基于窗口的光突发交换调度算法

针对光突发交换网(OBS)中的资源竞争和QoS支持等问题，提出了一种新型的基于窗口的调度算法。该算法利用边缘节点的电缓存，对调度窗口中的突发数据包进行批量BORA调度，可以有效地降低网络中发生资源竞争的概率；同时调度窗口中的优先级策略还可以进一步增强QoS。网络仿真结果表明，通过选择合适的调度窗口和最大允许时延，该调度算法在0．8的网络负载下使得高优先级突发数据包的阻塞率下降一个量级，信道利用率提高3．5％。     

一种基于QoS策略的光突发交换网络LSP共享算法

针对光突发交换（OBS）网络中已有的包括抢占和波长分离等服务质量（QoS）保证机制的不足,提出了一种改进的基于QoS的标签交换路径共享（QLS）算法。算法通过链路波长资源的统计复用,在保证高优先级业务传送的可靠性和有效性的同时,提升低优先级业务的QoS性能。使用开源离散事件仿真软件OMNeT++搭建了OBS/GMPLS仿真平台,对4×4对称型MESH网络和NSFNET网络分别采用WP算法和QLS算法进行了仿真。结果表明,QLS算法对于高QoS等级业务性能影响极小,MESH和NSFNET网络中class3业务的丢包率分别减少了近0.2和0.3,平均丢包率分别减少了约0.05和0.1。     

OBS网络中基于优先级与参数可调的偏射路由算法

为了保证OBS网络中不同优先级业务的服务质量和解决偏射算法在偏射控制上的问题,提出一种基于优先级与参数可调的偏射路由算法.该算法通过设置可调参数“偏射概率”来控制冲突突发包的偏射,并从可调丢包率和偏射路径长度意义上寻找最佳偏射路由.当冲突发生时,分割优先级低的突发包,并将分割突发包偏射到空闲的链路上;在空闲的链路中选择...     

Optimal Burst Scheduling in Optical Burst Switched Networks

Optical burst switching (OBS) is an emerging technology that allows variable size data bursts to be transported directly over dense wavelength division multiplexing links. In order to make OBS a viable solution, the burst-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. For example, for a 16-port OBS router with 64 wavelengths per link, each operating at 10 Gb/s, we need to process one burst request every 78 ns in order to support an average burst length of 100 kB. When implemented in hardware, the well-known horizon scheduler has O(1) runtime for a practical number of wavelengths. Unfortunately, horizon scheduling cannot utilize the voids created by previously scheduled bursts, resulting in low bandwidth utilization. To date, minimum starting void is the fastest scheduling algorithm that can schedule wavelengths efficiently. However, while its complexity is O(log m), it requires 10 log m memory accesses to schedule a single burst. This means that it can take up to several microseconds for each burst request, which is still too slow to make it a practical solution for OBS deployment. In this paper, we propose an optimal burst scheduler using constant time burst resequencing (CTBR), which has O(1) runtime. The proposed CTBR scheduler is able to produce optimal burst schedules while having processing speed comparable to the horizon scheduler. The algorithm is well suited to high- performance hardware implementation.     

一种基于门限的光突发交换受限偏射路由算法

提出了一种基于突发丢失门限的条件偏射路由算法（LDFD），该算法采用丢弃少量偏射的高优先级突发来保证偏射路由上较低优先级非偏射突发的服务质量（QoS）。当偏射的高优先级突发到达核心节点而该节点没有空闲数据信道时，就启用定义的偏射条件检测函数来判断是丢弃该突发还是允许其抢占非偏射的低优先级突发的资源，从而减少偏射突发与偏射路由上原有突发的竞争。仿真表明，该算法可以很好地控制偏射突发对偏射路由上正常流量的影响，并有效地提高整个网络的突发丢失性能。     

光突发交换网络中QoS方案的研究

光突发交换是构建下一代光网络的有效交换技术,在OBS网络中如何有效地支持QoS已成为一个重要的研究课题.介绍了光突发交换网络中基于偏置时间的QoS方案和波长分组QoS方案,最后提出了一种基于波长分组技术,结合突发分片技术和Min-Sv算法的QoS的解决方案,通过建立相应的模型时其进行了仿真,仿真结果表明所提出的方案可以更好地提供区分服务,同时有效地提高了信道的利用率,降低了整体的丢失率.     

