基于阈值的光突发交换网络数据信道调度算法

光突发交换(OBS)是实现下一代光互联网中的一种极具前景的方案。该文提出了一种基于阈值的OBS网络数据信道调度算法,对于长度大于阈值的光突发数据包采用LAUC算法进行调度,对于长度小于阈值的光突发数据包采用LAUC-VF算法进行调度。仿真结果表明,该算法在调度时间方面与已有的LAUC算法很接近;而在光突发数据包丢失率性能方面要优于LAUC-VF算法。     

OBS网络数据信道调度算法性能比较

光突发交换(OBS)网络中数据信道的调度算法是提高OBS网络性能的关键技术之一.文章给出了LAUC、LAUC-VF、BR和LAUC-VF-BS等几种数据信道调度算法的基本原理,通过仿真对这些调度算法进行了性能比较,结果表明LAUC-VF-BS算法能够更有效地降低突发丢失率,提高信道利用率,从而改善网络性能.     

光突发交换网络中基于标记可抢占的调度算法

根据光突发交换(OBS)网络核心节点的结构和功能 特点,分析了OBS网络核心节点的数据信道 调度算法,提出了一种新的基于标记可抢占调度算法(LPSA),并讨论和分析了算法的实 现过程。本文算法根据到达核心节点的控制包所属业务等级的突发数据(OB)包占用的网络带 宽决定 数据信道调度的方法,实现了合理的使用数据信道和各业务类别间的业务区分,最终达到改 善OBS网络性能的目的。     

基于虚拟突发的OBS数据信道重调度算法研究

基于虚拟突发的概念,提出了一种新的光突发交换(OBS)数据信道重调度算法,即(WCRA-VB).新算法一方面有效地克服了传统OBS网络中数据突发(DB)与控制分组(BHP)到达顺序不一致带来的问题,另一方面极大地增强了数据块重调度的灵活性.仿真结果表明:与传统OBS重调度算法(其重调度粒度为常规突发)和原虚拟突发调度方案相比较,本文的WCRA-VB算法具有以下优势:既能有效改善网络总的丢包率,也能提高链路利用率,同时具有很强的灵活性.     

一种改进的光突发交换调度算法研究

数据信道调度是OBS核心路由器的关键技术之一,文章对数据信道的几种调度算法进行了分析.在此基础上,介绍了一种改进的波长调度算法.网络仿真结果表明,该算法可以有效改善网络性能.     

光突发包交换关键技术概述

光突发包交换(OBS)技术是近年来出现的一种新型光交换技术，它结合了波长路由和光分组交换的优点，是一种未来一段时间内交换网络比较理想的过渡方案，为此介绍了OBS的基本原理，讨论了OBS中偏置时间的设置和交换信道的调度等关键技术，并就OBS的特点及仍需解决的问题作了总结。     

OBS网络的TCP性能分析与改进

光突发交换(OBS，Optical Burst Switch)是下一代IP-over-DWDM光网络最有前途的解决方案之一。Burst组装算法和数据通道调度算法是OBS网络的关键技术，TCP协议是当前主要的传输层协议。该文对OBS网络的TCP性能进行分析，并提出了基于源地址集的组装算法和ACK优先调度算法。仿真结果表明使用该算法可以显著改善OBS网络的TCP性能。     

OBS中的一种原波长优先批调度算法

光突发交换网络(OBS)中心节点使用波长转换器减少突发丢失率,但波长转换器价格昂贵且技术不成熟,中心节点需要减少波长转换器的使用数目.大部分数据信道调度算法都没有考虑波长转换器数目.为此,提出一种原波长优先批调度算法基于相同波长转换器数目下进一步减少突发丢失率.仿真结果表明,这种批调度算法在波长转换器不足条件下,与其它...     

OBS网络中的最小间隙组调度算法

根据OBS网络的结构和特点,分析了OBS网络核心节点的数据信道调度算法,提出了一种新的数据信道调度算法--最小间隙组调度(SGGS)算法,并详细讨论了该算法的具体实现.该算法将到达核心节点的控制包分组,然后将这一组控制包按数据包到达先后的次序调度数据信道,从而达到合理调度和使用数据信道,最终实现改善整个OBS网络性能的目的.     

多态OBS网络中基于信道整理的调度算法

多态光突发交换(POBS)网络能够有效地支持多种同步和异步业务的传输,但是其异步突发业务的丢失率较相同网络环境下的传统OBS丢失率要高。如何有效地对多态OBS中异步突发进行合理调度,是降低异步突发丢失率的关键所在。提出了一种基于信道整理的调度算法,将已经成功调度的突发重新调度到最合适的数据信道,使得信道资源得到充分的利用,从而降低了异步突发的丢失率。仿真结果表明,该算法能很好地降低多态OBS网络中异步突发的丢失率。     

OBS网络中的多BHP延迟调度算法

光突发交换 (Optical Burst Switching,OBS) 是下一代光网络中的有效核心交换技术之一。在OBS网络中,核心节点的调度方案是影响网络交换性能的重要因素。如何有效地对突发分组 (Burst) 进行合理调度,以减少丢包率正是关键问题所在。该文提出了一种多控制分组 (Burst Header Packet,BHP) 延迟调度算法,对于一个收集周期内到达的多个BHP所对应的突发数据,按照一定的方式对它们进行集中调度,实现对已预约资源的更改,使调度结果得到了优化。该算法根据不同的网络应用,可细化为4种具体的算法实现,以适用于不同的应用场景。仿真结果表明,该文提出的调度算法和已有算法相比,能够优化对突发分组的调度,提高对信道资源的有效使用,从而降低交换网络的丢包率。     

OBS网络数据信道调度算法性能比较与分析

光突发交换(0BS)网络中的数据信道调度算法是提高0BS网络性能的关键技术之一.首先介绍和分析了LAUC、LAUC-VF和0DBR基本原理和性能,结合国内外最新研究成果,介绍了四种支持QoS的数据信道调度算法,最后对其应用场合做出总结.     

