A Scalable Hybrid Time Protocol for a Heterogeneous Group

In peer-to-peer (P2P) applications, a scalable group of multiple peer processes (peers) are required to cooperate with each other. In this paper, we discuss a two-layered heterogeneous hybrid time (THHT) protocol which takes advantage of the linear time (LT) and physical time (PT) to causally order messages in a scalable heterogeneous group. In a heterogeneous type of group, the clock accuracy of each peer and the minimum delay time between every pair of peers are not the same. It depends on accuracy of each physical clock and minimum delay time between a pair of peers how messages can be ordered. Each peer has to hold group information on the clock accuracy of every peer and the minimum delay time of every pair of peers. In a scalable group of n peers, it is not easy, maybe impossible for each peer to hold the group information due to storage and computation overhead O(n
²
). In this paper, we newly consider a multi-layered model of a scalable heterogeneous group to reduce the information which each peer has to hold.