Slotted optical switching with pipelined two-way reservations

Optical burst switching is a core architecture designed to reconcile the available optical technology with the increasing burstiness of traffic. However, disappointing performance in terms of high packet loss and/or low system utilization discouraged broader experimental implementations. A method to avoid these losses by first sending over the control channel a short scout packet that simulates the events that the actual burst will experience is proposed in this paper. Once the scout message detects a drop at any intermediate node, it returns back to the source to avert the payload emission and repeat the process. The way the control works results in essential service quality features, i.e., no loss of bursts, no out-of-order emissions, increased efficiency, much reduced delay variation, and graceful throttling of the load respecting the contracted rates.     

Node dimensioning in optical burst switching networks

Network dimensioning should be progressed for pursuing the ultimate efficiency of network system resources in order to satisfy target performance. This article studies node dimensioning as a method of resource optimization in optical burst switching (OBS) networks. OBS is a new switching technology for pursuing bufferless transparent optical networks by sending control packets prior to data burst in order to provision resources for the burst. However, the basic assumption of a bufferless node implies burst contention at a core node when more than two bursts attempt to move forward the same output simultaneously. Thus, burst contention is a critical performance metric and this article takes it into account as a constraint on node dimensioning and target performance. In this article, we first present node dimensioning issues for OBS networks. Two constraints from the transport plane and the control plane which affect burst contention are then introduced. The effect of the burst assembly process on node dimensioning is also presented. From numerical analysis, the optimal number of wavelengths in a link, which provides the lowest blocking probability, is obtained to suggest a guideline for node dimensioning.     

光突发交换中的突发业务流模型及其应用

提出了一种光突发交换中的突发业务流模型,采用该模型对光突发交换中的LAUC-VF输出调度算法在不同的突发业务强度和突发长度下的性能进行了模拟仿真,分析比较了该算法在此突发业务流和普通业务流模型下的性能,仿真结果表明,该突发业务流模型具有一定的合理性。     

Techniques for optical packet switching and optical burst switching

Wavelength-division multiplexing appears to be the solution of choice for providing a faster networking infrastructure that can meet the explosive growth of the Internet. Several different technologies have been developed so far for the transfer of data over WDM. We survey two new technologies which are still in the experimental stage-optical packet switching and optical burst switching-and comment on their suitability for transporting IP traffic     

Burst noise in phototransistor optical isolators

Noise measurements were performed on several commercially available optical isolators in order to examine the signal detection limits of typical devices. It was found that, in general, optical isolators are very noisy devices exhibiting all of the common types of noise usually found in bipolar junction transistors. A large number of devices exhibited burst noise which dominated their low-frequency noise performance. Experimental data indicates that the source of burst noise is the phototransistor detector. A comparison of experimental data to existing burst noise theory is presented.     

Control architecture in optical burst-switched WDM networks

Optical burst switching (OBS) is a promising solution for building terabit optical routers and realizing IP over WDM. In this paper, we describe the basic concept of OBS and present a general architecture of optical core routers and electronic edge routers in the OBS network. The key design issues related to the OBS are also discussed, namely, burst assembly (burstification), channel scheduling, burst offset-time management, and some dimensioning rules. A nonperiodic time-interval burst assembly mechanism is described. A class of data channel scheduling algorithms with void filling is proposed for optical routers using a fiber delay line buffer. The LAUC-VF (latest available unused channel with void filling) channel scheduling algorithm is studied in detail. Initial results on the burst traffic characteristics and on the performance of optical routers in the OBS network with self-similar traffic as inputs are reported in the paper.     

A burst loss probability model with impatient customer feature for optical burst switching networks

We consider optical delay line buffer as a solution to reduce the number of lost burst in optical burst switching, one of the promising candidates for future networks. Such network takes burst loss as an important performance criteria in the design step. Network performance, however, cannot be captured efficiently using traditional queueing models, because they often ignore the impatience of messages traveling through optical switches which is one of the popular issues in communication networks. In this paper, we develop an analytic model for this system using queueing theory and considering special impatience features. Simulation results show that (i) the developed model with impatience features can decrease burst loss probability ( ? 10%) compared with other approaches, and (ii) applying that model, we demonstrate that shared buffer architecture in optical burst switching network with optical buffer often achieves lower burst loss probability than dedicated buffer way in several different scenarios. Copyright © 2014 John Wiley & Sons, Ltd.     

A phototransistor optical isolator noise model

A noise model for the phototransistor optical isolator is presented and used to predict optical isolator noise performance. Results are shown to agree with existing experimental data on phototransistor optical isolator noise. The model presented includes burst noise, flicker noise and shot noise.     

