DDN网管路由的优化调整

本文列举了因DDN和分组交换网络相互影响、相互牵制等原因所可能导致的恶性故障现象,并提出了彻底解决这一疑难故障的网管路由的优化调整方案。     

威海DDN本地网及用户接入方式

本文从威海ＤＤＮ本地网的实际制世与配置出发，面向网络建设介绍ＤＤＮ本地网规划 、建设、发展的策略，以及威海ＤＤＮ本地网、公用ＤＤＮ网提供的业务功能和用户层终端接入方式。     

DDN网管路由的优化调整

本列举了因DDN和分组交换网络相互影响，相互牵制等原因所可能导致的恶性故障现象，并提出了彻底解决这一疑难故障的网管路由的优化调整方案。     

扬州地区DDN网管路由的优化调整

长期以来，扬州地区的DDN和分组交换网络是相互依存、相互渗透、相互牵制的。DDN向分组交换网络提供64～128kbit/s的数字电路作为中继，而分组交换网络为DDN网管提供了一点对多点的呼叫路由。但是，这种组网方案在日常维护、故障处理以及网络优化等过程中都不可避免地会遇到这样的问题：当某一局向的DDN出现故障，使得该局向的分组交换机中继路由中断时，该局向的分组网络便陷于瘫痪状态。这是因为DDN的覆盖范围较分组交换网络要广，所以每台分组交换机上都汇接了若干条DDN网管路由，而这些DDN节点机是通过该局向的分组路由与DDN…     

DDN网测试方法的改进

１测试背景深圳市原骨干网为３个ＡＴ＆Ｔ公司的ＤＡＣＳＩＩ节点,第４期扩容后的骨干网为５个Ｎｅｗｂｒｉｄｇｅ公司的３６４５节点,共有１０２４个２Ｍｂ／ｓ端口,骨干中继为１４０条２Ｍｂ／ｓＥ１组成网状网。为了保证新建骨干网的传输及端口的质量,在新网启用前...     

提高DDN网中继资源利用率的方法

在ＤＤＮ网中，数字交叉连接复用设备之间的数字传输电路（也称为中继电路）是不同节点间数据传送的通道，常见的电路类型有Ｔ１，Ｅ１，Ｖ３５ＰＲＩ，Ｘ２１ＰＲＩ，其中Ｅ１在ＣＨＩＮＡＤＤＮ中应用广泛。它的带宽容量为２０４８ｋｂ／ｓ，分为３２个时隙，一个时...     

广东电信DDN网/帧中继网的发展策略

概要地叙述了ＤＤＮ／帧中继的技术特点及应用。以及广东电信ＤＤＮ／帧中继网的现状、存在问题，并从网络发展方向、节点布局、设备选型及人才培养角度来论述广东电信ＤＤＭ／帧中继的发展策略。     

DDN与ATM网的互通

１互通的必要性(１)网络一体化的发展趋势现有的数据通信基础网络有分组交换、ＤＤＮ、帧中继、ＡＴＭ等多种类型 ,从用户角度讲 ,开展不同的业务要申请不同的数据专线 ,线路多 ,不易使用 ;从网络运营商的角度讲 ,多类网络各有各的管理体系 ,不易维护 ,不利于综合化的发展。将现有网络合并到一个网络 ,为用户提供集数据、语音、图像为一体的服务通道成为向宽带网过渡的发展趋势。(２)ＤＤＮ网络中继资源日趋紧张ＤＤＮ是目前发展较成熟、用户量较大的数据通信网络。但由于ＤＤＮ传输基于电路交换方式 ,网络资源一旦被某一用户电路占用 ,即使…     

交换网络的组合分析

采用组合分析的方法对多级可重排交换网络的组成进行了研究,给出了一种新型的三级可重排交换网络的结构,当用2×2单元组成多级N×N交换网络时,所用单元的数量S=Nlog2N-N+1,比Benes网络逼近最佳理论值的速度高了一倍。另外对于网络阻塞,也根据其形成的机制分成了静态和动态特性的两种,并用组合分析的方法对交换网络的静态特性进行了计算。     

Novel Packet Switching for Green IP Networks

A green technology for reducing energy consumption has become a critical factor in ICT industries. However, for the telecommunications sector in particular, most network elements are not usually optimized for power efficiency. Here, we propose a novel energy‐efficient packet switching method for use in an IP network for reducing unnecessary energy consumption. As a green networking approach, we first classify the network nodes into either header or member nodes. The member nodes then put the routing‐related module at layer 3 to sleep under the assumption that the layer in the OSI model can operate independently. The entire set of network nodes is then partitioned into clusters consisting of one header node and multiple member nodes. Then, only the header node in a cluster conducts IP routing and its member nodes conduct packet switching using a specially designed identifier, a tag. To investigate the impact of the proposed scheme, we conducted a number of simulations using well‐known real network topologies and achieved a more energy‐ efficient performance than that achieved in previous studies.     

