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Transis is a group communication system that supports efficient group multicast for high availability.

Transis is developed in the High Availability Laboratory at the Computer Science Department of the Hebrew University of Jerusalem.

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The Transis Group Communication System

Transis is a multicast communication layer that facilitates the development of fault tolerant distributed applications in a network of machines. Transis supports reliable group communication for high availability applications. Transis contains a novel protocol for reliable message delivery that optimizes the performance for existing network hardware and tolerates network partitioning.

The Transis communication system supports process group communication. Groups are conveniently identified by a name (a string) that is selected by the user, such that messages are addressed to the entire group by specifying the group name. Using the group abstraction, the communication subsystem relieves the user from identifying the targets of messages explicitly, and from finding the network routes to them. In addition, it guarantees all-or-none delivery semantics, and handles message losses and transient network failures transparently.

Transis provides several forms of group multicast operations: FIFO ordered, causally ordered, totally ordered, and safely delivered. The multicast operations differ in their semantics and in their cost (e.g. latency). Generally, FIFO and causal communication are the cheapest and fastest. Intuitively, causal communication guarantees that a response to a certain message will never be delivered before the message. This makes programming somewhat easier, much in the same way that FIFO guarantees make it easier to program two-party interaction. Totally ordered communication incurs a higher delay, and is useful for supporting replicated information, of any kind. The safe multicast guarantees that delivery of a message occurs after all the machines in the network have received a copy of the message. It incurs the largest delay, because it explicitly waits for acknowledgment from all the participating machines.

The Transis approach to advanced group communication has acquired a wide recognition in the academic community, mainly due to the following desirable properties:

  1. It employs a highly efficient multicast protocol, based on the Trans protocol (developed by Melliar-Smith et al. at UCSB), that utilizes available hardware multicast.
  2. It can sustain extremely high communication throughput due to its effective flow control mechanism, and its simple group design.
  3. Is supports partitionable operation, and provides the means for consistently merging components upon recovery.
For a description of Transis, see: The Transis Approach to High Availability Cluster Communication, published in the CACM special issue on group communication, April 1996.


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The Transis logo was designed by Eyal Ofek.

Last modified: Thu Mar 18 11:10:49 IST 1999