Myrinet: A Gigabit-per-Second Local Area Network

Myrinet is a new type of local-area network (LAN) based on the technology used for packet communication and switching within "massivelyparallel processors " (MPPs). Think of Myrinet as an MPP message-passing network that can span campus dimensions, rather than as a wide-area telecommunications network that is operating in close quarters. The technical steps toward making Myrinet a reality included the development of (1) robust, 25m communication channels with flow control, packet framing, and error control; (2) self-initializing, low-latency, cut-through switches; (3) host interfaces that can map the network, select routes, and translate from network addresses to routes, as well as handle packet traffic; and (4) streamlined host software that allows direct communication between user processes and the network. Background. In order to understand how Myrinet differs from conventional LANs such as Ethernet and FDDI, it is helpful to start with Myrinet's genealogy. Myrinet is rooted in the results of two ARPA-sponsored research projects, the Caltech Mosaic, an experimental, fine-grain multicomputer [1], and the USC Information Sciences Institute (USC/ISI) ATOMIC LAN [2, 3], which was built using Mosaic components. Myricom, Inc., is a startup company founded by members of these two research projects. Multicomputer Message-Passing Networks. A multicomputer [4, 5] is an MPP architecture consisting of a collection of computing nodes, each with its own memory, connected by a message-passing network. The Caltech Mosaic was an experiment to "push the envelope " of multicomputer design and programming toward a system with up to tens of thousands of small, single-chip nodes rather than hundreds of circuit-board-size nodes. The fine-grain multicomputer places more extreme demands on the messagepassing network due to the larger number of nodes and a greater interdependence between the computing processes on different nodes. The message-passing-network technology developed for the Mosaic [6] achieved its goals so well that it was used in several other MPP systems

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