Error correction performance in digital subscriber looptransmission systems

The author describes an error correction system for digital subscriber loop transmission systems which use time compression multiplexing (TCM). An interleaved block code is used to correct the burst errors due to impulse noise from analog telephone circuits. This interleaving method requires no extra hardware and contributes no additional delay. To evaluate the transmission performance of this error correction system, the bit error rate after decoding is derived on the basis of a burst error model for 200 kb/s digital subscriber transmission using the alternate mark inversion (AMI) line code. The experimental results for a 200 kb/s TCM system show that burst errors are substantially reduced     

Design and implementation of an optical burst-switched network testbed

Optical burst switching has been receiving increased attention as a promising technology for building the next-generation optical Internet. This article presents the design and discusses the implementation of an overlay mode optical burst-switched network testbed. A flexible "transceiver + forwarding" edge node architecture is proposed to perform both electronic burst assembly/disassembly and optical burst forwarding. It is designed to provide class of service and wavelength selection for locally generated bursts, and transparency to cut-through bursts. The functional modules of the control plane and related key design issues are presented. In particular, we discuss a scheduling mechanism that efficiently combines two different contention resolutions in space and wavelength domains. Experimental results show the effectiveness of this scheme in reducing burst blocking probability. Furthermore, the performance of the network testbed and corresponding methods of improving it are discussed.     

A novel transfer mode to reduce burst loss rate for optical burst switching networks

A crucial issue in optical burst switching (OBS) networks is burst loss caused by resource contention. As a result, many methods are currently being proposed to reduce burst loss rate. These methods can be summed up into two categories: burst scheduling algorithms and contention resolutions. Both categories of methods can reduce burst loss rate to a certain degree. However, to make OBS to become a viable solution, the burst loss rate needs to be further reduced. Furthermore, almost all methods ignore the fact that an unfortunately scheduled, locally generated single-hop burst could block a number of future incoming transit bursts, though the burst just travels to its next downstream node. This phenomenon becomes more evident when links are heavily loaded in mesh OBS networks. To eliminate contention caused by single-hop traffic completely, this paper proposes a novel transfer mode called packet calking by differentiating between single-hop traffic from multihop traffic for OBS networks. An analysis model is developed to evaluate the performance of packet calking. Theoretical results are validated through extensive simulations in both ring and mesh networks. These results show that packet calking outperforms the transfer mode without packet calking in terms of burst loss rate and link utilization.     

Analytical framework for end-to-end design of optical burst-switched networks

This paper presents an analytical model of TCP throughput in optical burst-switched (OBS) networks. Several parameters characterize this system and influence the network design process, such as the assembly time, the access bandwidth, the burst loss rate, and they are taken into account in the formulation of TCP send rates. Moreover burst loss is considered a consequence of contention in core nodes and it is formulated in relation to a quite general core node architecture. The novelty of the work is represented by the possibility of analytically representing the whole end-to-end connection so that a fast and effective tool to evaluate the relationships between network and access design is provided. An application example is given to prove the practical significance of the approach. Simulation results are provided to validate the model and the related assumptions.     

Design of an ultra fast pipelined wavelength scheduler for optical burst switching

Optical Burst Switching (OBS) is an emerging technology that allows variable size data bursts to be transported directly over DWDM links without encountering O/E/O conversion. In OBS, before the transmission of a data burst, a burst header is transmitted through an electronic control path, setting up and tearing down optical paths on-the-fly. Data bursts can remain in the optical domain and pass through the OBS network transparently. Unfortunately, system performance will be greatly degraded, if burst scheduling requests cannot be processed in time. This article quantitatively studied the negative impact of control path overloading on the performance of OBS networks. Results have shown that control path overloading greatly affects the performance of the OBS routers, especially for systems with large WDM channel counts. In order to remove this performance bottleneck, we have designed and implemented an ultra fast pipelined burst scheduler that is able to process a burst request every two clock cycles, regardless of the number of WDM channels per link. The design has been implemented in Verilog HDL and synthesized to FPGAs. Circuit level simulation results confirm the correctness of the design. The circuit has achieved 100 MHz in Altera Cyclone II devices, allowing the scheduler to process a burst request every 20 ns. To the authors’ best knowledge, this is the fastest implementation of burst scheduling algorithms.     

