Myrinet, ANSI/VITA 26-1998, is a high-speed local area networking system designed by Myricom to be used as an interconnect between multiple machines to form computer clusters. Myrinet has much less protocol overhead than standards such as Ethernet, and therefore provides much better throughput and less latency while using the host CPU much less interference. Although it can be used as a traditional networking system, Myrinet is often used directly by programs that "know" about it, thereby bypassing a call into the operating system.
Myrinet physically consists of two fibre optic cables, upstream and downstream, connected to the host computers with a single connector. Machines are connected together via low-overhead routers and switches, as opposed to connecting one machine directly to another. Myrinet includes a number a fault-tollerance features, mostly backed by the switches. These include flow control, error control, and "heartbeat" monitoring on every link. The first generation provided 512 Mbit/s data rates in both directions, and later versions supported 1.28 Gbit/s and 2 Gbit/s.
Myrinet's throughput is close to the theoretical maximum of the physical layer. On the latest 2.0 Gbit/s links Myranet often runs at 1.98 Gbit/s of sustained throughput, considerably better than what Ethernet offers, from 0.6 and 1.9 Gbit/s depending on load.
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