一种自适应光突发装配映射机制及性能仿真

分组粗颗粒分类因有良好的扩展性,可作为OBS(Optical Burst Switching)网络的QoS(Quality of Service)实现基础。然而OBS网络因其固有限制而只能支持较少的突发优先级,因此OBS常采用多类别光突发装配技术。该文在粗颗粒分类基础上,提出了一种新的适用于这类装配的映射机制TQ-Map,即确定某一优先级光突发可以装配哪些类别分组。自适应性是该机制的突出特点,主要体现在:映射关系能随各类分组的QoS要求和负载的改变而自动进行调整。仿真表明:TQ-Map机制的自适应性能有效保证突发装配与上层QoS要求相匹配(以分组损失率为衡量指标)。     

A novel contention solution strategy based on priority for optical burst switching networks

A fundamental issue in optical burst switching (OBS) networks is to solve the burst contention for the core node. In this paper, a novel priority-based contention solution strategy for OBS networks is proposed. When the contention occurs, the burst priority is considered firstly, and then the burst segmentation method is used for the low priority bursts in this strategy. Ensuring the integrity of high priority bursts, part of the segmented bursts can be transmitted to the destination node via combining wavelength conversion and optical buffer method. Simulation results show that the proposed scheme not only ensures the integrity of high priority bursts, but also reduces the packet loss rate of the low priority bursts maximally, so that it can support good quality of service (QoS) for the network.     

A new scheduling algorithm to provide proportional QoS in optical burst switching networks

A new scheduling algorithm, which aims to provide proportional and controllable QoS （Quality of Service） in terms of burst loss probability for OBS （Optical Burst Switching） networks, is proposed on the basis of a survey of QoS schemes in current OBS networks. With simulations, performance analysis and comparisons are carried out in detail. The results show that, in the proposed scheme, burst loss probabilities are proportional to the given factors and the control of QoS performance can be achieved with better performance. This scheme will be beneficial to the OBS network management and the tariffpolicy making.     

定长光突发交换节点的QoS性能分析

分析了光突发交换网络中基于附加偏移时间(EOT,extra offset time)的业务优先等级区分服务的变长突发方案的不足，提出了一种定长光突发方案。它能在较小附加延迟的情况下保证高优先级的业务完全不受低优先级业务的阻塞，即使每个优先级的附加等待时间都减小到变长突发方案的1/3，同时使最高优先级业务的阻塞率更小，而且具有现实可行性。     

OBS网络中一种基于突发包优先级分割的可控重传方案

在光突发交换(OBS)网络中,突发包会由于竞争OBS核心节点输出端口的有限波长资源而发生冲突。突发包重传能够在一定程度上减少由于突发包在核心节点冲突而导致的数据损失,但重传次数的增加可能会加重网络负荷,反而增加数据丢失率。并且,在多业务存在的OBS网络中,重传方案需要能够实现区分服务以保证网络的服务质量(QoS)。据此,本文提出一种基于突发包优先级分割的可控重传方案,在实施优先级分割的同时,根据网络负荷赋予每次重传不同的概率,并对重传次数加以控制。最后,仿真分析了路径阻塞率和不同优先级业务的字节丢失率(ByLP,byte loss probability)性能。     

A framework of prioritized burst segmentation supporting controlled retransmission in OBS networks

In optical burst switching (OBS) networks, burst contentions in OBS core nodes may cause data loss. To reduce data loss, retransmission scheme has been applied. However, uncontrolled retransmission may increase network load significantly and data loss probability defeating the retransmission purpose. In addition, in a priority traffic existing OBS network, OBS nodes may apply different retransmission mechanisms to priorities bursts for quality-of-service (QoS) support. This study has developed a controlled retransmission scheme for prioritized burst segmentation to support QoS in OBS networks. Unlike previous works in the literature, we have set a different value to retransmission probability at each contention and propose a retransmission analytical model for burst segmentation contention resolution scheme. In addition, we have applied the proposed retransmission scheme to the prioritized burst segmentation for QoS support. We have taken into account the load at each link due to both fresh and retransmitted traffic, and have calculated the path blocking probability and byte loss probability (ByLP) for high-priority and low-priority burst to evaluate network performance. An extensive simulation has been proposed to validate our analytical model.     

Dynamic wavelength selection and delayed burst assignment schemes for Optical Burst Switching networks

Optical Burst Switching (OBS) has been proposed as a promising switching technology for the next generation of optical transport networks. In this paper, we address the issue of how to provide proportional differentiated services in OBS networks. Firstly, a Dynamic Wavelength Selection (DWS) scheme is introduced to provide proportional differentiated services in bufferless OBS networks by dynamically assigning more and longer periods of wavelengths to high priority classes. This scheme can also utilize wavelengths efficiently because the wavelengths are shared among different classes. Next, a Delayed Burst Assignment (DBA) scheme is introduced, by which bursts of the high priority class are given a higher probability for reserving wavelengths by scheduling the bursts of the low priority class with a delay to provide quality of service (QoS) in OBS networks. The integration of these two schemes provides proportional differentiated services and improves the burst loss performance by giving the burst head packet (BHP) two opportunities of scheduling its data burst (DB).     

