混合缓存型异步光分组交换的一种改进FF-VF算法

光纤延迟线（FDL）是异步光分组交换（OPS）采用的时域冲突解决方案,通过计算其分组丢失率（PLR）发现,在业务负载高,特别是业务负载大于0．7时,PLR性能较差。研究以FDL作为主要的常规缓存、以电存储器作为辅助缓存的光电混合缓存结构,并用改进的首选即中的填空（IFF-VF）算法调度冲突的分组,达到改善可变长OPS的PLR目的。分析和仿真结果表明,光电混合缓存和IFF-VF算法能改善可变长OPS在负载较高时的PLR性能,并减少FDL的数目。     

Analytical MMAP-Based Bounds for Packet Loss in Optical Packet Switching with Recirculating FDL Buffers

The major goal of optical packet switching (OPS) is to match switching technology to the huge capacities provided by (D)WDM. A crucial issue in packet switched networks is the avoidance of packet losses stemming from contention. In OPS, contention can be solved using a combination of exploitation of the wavelength domain (through wavelength conversion) and buffering. To provide optical buffering, fiber delay lines (FDLs) are used. In this paper, we focus on an optical packet switch with recirculating FDL buffers and wavelength converters. We introduce the Markovian arrival process with marked transitions (MMAP), which has very desirable properties as a traffic model for OPS performance assessment. Using this model, we determine lower and upper bounds for the packet loss rate (PLR) achieved by the aforementioned switch. The calculation of the PLR bounds through matrix analytical methods is repeated for a wide range of traffic conditions, including highly non-uniform traffic, both in space (i.e., packet destinations) and time (bursty traffic). The quality of these bounds is verified through comparison with simulation results.     

OBS中基于优先级与负载均衡的偏射路由算法

为了解决偏射算法在偏射控制七的问题,提出了一种基于优先级与负载均衡的偏射路由算法.当冲突发生时,分割优先级低的突发数据包;将冲突部分的突发包偏射到空闲的链路上,并在空闲的链路中选择若干条"当前最大剩余跳数小于源-目的节点的最大跳数"的路由作为候选路由;最后,在这些候选路由中选择一条可以使网络中各链路使用波长数的统计方差...     

Advanced Subcarrier Multiplexed Label Swapping in Optical Packet Switching Nodes for Next Generation Internet Networks

This paper presents the recent achievements and main results of the optical packet switching node with label swapping capabilities that was developed in the framework of the IST-LABELS project. The implemented functionalities allows the routing and forwarding of optical packets at 10 Gb/s based on the information conveyed in the 18 GHz-subcarrier multiplexed (SCM) label at 155 Mb/s. Specific functions of the optical packet switching demonstrator such as label extraction and rewriting are based on high-performance fiber Bragg grating filters (FBG) whereas semiconductor optical amplifier (SOA) based wavelength conversion allows payload 2R regeneration. Advanced aspects implemented in the high speed electronic control unit such as traffic shaping, multicast, and for the first time to our knowledge, a contention resolution algorithm with priority processing are thoroughly described in this paper. This paper also presents simulations exploring the effect of these advanced features in the global performance of an optical packet switched network. In particular, we found that the contention resolution algorithm based on parallel converters with 16 wavelengths contributes to improve up to four orders of magnitude the packet loss rate for low traffic loads whereas the improvement from traffic shaping policies was of 1 order of magnitude for both low and medium traffic loads. Along with the experimental results, the feasibility of the approach as the basis for the next generation internet networks is demonstrated.     

一种支持业务均衡的OBS自适应多可达性路由机制

针对光突发交换(OBS)网络中如何高效解决频繁发生的光突发竞争问题,提出了一种支持业务均衡的OBS自适应多可达性路由机制(AMR-LB).首先根据发送端发送业务量大小和当前网络业务承载状态,按需地为光突发确定多可达性路由;然后在非线性规划下,自适应地调整各条路由的业务承载比例.通过性能仿真,并与自适应替代路由算法(AA...     

全光包交换技术原理及其应用

全光包交换技术对带宽的利用率很高，其特有的优点（高容量、灵活性、高透明性及可伸缩性等）将会给下一代全光网络带来广阔的应用前景。文中讨论了光包交换的包结构、节点结构和网络结构，以及实现包交换的关键技术，最后就全光包交换技术在下一代城域网中的应用作了论述。     

Addressing self-similarity in optical switching networks by means of ant colony optimization

In this work, we propose the use of an Ant Colony Optimization (ACO) algorithm to mitigate packet loss in an optical packet switching network that carries self-similar traffic, which is known to have a great impact in the buffer performance in terms of loss probability as exemplified in this work. By adaptively routing the packets and balancing the network load, we demonstrate by some simulations the effectiveness of this approach when compared with a shortest-path routing scheme, achieving a performance that is comparable to the Poisson traffic scenario in some cases. The proposed algorithm can be used as a viable alternative to traffic shaping techniques.     

