• Tackling network partitions and providing tools for recovery from them. Transis was designed to support partitionable operation, in which multiple network components that are (temporarily) disconnected from each other operate autonomously. When network partitions occur, as in “Wiredville” and in more complicated situations, Transis provides enhanced facilities for an application programmer to construct applications that operate consistently in multiple components of a partitioned network, and to merge these components gracefully upon recovery.• Meeting the needs of a large network through a hierarchical communication structure, with gateways selectively filtering messages among domains.• Exploiting the available network multicast within each local-area network (LAN) and providing fast cluster communication. Transis has an efficient protocol for reliable multicast, derived from the Trans protocol [16], that employs the Deering IP-multicast mechanism [6] for disseminating messages using selective hardware-multicast. Coupled with a network-based flow control mechanism we developed, the protocol provides high-throughput group communication.