光突发交换网络中服务质量保证机制的研究

如何在光突发交换(OBS)网络中为承载的业务提供服务质量(QoS)保证,已经成为当前OBS领域的一个研究热点.从算法思想、QoS保证性能等方面,对当前几种主要的服务质量保证机制进行了研究:基于偏置时间的QoS机制、分段型QoS机制、比例型QoS机制、抢占式QoS机制、IP DiffServ over OBS的QoS机制以及基于数据信道分组的QoS机制.探讨了在设计一个有效的QoS保证机制时应考虑的因素以及今后的研究方向.     

光突发交换网络基于优先级与突发包分割的光缓存方法

为了保证光突发交换(OBS)网络中不同优先级业务的服务质量(Qos)和有效地降低突发包的丢失率,提出了一种基于优先级与突发包分割的光缓存方法.该方法通过在输出数据信道上设置光纤延迟线组来缓存被分割的冲突突发包.当冲突发生时,基于突发包的优先级进行"竞争突发包头部分割或者原突发包尾部分割,,处理;无冲突部分进行交换或者直...     

A Novel Optical Burst Assembly Technique Based on a Dynamic Threshold Mechanism to Support Scalable QoS

In IP networks, coarse packet classification is a scalable QoS solution. Similarly, it can also be utilized to an OBS network. In order to match IP QoS requirements with the data processing capacity and flexibility of OBS networks, we propose a novel optical burst assembly technique, which is based on mapping rules and a dynamic threshold mechanism called ATQ-DT. How to map the IP QoS to burst priority is resolved by the mapping rules, and how to efficiently allocate the assembly capacity among classes belonging to the same priority is answered by ATQ-DT. This mechanism determines the maximum share for each class, which is proportional to the current unused capacity. Among the three mapping rules we propose, TQ-MAP is the most reasonable one because it considers both the traffic condition and the QoS requirement. As shown by simulation results, the assembly technique ATQ-DT with TQ-MAP can most remarkably improve the packets loss probability (PLP) to support QoS.     

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.     

Delay-on-Demand: A Signaling Protocol to Reduce Blocking Probability in Optical Burst-Switching Networks

Optical burst switching (OBS) is emerging as one promising switching paradigm for the next generation optical networks. To support multiple services in burst-switching networks, the OBS paradigm should support some quality-of-service (QoS) provisioning. A major design issue in such networks is to reduce the blocking probability of the bursts arising due to resource contention at the intermediate core router. In this paper, we propose a signaling protocol which we call ‘Delay-on-Demand’ (OBS-DoD), to reduce blocking probability and support QoS in optical burst-switching networks. The proposed scheme guarantees that at least one of the bursts succeeds depending on its priority, propagation delay from the ingress router, and the burst-size when contention occurs at the core router. For this, we use a control packet to delay, in case of a contention, the transmission of bursts at the ingress router. We compare the performance of our proposal, by simulation, with an earlier proposed scheme, and show that the proposed OBS-DoD outperforms the earlier scheme in reducing the blocking probability. For simulation, we generated bursty traffic using an M/Pareto distribution.     

Burst scheduling for differentiated services in optical burst switching WDM networks

Optical burst switching (OBS) is one of the most important switching technologies for future optical wavelength division multiplexing (WDM) networks and the Internet. The model of differentiated services has been proposed to support quality of service (QoS) in the IP‐based Internet. It is also very important to have differentiated service support in OBS networks. When the burst scheduling in an OBS network is set up appropriately, network can support differentiated services. In this paper, we proposed a new burst scheduling scheme, called differentiated scheduling with identical priority offset time (DSIPO). In DSIPO, the same priority offset time is used for all the bursts destined to the same edge node regardless of their priorities. Differentiated services in terms of burst loss probability are achieved by processing the control packets of higher priority class bursts, thus reserving resources for their data bursts, more promptly upon their arrival than those of lower priority class bursts. Each intermediate (core) node can adjust the burst loss probabilities of various burst classes by choosing its own differentiated processing delay value for each priority class or its own differentiated processing delay difference value between any pair of adjacent priority classes. We model and analyse DSIPO in terms of the burst loss probability for each priority class with simulation validation. The performance of DISPO is evaluated by simulation. Copyright © 2004 John Wiley & Sons, Ltd.     

E-OBS网络中一种基于优先级的抢占窗口机制

为了有效地降低突发包的丢失率和保证网络的服务质量,提出了模拟光突发交换网络中一种基于优先级的抢占窗口机制.该机制在模拟光突发交换核心路由器的控制信道上设置抢占窗口,以此来决定是否允许高优先级突发包抢占低优先级突发包.冲突发生时,系统判断高优先级突发包对应的控制包的到达时间是否满足抢占条件,如果满足抢占条件,则允许高优先...