Burst Loss Probability Research Articles

Performance analysis of optical burst switching node with limited wavelength conversion capabilities

The systematical and scalable frameworks were provided for estimating the blocking probabilities under asynchronous traffic in optical burst switching (OBS) nodes with limited wavelength conversion capability (LWCC). The relevant system architectures of limited range and limited number of wavelength converters (WCs) deployed by a share-per-fiber (SPF) mode were developed, and the novel theoretical analysis of node blocking probability was derived by combining the calculation of discouraged arrival rate in a birth-death process and two-dimensional Markov chain model of SPF. The simulation results on single node performance verify the accuracy and effectiveness of the analysis models. Under most scenarios, it is difficult to distinguish the plots generated by the analysis and simulation. As the conversion degree increases, the accuracy of the analysis model worsens slightly. However, the utmost error on burst loss probability is far less than one order of magnitude and hence, still allows for an accurate estimate. Some results are of actual significance to the construction of next-generation commercial OBS backbones.

Improving Fairness With Novel Adaptive Routing in Optical Burst-Switched Networks

In most existing studies of optical burst-switched networks, adaptive routing is based on deflection routing and/or feedback from the past intervals which often introduces excessive transmission delay and architectural complexity. Our proposed novel adaptive routing schemes, however, consider the transient link congestion at the moment when the bursts arrive and have potential to reduce the overall burst loss probability. Moreover, they can utilize the same offset times for the same node pairs implying zero additional transmission delay and simplicity. The proposed hop-by-hop routing schemes also aim to address the intrinsic unfairness defect of existing popular signaling protocols by increasing the effective link utilization. The results show that the proposed schemes generally outperform shortest path routing and depending on the routing strategy involved, the network topology and the traffic load, this improvement can be substantial. We develop analytical loss models to demonstrate the need for such an adaptive routing scheme at each hop and show its effectiveness. We also verify the analytical results by simulation.

Integrated Contention Resolution and Control Algorithm for Optical Burst Switched Networks

This article compares the conventional and proposed integrated contention resolution and control algorithm in optical burst switching with respect to burst loss probability and network throughput. Results have shown that the proposed approach behaves well in practice and responds quickly to any change in network status, while improving the overall network performance. It is shown that the proposed algorithm (ICRCA) not only provides significantly better burst loss performance than the conventional algorithms, but is also void of any packet re-orderings.

Using updated neighbor state information for efficient contention avoidance in OBS networks

In this paper, we introduce and evaluate a preventive contention avoidance protocol to reduce the burst loss probability in emerging OBS networks. The proposed solution reacts to highly loaded downstream node situations by preventively deflecting the bursts towards less loaded neighbors. To keep pace with OBS traffic dynamics while minimizing the related control overhead, we propose the current node state information to be propagated downstream in the burst control packet. As a result, accurate adjacent nodes state information can be maintained, improving either preventive or reactive deflection routing decisions. Using this information, two different routing heuristics are presented aiming to reduce the computational costs at intermediate nodes. Our proposals are discussed and further assessed by extensive simulation results, showing a significant burst loss reduction especially when the burst size increases.

Contention Resolution for Transmission Control Protocol over Optical Burst-Switching Networks Using Random Segment Dropping

Optical burst switching (OBS) is a promising method for data transfer in photonic networks based on a Wavelength Division Multiplexing (WDM) technology. Transmission control protocol (TCP)-based applications generate the majority of data traffic in the Internet; thus, understanding and improving the performance of TCP over OBS networks is critical. In this paper, we develop a novel burst-dropping strategy to improve the quality of service provided by TCP over OBS networks. Our approach relies on random-segment dropping according to the capacity of a special optical component, called the optical virtual memory, which is used for buffering purposes within the optical switches. The core node predicts incipient congestion by computing the average blocking duration in the optical virtual memories. When this size exceeds a threshold, segments are randomly dropped. Simulation results show that the proposed method performs better than common techniques in terms of burst loss probability and transmission delay.

