Switch fabric design and performance evaluation: metrics and pitfalls

The rapid growth of the Internet and the demand for carrying mixed mode traffic to deliver the commodity services, voice and data, at reasonable cost, to end users has put new pressures on the designers of switches and routers. The traditional architectures of routers with shared memory or crossbar are inefficient and fall short in their ability to meet this challenge. The need for faster optical switches fuelled by this rising demand is fraught with risks and fundamental physics problems that need to be addressed. We first examine the problem of designing a switch fabric that forms the core of the router as a multivariate optimization problem and in that context examine the limitations of the traditional crossbar or shared-memory approaches. We present a novel architecture that utilizes a combination of both space and time division multiplexing to deliver higher orders of throughput for a given switch size.