Buffering-deflection tradeoffs in optical burst switching

A very important issue in optical burst switching (OBS) networks is the excessive burst drop when no suitable network resources are found during path reservation. In this study, a network scenario is evaluated in which AWG-based optical nodes are used as burst router nodes within the optical network. The two classical solutions to solve the burst contentions on the channels outgoing from the node are considered, that is, either based on buffering within the node, or by exploiting deflection routing. A performance evaluation is carried out to evaluate and compare these solutions for different network topologies with different node and traffic parameters. Our main contribution is to set numerical tradeoffs between burst deflection through the network and buffering in the node, so that a guidance in optical network design is provided where node buffering is inherently technologically limited.     

Burst loss and delay in optical buffers with offset-time management

In this paper, we study the loss and delay of data bursts in an optical buffer. We assume that this buffer consists of a number of fiber delay lines (FDLs). In order to guarantee quality of service (QoS) differentiation in such a buffer, we investigate analytically an offset-time based scheduling mechanism. We consider a system with C QoS classes, where the high-priority QoS classes have a larger offset time than the low-priority QoS classes. For this system, we calculate the total burst loss probability and the burst loss probability within each QoS class. Furthermore, we study the delay of an arbitrary arriving data burst, as well as the delay of an arriving data burst of a certain QoS class. MACS: Stochastic Modeling and Analysis of Communication Systems     

E-PON系统突发模式光收发一体模块设计

本文介绍了E-PON系统以及对OLT和ONU收发一体模块的设计要求.讨论了OLT、ONU BiDi突发模式光收发一体模块的基本原理和设计方法,并给出了实验结果.     

On optical burst switching and self-similar traffic

In this letter we consider burst switching for very high speed routing in the next generation Internet backbone. In this scenario, Internet protocol (IP) packets to a given destination are collected in bursts at the network edges. We propose a burst assembly mechanism that can reduce the traffic autocorrelation or degree of self-similarity, and at the same time keep the delay due to burst formation limited at the network edges     

TCP over optical burst-switched networks with controlled burst retransmission

For optical burst-switched (OBS) networks in which TCP is implemented at a higher layer, the loss of bursts can lead to serious degradation of TCP performance. Due to the bufferless nature of OBS, random burst losses may occur, even at low traffic loads. Consequently, these random burst losses may be mistakenly interpreted by the TCP layer as congestion in the network. The TCP sender will then trigger congestion control mechanisms, thereby reducing TCP throughput unnecessarily. In this paper, we introduce a controlled retransmission scheme in which the bursts lost due to contention in the OBS network are retransmitted at the OBS layer. The OBS retransmission scheme can reduce the burst loss probability in the OBS core network. Also, the OBS retransmission scheme can reduce the probability that the TCP layer falsely detects congestion, thereby improving the TCP throughput. We develop an analytical model for evaluating the burst loss probability in an OBS network that uses a retransmission scheme, and we also analyze TCP throughput when the OBS layer implements burst retransmission. We develop a simulation model to validate the analytical results. Simulation and analytical results show that an OBS layer with controlled burst retransmission provides up to two to three orders of magnitude improvement in TCP throughput over an OBS layer without burst retransmission. This significant improvement is primarily because the TCP layer triggers fewer time-outs when the OBS retransmission scheme is used.     

A unified study of burst assembly in optical burst switching networks

This article presents a comprehensive study of burst assembly in optical burst switching (OBS) networks. This investigation aims to provide a unified study of burst assembly algorithms. After analyses of conventional assembly algorithms, we present an adaptive burst assembly algorithm: data-length time-lag product assembly algorithm. Numerical results show that the proposed algorithm takes the real-time traffic state into account to adapt burst length and its injected intervals. It obtains a more acceptable performance. Moreover, we investigated the impact of burst assembly applied at the edge of OBS networks. We analyze the Hurst parameter of the input traffic to the output traffic that results from the burst assembly. Two formulas are presented to describe changes of the Hurst parameter. Theoretical results are validated through extensive simulations in time-based, length-based, and adaptive assembly algorithms, respectively.     

United stabilizing scheme for edge delay in optical burst switched networks

A novel scheme, namely united stabilizing scheme for edge delay, is introduced in optical burst switched networks. In the scheme, the limits of burst length and assembly time are both set according to certain qualifications. For executing the scheme, the conception for unit input bit rate is introduced to improve universality, and the assembly algorithm with a buffer safety space under the self-similar traffic model at each ingress edge router is proposed. Then, the components of burst and packet delay are concluded, and the equations that limits of burst length and assembly time should satisfy to stabilize the burst edge delay under different buffer offered loads are educed. The simulation results show that united stabilizing scheme stabilizes both burst and packet edge delay to a great extent when buffer offered load changes from 0.1 to 1, and the edge delay of burst and packet are near the limit values under larger offered load, respectively.