A publisher subscriber system is an event notification service where events generated by the publishers are routed to subscribers with matching subscriptions. Our work on publisher-subscriber systems in peer-to-peer (p2p) networks is motivated by the question: "What if the nodes in the network do not have the bandwidth to route all the events generated?" In such a case nodes may not receive all notifications because of lack of bandwidth, and even those with high bandwidth may starve for notifications if its neighbours do not have the bandwidth to send event notifications. In this paper, we consider Sub-2-Sub architecture for content based publisher subscriber systems and show with the help of simulations that the event dissemination rate will actually be much slower than expected when the publishing rate is very high. We propose a topology design and event dissemination mechanism which removes nodes which become bottleneck in dissemination. Side by side, it allows a node to receive more events if it has more bandwidth. Our system is built on top of Sub-2-Sub publisher subscriber system, and provides much improved performance over it in terms of percent of event received by nodes, and ratio of uploads to downloads (which shows the removal of bottleneck nodes in dissemination).
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