A Multi-layered Communication Model with Hybrid Clocks in P2P Overlay Networks

A group of multiple peers are required to cooperate with each other in distributed peer-to-peer (P2P) applications. Here, messages have to be causally delivered to every peer. In our approach to realizing a scalable P2P group, messages are ordered by taking advantage of linear time (LT) and physical time (PT) since message length is O(1). Here, each peer has to hold information on clock accuracy of every peer and minimum delay time between every pair of peers. In a scalable group, it is difficult, maybe impossible for each peer to hold the information on every peer due to storage overhead. It is also difficult for each peer to directly send messages to every peer due to communication overheads. In this paper, we newly discuss a multi-layered model to realize a scalable P2P group. A group is hierarchically decomposed into subgroups, where every peer is in a leaf peer. We discuss how each peer to order messages by taking advantage of PT and LT in a multilayered group. We evaluate the multi-layered group protocol in terms of the size of group information and delay time among peers compared with a flat group.