光突发交换网络试验平台

研究并实现了几种光突发交换网络的关键技术,包括高速的突发组装技术、突发调度技术及突发光发射及接收技术等,其中突发接收具有较高的灵敏度和小于80 ns的时钟数据恢复时间.在这些技术的基础上,建立了一个灵活且可扩展的光突发交换网络实验平台.在OBS网络平台上进行了TCP性能评估实验和多QoS业务传输实验。实验结果表明光突发网络中丢包率严重影响其上TCP的性能,但若丢包率小于0.1%,则TCP性能可得到一定程度的保证.光突发交换网络实验平台上的TCP传输实验还表明了OBS物理层带来的额外延时对上层TCP带宽有极大的影响.实验结果还验证了OBS网络中的QoS保证机制.     

一种适用于光突发交换的区分型资源预留机制

将边缘结点突发汇聚算法与核心结点资源预留机制有机结合，提出了一种适用于光突发交换的区分型资源预留机制.引入“突发流”的概念，在边缘结点采用基于线性预测的突发汇聚算法将输入IP分组汇聚为单个突发或突发流；在核心结点引入“搭载请求”的思想，对单个突发和突发流采用不同的资源预留方案.仿真结果表明区分型资源预留机制可以明显改善光突发交换网络的丢失性能.     

适用于光突发交换网的可编程光缓存器

提出了两种适用于光突发交换网的可编程光缓存器结构：交叉型和多端口开关型.两种结构都能满足突发包缓存的超长性和可变性的要求，且结构简单紧凑，成本低，可扩展.交叉型缓存器通过指定信号在每个子缓存模块的光纤环中的循环次数即能实现可变时间的延迟.多端口开关型缓存器通过指定信号在两个多端口开关相应端口与所接光纤延迟线组成的光纤环中的循环次数实现可变时间的延迟.仿真结果表明，两种可编程光缓存器都能对光突发包实现ns级指定时间延迟，可用于解决光突发交换网突发包的冲突问题.     

光弹性分组环节点光分组的组装及时延分析

分析了光弹性分组环(ORPR)网络中流量成型时光分组组装算法,提出一种适合ORPR网络的基于控制发送时间的光分组组装算法,并给出了该算法的算法结构.该算法在混合门限组装算法的基础上,通过增加一个控制分组发送间隔的参数,使得光分组单位时间内流量的突发性被平滑,并可以保证ORPR网络的服务质量(QoS)性能,适合于使用容量有限光缓存的ORPR网络.对ORPR节点光分组平均组装时延进行了详细的分析,新算法通过对分组发送间隔的调整,使在不同负载条件下,组装时延的概率分布基本相同.在ORPR中,平均组装时延的稳定对ORPR网络的QoS性能和公平性调度有重要意义,而发送时机的合理选择,可以保证ORPR网络的QoS性能以及公平性.仿真结果表明,新算法使得ORPR网络中的光分组平均组装时延相对稳定,在大多数情况下,可以保证ORPR网络的调度要求.     

一种新型的突发汇聚算法研究

分析了现有的突发汇聚算法,同时针对现有汇聚算法的一些特点,提出了一种新型突发包汇聚算法,可以实现在不同网络负载的情况下,根据到达边缘节点的速率同时结合网络的性能(丢包率),动态的调整突发包汇聚的门限值,从而实现了智能组包,克服了原有算法简单,不灵活的缺点.通过仿真结果可以得知,该算法可以明显改善光突发交换网络的丢包率和时延性能,能够很好地支持实时性要求很高的数据业务.     

用于WDM光突发交换网的改进JIT信令协议

提出了一种用WDM光突发交换网的良好时间通信协议(MJIT-SP)该协议结合了光线路交换和光分组交换的优点与用于光突发交换的其他信令协议相似,MJIT-SP的特点也是采用带外控制信号处理来排除核心节点处对光缓存器的需求然而,与其它协议如JIT-SP相比,它能最小化数据源端的建立时间和最大化交叉连接的带宽利用率而且,MJIT-SP还能支持光网络中无连接和面向连接的数据包传递并介绍了MJIT-SP的基本结构并从三个方面分析了它的基本性能,即建立时间、端到端延时和信道占用时间然后,对本协议与JIT-SP的性能进行了比较,结果显示:MJIT-SP不仅优于JIT-SP,而且还克服了JIT-SP的一个缺点,即过长的信道占用时间此外,还给出了MJIT-SP的信令信息,尤其是非常关键的信号与脉座电平差(SETUP)消息MJIT-SP中的SETUP与JIT-SP中的SETUP不同,它需要给出数据包路由和交换所需的信息,包括数据包长度、比特率、SETUP与数据包之间的偏置时间以及数据业务的质量控制系统(QoS)要求等最后讨论了MJIT-SP两种可能的变化并且分析了它们的优缺点.     

