Group communication for event dissemination in dynamic distributed networks

The paper describes a service model for cost-effective event reporting to clients over a wide-area network. The service provider (SP) maintains multiple protocol mechanisms to replicate the event pages at different proxy nodes of the distribution network. The mechanisms, which embody server-driven and client-driven replica update schemes to synchronize the page copies, reduce the access latency on the event pages retrieved by clients. Each protocol mechanism excels over the others in a distinct operating range of the distribution infrastructure. So, the SP may select an optimal protocol to meet the client-prescribed QoS obligations under the current levels of link delays and client traffic. We use the `degree of proxy spread-out´ as a protocol-level metric for the infrastructure resource usage - and hence the cost incurred for event reporting. Our model allows dynamic switching from one protocol to another as the infrastructure-level cost changes. Simulation results are provided to corroborate the concept of protocol switching.