1/26/95 – 1 – Rev 7 The Supercomputer Supernet: AScalableDistributedTerabitNetwork Leonard Kleinrock, Mario Gerla, Nicholas Bambos, Jason Cong, and Eli Gafni University of California, Los Angeles, CA Larry Bergman Jet Propulsion Laboratory California Institute of Technology Pasadena, CA Joseph Bannister Aerospace Corporation El Segundo, CA ABSTRACT — Conventional supercomputer interconnection networks con- sist of crossbar modules, which are connected by point–to–point copper or fiber links to create distributed mesh topologies (e.g., CP*, Nectar). This type of ”physical networking” topology creates cable layout problems, deal- ing with bundles of cables/fibers between various pairs of modules. It also introduces several routing hops, increasing the probability of interference be- tween connections and making it difficult to guarantee quality of service to real time applications. We describe a new network called the Supercomputer Supernet (SSN) that attempts to overcome these problems by replacing the point–to–point links with an fiber optic interconnect system. The novel scheme employs asynchronous pipeline crossbar switches (APCS) used in parallel supercomputers to interconnect multi-channel wavelength division multiplexed (WDM) fiber optic links to an optical star (or tree) ”physical” topology. WDM will be used to subdivide the very large fiber bandwidth into several channels, each of Gb/s bandwidth. WDM channels (supporting also time division multiplexing) will be established between modules, thus defin- ing a dense ”virtual” interconnection topology, which is dynamically recon- figurable, responding to changing traffic patterns. A pool of channels will be set aside for direct, end–to–end connections between crossbars, providing circuit–switched service for real–time traffic applications. 1. INTRODUCTION The Supercompuer Supernet (SSN) is a novel, high–performance, scalable optical interconnection network for supercomputers, which is based on asynchronous wormhole routing crossbar switches. The geographic coverage ranges from interdepartmental to campus and even to metropolitan areas. The network provides very high-speed multiple services, supporting hybrid circuit–switched and datagram traffic, and direct or multi–hop connections that are dynamically reconfigurable. At a first networking level, the crossbars locally interconnect workstations, supercomputers, peripheral de- vices, mass memory etc. through host interfaces. At a higher networking level, the crossbars are fully interconnected with optical fibers supporting multiple wavelength division multiplexed (WDM) channels, allowing communication between devices connected to distinct crossbars. These asynch-