波长转换器和光纤延迟线在WDM光分组交换中的结构设计和性能研究

介绍了两种新颖的光分组交换结构——MOD1和MOD2,用于解决分组冲突问题.其特点在于,MOD1共享了一组非简并的延迟线,而MOD2则是共享了一组简并的延迟线和波长转换器.研究表明,对于非突发业务,两种结构都只需要少量的延迟线即可获得理想的性能.此时,MOD1比MOD2更加能降低系统体积和成本.而对于突发业务,如果MOD1所共享的延迟线数量和MOD2所共享的延迟线和转换器的总数量相等,MOD2的分组丢弃率要远远低于MOD1.随着业务突发程度的增加,MOD2中的转换器数量也需要增加才能维持给定的分组丢弃率,但即使业务突发程度很高,MOD2在体积、成本和性能等三方面均可取得较理想的折衷.     

一种新型的突发汇聚算法研究

分析了现有的突发汇聚算法,同时针对现有汇聚算法的一些特点,提出了一种新型突发包汇聚算法,可以实现在不同网络负载的情况下,根据到达边缘节点的速率同时结合网络的性能（丢包率）,动态的调整突发包汇聚的门限值,从而实现了智能组包,克服了原有算法简单,不灵活的缺点.通过仿真结果可以得知,该算法可以明显改善光突发交换网络的丢包率和时延性能,能够很好地支持实时性要求很高的数据业务.     

光突发交换中交换矩阵配置时间的影响研究

光突发交换是近几年出现的一种很有前途的交换技术。在光突发交换网络的核心节点中,光交换矩阵是一个关键部件,其配置时间影响到光突发交换网络的性能。这种影响表现在对数据信道可用时间施加了限制。在考虑光交换矩阵配置时间的基础上给出了修正后的LAUC算法,并通过计算机仿真研究了这种配置时间对光突发交换性能的影响。结果表明,光交换矩阵配置时间的增大会导致输出数据信道利用率的降低,进而增大了数据丢失率。     

光分组交换网络中多组光正交码组合光标签识别处理及实验

报道了光分组交换网络中基于多组光正交码组合光标签的识别与接收实验,光标签采用了码长为19,码重为3的2组光正交码组合光标签方案.给出了基于多组光正交码光标签的光分组交换网络(MOOC-OPS)基本原理,通过分析指出在MOOC-OPS网络中处理多组在时域上非连续、随机、突发光标签是现实MOOC-OPS关键技术之一.设计出了基于展宽网络和放大器级联方式接收多组低功率窄脉冲(MOOC-OPS网络的光标签)的实验方案,完成了实验电路板制作与实验验证.实验结果表明成功地实现了MOOC-OPS网络中周期为2ns基于多组光正交码光标签脉冲的识别接收,验证了该方案的可行性.     

A new burst assembly technique for supporting QoS in optical burst switching networks

This letter proposes a new burst assembly technique for supporting QoS in optical burst switching (OBS) networks. It consists of the adaptive-threshold burst assembly mechanism and QoS-based random offset-time scheme. The assembly mechanism, which is fit well to multi-class burst assembly, not only matches with IP QoS mechanism based on packet classification, and also utilizes fairly and efficiently assembly capacity. Based on token-bucket model and burst segment selective discard (BSSD), the offset-time scheme can smooth the traffic to support OBS QoS. The simulation results show that the technique can improve the performance in terms of packet loss probability (PLP).     

An optimal burst assembly approach employing traffic shaping (OBATS) for OBS

Optical burst switching (OBS) aims at combining the strengths of packet and circuit switching and is considered as a promising technology for implementing the next generation optical Internet, required to cope with the rapid growth of Internet traffic and the increased deployment of new services. In this paper, an optimal burst assembly approach employing traffic shaping (OBATS) for OBS networks has been proposed in order to improve network performance in terms of reduced blocking probability, congestion control and better utilization of bandwidth. Particularly, the proposed scheme aims at reducing the average delay experienced by the packets during the burstification process in optical burst switched (OBS) networks, for a given average size of the bursts produced. Reducing the packet burstification delay, for a given average burst size, is essential for real-time applications; correspondingly, increasing the average burst size for a given packet burstification delay is important for reducing the number of bursts injected into the network and the associated overhead imposed on the core nodes. Simulation results show that the proposed burst assembly approach gives better network performance in terms of burst drop, resource contention and delay as compared to conventional burst assembly approaches.     

OBS网络中一种基于优先级和门限的偏射路由算法

为了解决偏射算法在偏射控制上的问题,提出了一种基于优先级和门限的偏射路由算法.该算法采用丢弃少量偏射的高优先级分割突发数据包来保证偏射路由上低优先级非偏射突发数据包的QoS.当冲突发生时,分割偏射优先级低的突发数据包,从而保护高优先级突发数据包|在偏射路由上,通过启用偏射检测函数来判断是允许偏射的分割突发数据包抢占资源或是丢弃偏射的分割突发数据包.仿真结果表明,虽然该算法增加了少量的端到端的传输时延,但这种算法可以很好地控制偏射突发对网络偏射路由上正常流量的影响,并且能够有效地降低整个网络的丢包率,很好地保护高优先级突发数据包的完整性.故这种方法能够有效地提高OBS网络的性能.     

