Towards hybrid mechanism on wide-area distributed services

With the increasing in the scale of distributed services in wide-area environment, it is difficult to provide efficient discovery and delivery of high-demand services to end-users, especially to different types of services, i.e. replica services and non-replica services. Replication technique has been proposed to provide scalable deployment of high-demand network services by allowing an arbitrary service to be performed by multiple service replicas. However, some network services need specific resources and environment to run them and cannot be replicated and run on arbitrary servers. In this paper, we present a hybrid model called HM-WADS for service discovery and delivery in wide-area environment to address the confronted issues, which adopts a hierarchical structure. It is focused on the delivery of replica services and non-replica services with hybrid mechanism by supporting QoS feedback capability on service clients for finding qualified service providers with non-replica services and incorporating the capability of dynamic creation and deletion of services replicas on service manager. Through the hybrid mechanism, which is service-specific, HM-WADS can achieve scalability, minimize network overhead and support load balance and QoS requirements efficiently.