부산대학교 도서관

A recent theoretical result proposed Sigma, a novel GM protocol that forms views using a singleround of message exchange. Prior GM protocols have required more rounds in the worst-case. In this paper, we investigate how well Sigma performs in practice. We simulate Sigma using WAN connectivity traces and compare its performance to two leading GM protocols, Moshe and Ensemble. Our simulations show, consistently with theoretical results, that Sigma always terminates within one round of message exchange, faster than Moshe and Ensemble. Moreover, Sigma has less message overhead and produces virtually the same quality of views. We also observe that view-oriented GM in dynamic WAN-like environments is practical only in applications where GM need not respond to every disconnect immediately when detected. These applications are able, and prefer, to delay GM response and ignore transient disconnects, avoiding frequent futile view changes and associated overhead. We reference some applications in this category.