A New Architecture for Nonblocking Optical Switching Networks

With the current technology, all-optical networks require nonblocking switch architectures for building optical cross-connects. The crossbar switch has been widely used for building an optical cross-connect due to its simple routing algorithm and short path setup time. It is known that the crossbar suffers from huge signal loss and crosstalk. The Clos network uses a crossbar as building block and reduces switch complexity, but it does not significantly reduce signal loss and crosstalk. Although the Spanke's network eliminates the crosstalk problem, it increases the number of switching elements required considerably (to 2N ² - 2N). In this paper, we propose a new architecture for building nonblocking optical switching networks that has much lower signal loss and crosstalk than the crossbar without increasing switch complexity. Using this architecture we can build non-squared nonblocking networks that can be used as building block for the Clos network. The resulting Clos network will then have not only lower signal loss and crosstalk but also a lower switch complexity.     

Adaptive Storage Policy Switching for Wireless Sensor Networks

In wireless sensor networks, storage policies can be categorized into external storage, local storage and data centric storage. Each storage police has its suitable network environments. If a correct storage policy is chosen for a given network condition, unnecessary control messages can be significantly reduced. Then the network lifetime can be increased. In this paper, adaptive data storage (ADS) policy which can dynamically choose suitable storage policy for wireless sensor network according to the frequencies of user queries and events happening is proposed. Through collection and computation of user query and event rates, the proposed algorithm switches between local storage and data centric storage policies adaptively. Simulations are given to justify that the proposed adaptive storage policy indeed reduces the traffic in network and increases network lifetime.

异构网络终端接入智能切换系统研究

伴随着无线网络的迅速发展,智能终端日益普及。如何根据不同网络的通信速度、链路状态、通信费用以及不同类型业务流的特点等因素,在终端所接入的网络之间合理地切换则成为一个重要问题。提出了一种在Android系统下,通过对当前业务流流量特征的采集分析,同时结合当前各种网络的链路状态对接入网络实现合理切换的控制方法。最后使用Android手机与PC完成了系统搭建与测试,实现了基于流量信息合理选择接入网络的目的。     

ATM同播交换中的拷贝网络的设计

文章针对ＡＴＭ同播树型交换网络的设计，提出了一种模块化ＡＴＭ拷贝网的设计方法，它克服了拷贝风设计中对复制信元数的限制和转换表的复杂性问题，可用在大规模同播交换网的设计中。性能分析表明，它有良好的性能。     

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.     

分数Fourier变换、矩阵群和时-频分析

本文从矩阵群的观点出发讨论了分数Fourier变换的数学描述并通过数字仿真直观地说明了它进行信号时-频分析的两个特点.结果表明,在矩阵描述下,经典的Fourier变换相当于一个置换矩阵;一般的分数Fourier变换相当于一个广义置换矩阵;分数Fourier变换全体构成的变换族可以用一个矩阵群来描述,多次变换运算完全转化为相应的矩阵乘法运算.最后,数字信号分数Fourier变换的仿真计算表明,分数Fourier变换具有独特的时-频分析性质.     

Dilated Networks for Photonic Switching

We present some novel architectures for rearrangeably nonblocking multistage photonic space switches implemented using arrays ofTi:LiNbO_{3}directional couplers. Multistage networks, studied mostly in the electronic domain, are obtained by minimizing the number of 2 × 2 elements needed to implement a switch. Unfortunately, straightforward extensions of these networks to the photonic domain show that the switch size has to be severely limited by the crosstalk in each of theTi:LiNbO_{3} 2 times 2switching elements. Our networks, on the other hand, have a controllable (including almost zero) amount of crosstalk, low optical path loss, and an asymptotically optimal number of directional coupler switches for a given switch size. In addition, the switch has a simple control algorithm and its performance for light loading appears very promising. The switch is easily decomposable into smaller arrays of no more than two types, making it easy to partition the switch into chips. At the cost of a slight increase in crosstalk, the switch can be made single fault tolerant in terms of its ability to connect any input to any output.     

多目标约束下的光突发交换网络组装参数分析

该文分析和研究了光突发交换网络中控制平面处理时延、数据平面资源利用效率以及数据平面突发丢失率等性能需求对边缘节点组装算法的约束性。分析结果证实数据平面的性能对边缘节点的组装算法参数更加敏感。在网络性能多目标约束条件下,基于无波长转换器核心节点的光突发交换网络几乎不存在有效的组装门限。在核心节点采用主流光交换矩阵且期望突发碰撞概率在10-4以下时,核心节点输出端口的单纤波长转换器数量至少需要30个以满足网络性能需求的约束条件。