Conventional Optical Burst Switching Research Articles

Study on the problem of routing, wavelength, and time-slot assignment towards optical time-slot switching technology

Conventional optical burst switching (OBS) is incapable of providing connection-oriented service, and burst loss is more likely to occur with increasing of traffic load due to its inherent architecture where the burst size is variable. In this paper, we propose and evaluate the optical time-slot switching technology, in which the fixed-size time-slot is adopted as the basic switching granularity, and switching is done in the time domain, rather than the wavelength domain. Also, we prove that time-slot switching has an equivalent function to eliminate data conflict relative to wavelength converter. Subsequently, the routing, wavelength, and time-slot assignment problem is studied in this paper. An adaptive weight function is introduced to the routing and wavelength selection algorithm, then several useful approaches, such as the train approach, wagon approach and p-distribution approach, are presented for time-slot assignment and scheduling. The results show that our scheme can perform better than conventional OBS in the aspect of blocking performance, quality of service, and class of service.

Comparison analysis of optical burst switched network architectures

Optical burst switching (OBS) is a promising paradigm for the next-generation Internet infrastructure. In this paper, a novel efficient network architecture for OBS has been presented and compared with conventional OBS architectures. To enhance OBS system performance, the architecture employs a novel proposed burst assembly algorithm, fiber delay lines (FDLs) and dynamic route selection technique. A queuing model is used to predict the system behavior for both classless and prioritized traffic. Simple closed-form expressions are obtained for the burst-loss probability of both classless and prioritized traffic. Numerical results show that the proposed architecture provides an accurate fit for the performance of the highest traffic class and lower bounds for the other traffic classes that are tighter than earlier known results.

Performance Overview of the Offset Time Emulated OBS Network Architecture

Optical burst switching (OBS) control architecture considers two different models for the management of the offset time in the network. The conventional OBS (C-OBS) introduces the offset time in soft-way by delaying the transmission of the burst relative to its control packet in the edge node. Another idea for an OBS architecture (E-OBS) comes from optical packet switching world and it intends to emulate offset time by means of an additional fiber delay unit introduced in the data path at the input port of the nodes. Although C-OBS has attracted lots of attention, in this paper we highlight that it possesses many difficulties that can be entirely removed in E-OBS. Issues such as unfairness in resource reservation, efficiency and complexity of burst scheduling, difficulty with alternative and backup routing, and quality of service (QoS) provisioning are studied. Moreover, E-OBS facilitates the application of several enhanced mechanisms. As an example, in this paper we analyze a QoS application based on a preemption window mechanism, which expands look-ahead processing window technique to the burst preemption context. Results show that this mechanism can achieve the performance of the conventional preemption scheme while avoiding the well-known problem of phantom burst generation.

Providing absolute QoS in an OBS/WR architecture

By employing optical burst switching (OBS) in its metropolitan portion and wavelength routing (WR) in the backbone portion, the hybrid OBS/WR architecture provides end-to-end all-optical connections to end users while inheriting the fine granularity of OBS and the low loss probability of WR. However, the original OBS/WR architecture can provide only relative quality of service (QoS). That is, the burst loss possibilities of high-priority traffic flows are guaranteed to be lower than those of low-priority traffic flows, but the upper burst loss bound cannot be guaranteed with this model. We propose a call admission control (CAC) scheme to provide absolute QoS in an OBS/WR architecture and a dynamical priority allocation algorithm (DPAA) to enhance the blocking probability performance of the proposed CAC scheme. We first analyze the burst loss performance of traffic flows in the OBS/WR architecture. Based on the analytical results, a CAC scheme is proposed to provide absolute burst loss guarantee. Besides the CAC scheme, we also design a DPAA that assigns priorities to incoming traffic flows according to their QoS requirements to further improve the performance. The analysis and simulation results show that the proposed CAC scheme guarantees upper burst loss bound to different traffic flows while achieving significantly higher bandwidth utilization than other existing absolute QoS schemes in conventional OBS networks, and the proposed DPAA can achieve lower blocking probability than the original CAC scheme while maintaining the absolute QoS.

