e., average lookup delay (ALD) and Average lookup rounds (ALR). Simulation results verify that the proposed mechanism achieves better efficiency in terms of ALD and ALR with a lower update cost than other similar schemes, i.e., the stochastic mapping-based original chord ring scheme (ORCO) and physical location-aware mapping-based wireless location-aware scheme (WILCO).