Tapping TCP streams

Providing transparent replication of servers has been a major goal in the fault tolerance community. Transparent replication is particularly challenging for highly nondeterministic applications, such as the ones that use multithreading. For such applications, keeping replicas in a consistent state becomes non-trivial. One way to deal with the non-determinism is to use a leader/follower approach. In this paper we describe the design and performance of a TCP tapping mechanism we implemented. This mechanism was designed to improve the efficiency of leader/follower replication. We argue that TCP tapping can address a major efficiency bottleneck of leader/follower replication