High-performance architectures for high-radix switches.

Abstract

As the optimal radix for switches increases due to the benets in lower latencies, overall reduction in cost and power consumption; the traditional switch architectures are no longer valid because of either low-performance or non-scalability with the number of ports.This dissertation proposes a new switch architecture suitable for highradix switches called Partitioned Crossbar Input Queued (PCIQ) that deals with one of the main constraints in high-radix switch design, the excessive memory requirements. Also, in general terms, PCIQ forms a new family of switch microarchitectures.PCIQ relies on a smart partition of the crossbar into sub-crossbars, thus requiring less memory resources than other proposals for high-radix, yet obtaining high-performance and also increasing the arbiter eciency. PCIQ uses two round-robin packet-based arbiters (one for each crossbar) that exhibit a linear cost and a logarithmic response time as the radix of the switch increases.Here it is shown that PCIQ exhibits a cost (measured in terms of memory requirements, crossbar complexity and arbiter complexity) similar to or lower than basic organizations like CIOQ. However, it is able to achieve maximum switch eciency for uniform trac distribution, thus leveling costly organizations like BC.The other big issue on high-radix switches is the HOL blocking problem, which reduces dramatically the switch performance. Traditional solutions for removing the HOL blocking problem were based on VOQ schemes, but having high number of ports on a high-radix switch prevents the use of any of them. In this dissertation, a new congestion management technique has been proposed. This solution is called RECN-IQ, is specic for IQ switches and diers from the original RECN idea (suitable only for CIOQ switches) in being highly ecient and simple to implement, reducing the memory requirements to the maximum. RECN-IQ introduced by rst time a novel statistical approach for detecting congestion using just a single queue per input port. Results proved that by using RECN-IQ switches, the network will benet from low cost switches and high-eciency under any type of trac pattern or network circumstances. All this makes the network predictable and stable in performance, no more drops in throughput because of congestion. AcknowledgementsAbove all I would like to acknowledge my darling Raquel. We have walked together this life since we decided to share our lives many years ago, helping each other, growing, and sharing many experiences jointly. She was responsible of supporting me in pointing my career towards computers, so I could nally pursue my passion since I had my rst computer (a C-64 by the way).She has been my muse all this years; inspiring me in putting passion, eciency and love in this job. For that and many other moments in which she has been essential, this work should be honored to her as well. This work represents an academic milestone for us as a couple. Now it should be time for us to have her pursuing her PhD in Physics. José Duato opened to me this worl...