Modelling & simulating chained negotiation to enable sharing of notifications

Notification services (NSs) are middleware components providing asynchronous message delivery between publishers and consumers. Multiple interconnected NSs form a distributed NS, with each NS routing notifications between publishers and consumers at different locations, enabling consumers to share subscriptions, reducing the number of messages sent. Consumers can specify quality of service (QoS) levels when subscribing to a NS, using negotiation to find QoS levels acceptable to both parties. However, if consumers specify sufficiently different QoS levels, notifications cannot be shared and new subscriptions must be made. Chained negotiation can be used to negotiate QoS levels through intermediate NSs, enabling the reuse of existing subscriptions for additional consumers. In this paper, we present a chained negotiation engine, evaluating its performance and behaviour, showing that it enables negotiation over QoS while still sharing notifications, and that it provides better results for a consumer by negotiation directly with the publisher.