Evaluation of Flexible Synchronization Protocol to Prevent Illegal Information Flow in P2PPS Systems

We consider the peer-to-peer type of topic-based publish/subscribe (P2PPS) model where each process (peer) can publish and subscribe event messages with no centralized coordinator. Some information of a peer may flow to target peers by exchanging event messages. Here, the peer forgets topics which are in a publication of the event message but not in the subscription of the peer. In our previous studies, the flexible synchronization (FS) protocol and the relevance concept of topics are proposed. However, it is difficult, maybe impossible for each peer to know about every topic in a system. Each time a peer receives an event message, topics carried by the event message which the peer does not know but are related with subscribed topics are obtained in the peer. Thus, each peer learns and obtains new topics through receiving event messages. In the evaluation, we show the more number of topics each peer can initially subscribe, the fewer number of notifications are banned and the more number of forgotten topics are added to the subscription. However, the advantage obtained by initially including more number of topics decreases as the number of event messages exchanged among peers increases.