基于网络延迟瓶颈定位算法的研究

对延迟瓶颈定位算法中的ICMP慢速路由器修正算法和未响应路由器延迟分配算法进行改进,在ICMP慢速路由器修正算法中提出均值估计修正算法,在未响应路由器的延迟分配算法中提出改进型未响应算法和二次测量辅助定位算法。通过对12条路径进行测量,结果证明,改进后的延迟瓶颈定位算法定位更准确,数据有效利用率更高。     

IP交换技术

随着Internet网络规模的快速扩展和运行各种多媒体业务的需要，IP交换技术越来越受到人们的重视，因为它将网络交换机的高速性和路由器的灵活性结合起来，解决了传统IP网络在运行实时业务时不能保证服务质量（QOS）的问题，并且克服了传统路由器包转发速度太慢造成的网络瓶颈问题。文中依次讨论了IP交换的关键技术，分析比较了几种不同的IP交换方式，指出了尚存在的问题。     

4类防火墙简介

防火墙的基本类型包括4大类:网络级防火墙(也叫包过滤型防火墙)、应用级网关、电路级网关和规则检查防火墙。1.网络级防火墙一般是基于源地址和目的地址、应用或协议以及每个IP包的端口来作出通过与否的判断。一个路由器便是一个“传统”的网络级防火墙,大多数的路由器都能通过检查这些信息来决定是否将所收到的包转发,但它不能判断出一个IP包来自何方,去向何处。     

三维成像微波高度计对流层延迟估计模型研究

对流层延迟是引起高度计高程测量误差的重要来源,三维成像微波高度计(InIRA)相对于传统剖面高度计有着更大的天线视角范围,不能直接沿用其对流层延迟估计方法.文中以Sentinel-3A数据为基准,对常用的垂向对流层延迟估计.模型进行对比筛选,并将筛选出来的模型进行适用于InIRA的改进,并结合第三方气象数据计算出改进后...     

OBS核心路由器中一种改进的数据输出模型研究

在光突发交换核心路由器中,突发数据分组的输出特性会影响路由器的输出性能.给出了一种改进的基于多概率输出环境的突发教据分组输出模型并进行了研究.改进的数据输出模型根据不同目的地路径长短而选择输出概率,更符合实际网络运行情况.对分组阻塞率、系统通过率等性能参数进行了分析和讨论.     

基于改进射线描迹法的对流层斜延迟估计

该文针对传统对流层延迟模型和射线描迹法在估计对流层延迟方面的局限性,如效率低、成本高、精度受地表参数和探空数据限制等不足,提出一种基于改进射线描迹法的对流层斜延迟估计方法。该方法结合中纬度大气模式气象参数公式和UNB3m气象参数模型,改进了射线描迹法中折射率剖面的计算,克服了气象数据对射线描迹法的限制。选取亚洲地区10个站点2012年的气象数据,分别采用改进射线描迹法和传统对流层延迟模型估计各个站天顶方向至 高度角区间15个方向的对流层斜延迟,并与基于探空数据获取的对流层斜延迟真值进行比较,计算结果表明该方法的估计精度优于传统对流层延迟模型,为非气象数据情况下对流层斜延迟实时估计提供了新的思路。     

基于WDM的光学Internet技术

（上接２０００年第２场４１页）３路由器技术进展 根据权威的＜＜数据通信＞＞（Ｄａｔａ　Ｃｏｍｍｕｎｉｃａｔｉｏｎ）杂志预测：从现在起的 ３～５年,太比特交换路由器（Ｔｅｒａｂｉｔ Ｓｗｉｔｃｈ Ｒｏｕｔｅｒ）和主干 ＡＴＭ交换机（Ｃｏｒｅ ＡＴＭ Ｓｗｉｔｃｈ）技术将共同主宰整个新一代Ｉｎｔｅｒｎｅｔ主干网,并将在迈入公元２１世纪时,通过ＤＷＤＭ技术使Ｉｎｔｅｒｎｅｔ主干网带宽提升到一根光纤跑 １０００ Ｇｂｉｔ／ｓ（太比特Ｔｅｒａｂｉｔ）的速率。一 传统路由器采用软件实现路由识别、计算和包转发,因而其速…     

一种自适应动态缓存策略准入控制算法

针对片上网络的死锁问题,基于虚拟网络的自适应路由算法,设计了一个完全自适应片上路由器.重点介绍了路由算法及路由器的系统结构,设计实现了一个低代价、高效的完全自适应路由器,并在2DMesh拓扑结构下对其性能进行了模拟验证.实验结果表明,该路由器实现了无死锁的自适应路由,并提高了网络吞吐量,降低了平均网络延迟.     

移动自组网的主观信任建模与仿真

不同于以往只考虑最短路径或只依靠转发行为评价信任或基于推荐机制的传统路由算法,提出了一种兼顾通信可靠性和路径长度的主观信任路由模型.通过引入属性相似度概念将邻居选择、信任评估、数据转发等路由环节紧密相连,进一步建立一种新的动态包转发规则,并给出了一种计算属性相似度的推荐方法.实验结果表明主观信任路由模型较传统的DSR(...     

