Reliable group multicasts provide a nice abstraction forcommunicating data reliably among group members and have been used for avariety of applications. In this paper we present Corona, a groupcommunication service for building collaboration tools and reliable datadissemination services in Web-based environments, where clients connectindependently of other clients and are not necessarily connected to thegroup multicast services all the time. The key features of Corona are:(1) the shared state of a group consists of a set of objects sharedcollectively among group members; (2) Corona supports multiple statetransfer policies to accommodate clients with different needs andresources; (3) the communication service provides the current groupstate or state updates to new clients even when other clients are notavailable; (4) the service supports persistent groups that tolerateclient failures and leaves. We show that the overhead incurred by themulticast service in managing each group's shared state has littleimpact on the latency seen by the clients or the server throughput. Wealso show that the multicast service does not have to be aware of theclient-specific semantics of the objects in the group's state
展开▼