Fair Bandwidth Allocation in Optical Burst Switching Networks

Optical burst switching (OBS) is a promising switching technology for next-generation Internet backbone networks. One of the design challenges is how to provide fair bandwidth allocation in OBS networks; the schemes proposed for general store-and-forward IP switching networks can not be used because of the non-buffering and un-fully utilized bandwidth characteristics of OBS networks. We propose a rate fairness preemption (RFP) scheme to achieve approximately weighted max-min fair bandwidth allocation in OBS networks. We present an analysis of the burst loss probability in RFP-based OBS networks. The analysis and simulation results show that the RFP scheme provides fair bandwidth allocation in OBS networks.

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.

Multipath traffic engineering in WDM optical burst switching networks

In this paper, we investigate the problem of multipath traffic engineering in optical burst switching (OBS) networks. The main goal of this work is to minimize burst loss rate in the network by adaptively balancing the burst traffic among multiple paths based on the measurement and analysis of path congestion. We develop three distributed traffic splitting algorithms by considering the special features of OBS networks. Among these three algorithms, one algorithm considers burst level traffic distribution, and the other two algorithms consider flow level traffic distribution to avoid packet reordering problem. The proposed multipath traffic engineering algorithms achieve significant performance improvement in reducing burst loss probability in a distributed manner in OBS networks. Further, through theoretical analysis and simulations, we show that the proposed algorithms converge quickly on a sudden traffic increase in the network.

An efficient scheme for optimizing channel utilization in OBS networks

Optical burst switching (OBS) is an emerging technology that allows variable size data bursts to be transported directly over DWDM links. In order to make OBS a viable solution, the wavelength scheduling algorithms need to be able to utilize the available wavelengths efficiently, while being able to operate fast enough to keep up with the burst incoming rate. Unfortunately, horizon scheduling cannot utilize the voids created by previously scheduled bursts, resulting in low bandwidth utilization. To date, Min-SV is the fastest scheduling algorithm that can schedule wavelengths efficiently. However, its complexity is O (log m) and it requires 10 log ( m) memory accesses to schedule a single burst. This means that it can take upto several microseconds for each burst request, which is still too slow to make it a practical solution for OBS deployment. In this paper, an efficient scheme has been proposed for optimizing channel utilization in OBS networks. In the proposed approach, a burst is represented by an interval of time. The process of scheduling a number of bursts, thus, turns to be a process of fitting a set of the corresponding time intervals on a channel time line that represents a channel-time resource. By doing so, the scheduling process can be formulated as a combinatorial optimization problem. Then, graph theory is applied to schedule as many non-overlapping intervals as possible onto the channel time line. The underlying concept of the proposed scheduling scheme is that of briefly delaying the scheduling of a burst so that a much better decision can be made about a number of bursts all-together. This scheme is shown, through simulations, to improve performance in terms of burst loss probability, channel utilization, fairness-control and data throughput over existing schemes. Thus the proposed scheme is well suited for high performance networks in terms of reliability.

HYBRID CONTENTION RESOLUTION SCHEMES FOR OPTICAL BURST SWITCHED HIGH-SPEED NETWORKS

Optical burst switching (OBS) has attracted interest as a transport network architecture for the future optical Internet. However, many challenging issues have to be solved in order to pave the way for an effective implementation of OBS. Contention, which may occur when two or more bursts compete for the same wavelength on the same link, is a critical issue. This paper compares the basic and hybrid contention resolution strategies with respect to burst loss probability and end-to-end transfer delay. The simulation results show that hybrid techniques lead an effective reduction of the burst average loss rate compared to existing techniques. It is also observed that a significant differentiation with regard to burst loss has been achieved, when burst priorities are considered.

Reservation signalling mechanism for reducing blocking probability in optical burst switching networks with limited wavelength conversion capabilities

First, the optical burst switching (OBS) network with limited wavelength conversion capability (LWCC) is decomposed into multiple wavelength continuous segments according to the position of wavelength converters. Based on the decomposed network model, two reservation signalling mechanisms for OBS-LWCC networks, namely wavelength-amend-on-demand (WAoD) and contention-based limited signalling protocol (CLSP), are proposed to reduce the blocking probability in the OBS-LWCC networks. In WAoD, the congested node sends a feedback message to the closest upstream switch with wavelength conversion capability. The notified switch will change the burst wavelength to the one assigned by the congested node to avoid collision in advance. Extensive simulation results indicate that by applying the wavelength reconfiguration method to the core nodes without wavelength conversion capability, the proposed WAoD scheme can improve the blocking performance in the OBS-LWCC networks significantly. Furthermore, CLSP, which combines the burst time-slot reconfiguration with the wavelength reconfiguration of WAoD, always has the lowest burst loss probability when compared with both the conventional and the proposed reservation mechanisms.

