Input queueing is becoming increasingly used for highbandwidth switches and routers. In previous work, it was proved that it is possible to achieve 100% throughput for input-queued switches using a combination of virtual output queueing and a scheduling algorithm called LQF. However, this is only a theoretical result: LQF is too complex to implement in hardware. In this paper we introduce a new algorithm called Longest Port First (LPF), which is designed to overcome the complexity problems of LQF, and can be implemented in hardware at high speed. By giving preferential service based on queue lengths, we prove that LPF can achieve 100% throughput.

-In this paper, we present the Tiny Tera: a small packet switch with an aggregate bandwidth of 320Gb/s. The Tiny Tera is a CMOS-based input-queued, fixed-size packet switch suitable for a wide range of applications such as a highperformance ATM switch, the core of an Internet router or as a fast multiprocessor interconnect. Using off-the-shelf technology, we plan to demonstrate that a very highbandwidth switch can be built without the need for esoteric optical switching technology. By employing novel scheduling algorithms for both unicast and multicast traffic, the switch will have a maximum throughput close to 100%. Using novel highspeed chip-to-chip serial link technology, we plan to reduce the physical size and complexity of the switch, as well as the system pin-count.

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-It is well known that head-of-line (HOL) blocking limits the throughput of an input-queued switch with FIFO queues. Under certain conditions, the throughput can be shown to be limited to approximately 58%. It is also known that if non-FIFO queueing policies are used, the throughput can be increased. However, it has not been previously shown that if a suitable queueing policy and scheduling algorithm are used then it is possible to achieve 100% throughput for all independent arrival processes. In this paper we prove this to be the case using a simple linear programming argument and quadratic Lyapunov function. In particular, we assume that each input maintains a separate FIFO queue for each output and that the switch is scheduled using a maximum weight bipartite matching algorithm. We introduce two maximum weight matching algorithms: LQF and OCF. Both algorithms achieve 100% throughput for all independent arrival processes. LQF favors queues with larger occupancy, ensuring that larger queues will eventually be served. However, we find that LQF can lead to the permanent starvation of short queues. OCF overcomes this limitation by favoring cells with large waiting times.