简讯

中兴通讯推出系列电信级高端路由器产品 最近,在第十届上海国际信息通信展上,中兴通讯展示了其自主开发的国内第一个全系列的真正具备产业化能力的高端路由器──中兴 ＺＸＲ１０－ ＴＳＲ电信级高端路由器。 ＺＸＲ１０- ＴＳＲ采用先进的模块化结构和统一的系统软件平台,在交换容量、端口速率、端口密度及包转发能力等方面都处于国内领先的地位。该系列产品在系统的分布式处理能力、协议的支持能力等方面远远超过部分以普通ＡＴＭ交换机包装成的“高端路由器”产品。与传统路由器采用软件来转发数据包不同的是,ＺＸＲ１０－ＴＳＲ是通…     

GeoSVR: A map-based stateless VANET routing

Compared with traditional routing techniques, geographic routing has been proven to be more suitable for highly mobile environments like Vehicular Ad-Hoc Networks (VANETs) because of enhanced scalability and feasibility. These routings use greedy modes or forwarding paths to forward packets. However, the dynamic nature of vehicular network such as frequently changed topology, vehicles density and radio obstacles, could create local maximum, sparse connectivity and network partitions. We propose GeoSVR, a geographic stateless routing combined with node location and digital map. The proposed GeoSVR scheme enhances forwarding path to solve local maximum and sparse connectivity problem, and the proposed restricted forwarding algorithm overcomes unreliable wireless channel issues. In our study, simulations and real world experiments were conducted to evaluate the efficacy and efficiency of the proposed solution. Our results show GeoSVR can provide higher packet delivery ratio with comparable latency to other geographic routing schemes.     

基于网络预测的改进型PMIPv6快速切换方法

针对PMIPv6协议切换效率较低的问题,该文提出了一种基于网络预测的改进型PMIPv6快速切换方法。该方法在不变更切换决策主体的前提下,通过学习先验切换经验,利用距离加权最近邻算法来预测移动节点的切换目的地;同时采用软转发机制来保护在切换过程中到达移动节点的数据分组。仿真结果表明,改进方法产生的切换延迟和分组丢失数量明显少于PMIPv6。     

DFR: an efficient directional flooding‐based routing protocol in underwater sensor networks

Unlike terrestrial sensor networks, underwater sensor networks (UWSNs) have salient features such as a long propagation delay, narrow bandwidth, and high packet loss over links. Hence, path setup‐based routing protocols proposed for terrestrial sensor networks are not applicable because a large latency of the path establishment is observed, and packet delivery is not reliable in UWSNs. Even though routing protocols such as VBF (vector based forwarding) and HHVBF (hop‐by‐hop VBF) were introduced for UWSNs, their performance in terms of reliability deteriorates at high packet loss. In this paper, we therefore propose a directional flooding‐based routing protocol, called DFR, in order to achieve reliable packet delivery. DFR performs a so‐called controlled flooding, where DFR changes the number of nodes which participate in forwarding a packet according to their link quality. When a forwarding node has poor link quality to its neighbor nodes geographically advancing toward the sink, DFR allows more nodes to participate in forwarding the packet. Otherwise, a few nodes are enough to forward the packet reliably. In addition, we identify two types of void problems which can occur during the controlled flooding and introduce their corresponding solutions. Our simulation study using ns‐2 simulator proves that DFR is more suitable for UWSNs, especially when links are prone to packet loss. Copyright © 2011 John Wiley & Sons, Ltd.     

Routing protocol over lossy links for ISA100.11a industrial wireless networks

This paper proposes novel routing and topology control algorithms for industrial wireless sensor networks (IWSNs) based on the ISA100.11a standard. The proposed algorithms not only reduces energy consumption at the node level but also reduces packet latency at the network level. Using the residual energy and packet reception rate of neighbor nodes, the source node can estimate the highest election weight. Hence, packets are conveyed by a multi-hop forwarding scheme from source nodes to the sink by the optimal path. Furthermore, energy consumption and network latency are minimized using integer linear programming. Simulation results show that the proposed algorithms are fully effective in terms of energy conservation and network latency for IWSNs.     

Energy-neutral scheduling and forwarding in environmentally-powered wireless sensor networks

In environmentally-powered wireless sensor networks (EPWSNs), low latency wakeup scheduling and packet forwarding is challenging due to dynamic duty cycling, posing time-varying sleep latencies and necessitating the use of dynamic wakeup schedules. We show that the variance of the intervals between receiving wakeup slots affects the expected sleep latency: when the variance of the intervals is low (high), the expected latency is low (high). We therefore propose a novel scheduling scheme that uses the bit-reversal permutation sequence (BRPS) – a finite integer sequence that positions receiving wakeup slots as evenly as possible to reduce the expected sleep latency. At the same time, the sequence serves as a compact representation of wakeup schedules thereby reducing storage and communication overhead. But while low latency wakeup schedule can reduce per-hop delay in ideal conditions, it does not necessarily lead to low latency end-to-end paths because wireless link quality also plays a significant role in the performance of packet forwarding. We therefore formulate expected transmission delay (ETD), a metric that simultaneously considers sleep latency and wireless link quality. We show that the metric is left-monotonic and left-isotonic, proving that its use in distributed algorithms such as the distributed Bellman–Ford yields consistent, loop-free and optimal paths. We perform extensive simulations using real-world energy harvesting traces to evaluate the performance of the scheduling and forwarding scheme.     

