Non-blocking message total ordering protocol

Abstract

Message total ordering is a critical part in active replication in order to maintain consistency among members in a fault tolerant group. The paper proposes a non-blocking message total ordering protocol (NBTOP) for distributed systems. Non-blocking property refers to that the members in a fault tolerant group keep on running independently without waiting for installing the same group view when a fault tolerant group evolves even when decision messages collide. NBTOP takes advantage of token ring as its logical control way. Members adopt re-requesting mechanism (RR) to obtain their lost decisions. Forward acknowledgement mechanism (FA) is put forth to solve decision collisions. The paper further proves that NBTOP satisfies the properties of total order, agreement, and termination. NBTOP is implemented, and its performance test is done. Comparing with the performance of Totem, the results show that NBTOP has a better total ordering delay. It manifests that non-blocking property helps to improve protocol efficiency.

A Nonblocking Approach for Reaching an Agreement on Request Total Orders

“…The FC approach is added to the previous protocol in [22] called NBTOP, which is implemented with Visual C++ 6.0. We compare the performance of NBTOP with the Totem protocol under the same circumstances.…”

“…In our previous work [22], we proposed a nonblocking total ordering protocol under the assumption that no two successive replicas fail simultaneously. The assumption is relatively strong in practice.…”

“…We relax this in the FC approach and address a more general problem: replicas reach an agreement on the total-order values of client requests when up to k(0 ≤ k ≤ n/2 − 1) successive replicas fail simultaneously. Note that the FC approach does not affect the other parts of the protocol presented in [22], including token, request, and membership management. Regarding the issues of handling multiple tokens, ring (re)construction and group membership, please refer to [22].…”

“…Note that the FC approach does not affect the other parts of the protocol presented in [22], including token, request, and membership management. Regarding the issues of handling multiple tokens, ring (re)construction and group membership, please refer to [22].…”

Effect of Urbanization on Precipitation in Yangtze River Delta

“…In China, there are also many studies on scale of city and area which made similar conclusion [9,10]. Wang studied the rainfall distribution of the Beijing area and found that the process of urbanization made the precipitation in winter increased [11]. DING made a study on the area of Hangjiahu and Suxichang, and made the conclusion that the rainfall effect of the cities was significant [12,13].…”