基于时频二维竞争解决机制的光数据包交换节点性能分析

针对光数据包交换的应用需求,提出了基于时频二维竞争解决机制的光数据包交换节点结构,建立了该节点基于排队论的丢包率分析模型,分析讨论了光交换节点竞争解决机制对丢包率的影响。输出端口归一化负载为0.8时,时频二维竞争解决机制在8波复用和8根延迟线结构下使丢包率降低至约10-7。数值分析结果表明,高端口负载下增加复用波长个数对减小端口丢包率比较有效,低端口负载下增加FDL延迟线数量对减小端口丢包率比较有效。     

Iterative approach to optimizing convergence routing priorities

This paper shows how to optimize the routing decisions in a nondeterministic routing algorithm called convergence routing in which routes may change depending on the traffic conditions. The routing algorithm guarantees a loss-free delivery of data packets from bursty sources, and a deterministic bound on the route length in arbitrary topology networks. The routing decisions are based on assigning routing priorities to the links such that a packet is forwarded to the highest priority link which is not blocked. Routing priorities are assigned using a local-greedy metric which minimizes the distance (number of hops) to the destination. This work shows that routing decisions using a local-greedy metric are not optimal, and the performance of the algorithm can be improved substantially by using new measures. Thus, various look-ahead metrics which take into account the potential gain on the other switching nodes toward the destination of a packet are suggested. The contributions of this work are: (1) a new analytical model to capture the behavior of a switching node; (2) an iterative optimization technique to set routing priorities according to various look-ahead measures; and (3) heuristics to ensure the stability of the routing priorities. The optimization objective is to maximize the throughput by minimizing the maximum total flow carried on a link in the network under static traffic model. The performance is studied computationally on various networks and traffic matrices. It is shown that up to a 50% performance increase can be obtained by optimizing the routing priorities     

一种用于光网络的高效业务疏导辅助图及动态业务疏导算法

利用辅助图,研究了光网络中的业务疏导技术。为解决传统的辅助图存在着模型复杂、波长通道的带宽利用率不高等问题,提出一种新的业务疏导辅助图,能够更有效地利用已有波长通道,避免低效的路由;为了降低动态业务疏导算法的复杂度,提出了一种简化的k最短路径算法,并以此为基础提出了多种疏导策略。仿真结果表明,本文提出的辅助图及其业务疏导算法,可以有效地减少阻塞率。     

异步光分组交换的缓存排序方案及性能

分析了简单的先到先服务(FCFS)光纤延迟线(FDL)循环占用方案性能,发现其分组丢失率(PLR)较高,提出3种输入分组按长度排序,寻找最小的FDL缓存优化分配方案.分析和仿真结果表明:约10%的分组排序后使3种方案都大大地能减小PLR,最小长度分组占用最小可用FDL缓存方案的性能最好.业务负载低于0.8时,排序的缓存方案对管理有限的FDL是有效的.     

A distributed backoff-channel deflection algorithm with load balancing for optical burst switching networks

Optical burst contention is one of the major factors that cause the burst loss in the optical burst switching (OBS) networks. So far, various contention resolution schemes have been proposed. Among them, the deflection path is more attractive due to its low requirement for optical buffer in capability and quantity. However, these deflection path algorithms do not consider the successful transmission rate of deflection traffic, and the deflection traffic??s impacts on the original traffic of the deflection path are not concerned. Meanwhile, the offset-time deficit problem for deflected bursts is ignored. Therefore, in order to reduce the burst loss probability in OBS networks, a Distributed Backoff-channel DeFlection algorithm with load balancing, for short DBDF-LB, is proposed. It consists of two parts, that is, the deflection with load balancing and the backoff-channel buffering scheme. Firstly, from the perspective of the network-wide load balancing, the optimal deflection path, on which the contention-failure burst is deflected with the minimum hops and the least burst loss probability, is selected. Secondly, the extra offset-time for the deflected burst is provided through the backoff-channel scheme. Finally, by numerical simulations, compared with the classical shortest path deflection algorithm, the DBDF-LB can obviously reduce the burst loss probability, about 50%, with a little extra overhead.     

适用于Pbit/s光分组交换网络的丢包率下限模型

文章针对通过优化路由来改善光分组交换网络性能这一方法进行了深入地分析。文章认为在输出光缓存结构下可以计算出网络丢包率下限的理论模型,通过将该模型得到的丢包率下限与在已有路由算法下由仿真得到的丢包率进行比较,能够预测出最佳路由算法下的丢包率,从而进一步预测通过优化路由所能获得的最大性能提升。     

不同长度分布下的光分组交换性能研究

通过分析不同分组长度分布(PLD)对光分组交换(OPS)性能的影响,以便为OPS在不同长度业务下配置不同的冲突解决方案.研究了光分组在固定长度分布、指数分布和因特网经验长度分布下分别对没有光纤延迟线(FDL)和有FDL下的OPS的性能影响.分析和仿真表明,因特网经验长度分布的业务在没有FDL缓存的条件下,获得最低的分组丢失率(PLR)性能;而固定长度分布的业务,仅在OPS配置有FDL时才可以获得最低的PLR性能.     

