A Novel Buffer And Its Application Performance For Optical Packet Switching

Wavelength division multiplexing (WDM) has been widely deployed to satisfy the dramatically increasing requirements for the bandwidth capacity introduced by the emerging broadband applications on the Internet. The current optical circuit switch limits the bandwidth utilization and networking functionality. To achieve high efficiency and flexibility in bandwidth management, optical packet switching (OPS) is considered as a potential solution by reducing the available bandwidth granularity.One of the critical issues is the resolution of packet contention in OPS, which happens especially when multiple packets with the same wavelength are destined to the same output port in the same time slot. As packet contention has significant impact on system throughput, it is important to resolve packet contention in OPS networks. Generally, optical packet contention can be resolved in the space, wavelength and time domain, respectively. For example, resolutions have been proposed to resolve contention by using deflection routing and wavelength conversion in the space and wavelength domains. Optical buffering is a more common approach to solve contention in the time domain. Since there is no equivalent device of the electronic random access memory in the optical domain today, the optical buffer is mostly implemented using fiber delay lines (FDLs).To guarantee the quality-of-service (QoS) of high priority packets, preemption is considered as an effective method. Some OPS node architectures configure the packets delay time before packets enter the FDLs. In these schemes, to realize preemption, some packets have to be discarded. Therefore, it's very necessary to propose an optical buffer which is able to realize preemption and packet delay time manageable.In this paper, we introduce the development of optical packet switching and the generic architecture of the OPS node. Some classical switching structures are presented and explained. We also show the key technologies in OPS node, such as header labeling, synchronization and contention resolution, and review some famous OPS projects all over the world.We propose a novel wavelength converted broadcast-selective (WCBS) buffer in this paper. We show how it works to realize preemption and service differentiation. We discuss the wavelength requirements under different conditions. The results show that we can dramatically relax the wavelength requirement by using some simple buffering strategies. We also show the scalability of the WCBS buffer.We propose an output-buffered OPS node using WCBS buffer in this paper. We show how the node works and present some switching strategies to operate the switching node efficiently. Then we establish a simple theoretical model to describe the operation of the node. Some simulation results are made to confirm the theoretical analysis. The relations among different structure parameters are presented and discussed. We establish a theoretical model to describe the operation of high priority packets. The analysis and simulation results show that the switching node significantly improves the performances of high priority packets.