OBS网络中基于优先级与概率的偏射路由算法*

摘 要：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,提出了一种基于优先级与概率的偏射路由算法。该算法根据突发包的优先级和转发概率来控制突发包的偏射,并从网络突发阻塞概率的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;节点根据链路上指定的权值,按概率为分割突发包选择一条可以使网络突发阻塞概率最小的最佳偏射路由。仿真结果表明,虽然网络中可选路由数目的增加对网络性能的改善非常有限,但是该算法能够有效的降低整个网络的丢包率,并且得到的高优先级突发包的丢失率低于低优先级突发包的丢失率,从而很好的保障了网络的服务质量。故这种方法能够有效的提高OBS网络的性能。     

光突发交换网络中无缓存冲突解决模型的研究

光突发交换网络被认为是未来光网络发展的趋势,而突发包在节点的冲突问题却是光突发交换网络中一个非常需要解决的问题,目前很多情况下使用的光缓存技术虽然可以缓解冲突问题,但是却增加了节点结构的复杂性和噪声。论文首先提出一种基于优先级的冲突解决方法,并给出了突发包的封装格式,然后利用三种无缓存的冲突解决模型对不同优先级突发包的冲突问题进行了详细的叙述和比较。     

一种改进的光突发交换数据包竞争解决算法

光突发交换技术是近年出现的一种新型交换技术,偏射路由在解决突发数据包竞争具有自己独特的优点.对光突发竞争机制进行了分析比较,针对目前数据包竞争算法存在的问题,研究一种改进的偏射路由算法和实现机制,相比未改进的算法,模拟仿真结果表明在业务流量负栽增加的情况下具有更好的性能.     

解决BGP路由策略冲突的振荡抑制机制

边界网关协议(border gateway protocol,BGP)允许网络中的每个自治系统(autonomous system,AS)设定自己的路由策略来选择和通告路由。尽管这种自治性会使BGP路由策略的配置更加灵活,但有可能引发路由策略冲突,即路由振荡和发散,导致网络性能下降。为此,提出了振荡抑制机制以解决BGP路由策略冲突问题。该机制通过分析路由通告报文发现振荡路径,根据振荡次数修正路径的本地优先属性值,使稳定路径的本地优先属性值比振荡路径的大,从而使得稳定路径在路由决策阶段比振荡路径被选中的优先级高,达到抑制振荡路径进而解决路由策略冲突。在原型系统上实现并部署了所提出的机制,并对其进行了性能评价。结果表明,该机制具有较好的性能。     

OBS网络中多优先级业务冲突解决模型研究*

为了充分认识光突发交换（OBS）网络核心节点中的多业务冲突性能,以OBS网络核心节点为研究对象,采用基于优先级的信道抢占原则,给出了在配置光缓存情况下,多优先级业务的冲突解决模型。结果表明,所提出的模型保证了OBS网络的服务质量,有效解决了以往研究中出现的两个局限性问题,所得参数对OBS网络的实验化建设提供了理论依据。     

光突发交换竞争解决机制研究

作为下一代互联网的关键技术之一的光突发交换技术已受到业界的广泛关注。本文在介绍光突发交换基本概念、特点的基础上,重点探讨了解决光突发交换网中突发数据包之间争夺链路资源问题的竞争解决机制,主要包括光缓存、波长转换、偏转路由以及突发分片等技术,对这些技术的优缺点进行了分析比较,并给出了一种偏转路由和突发分片技术结合的竞争解决方法。     

稀疏分光配置OBS网络中的多播机制*

针对在稀疏分光配置的光突发交换（OBS）网络中进行多播的问题,提出了一种基于优先级的共享多播机制。该机制对包含相同分光节点的业务进行汇聚,并且在资源预约过程中引入了优先级来区分主干链路和分支链路,保证多播树的主干链路能优先抢占资源。通过仿真发现,相比传统多播机制,该方式能减少多播业务的丢包率和冗余包的数量,提高资源利用率。     

