IP网络分组传送性能讲座第3讲:IP分组传送时延

1 IP分组传送时延(IPTD,IP Packet Transfer Delay) IP分组传送时延被定义为所有成功或差错IP分组结果通过一个基本段或NSE所用的时间.即IPTD是发生两个相关IP分组传送参考事件的时间差(t2-t1),其中输入事件发生在t1,输出事件发生在t2,这里t2＞t1,并且t2-t1≤Tmax.     

网络测试及性能评价模型研究

从面向应用的角度，提出了网络测试及性能评价的模型，探讨了网络测试的内容，以及依据所测试的内容如何来对网络性能进行评价。     

一种IP网络带宽和时延的有效测量模型

提出了一种同时测量IP网络带宽利用率和路径时延的测量模型,能够有效降低网络测量的开销。以顶点覆盖和边覆盖的相关理论为基础,证明了以最小代价混合覆盖全网的问题是NP难的。同时提出了一种改进两阶段算法,可以有效地确定最小覆盖集。性能仿真结果显示改进后的算法对大范围的网络拓扑有效。     

B—DMB快速分组交换机的性能分析

由于不能预先对进入B-DMB交换机的各分组进行调整,可能出现同一时隙有2个或2个以上的分组都要到达某一输出端的情形,因此在B-DMB交换机中不可避免地要加进一些缓冲器。本文对B-DMB交换机的输入、输出缓冲器长度和分组时延进行了分析和计算,得出了一些有用的结论。     

IP网络分组传送性能讲座 第1讲:IP网络性能参考模型

随着IP技术的发展,其应用领域不断扩大.现有的IP网络能够较好地支持非实时数据业务,为r使它也能够支持各种实时业务与多媒体业务,就必须研究和规范IP网络传送信息的性能.本讲座在研究和分析ITU-T关于IP网络性能的标准和实际解决工程技术问题的基础上,讨论和介绍了IP网络性能方面的有关内容.其中包括:IP业务性能描述的参考模型、IP业务性能测试的环境与条件、IP业务的性能参数、IP业务的可用性等.     

移动IPv6及其扩展协议性能分析

本文主要对这几种移动IP技术进行描述,然后在NS-2(一种开放源码的网络模拟工具)仿真平台下设定一定的切换场景进行仿真实现,对这几种协议进行切换时延和切换期间丢包数量的比较.     

IP网络QoS模型技术比较

构架在传统的电信网上的因特网,业务爆炸性增长给传统电信网造成了严重的拥塞。解决因特网服务质量问题的核心在于建立一个宽带的骨干网。宽带IP网具有支持多种业务、廉价、通用性强和较好的扩展性等优势。随着MPLS协议和各种IP QoS建议的标准化,宽带IP将有效支持具有服务质量要求的IP业务。为了提高IP网的整体性能,各种新的QoS服务结构层出不穷。本文通过介绍IP网中几种QoS服务模型,强调MPLS是在大型IP网络中作为提供QoS保证的最具发展前景的技术。     

基于IP的专用网络性能仿真与分析

基于IP技术的专用网络面向对象与服务,使用灵活、方便,但服务质量难以保证。由于专用网络中信息传输的实时性、可靠性和安全性要求很高,为验证所设计的专用网络的性能,通过OPNET仿真工具对专用网络进行建模仿真,得出了IP专用网络中时延、时延抖动和丢包率与业务类型、网络流量负荷、不同传输速率及电路误码率间的关系,并对实验数据进行了分析,最后针对IP专用网络中的业务配置和流量控制给出了建议。     

超宽带IP网络环境下的视频分组丢失修复技术研究

基于IP超宽带网络传送视频节目已经成为三网融合背景下的发展趋势。相对于传统广电运营商的同轴广播网,IP网络更加复杂,出现分组丢失的可能性更大,可能会影响用户的观赏体验。目前的视频编码技术本身的冗余机制大多适用于同轴网络,因此有必要对IP网络中的视频分组丢失修复机制进行研究。本文分析了分组丢失对视频质量的影响,并对目前主流的分组丢失修复技术进行了针对性分析和比较,结合测试结果,给出了可行的分组丢失修复技术应用建议。     

The impact of stochastic resource availability on cognitive network performance: modeling and analysis

Cognitive radio networks emerge as a promising solution for overcoming shortage and inefficient use of bandwidth resources by allowing secondary users (SUs) to access the primary users' (PUs) channel so long as they do not interfere with them. The dynamical spectrum availability makes SU's packet average delay one of the most important performance measures of a cognitive network. It is important to understand the nature of delay, as well as its dependence on PU behaviors. In this paper, we analytically model and analyze the dynamics of the spectrum availability and their impact on the SU's packet delay. The cognitive network is modeled as a discrete‐time queueing system. PU channel occupancy is modeled as a two‐state Markov chain. Our contribution in this paper is defining and characterizing the properties of the random process that describes the availability of the opportunistic resources. In addition, we apply the mean residual service time concept to achieve an analytical solution for the queueing delay. Moreover, inspired by the slotted Aloha system, we model the packet service mechanism and determine the manner in which it depends on the resource availability. The delay becomes unbounded if the spectrum availability dynamics are not carefully considered in network design. Copyright © 2015 John Wiley & Sons, Ltd.     

