Causally ordered delivery with global clock in hierarchical group

In peer-to-peer (P2P) networks, large number of peer processes are cooperating. In this paper, we discuss a scalable group of processes where processes are widely distributed in networks. Clocks of computers in every local network are synchronized by using the network time protocol (NTP) with a GPS time server. We discuss a global clock group (GCG) protocol where messages are causally ordered by using the physical time stamps. Messages not to be ordered by physical clock are furthermore ordered by using linear clock. We evaluate the protocol in terms of the number of messages ordered compared with the vector clock.