光突发交换中路由技术的研究

光突发交换网络中路由的实现是网络生存性和健壮性的一个保证。文章提出了一种光突发交换网络路由技术的新方案,将免疫遗传算法这种仿生物体的智能算法,应用到光突发交换网络路由算法中,保证群体多样性,控制收敛方向。仿真结果表明,该方案可以降低OBS网络中的数据丢失率。     

光突发交换中路由技术的研究

光突发交换网络中路由的实现是网络生存性和健壮性的一个保证。文章提出了一种光突发交换网络路由技术的新方案,将免疫遗传算法这种仿生物体的智能算法,应用到光突发交换网络路由算法中,保证群体多样性,控制收敛方向。仿真结果表明,该方案可以降低OBS网络中的数据丢失率。     

WDM光网络中支持优先级的备用路由算法

论文提出了一种在WDM光网络中支持优先级的备用路由算法,该算法结合波长的使用情况,通过给优先级较高的光路建立请求预留较多的备用路由,从而降低了高优先级的光路连接的阻塞率。同时由于使用了备用路由,使较低优先级的光路建立请求性能得到优化。同现有的支持优先级的算法相比,该算法更多地考虑了路由问题,而且也增强了网络的抗毁性。计算机仿真结果表明,该算法在支持优先级的同时能有效降低网络各优先级光路的阻塞率。     

NP控制平面OS中基于分组属性的进程调度技术

在基于NP的网络处理系统中，存在各种各样的控制平面和数据平面交互信息。不同的信息分组具有不同的重要性，某些重要分组若得不到及时处理会导致系统和网络行为的紊乱，因此需要降低分组经历的时延，且越重要的分组经历的时延应该越小。从控制层面操作系统的角度来看，这要求分组处理进程的调度属性应该与所处理分组的属性关联起来。该文提出了一种基于分组属性的进程调度策略，给出了有关设计与实现。实验结果表明，该策略较好地达到了预期的目标。     

多通道并行传输中接收缓存阻塞的缓解方法

针对多通道并行传输中的接收缓存阻塞问题,分析了引起接收缓存阻塞的原因,提出一种改进的缓解接收缓存阻塞的数据包调度方法,综合考虑通道的带宽、时延和丢包率,引入通道质量的评价函数,优化多通道之间的数据包调度,选择质量最好的通道进行传输,减少由于通道特性不同造成的接收端数据包乱序;提出一种改进的数据包重传策略,基于时延和丢包率选择能使数据包最快到达接收端的通道进行重传;提出一种根据通道的带宽-延迟积估算所需接收缓存大小的方法。仿真实验表明,所提出的调度方法和重传策略能够有效地减轻接收缓存阻塞,与CMT-SCTP相比具有更优的性能,所提出的缓存大小的估算方法也能够准确估算所需接收缓存的大小。     

基于BPF包过滤机制的数据采集系统的设计与实现

为了捕获校园网中访问各个数据库检索系统的数据包，利用BPF包过滤机制、以太网的广播传输特性等技术设计和实现数据采集系统。同时为了提高了系统的效率，还引人多线程技术，使得数据采集系统在同一时刻既能采集数据包又能实时处理数据包并写入后台数据库中。     

On Delivery Times in Packet Networks under Adversarial Traffic

We consider packet networks and make use of the "adversarial queuing theory" model [10]. We are interested in the question of guaranteeing that all packets are actually delivered to destination, and of having an upper bound on the delivery times of all packets. Whether this is possible against all adversarial queuing theory rate-1 adversaries was previously posed as an open question [13],[10]. Among other things, we give a queuing policy that guarantees bounded delivery time whenever the rate-1 adversary injects a sequence of packets for which there exists a schedule with a finite upper bound on the delivery times of all packets, and adheres to certain additional conditions. On the negative side we show that there exist rate-1 sequences of packets for which there is no schedule with a finite upper bound on the delivery times of all packets. We thus answer an open question posed by Gamarnik [13]. We further show that delivering all packets while maintaining stability (we coin the term "reliability" for this property) can be done by an offline scheduler whenever the injection of packets is done at rate of at most 1. However, on the other hand, we also show that there is no online protocol (even centralized) that can achieve that property against all rate-1 adversaries. We thus answer an open question of Borodin et al. [10].     