The impact of Ajax on network performance

Web 2.0 has been becoming the new tendency of the Internet development. In order to get better management of web 2.0 network resource and guarantee of service quality, the architecture and the advantages of web 2.0 over Ajax technology is analyzed, and the impact of Ajax on bandwidth performance of web application is discussed.     

自适应弹性环光缓存结构设计及其网络性能分析

最大缓存时间限制、时延粒度限制、光分组长度限制3大限制因素,对传统光缓存器的前馈型和反馈型两种结构进行了分析。分析表明,影响光缓存器性能的3大限制因素在两种结构中的相互制约关系限制了光缓存器性能的进一步提高。在此基础上提出的一种自适应弹性环光缓存器(E-FLOB)结合了两种传统结构的优势,并分离了3大限制因素间的相互制约关系。结构分析显示,E-FLOB在缓存级数为16时可减少反馈型光缓存器噪声积累约3个数量级。网络性能仿真表明,弹性环结构比前馈型结构使用更少的缓存级数,获得比两种传统结构更低的分组丢失率。     

一种基于捕获的扩频分组无线网MAC层协议及其性能分析

在分组接入过程中,当每个用户终端以随机竞争的方式获得所需的频谱资源时,会引起用户间的冲突和资源的浪费,造成系统性能的降低。本文引入了一种基于捕获的接入方法,当一个时隙中存在多个干扰分组时,该方法仍有捕获到某个分组的可能,该方法在系统高负载的情况下能有效地利用资源。性能分析和计算结果表明,基于捕获的方法改善了系统的性能。     

A framework for fiber delay‐line buffers in packet‐based asynchronous multifiber optical networks (PAMFONET)

A major challenge in packet‐based optical networks is packet contention, which occurs when two or more packets are heading to the same output at the same time. To resolve contention in the optical domain, a fundamental approach is fiber delay‐line (FDL) buffering, in which packets can be delayed for a fixed amount of time. In the literature, the performance of FDL buffering has been studied extensively. However, most existing works are based on an assumption that there is only one fiber per link in the network. In this paper, we address the architecture and performance of FDL buffers in packet‐based asynchronous multifiber optical networks (PAMFONET), in which each link in the network may consist of multiple optical fibers. We propose a framework for FDL buffers in PAMFONET, in which we provide three essential architectures and corresponding packet scheduling policies. Extensive simulation results show that, with appropriate settings, the same number of FDLs can lead to better performance in multifiber networks than in single‐fiber networks. Copyright © 2011 John Wiley & Sons, Ltd.     

基于延时及带宽约束的组播路由算法

本文分析了网络中基于延时和带宽受限的组播路由优化问题,提出了一种新的启发式算法,并进行了实验和分析。文中构造的路由方案成功地解决了当网络中存在多组组播通信时的QoS路由选择问题。此方案不仅保证了组播业务所需的带宽、端到端延时、减小了丢包率,而且有效地控制了算法的复杂性并可适用于大规模的网络中。     

IP Telephony问题研究综述

文中从对集成服务网络的主要应用之一分组网络语音传输应用的体系结构分析入手,从集成服务网络研究的观点出发,综述了以ＩＰ Ｔｅｌｅｐｈｏｎｙ为代表的分组网络语音传输技术体系中上前尚有待研究解决的问题。通过文中的分析,我们讨论了电信网与因特网通过诸多技术方面的融合,走向合一网络的发展趋势。     

End‐to‐end delay and packet drop rate performance for a wireless sensor network with a cluster‐tree topology

In this paper, we study the delay performance in a wireless sensor network (WSN) with a cluster‐tree topology. The end‐to‐end delay in such a network can be strongly dependent on the relative location between the sensors and the sink and the resource allocations of the cluster heads (CHs). For real‐time traffic, packets transmitted with excessive delay are dropped. Given the timeline allocations of each CH for local and inter‐cluster traffic transmissions, an analytical model is developed to find the distribution of the end‐to‐end transmission delay for packets originated from different clusters. Based on this result, the packet drop rate is derived. A heuristic scheme is then proposed to jointly find the timeline allocations of all the CHs in a WSN in order to achieve the minimum and balanced packet drop rate for traffic originated from different levels of the cluster tree. Simulation results are shown to verify the analysis and to demonstrate the effectiveness of the proposed CH timeline allocation scheme. Copyright © 2012 John Wiley & Sons, Ltd.     

IP网络性能指标体系的研究

网络性能指标是网络测评的基础。本文从网络测评的不同角度对IP网络的性能指标进行了综合分析，指出了一种能系统反映IP网络性能的指标体系，并给出了IP网络性能指标体系的形式描述。在此基础上引入了泛化指标和确定性指标的概念，探讨了确定性指标的内容有及描述框架。该研究突破了目前IP网络性能指标体系研究的简单性、局限性，对IP网络测试和性能评价具有指导意义。