A Succeeding Transmission Scheme for Burst Transfer in Optical Burst Switched Networks

Optical Burst Switched (OBS) networks are considered as promising candidates for the next generation network architecture which does not need high-speed switch technologies. In OBS networks, contention resolution is one of the significant problems. Generally, setup reservations are operated per burst in OBS networks. To transmit multiple successive bursts successfully, the effective wavelength reservation must be implemented and enhanced network performance must be realized. In the proposed method, when an optical burst is generated and its destination is the same as that of the preceding burst or the path until the destination includes the entire path of the preceding burst, the subsequent burst is assigned to the same wavelength as the preceding burst and transmitted sequentially. The main aim in the proposed method is the efficient use of wavelength resources and the reduction of burst loss probability. We simulate and evaluate the effectiveness of the proposed method. As a result, it is verified that the proposed method can reduce the burst loss probably.

Priority-based offline wavelength assignment in OBS networks

Optical burst switching (OBS) is a promising technique for wavelength division multiplexing (WDM) networks. In practice, wavelength converters (WCs) are either absent or only sparsely deployed in WDM networks due to economic and technical limitations. Thus, wavelength assignment is expected to be an important component of OBS networks. In this paper, an offline wavelength assignment scheme in OBS networks without wavelength conversion capability is proposed. The key idea of the scheme is to decide the wavelength searching order of each traffic connection at edge nodes according to the wavelength priorities determined by the calculated burst loss probabilities on different wavelengths. Simulation results indicate that the proposed scheme can reduce the network-wide burst loss probability significantly compared with other schemes. It is also illustrated that the performance of the proposed scheme can be further enhanced by a larger number of wavelengths per link and a reasonable delay bound at edge nodes.

Addressing conversion cascading constraint in OBS networks through proactive routing

The negative impact of cascaded wavelength conversions has been largely ignored in optical burst switching performance evaluations. When optical bursts are transmitted all optically from source to destination, each wavelength conversion performed along the lightpath may cause some signal-to-noise deterioration. If the distortion of the signal quality becomes significant enough, the receiver would not be able to recover the original data. In this paper we examine the performance degradation when an upper bound on the number of wavelength conversions that a signal can go through is enforced. We refer to this constraint as conversion cascading constraint. We propose a novel proactive routing scheme under this constraint that considers the instantaneous link congestion at the moment when the bursts arrive. It has three major advantages: (1) utilize the same offset times for the same node pairs while providing dynamic routing without using any fiber delay lines (FDL); (2) decrease burst loss probability to a great extent; (3) mitigate unfairness among the bursts with different hop counts, which is even worse under the conversion cascading constraint if without any special treatment. We also extend the proposed mechanism to embrace a variant of regulated deflection routing which can further improve network performance.

Performance comparisons of restoration techniques in optical burst switching networks

This paper describes restoration techniques for OBS networks. First, we introduce the design issues to be essentially considered, when restoration techniques will be built into OBS networks. Second, considering the design issues, we propose a novel restoration model named “Recover-Then-Reserve,” which can enhance the restoration performance. Third, we develop a simulator using the NS-2 platform to verify the performance of the restoration techniques (path, link, and sub-path) designed by each restoration model (GMPLS-based OBS restoration and our proposal). Performance is evaluated on the following metrics: restoration success rate, restoration time, connection availability, and burst loss probability. The effects of the failure frequency and the number of the restoration attempts on the restoration performance are also investigated. Our experiments show that the proposal can reduce the restoration time by about 25 ms compared to the GMPLS-based OBS restoration model. Also, path restoration technique has better performance than link and sub-path restoration techniques because it has the highest restoration success rate, allowing similar restoration time. Our experiments also show that the more the restoration attempts made and the less the failure frequency becomes, the better the restoration performance obtained.