OBS网络中基于优先级与突发包分割的偏射路由机制

为了有效地降低突发包的丢失率和保证OBS网络中不同优先级业务的服务质量,提出了一种基于优先级与突发包分割的偏射路由机制.当冲突发生时,首先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;无冲突部分直接在事先预留的输出数据信道上处理,冲突部分的分割突发包根据参数可调的偏射路由机制被偏射到最佳偏射路径上.仿真结果表明,该机制能够有效地降低整个网络的丢包率和端到端的延时,并且得到高优先级突发包的丢失率和延时低于低优先级突发包.由此可知,基于优先级与突发包分割的偏射路由机制能够有效地解决突发包的冲突问题,从而提高整个OBS网络的性能.     

Performance analysis of an improved burst-outputted model for an OBS core router

Differentiated probability outputted scheme (DPOS) is an improved burst-outputted paradigm in optical burst switching (OBS) core routers. In this paper, the blocking performance for multi-priority traffic in a DPOS applied OBS core router with limited buffers has been analyzed and discussed firstly. Several simulation results indicted that DPOS had a better performance in blocking than the outputted model presented in the previous work had. Besides, our proposed scheduling mechanism can supported the quality-of-service (QoS) efficiently for OBS networks.     

Analysis of burst/packet assembly techniques in high-speed optical switching network

In the Optical Burst Switching (OBS) Network, the burst assembly technique is one of the challenging issues in the implementation of the system. It has the influence on the burst characteristic, which gives an impact on the network performance. Burst assembly is the process of assembling incoming data from the higher layer into bursts at the ingress edge node of the OBS network. The burst assembly mechanism must then place these packets into bursts based on some assembly policy. In this paper, the OBS system performance has been observed in simulated 12-node network based on Just-Enough-Time (JET) reservation protocol with various burst assembly techniques under the standard drop policy (DP) and the segmentation policy for contention resolution. The simulation results show that the performance of the proposed Adaptive-Threshold with Fixed Maximum Time Limitation (ATH-FMTL) burst assembly scheme is better than conventional burst assembly schemes in terms of loss probability and average assembly delay. Also, the proposed scheme avoids a sudden increase in the burst size and makes the burst sent out smoother as compared to conventional schemes.     

An optimal protection and restoration scheme (OPARS) for optical networks

Protection and restoration are critical network design issues for optical networks since even a single failure for a short duration may result in huge data loss due to the large capacity of optical fibers. However, few studies have been done on these issues for optical burst switching (OBS) networks. Protection and restoration are essential mechanisms for guaranteeing more reliable traffic delivery services. But it is not easy to apply existing mechanisms to optical burst switching (OBS) networks due to its one-way reservation signaling and the statistical burst multiplexing. Thus, to achieve the high transmission performance and reliability simultaneously, unique properties of OBS must be considered in the design of protection scheme. In this paper, an optimal protection and restoration scheme (OPARS) has been introduced that not only optimizes the number of provisioned protection wavelengths adaptively based on the traffic load as well as the quality of service (QoS) requirements of bursts in high speed networks but also minimizes burst loss rates. In addition, the proposed scheme has been used as an efficient contention resolution technique. The simulation results verify that the proposed scheme improve the network resource and channel utilization while guaranteeing the targeted protection reliability and QoS requirements of bursts.     

A novel scheme based on minimum delay at the edges for optical burst switching networks

This paper proposes a novel scheme based on minimum delay at the edges (MDE) for optical burst switching (OBS) networks. This scheme is designed to overcome the long delay at the edge nodes of OBS networks. The MDE scheme features simultaneous burst assembly, channel scheduling, and pre-transmission of control packet. It also features estimated setup and explicit release (ESXR) signaling protocol. The MDE scheme can minimize the delay at the edge nodes for data packets, and improve the end-to-end latency performance for OBS networks. In addition, comparing with the conventional scheme, the performances of the MDE scheme are analyzed in this paper.     

Hybrid OCS/OBS interconnect in intra-data-center network

We report on a data center network(DCN) architecture based on hybrid optical circuit switching(OCS) and optical burst switching(OBS) interconnect for dynamic DCN connectivity provisioning. With the combination of the centralized and distributed control of the software-defined optical networks, the proposed interconnect can achieve unprecedented flexibility in dealing with both mice and elephant flow in the DCN. Numerical simulation is employed to investigate the performance of the proposed architecture. The results show that the OBS module has preferable performance in dealing with a larger burst packet, and the throughput is constrained by the capacity of the server random access memory module.