The Impact of Deployment Pattern and Routing Scheme on the Lifetime in Multi-Sink Wireless Sensor Network

Extensive use of sensor and actuator networks in many real-life applications introduced several new performance metrics at the node and network level. Since wireless sensor nodes have significant battery constraints, therefore, energy efficiency, as well as network lifetime, are among the most significant performance metrics to measure the effectiveness of given network architecture. This work investigates the performance of an event-based data delivery model using a multipath routing scheme for a wireless sensor network with multiple sink nodes. This routing algorithm follows a sink initiated route discovery process with the location information of the source nodes already known to the sink nodes. It also considers communication link costs before making decisions for packet forwarding. Carried out simulation compares the network performance of a wireless sensor network with a single sink, dual sink, and multi sink networking approaches. Based on a series of simulation experiments, the lifetime aware multipath routing approach is found appropriate for increasing the lifetime of sensor nodes significantly when compared to other similar routing schemes. However, energy-efficient packet forwarding is a major concern of this work; other network performance metrics like delay, average packet latency, and packet delivery ratio are also taken into the account.

     

DCMA: A Label Switching MAC for Efficient Packet Forwarding in Multihop Wireless Networks

This paper addresses the problem of efficient packet forwarding in a multihop, wireless "mesh" network. We present an efficient interface contained forwarding (ICF) architecture for a "wireless router," i.e., a forwarding node with a single wireless network interface card (NIC) in a multihop wireless network that allows a packet to be forwarded entirely within the NIC of the forwarding node without requiring per-packet intervention by the node's CPU. To effectively forward packets in a pipelined fashion without incurring the 802.11-related overheads of multiple independent channel accesses, we specify a slightly modified version of the 802.11 MAC, called data driven cut-through multiple access (DCMA) that uses multiprotocol label switching (MPLS)-like labels in the control packets, in conjunction with a combined ACK/RTS packet, to reduce 802.11 channel access latencies. Our proposed technique can be used in combination with "frame bursting" as specified by the IEEE 802.11e standard to provide an end-to-end cut-through channel access. Using extensive simulations, we compare the performance of DCMA with 802.11 DCF MAC with respect to throughput and latency and suggest a suitable operating region to get maximum benefits using our mechanism as compared to 802.11     

内容中心网络状态感知路由设计

为了提高内容中心网络的内容分发效率及降低网络开销,提出了网络状态感知的路由机制NSAR(network status aware routing)。NSAR利用从内容服务节点返回的数据分组收集当前网络状态信息,并在回传过程中对路径上各节点上匹配端口的转发概率进行更新,在对后续的兴趣分组进行转发决策时引入转发概率,从而提高内容分发效率。仿真实验表明,与传统内容中心网络路由算法相比,NSAR可以有效地降低内容请求平均时延,减少网络流通分组数以及降低网络带宽开销。     

面向软件定义核心网的OpenFlow分组转发优先制排队模型研究

软件定义网络（Software-Defined Networking,SDN）作为一种数据转发与控制逻辑相解耦、并开放底层编程接口的创新网络架构,为降低核心网的部署运营成本、提升应用业务性能提供了全新的解决思路.然而,在SDN架构下,逻辑上集中的控制平面容易出现性能瓶颈,进而加大分组转发时延,因此有必要理解其分组转发性能特性.为此,本文首先介绍了软件定义核心网的典型部署场景,分析了控制平面的Packet-in消息到达过程和数据平面的分组到达过程,进而应用M/M/n/m和M/M/1/m排队模型分别刻画控制器集群的Packet-in消息处理过程和OpenFlow交换机的分组处理过程.在此基础上,建立OpenFlow分组转发优先制排队模型,进而推导出不同优先级的分组转发时延及其累积分布函数CDF.最后,借助控制器性能测量工具OFsuite_Performance进行实验评估,结果表明：与现有模型相比,本文所提的M/M/n/m模型更能准确估计控制器集群的实际性能.同时,采用数值分析的方法对比了多种情况下不同优先级的分组转发时延及CDF曲线,为软件定义核心网的实际应用部署提供有效参考.     

分布式能量均衡的WSN动态数据转发策略

针对无线传感器网络中存在的能量空洞问题,该文提出一种能量均衡的层次型数据转发策略。根据节点可用能量、节点之间相对位置及不同网络区域簇头能量消耗速率构建非均匀层次化结构。进而,综合考虑节点簇内通信开销和节点关系选取中继转发节点,并在多跳簇间数据转发时执行数据融合进一步降低转发数据量以实现簇间多跳通信的能量有效性。数值结果表明,所提机制可以有效地均衡网络负载,延长网络生命周期,改善网络数据转发性能。