Burst-cluster transmission with probabilistic pre-emption for reliable data transfer in high-performance OBS networks

Recently, optical switching and packet processing technologies have been developed and high-performance optical burst switching (OBS) networks are constructed by using these technologies. In high-performance OBS networks, several types of applications such as Grid computing and HDTV can be provided for users according to immediate reservation protocol. Because some applications require that data is transmitted reliably over high-performance OBS networks, it is indispensable to provide reliable data transfer service for high-priority users. Therefore, in this paper, we propose a reliable burst transmission method which can be available for the immediate reservation protocol. In the proposed method, both burst-cluster transmission and probabilistic pre-emption are used at edge and core nodes. By using these methods together, the reliable data transfer and the service differentiation can be provided. We evaluate by simulation the performance of the proposed method in the 14-node NSFNET. Numerical examples show that the proposed method can transmit higher-priority bursts more reliably than the conventional method while not increasing the overall burst loss probability so much. In addition, we investigate effective parameter settings from some simulation results.

Using multiple per egress burstifiers for enhanced TCP performance in OBS networks

Burst assembly mechanism is one of the fundamental factors that determine the performance of an optical burst switching (OBS) network. In this paper, we investigate the influence of the number of burstifiers on TCP performance for an OBS network. The goodput of TCP flows between an ingress node and an egress node traveling through an optical network is studied as the number of assembly buffers per destination varies. First, the burst-length independent losses resulting from the contention in the core OBS network using a non-void-filling burst scheduling algorithm, e.g., Horizon, are studied. Then, burst-length dependent losses arising as a result of void-filling scheduling algorithms, e.g., LAUC-VF, are studied for two different TCP flow models: FTP-type long-lived flows and variable size short-lived flows. Simulation results show that for both types of scheduling algorithms, both types of TCP flow models, and different TCP versions (Reno, Newreno and Sack), TCP goodput increases as the number of burst assemblers per egress node is increased for an OBS network employing timer-based assembly algorithm. The improvement from one burstifier to moderate number of burst assemblers is significant (15–50% depending on the burst loss probability, per-hop processing delay, and the TCP version), but the goodput difference between moderate number of buffers and per-flow aggregation is relatively small, implying that an OBS edge switch should use moderate number of assembly buffers per destination for enhanced TCP performance without substantially increasing the hardware complexity.

Dynamic CANON: a scalable multidomain core network

The explosion of current demand has brought the contemporary multidomain core network paradigm to its limit. In the quest for new approaches that exploit recent developments in optical technology, a novel network architecture that obviates most of the expensive and loss-prone centralized all-optical switches is described in this work. It is based on clustered architecture for nodes in optical networks and features a reconciliation between dynamic resource allocation and guaranteed end-to-end network performance in a multidomain network. This article enhances the distributed, collision-free slot aggregation inside domains of clustered core nodes with dynamic switching of slots/frames between the domains. Thus, it can support dynamic sub-wavelength allocations between network domains, using standard burst-switching techniques. This extends the high efficiency and multiplexing gain into the inter-domain network even under highly bursty traffic. It features both low-cost optical add/drop edge nodes exploiting WDM transmission and agile and modular centralized electro-optical switches that are presented in conjunction with the overall network architecture. Its performance exhibits very low burst loss probability traded for a higher but tolerable and bounded delay.

Retransmission management for RWA using the suitability index in OBS networks

We focus on the collision avoidance problem in distributed optical burst switching (OBS) networks. Our proposal involves cooperation between the routing and the wavelength assignment tasks. The main idea is to classify each wavelength at an output link of a node as suited either to sending or to relaying data bursts. Furthermore, burst retransmission management is important to realize OBS networks. We propose the cooperation method considering retransmission. Simulation results show that the proposed method can reduce the burst loss probability, particularly for long-distance transmissions. As a result, unfairness in the treatment of short and long hop bursts can be alleviated.

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.