CORNet: An OBS metro ring network with QoS support and fairness control

The rapid evolution of networks has been driven by new advances in enabling technologies and the explosive growth of Internet traffic. Optical Burst Switching (OBS) is not only cost-effective, but also provides high throughput, high bandwidth utilization, and low transmission latency. These benefits make OBS a viable solution for next-generation Metro Area Networks (MANs) in which the traffic models will be changed more dramatically than in today's networks. This paper employs Wavelength Division Multiplexing (WDM) technology to construct a loss-free OBS metro ring architecture designated as the Collision-free Optic-burst Ring Network (CORNet). The proposed architecture ensures a collision-free transmission of data bursts, while retaining the advantage of the statistical multiplexing provided by conventional OBS networks. A novel distributed Medium Access Control (MAC) protocol to integrate the support of differentiated service and fairness access in CORNet is presented. The proposed Quality of Service (QoS) provisioning mechanism adopts a bandwidth-reservation approach which combines real-time transmission establishment and termination routines. Furthermore, a credit-based fairness control scheme is designed to guarantee the transmission fairness of best-effort traffic. Simulation results are presented to demonstrate that the proposed CORNet system provides good performance for real-time traffic while simultaneously providing significant performance improvements for best-effort traffic.

Intermediate-Hop Preemption to Improve Fairness in Optical Burst Switching Networks

In optical burst switching (OBS) networks, burst with different numbers of hops experience unfairness in terms of the burst loss probability. In this paper, we propose a preemptive scheme based on the number of transit hops in OBS networks. In our proposed scheme, preemption is performed with two thresholds; one is for the total number of hops of a burst and the other is for the number of transit hops the burst has passed through. We evaluate the performance of the scheme by simulation, and numerical examples show that the proposed scheme improves the fairness among the bursts with different numbers of hops, keeping the overall burst loss probability the same as that for the conventional OBS transmission without preemption.

一种新颖的高速光突发交换网络结构

A novel optical burst switching (OBS) high speed network architecture has been proposed. To verify its feasibility and evaluate its performance, just-enough-time (JET) signaling has been considered as a high performance protocol. In the proposed architecture, to avoid burst losses, firstly, a short-prior-confirmation-packet (SPCP) is sent over the control channel that simulates the events that the actual packet will experience. Once SPCP detects a drop at any of the intermediate nodes, the actual packet is not sent but the process repeats. In order to increase network utilization, cost effectiveness and to overcome some limitations of conventional OBS, inherent codes (e.g., orthogonal optical codes (OOC)), which are codified only in intensity, has been used. Through simulations, it shows that a decrease in burst loss probability, cost effectiveness and a gain in processing time are obtained when optical label processing is used as compared with electronic processing.

Time-Space Label Switching Protocol (TSL-SP)—A New Paradigm of Network Resource Assignment

In this paper we propose a new protocol called time-space label switching protocol (TSL-SP) in optical burst switching (OBS), and define the terms time-space label (TSL) and time-space routing (TSR). An important concept of response time is introduced in the time label mechanism. The TSL-SP is a new technology that can quickly and efficiently forward data with a label on the optical networks. A two-dimension label switched path (TD-LSP) can be set up, that is maintained and deleted by the TSL-SP. For clearly illuminating the operation principles of the TSL-SP, we propose a new approach of orthogonal time-space coordinates in which the vertical coordinate is the space label and the horizontal coordinate is the time label. The proposed TD-LSP can dramatically reduce the routing failure probability and greatly improve the link network efficiency compared with other signaling protocols. Moreover, we define the time-space label control plane that can achieve the higher efficiency. When the TSL-SP is applied to networks, switching performance can be improved by two orders compared to the switching performance with the conventional OBS signaling protocols. The fundamental goal of TSL-SP is to band the signaling and routing functions together closely. Also, the TSL-SP can reduce the complexity of the network, support automatic service offering, and provide traffic engineering.