基于PSO的OBS路由优化选择算法研究

光突发交换(OBS)被认为是下一代光交换技术.利用粒子群优化算法(PSO)对OBS网络路由优化选择问题进行了研究和分析,仿真结果表明,基于PSO的OBS路由算法在计算代价方面要优于传统的最短路径算法,结论对改进OBS的路由选择协议有一定的理论指导意义.     

OBS网络中一种基于蚁群探测的路由机制

光突发交换技术是最具发展潜力的光交换技术之一,而减少突发丢失是其首要问题。传统的静态路由机制不能随着网络负载的变化而更改路由,不能有效应对动态业务。为此,在研究现有动态负载平衡路由机制的基础上,提出了一种基于蚁群探测的路由机制。蚁群根据节点出度链路上的负载变化选择下一跳节点,当转发到目的节点时收集蚁群探测到的所有备选路径,然后根据备选路径中记录的链路负载选择可使丢包最小的路径,通过选择更加合理的路由,达到减少突发丢失率的目的。仿真结果表明,与其他算法相比,所提出的机制表现出比较好的性能,有效降低至少15%突发丢失率。     

LEO星座中基于不完全信息的路由联盟博弈策略

针对LEO卫星网络在多跳转发数据包时流量分布不均问题,提出了一种基于不完全信息的最优收益路由联盟博弈算法.各节点协同联盟邻居节点,共同确定数据报文当前最优转发路径,从而分配和平衡节点间流量负载.仿真结果表明,与最短路径卫星路由DSP或智能路由TLR相比,本文算法的平均数据传输延迟降低了18.5%,节点流量负载均衡度提高了65.6%.     

Dynamic Routing in WDM Grooming Networks

Traffic grooming in optical networks has gained significant importance in recent years due to the prevailing sub-wavelength traffic requirement of end-users. In this paper, a methodology for dynamic routing of fractional-wavelength traffic in WDM grooming networks is developed. To evaluate the performance of routing algorithms, a new performance metric that reflects the network utilization is also proposed. The performances of shortest-widest path, widest-shortest path, and available shortest path routing algorithms are evaluated on a class of WDM grooming networks by considering traffic of different capacity requirements. The effect of dispersity routing, where higher capacity requests are broken into multiple unit capacity requests, is also investigated. The most interesting counter-intuitive result that is observed is that increasing the grooming capability in a network could result in degrading the performance of the widest-shortest path algorithm.     

Wavelength Routing Algorithm of All Optical Network Based on Traffic Engineering

General multi-protocol label switching （GMPLS） based on traffic engineering is one of the possible methods to implement all-optical network. This method implements the network with IP technique and guarantees the quality of service with traffic engineering. Based on the establishment of selecting schemes of optical path and methods of traffic calculation, the wavelength routing algorithm of all-optical network based on traffic engineering is presented by combining with prior route of shortest path and traffic engineering, the algorithm procedures are given, and the actual examples are introduced as well as the analysis on simulation calculation. This research results have certain significance for the achievement of optical switching technique of all-optical network.     

Routing and Wavelength Assignment in Optical Networks Using Logical Link Representation and Efficient Bitwise Computation

In this paper, we propose and evaluate a new approach for implementing efficient routing and wavelength assignment (RWA) in wavelength division multiplexing (WDM) optical networks. In our method, the state of a fiber is given by the set of free wavelengths in this fiber and is efficiently represented as a compact bitmap. The state of a multiple-fiber link is also represented by a compact bitmap computed as the logical union of the individual bitmaps of the fibers in this link. Likewise, the state of a lightpath is represented by a similar bitmap computed as the logical intersection of the individual bitmaps of the links in this path. The count of the number of 1-valued bits in the bitmap of the route from source to destination is used as the primary reward function in route selection. A modified Dijkstra algorithm is developed for dynamic routing based on the bitmap representation. The algorithm uses bitwise logical operations and is quite efficient. A first-fit channel assignment algorithm is developed using a simple computation on the bitmap of the selected route. The resulting bitwise routing algorithm combines the benefits of least loaded routing algorithms and shortest path routing algorithms. Our extensive simulation tests have shown that the bitwise RWA approach has small storage overhead, is computationally fast, and reduces the network-wide blocking probability. The blocking performance of our RWA method compares very favorably with three routing methods: fixed alternate routing, shortest path using flooding, and Dijkstra’s algorithm using mathematical operations. Our simulation experiments have also evaluated the performance gain obtained when the network access stations are equipped with finite buffers to temporarily hold blocked connection requests.