Up-and-Down Routing Through Nested Core-Periphery Hierarchy in Mobile Opportunistic Social Networks

Routings in mobile opportunistic social networks (MOSNs) are challenging problems due to their dynamic network structures. This paper finds that MOSNs exhibit a nested core-periphery hierarchy (NCPH). In the NCPH, few active nodes with large weighted degrees are the network core, while the network peripheries are composed of inactive nodes with small weighted degrees. “Nested” indicates that the NCPH is preserved when periphery nodes are iteratively removed. A distributed labeling scheme is proposed to determine the NCPH with a granularity control. Based on the NCPH, this paper proposes an up-and-down routing protocol for MOSNs, which includes an upload phase and a download phase. A message can be uploaded from the source to the network core by iteratively forwarding the message to a relay that has a higher position in the NCPH. Then, space-efficient Bloom-filter-based routing hints are introduced to download messages from the network core to the destination. Compared to traditional hierarchical routings, the up-and-down routing protocol achieves a better balance among the data delivery delay, ratio, and cost. Extensive experiments demonstrate that the proposed routing protocol achieves a competitive performance on the data delivery delay and ratio, with a small cost on the prior information maintenance and a low forwarding cost.