Physical impairment aware scheduling in optical burst switched networks

Optical burst switching (OBS) presents itself as a promising technology for bridging the gap between optical wavelength switching and optical packet switching. Increasingly, researchers attempt to incorporate more realistic constraints into the design of OBS networks. 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 impairments may be significant enough such that the bit-error rate of received signals is unacceptably high at the destination, rendering the signal not usable. In this paper, based on earlier work, we study the burst scheduling problem in OBS networks, taking into account physical impairment effects. We propose three effective burst scheduling algorithms: (1) a JET based Physical Impairment Constrained Algorithm (JETPIC), (2) an Integrated Physical Impairment Constrained Algorithm (IPIC), and (3) an Enhanced Integrated Physical Impairment Constrained Algorithm (EIPIC). At an OBS node, the proposed algorithms schedule bursts for transmission by searching for available resources as well as verifying signal quality. Our simulation results show that the proposed algorithms are effective in terms of reducing the burst blocking probability. In general, algorithm JETPIC outperforms algorithms IPIC and EIPIC in burst blocking probability and average end-to-end delay performance.

Traffic statistics and performance evaluation in optical burst switched networks

Optical burst switching (OBS) is a promising switching technology to exploit the potential benefits of optical communication and, at the same time, support statistical multiplexing of data traffic at a fine granularity. To quantify its benefits, the paper describes several typical burst assembly algorithms and studies their impact on the assembled burst traffic characteristics as well as the performance of TCP traffic. Also described is a proactive burst scheduling algorithm, called burst overlap reduction algorithm (BORA), which schedules locally assembled bursts in such a way as to reduce burst contention at downstream nodes in OBS networks. Furthermore, to provide analytical insights into performance evaluation of OBS networks, a burst loss model at an OBS node and its extension to different reservation protocols are presented.     

有限波长转换能力的OBS网波长分配算法研究

结合国内外最新的研究动态,针对有限波长转换能力的光突发交换网中亟待解决的突发包资源竞争问题,探讨了各种传统的波长分配算法,并通过对其特点的分析和综合比较,提出了一种新的适合有限波长转换能力光突发交换网特点的动态波长分配算法,此算法可以实现更低的全网突发包阻塞率.     

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.     

Group-Scheduling for Multi-Service Optical Burst Switching (OBS) Networks

We propose a new burst scheduling mechanism for Optical Burst-Switched (OBS) networks. The new approach is made possible by gathering data bursts into groups and performing the scheduling decision for each group collectively. In OBS group-scheduling, bursts will not be considered for scheduling until a pre-defined time period elapses, during which the group of burst header packets would be gathered. By transforming a set of data bursts into a set of corresponding time intervals, the problem of scheduling these bursts is transformed into a combinatorial optimization problem. Graph algorithms are applied to obtain the maximum number of non-overlapping bursts. The proposed OBS group-scheduling scheme is shown to improve the performance of OBS networks over existing scheduling schemes in terms of burst loss probability and channel utilization. With an extension through a sequential optimization, using a Branch-and-Bound technique, the proposed scheme can support multiple classes of service. It is shown that the new scheduling approach has several desired characteristics including fairness and service differentiability among classes in terms of burst loss probability and channel utilization.     

Efficient burst scheduling algorithms in optical burst-switched networks using geometric techniques

Optical burst switching (OBS) is a promising paradigm for the next-generation Internet. In OBS, a key problem is to schedule bursts on wavelength channels, whose bandwidth may become fragmented with the so-called void (or idle) intervals, using both fast and bandwidth efficient algorithms so as to reduce burst loss. To date, two well-known scheduling algorithms, called Horizon and LAUC-VF, have been proposed in the literature, which trade off bandwidth efficiency for fast running time and vice versa, respectively. In this paper, we propose a set of novel burst scheduling algorithms for OBS networks with and without fiber delay lines (FDLs) utilizing the techniques from computational geometry. In networks without FDLs, our proposed minimum-starting-void (Min-SV) algorithm can schedule a burst in O(logm) time, where m is the total number of void intervals, as long as there is a suitable void interval. Simulation results suggest that our algorithm achieves a loss rate which is at least as low as LAUC-VF, but can run much faster. In fact, its speed can be almost the same as Horizon (which has a much higher loss rate). In networks with FDLs, our proposed batching FDL algorithm considers a batch of FDLs to find a suitable FDL to delay a burst which would otherwise be discarded due to contention, instead of considering the FDLs one by one. The average running time of this algorithm is therefore significantly reduced from that of the existing burst scheduling algorithms. Our algorithms can also be used as algorithmic tools to speed up the scheduling time of many other void-filling scheduling algorithms.     

光突发交换试验网的可行性分析

文章对光突发交换网络的产生背景、光突发交换网络模型及技术实现的可行性,以及进一步发展光突发交换网络需要关注的核心技术予以分析,最后对建设中国下一代高速光因特网提出一些建议与思考。