Burst scheduling, grooming and qos provisioning in optical burst-switched networks

Yuqi Fan, Ph.D., Department of Computer Science and Engineering, Wright State University, 2009. Burst Scheduling, Grooming and QoS Provisioning in Optical BurstSwitched Networks. The demand of network capacity has been increasing steadily with more users than ever connected to the Internet through broadband access and the popularity of video based applications, such as YouTube. Optical wavelength division multiplexing (WDM) networks [1] are expected to form the next-generation backbone network and to fulfill the insatiable appetite for bandwidth. Wavelength routed WDM optical networks offer the granularity of switching at a fiber, waveband, or a wavelength level. The finest granularity offered is at a wavelength level by provisioning lightpaths for different clients/services. All-optical packet switching is still deemed technically infeasible and its competitiveness as a backbone technology is debatable. Optical burst switching (OBS) presents itself as a promising technology for bridging the gap between optical wavelength switching and optical packet switching. OBS operates at the sub-wavelength level and is designed to improve the bandwidth utilization of wavelengths by exploring statistical multiplexiii ing to deal with bursty traffic, and is therefore more resource efficient than optical wavelength switching. In OBS networks, arriving data packets (e.g., IP packets) are assembled at the ingress OBS nodes to form a data burst. A burst control packet (CP) is sent on a control channel ahead of the data burst to reserve resources and configure the switches along the route traversed by the data burst [2, 3]. In this dissertation, we will explore several important and challenging issues in OBS networks in order to improve the utilization of network resource. To reduce the switching overhead, small bursts may be groomed to reduce resource waste and switching penalty. We have studied the per-hop burst grooming problem where bursts with the same next hop may be groomed together to minimize the number of formed larger bursts and strike a proper balance between burst grooming and grooming cost, assuming all the network nodes have the grooming capability. In order to reduce computation overhead and processing delay incurred at the core nodes, we assume that grooming can only be performed at edge nodes and the core node can send a burst to multiple downstream links, that is, the core node has light-splitting capability. We have attempted to groom small bursts into larger bursts, and select a proper route for each large burst, such that total network resources used and/or wasted for delivering the small bursts is minimized. Optical signal transmission quality is subject to various types of physical impairment introduced by optical fibers, switching equipment, or other network components. The signal degradation due to physical impairment may be significant enough such that the bit-error rate of received signals is unacceptably high at the destination, rendering the signal not usable. Based on earlier work, we have studied scheduling iv and QoS provisioning problems in OBS networks, taking physical impairments into consideration. In the context of the JET signaling protocol, we have studied the burst scheduling problem and proposed three effective burst scheduling algorithms in OBS networks, taking into account physical impairment effects. Because the offset time of bursts varies in OBS networks, the voids or fragmentation on the channels in the outgoing links can severely degrade the network throughput and blocking probability performance, if not dealt with carefully. A signalling architecture called Dual-header Optical Burst Switching (DOBS) is proposed to reduce the scheduling algorithm complexity. We study the burst scheduling problem and propose an impairment aware scheduling algorithm in DOBS networks. QoS provisioning is an important issue in OBS networks. We have dealt with relative QoS support problem and proposed a QoS provisioning algorithm subject to the physical impairment constraints. A high-priority burst requires a better quality of service in terms of blocking probability, and at the same time, the transmission of the burst should satisfy physical impairment constraints.