Design And Analysis Of Diagonalized Contention-Tolerant Crossbar Switch

The rapid development of internet makes higher and higher demands on the performance of the exchange equipment. However, as the core of the exchange equipment, the performance of switch fabric affects directly the performance of the exchange equipment. In this paper, at first, we introduce the exchange system and analyse its existing problems. Then the switch fabric of crossbar is illustrated. It can be said the full paper is based on the switch fabric of crossbar.We propose an improved crossbar switch- Tolerant-Contention Crossbar Switch, denoted as CTC(N). Compared to conventional crossbar, CTC(N) don't need the sophisticated arbitration mechanism to solve the problem of output contentions. It uses the circuitry reconstruction mechanism, which allow output contention, solves the problem. What's more, CTC(N) greatly improves the expansibility of the exchange structure , because it can realize the control mechanism of the distribution. By analyzing the staggered polling (SP) scheduling algorithms'switching throughput rate of First-In-First-Out(FIFO) queue and virtual output queues (VOQs), we've come to the conclusion and theoretical analysis are in agreement. The excellent scalability of CTC(N) provides a convenient way for us to improve the performance, which is the key of this paper.In order to enhance the performance of CTC(N), we present an improved contention-tolerant crossbar switch called diagonalized contention-tolerant crossbar, denoted as DiaCTC(N). DiaCTC(N) is exactly the same in all aspects of CTC(N), except the connections in each SE column. Compared with CTC(N), DiaCTC(N) balances the aggregate upstream traffics over all input ports without additional hardware cost. Because DiaCTC(N) and CTC(N) have the same full distribution control characteristic and low complexity, SP scheduling algorithm can operate on DiaCTC(N) without any change. DiaCTC(N) enhances the performance through balancing the aggregate upstream traffics over all input ports. In summary, DiaCTC(N) is a new improved architecture based on CTC(N). However, out of sequence problem, which exists in CTC(N), remains a challenging open problem for DiaCTC(N). It can be reduced by designing sophisticated scheduling algorithms and queue management methods. On the other hand, according to other QoS measure, more algorithms can be designed for achieving good performance.The study is based on the development of the Stanford discrete time exchange structure simulator, which realizes the switching fabric of contention-tolerant crossbar switch and many traffic model. Although it's efficiency is not high when simulates low load, it can make simulator run faster by using discrete time simulation on high simulated load. Through the emulator-SIM simulator, we realize the switching fabric of contention-tolerant crossbar switch and many traffic model that provide convenient for our follow-up study.Finally, some uniform Traffic models and some non-uniform traffic models are introduced and described as detailed as we can. In this traffic model, we have compared the performance of the DiaCTC(16)SP dispatching algorithm, CTC(16)SP_Random dispatching algorithm and traditional Expandable Crossbar Scheduler Based on iSLIP Algorithm. The performance mainly contains exchange throughput rate and cell transmission delay. Experimental results show that: in various traffic models, DiaCTC(16)SP dispatching algorithm is better than the others.