基于RTCP反馈和被叫信息的语音分组QoS动态控制

分析了已有的源端编码变换和静态语音分组优先级设置等语音分组Qos控制机制和根据RTCP报告计算Qos参数的方法,提出了基于RTCP反馈和某些预定规则的语音分组Qos动态控制策略。模拟实验结果表明,该方法具有可行性。     

Optimization of parallel firewalls filtering rules

As filtering policies are getting larger and more complex, packet filtering at firewalls needs to keep low delays. New firewall architectures are needed to enforce security and meet the increasing demand for high-speed networks. Two main architectures exist for parallelization, data-parallel and function-parallel firewalls. In the first, packets are distributed across a set of identical firewalls that implement the entire policy. In the second, each firewall implements a subset of the policy with a fewer number of rules, but the packets have to be duplicated and processed by all the firewalls. This paper proposes a new architecture function-parallel with pre-processing that combines the advantages of both architectures. The proposed architecture has the advantage of not duplicating the data, so that the processing time can be significantly reduced. Moreover, our architecture enables stateful inspection of packets, which is necessary to prevent multiple types of attacks. The performances of this architecture have been proven to be scalable for large security policies.

     

Enhanced bulk scheduling for supporting delay sensitive streaming applications

Providing end-to-end delay guarantees for delay sensitive applications is an important packet scheduling issue with routers. In this paper, to support end-to-end delay requirements, we propose a novel network scheduling scheme, called the bulk scheduling scheme (BSS), which is built on top of existing schedulers of intermediate nodes without modifying transmission protocols on either the sender or receiver sides. By inserting special control packets, which called TED (Traffic Specification with End-to-end Deadline) packets, into packet flows at the ingress router periodically, the BSS schedulers of the intermediate nodes can dynamically allocate the necessary bandwidth to each flow to enforce the end-to-end delay, according to the information in the TED packets. The introduction of TED packets incurs less overhead than the per-packet marking approaches. Three flow bandwidth estimation methods are presented, and their performance properties are analyzed. BSS also provides a dropping policy for discarding late packets and a feedback mechanism for discovering and resolving bottlenecks. The simulation results show that BSS performs efficiently as expected.     

层次编码流媒体发送调度的研究

文章针对层次编码流媒体数据在Internet上进行传输的问题,研究服务端包发送调度技术。根据发送缓冲区中层次编码流媒体数据包之间存在的多重依赖关系和传输时间限制,提出了服务端发送调度的马尔科夫模型,在该模型的基础上,用值迭代法实现一个最优的发送策略。该策略能够在带宽受限的条件下,保证重要性较高的数据包优先发送出去。通过实验证明,与顺序发送方法比较,该调度算法能够在客户端获得更好的播放质量。     

无线网络非理想反馈下有序数据的渐进式传输

“有序”数据指的是数据间具有特定优先级关系的一类数据。降低“有序”数据传输时的排序时延和解码时延是提高“有序”数据业务的用户服务体验的关键问题。在非理想反馈条件下,基站仅能正确接收到部分用户反馈信息,导致重传效率降低。针对反馈丢失情况下的包重传问题进行研究,对发送端无法接收到反馈信息的事件进行了分析,提出了三种启发式的包更新策略。大量的仿真实验结果表明,在所提出的三种包更新策略中,全包更新策略对应的包重传方案的完成时间和总接入时间优于其余两种策略。     

A path switching scheme for SCTP based on round trip delays

Due to the rapid development of network applications, today the Internet plays an important role in our everyday life. Users hope that the network is always speedy enough to help them access the Internet without any delay. But the real situation is far from the ideal case. In the future, network researchers will continuously improve the network speed, and try to develop networks that are robust, without any crashes or packet loss. In this paper, we propose an aggressive path switching scheme for SCTP. Before data transmission, the scheme selects the fastest path as the primary path to transmit packets. When the path fails or transmission quality is poor, this scheme evaluates alternate paths, and selects the one with the best quality as the new primary path to substitute for the original one. After that, packets are delivered through the new path. Several factors are considered in the evaluation, including bandwidth, encryption/decryption, size of the congestion window, retransmission policy, routing policy, etc.